Bug Summary

File:lib/Transforms/InstCombine/InstCombineCompares.cpp
Warning:line 2299, column 53
Called C++ object pointer is null

Annotated Source Code

1//===- InstCombineCompares.cpp --------------------------------------------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements the visitICmp and visitFCmp functions.
11//
12//===----------------------------------------------------------------------===//
13
14#include "InstCombineInternal.h"
15#include "llvm/ADT/APSInt.h"
16#include "llvm/ADT/SetVector.h"
17#include "llvm/ADT/Statistic.h"
18#include "llvm/Analysis/ConstantFolding.h"
19#include "llvm/Analysis/InstructionSimplify.h"
20#include "llvm/Analysis/MemoryBuiltins.h"
21#include "llvm/Analysis/TargetLibraryInfo.h"
22#include "llvm/Analysis/VectorUtils.h"
23#include "llvm/IR/ConstantRange.h"
24#include "llvm/IR/DataLayout.h"
25#include "llvm/IR/GetElementPtrTypeIterator.h"
26#include "llvm/IR/IntrinsicInst.h"
27#include "llvm/IR/PatternMatch.h"
28#include "llvm/Support/Debug.h"
29#include "llvm/Support/KnownBits.h"
30
31using namespace llvm;
32using namespace PatternMatch;
33
34#define DEBUG_TYPE"instcombine" "instcombine"
35
36// How many times is a select replaced by one of its operands?
37STATISTIC(NumSel, "Number of select opts")static llvm::Statistic NumSel = {"instcombine", "NumSel", "Number of select opts"
, {0}, false}
;
38
39
40static ConstantInt *extractElement(Constant *V, Constant *Idx) {
41 return cast<ConstantInt>(ConstantExpr::getExtractElement(V, Idx));
42}
43
44static bool hasAddOverflow(ConstantInt *Result,
45 ConstantInt *In1, ConstantInt *In2,
46 bool IsSigned) {
47 if (!IsSigned)
48 return Result->getValue().ult(In1->getValue());
49
50 if (In2->isNegative())
51 return Result->getValue().sgt(In1->getValue());
52 return Result->getValue().slt(In1->getValue());
53}
54
55/// Compute Result = In1+In2, returning true if the result overflowed for this
56/// type.
57static bool addWithOverflow(Constant *&Result, Constant *In1,
58 Constant *In2, bool IsSigned = false) {
59 Result = ConstantExpr::getAdd(In1, In2);
60
61 if (VectorType *VTy = dyn_cast<VectorType>(In1->getType())) {
62 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
63 Constant *Idx = ConstantInt::get(Type::getInt32Ty(In1->getContext()), i);
64 if (hasAddOverflow(extractElement(Result, Idx),
65 extractElement(In1, Idx),
66 extractElement(In2, Idx),
67 IsSigned))
68 return true;
69 }
70 return false;
71 }
72
73 return hasAddOverflow(cast<ConstantInt>(Result),
74 cast<ConstantInt>(In1), cast<ConstantInt>(In2),
75 IsSigned);
76}
77
78static bool hasSubOverflow(ConstantInt *Result,
79 ConstantInt *In1, ConstantInt *In2,
80 bool IsSigned) {
81 if (!IsSigned)
82 return Result->getValue().ugt(In1->getValue());
83
84 if (In2->isNegative())
85 return Result->getValue().slt(In1->getValue());
86
87 return Result->getValue().sgt(In1->getValue());
88}
89
90/// Compute Result = In1-In2, returning true if the result overflowed for this
91/// type.
92static bool subWithOverflow(Constant *&Result, Constant *In1,
93 Constant *In2, bool IsSigned = false) {
94 Result = ConstantExpr::getSub(In1, In2);
95
96 if (VectorType *VTy = dyn_cast<VectorType>(In1->getType())) {
97 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
98 Constant *Idx = ConstantInt::get(Type::getInt32Ty(In1->getContext()), i);
99 if (hasSubOverflow(extractElement(Result, Idx),
100 extractElement(In1, Idx),
101 extractElement(In2, Idx),
102 IsSigned))
103 return true;
104 }
105 return false;
106 }
107
108 return hasSubOverflow(cast<ConstantInt>(Result),
109 cast<ConstantInt>(In1), cast<ConstantInt>(In2),
110 IsSigned);
111}
112
113/// Given an icmp instruction, return true if any use of this comparison is a
114/// branch on sign bit comparison.
115static bool isBranchOnSignBitCheck(ICmpInst &I, bool isSignBit) {
116 for (auto *U : I.users())
117 if (isa<BranchInst>(U))
118 return isSignBit;
119 return false;
120}
121
122/// Given an exploded icmp instruction, return true if the comparison only
123/// checks the sign bit. If it only checks the sign bit, set TrueIfSigned if the
124/// result of the comparison is true when the input value is signed.
125static bool isSignBitCheck(ICmpInst::Predicate Pred, const APInt &RHS,
126 bool &TrueIfSigned) {
127 switch (Pred) {
128 case ICmpInst::ICMP_SLT: // True if LHS s< 0
129 TrueIfSigned = true;
130 return RHS == 0;
131 case ICmpInst::ICMP_SLE: // True if LHS s<= RHS and RHS == -1
132 TrueIfSigned = true;
133 return RHS.isAllOnesValue();
134 case ICmpInst::ICMP_SGT: // True if LHS s> -1
135 TrueIfSigned = false;
136 return RHS.isAllOnesValue();
137 case ICmpInst::ICMP_UGT:
138 // True if LHS u> RHS and RHS == high-bit-mask - 1
139 TrueIfSigned = true;
140 return RHS.isMaxSignedValue();
141 case ICmpInst::ICMP_UGE:
142 // True if LHS u>= RHS and RHS == high-bit-mask (2^7, 2^15, 2^31, etc)
143 TrueIfSigned = true;
144 return RHS.isSignMask();
145 default:
146 return false;
147 }
148}
149
150/// Returns true if the exploded icmp can be expressed as a signed comparison
151/// to zero and updates the predicate accordingly.
152/// The signedness of the comparison is preserved.
153/// TODO: Refactor with decomposeBitTestICmp()?
154static bool isSignTest(ICmpInst::Predicate &Pred, const APInt &C) {
155 if (!ICmpInst::isSigned(Pred))
156 return false;
157
158 if (C == 0)
159 return ICmpInst::isRelational(Pred);
160
161 if (C == 1) {
162 if (Pred == ICmpInst::ICMP_SLT) {
163 Pred = ICmpInst::ICMP_SLE;
164 return true;
165 }
166 } else if (C.isAllOnesValue()) {
167 if (Pred == ICmpInst::ICMP_SGT) {
168 Pred = ICmpInst::ICMP_SGE;
169 return true;
170 }
171 }
172
173 return false;
174}
175
176/// Given a signed integer type and a set of known zero and one bits, compute
177/// the maximum and minimum values that could have the specified known zero and
178/// known one bits, returning them in Min/Max.
179/// TODO: Move to method on KnownBits struct?
180static void computeSignedMinMaxValuesFromKnownBits(const KnownBits &Known,
181 APInt &Min, APInt &Max) {
182 assert(Known.getBitWidth() == Min.getBitWidth() &&((Known.getBitWidth() == Min.getBitWidth() && Known.getBitWidth
() == Max.getBitWidth() && "KnownZero, KnownOne and Min, Max must have equal bitwidth."
) ? static_cast<void> (0) : __assert_fail ("Known.getBitWidth() == Min.getBitWidth() && Known.getBitWidth() == Max.getBitWidth() && \"KnownZero, KnownOne and Min, Max must have equal bitwidth.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 184, __PRETTY_FUNCTION__))
183 Known.getBitWidth() == Max.getBitWidth() &&((Known.getBitWidth() == Min.getBitWidth() && Known.getBitWidth
() == Max.getBitWidth() && "KnownZero, KnownOne and Min, Max must have equal bitwidth."
) ? static_cast<void> (0) : __assert_fail ("Known.getBitWidth() == Min.getBitWidth() && Known.getBitWidth() == Max.getBitWidth() && \"KnownZero, KnownOne and Min, Max must have equal bitwidth.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 184, __PRETTY_FUNCTION__))
184 "KnownZero, KnownOne and Min, Max must have equal bitwidth.")((Known.getBitWidth() == Min.getBitWidth() && Known.getBitWidth
() == Max.getBitWidth() && "KnownZero, KnownOne and Min, Max must have equal bitwidth."
) ? static_cast<void> (0) : __assert_fail ("Known.getBitWidth() == Min.getBitWidth() && Known.getBitWidth() == Max.getBitWidth() && \"KnownZero, KnownOne and Min, Max must have equal bitwidth.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 184, __PRETTY_FUNCTION__))
;
185 APInt UnknownBits = ~(Known.Zero|Known.One);
186
187 // The minimum value is when all unknown bits are zeros, EXCEPT for the sign
188 // bit if it is unknown.
189 Min = Known.One;
190 Max = Known.One|UnknownBits;
191
192 if (UnknownBits.isNegative()) { // Sign bit is unknown
193 Min.setSignBit();
194 Max.clearSignBit();
195 }
196}
197
198/// Given an unsigned integer type and a set of known zero and one bits, compute
199/// the maximum and minimum values that could have the specified known zero and
200/// known one bits, returning them in Min/Max.
201/// TODO: Move to method on KnownBits struct?
202static void computeUnsignedMinMaxValuesFromKnownBits(const KnownBits &Known,
203 APInt &Min, APInt &Max) {
204 assert(Known.getBitWidth() == Min.getBitWidth() &&((Known.getBitWidth() == Min.getBitWidth() && Known.getBitWidth
() == Max.getBitWidth() && "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth."
) ? static_cast<void> (0) : __assert_fail ("Known.getBitWidth() == Min.getBitWidth() && Known.getBitWidth() == Max.getBitWidth() && \"Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 206, __PRETTY_FUNCTION__))
205 Known.getBitWidth() == Max.getBitWidth() &&((Known.getBitWidth() == Min.getBitWidth() && Known.getBitWidth
() == Max.getBitWidth() && "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth."
) ? static_cast<void> (0) : __assert_fail ("Known.getBitWidth() == Min.getBitWidth() && Known.getBitWidth() == Max.getBitWidth() && \"Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 206, __PRETTY_FUNCTION__))
206 "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth.")((Known.getBitWidth() == Min.getBitWidth() && Known.getBitWidth
() == Max.getBitWidth() && "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth."
) ? static_cast<void> (0) : __assert_fail ("Known.getBitWidth() == Min.getBitWidth() && Known.getBitWidth() == Max.getBitWidth() && \"Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 206, __PRETTY_FUNCTION__))
;
207 APInt UnknownBits = ~(Known.Zero|Known.One);
208
209 // The minimum value is when the unknown bits are all zeros.
210 Min = Known.One;
211 // The maximum value is when the unknown bits are all ones.
212 Max = Known.One|UnknownBits;
213}
214
215/// This is called when we see this pattern:
216/// cmp pred (load (gep GV, ...)), cmpcst
217/// where GV is a global variable with a constant initializer. Try to simplify
218/// this into some simple computation that does not need the load. For example
219/// we can optimize "icmp eq (load (gep "foo", 0, i)), 0" into "icmp eq i, 3".
220///
221/// If AndCst is non-null, then the loaded value is masked with that constant
222/// before doing the comparison. This handles cases like "A[i]&4 == 0".
223Instruction *InstCombiner::foldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
224 GlobalVariable *GV,
225 CmpInst &ICI,
226 ConstantInt *AndCst) {
227 Constant *Init = GV->getInitializer();
228 if (!isa<ConstantArray>(Init) && !isa<ConstantDataArray>(Init))
229 return nullptr;
230
231 uint64_t ArrayElementCount = Init->getType()->getArrayNumElements();
232 // Don't blow up on huge arrays.
233 if (ArrayElementCount > MaxArraySizeForCombine)
234 return nullptr;
235
236 // There are many forms of this optimization we can handle, for now, just do
237 // the simple index into a single-dimensional array.
238 //
239 // Require: GEP GV, 0, i {{, constant indices}}
240 if (GEP->getNumOperands() < 3 ||
241 !isa<ConstantInt>(GEP->getOperand(1)) ||
242 !cast<ConstantInt>(GEP->getOperand(1))->isZero() ||
243 isa<Constant>(GEP->getOperand(2)))
244 return nullptr;
245
246 // Check that indices after the variable are constants and in-range for the
247 // type they index. Collect the indices. This is typically for arrays of
248 // structs.
249 SmallVector<unsigned, 4> LaterIndices;
250
251 Type *EltTy = Init->getType()->getArrayElementType();
252 for (unsigned i = 3, e = GEP->getNumOperands(); i != e; ++i) {
253 ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i));
254 if (!Idx) return nullptr; // Variable index.
255
256 uint64_t IdxVal = Idx->getZExtValue();
257 if ((unsigned)IdxVal != IdxVal) return nullptr; // Too large array index.
258
259 if (StructType *STy = dyn_cast<StructType>(EltTy))
260 EltTy = STy->getElementType(IdxVal);
261 else if (ArrayType *ATy = dyn_cast<ArrayType>(EltTy)) {
262 if (IdxVal >= ATy->getNumElements()) return nullptr;
263 EltTy = ATy->getElementType();
264 } else {
265 return nullptr; // Unknown type.
266 }
267
268 LaterIndices.push_back(IdxVal);
269 }
270
271 enum { Overdefined = -3, Undefined = -2 };
272
273 // Variables for our state machines.
274
275 // FirstTrueElement/SecondTrueElement - Used to emit a comparison of the form
276 // "i == 47 | i == 87", where 47 is the first index the condition is true for,
277 // and 87 is the second (and last) index. FirstTrueElement is -2 when
278 // undefined, otherwise set to the first true element. SecondTrueElement is
279 // -2 when undefined, -3 when overdefined and >= 0 when that index is true.
280 int FirstTrueElement = Undefined, SecondTrueElement = Undefined;
281
282 // FirstFalseElement/SecondFalseElement - Used to emit a comparison of the
283 // form "i != 47 & i != 87". Same state transitions as for true elements.
284 int FirstFalseElement = Undefined, SecondFalseElement = Undefined;
285
286 /// TrueRangeEnd/FalseRangeEnd - In conjunction with First*Element, these
287 /// define a state machine that triggers for ranges of values that the index
288 /// is true or false for. This triggers on things like "abbbbc"[i] == 'b'.
289 /// This is -2 when undefined, -3 when overdefined, and otherwise the last
290 /// index in the range (inclusive). We use -2 for undefined here because we
291 /// use relative comparisons and don't want 0-1 to match -1.
292 int TrueRangeEnd = Undefined, FalseRangeEnd = Undefined;
293
294 // MagicBitvector - This is a magic bitvector where we set a bit if the
295 // comparison is true for element 'i'. If there are 64 elements or less in
296 // the array, this will fully represent all the comparison results.
297 uint64_t MagicBitvector = 0;
298
299 // Scan the array and see if one of our patterns matches.
300 Constant *CompareRHS = cast<Constant>(ICI.getOperand(1));
301 for (unsigned i = 0, e = ArrayElementCount; i != e; ++i) {
302 Constant *Elt = Init->getAggregateElement(i);
303 if (!Elt) return nullptr;
304
305 // If this is indexing an array of structures, get the structure element.
306 if (!LaterIndices.empty())
307 Elt = ConstantExpr::getExtractValue(Elt, LaterIndices);
308
309 // If the element is masked, handle it.
310 if (AndCst) Elt = ConstantExpr::getAnd(Elt, AndCst);
311
312 // Find out if the comparison would be true or false for the i'th element.
313 Constant *C = ConstantFoldCompareInstOperands(ICI.getPredicate(), Elt,
314 CompareRHS, DL, &TLI);
315 // If the result is undef for this element, ignore it.
316 if (isa<UndefValue>(C)) {
317 // Extend range state machines to cover this element in case there is an
318 // undef in the middle of the range.
319 if (TrueRangeEnd == (int)i-1)
320 TrueRangeEnd = i;
321 if (FalseRangeEnd == (int)i-1)
322 FalseRangeEnd = i;
323 continue;
324 }
325
326 // If we can't compute the result for any of the elements, we have to give
327 // up evaluating the entire conditional.
328 if (!isa<ConstantInt>(C)) return nullptr;
329
330 // Otherwise, we know if the comparison is true or false for this element,
331 // update our state machines.
332 bool IsTrueForElt = !cast<ConstantInt>(C)->isZero();
333
334 // State machine for single/double/range index comparison.
335 if (IsTrueForElt) {
336 // Update the TrueElement state machine.
337 if (FirstTrueElement == Undefined)
338 FirstTrueElement = TrueRangeEnd = i; // First true element.
339 else {
340 // Update double-compare state machine.
341 if (SecondTrueElement == Undefined)
342 SecondTrueElement = i;
343 else
344 SecondTrueElement = Overdefined;
345
346 // Update range state machine.
347 if (TrueRangeEnd == (int)i-1)
348 TrueRangeEnd = i;
349 else
350 TrueRangeEnd = Overdefined;
351 }
352 } else {
353 // Update the FalseElement state machine.
354 if (FirstFalseElement == Undefined)
355 FirstFalseElement = FalseRangeEnd = i; // First false element.
356 else {
357 // Update double-compare state machine.
358 if (SecondFalseElement == Undefined)
359 SecondFalseElement = i;
360 else
361 SecondFalseElement = Overdefined;
362
363 // Update range state machine.
364 if (FalseRangeEnd == (int)i-1)
365 FalseRangeEnd = i;
366 else
367 FalseRangeEnd = Overdefined;
368 }
369 }
370
371 // If this element is in range, update our magic bitvector.
372 if (i < 64 && IsTrueForElt)
373 MagicBitvector |= 1ULL << i;
374
375 // If all of our states become overdefined, bail out early. Since the
376 // predicate is expensive, only check it every 8 elements. This is only
377 // really useful for really huge arrays.
378 if ((i & 8) == 0 && i >= 64 && SecondTrueElement == Overdefined &&
379 SecondFalseElement == Overdefined && TrueRangeEnd == Overdefined &&
380 FalseRangeEnd == Overdefined)
381 return nullptr;
382 }
383
384 // Now that we've scanned the entire array, emit our new comparison(s). We
385 // order the state machines in complexity of the generated code.
386 Value *Idx = GEP->getOperand(2);
387
388 // If the index is larger than the pointer size of the target, truncate the
389 // index down like the GEP would do implicitly. We don't have to do this for
390 // an inbounds GEP because the index can't be out of range.
391 if (!GEP->isInBounds()) {
392 Type *IntPtrTy = DL.getIntPtrType(GEP->getType());
393 unsigned PtrSize = IntPtrTy->getIntegerBitWidth();
394 if (Idx->getType()->getPrimitiveSizeInBits() > PtrSize)
395 Idx = Builder->CreateTrunc(Idx, IntPtrTy);
396 }
397
398 // If the comparison is only true for one or two elements, emit direct
399 // comparisons.
400 if (SecondTrueElement != Overdefined) {
401 // None true -> false.
402 if (FirstTrueElement == Undefined)
403 return replaceInstUsesWith(ICI, Builder->getFalse());
404
405 Value *FirstTrueIdx = ConstantInt::get(Idx->getType(), FirstTrueElement);
406
407 // True for one element -> 'i == 47'.
408 if (SecondTrueElement == Undefined)
409 return new ICmpInst(ICmpInst::ICMP_EQ, Idx, FirstTrueIdx);
410
411 // True for two elements -> 'i == 47 | i == 72'.
412 Value *C1 = Builder->CreateICmpEQ(Idx, FirstTrueIdx);
413 Value *SecondTrueIdx = ConstantInt::get(Idx->getType(), SecondTrueElement);
414 Value *C2 = Builder->CreateICmpEQ(Idx, SecondTrueIdx);
415 return BinaryOperator::CreateOr(C1, C2);
416 }
417
418 // If the comparison is only false for one or two elements, emit direct
419 // comparisons.
420 if (SecondFalseElement != Overdefined) {
421 // None false -> true.
422 if (FirstFalseElement == Undefined)
423 return replaceInstUsesWith(ICI, Builder->getTrue());
424
425 Value *FirstFalseIdx = ConstantInt::get(Idx->getType(), FirstFalseElement);
426
427 // False for one element -> 'i != 47'.
428 if (SecondFalseElement == Undefined)
429 return new ICmpInst(ICmpInst::ICMP_NE, Idx, FirstFalseIdx);
430
431 // False for two elements -> 'i != 47 & i != 72'.
432 Value *C1 = Builder->CreateICmpNE(Idx, FirstFalseIdx);
433 Value *SecondFalseIdx = ConstantInt::get(Idx->getType(),SecondFalseElement);
434 Value *C2 = Builder->CreateICmpNE(Idx, SecondFalseIdx);
435 return BinaryOperator::CreateAnd(C1, C2);
436 }
437
438 // If the comparison can be replaced with a range comparison for the elements
439 // where it is true, emit the range check.
440 if (TrueRangeEnd != Overdefined) {
441 assert(TrueRangeEnd != FirstTrueElement && "Should emit single compare")((TrueRangeEnd != FirstTrueElement && "Should emit single compare"
) ? static_cast<void> (0) : __assert_fail ("TrueRangeEnd != FirstTrueElement && \"Should emit single compare\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 441, __PRETTY_FUNCTION__))
;
442
443 // Generate (i-FirstTrue) <u (TrueRangeEnd-FirstTrue+1).
444 if (FirstTrueElement) {
445 Value *Offs = ConstantInt::get(Idx->getType(), -FirstTrueElement);
446 Idx = Builder->CreateAdd(Idx, Offs);
447 }
448
449 Value *End = ConstantInt::get(Idx->getType(),
450 TrueRangeEnd-FirstTrueElement+1);
451 return new ICmpInst(ICmpInst::ICMP_ULT, Idx, End);
452 }
453
454 // False range check.
455 if (FalseRangeEnd != Overdefined) {
456 assert(FalseRangeEnd != FirstFalseElement && "Should emit single compare")((FalseRangeEnd != FirstFalseElement && "Should emit single compare"
) ? static_cast<void> (0) : __assert_fail ("FalseRangeEnd != FirstFalseElement && \"Should emit single compare\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 456, __PRETTY_FUNCTION__))
;
457 // Generate (i-FirstFalse) >u (FalseRangeEnd-FirstFalse).
458 if (FirstFalseElement) {
459 Value *Offs = ConstantInt::get(Idx->getType(), -FirstFalseElement);
460 Idx = Builder->CreateAdd(Idx, Offs);
461 }
462
463 Value *End = ConstantInt::get(Idx->getType(),
464 FalseRangeEnd-FirstFalseElement);
465 return new ICmpInst(ICmpInst::ICMP_UGT, Idx, End);
466 }
467
468 // If a magic bitvector captures the entire comparison state
469 // of this load, replace it with computation that does:
470 // ((magic_cst >> i) & 1) != 0
471 {
472 Type *Ty = nullptr;
473
474 // Look for an appropriate type:
475 // - The type of Idx if the magic fits
476 // - The smallest fitting legal type if we have a DataLayout
477 // - Default to i32
478 if (ArrayElementCount <= Idx->getType()->getIntegerBitWidth())
479 Ty = Idx->getType();
480 else
481 Ty = DL.getSmallestLegalIntType(Init->getContext(), ArrayElementCount);
482
483 if (Ty) {
484 Value *V = Builder->CreateIntCast(Idx, Ty, false);
485 V = Builder->CreateLShr(ConstantInt::get(Ty, MagicBitvector), V);
486 V = Builder->CreateAnd(ConstantInt::get(Ty, 1), V);
487 return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0));
488 }
489 }
490
491 return nullptr;
492}
493
494/// Return a value that can be used to compare the *offset* implied by a GEP to
495/// zero. For example, if we have &A[i], we want to return 'i' for
496/// "icmp ne i, 0". Note that, in general, indices can be complex, and scales
497/// are involved. The above expression would also be legal to codegen as
498/// "icmp ne (i*4), 0" (assuming A is a pointer to i32).
499/// This latter form is less amenable to optimization though, and we are allowed
500/// to generate the first by knowing that pointer arithmetic doesn't overflow.
501///
502/// If we can't emit an optimized form for this expression, this returns null.
503///
504static Value *evaluateGEPOffsetExpression(User *GEP, InstCombiner &IC,
505 const DataLayout &DL) {
506 gep_type_iterator GTI = gep_type_begin(GEP);
507
508 // Check to see if this gep only has a single variable index. If so, and if
509 // any constant indices are a multiple of its scale, then we can compute this
510 // in terms of the scale of the variable index. For example, if the GEP
511 // implies an offset of "12 + i*4", then we can codegen this as "3 + i",
512 // because the expression will cross zero at the same point.
513 unsigned i, e = GEP->getNumOperands();
514 int64_t Offset = 0;
515 for (i = 1; i != e; ++i, ++GTI) {
516 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
517 // Compute the aggregate offset of constant indices.
518 if (CI->isZero()) continue;
519
520 // Handle a struct index, which adds its field offset to the pointer.
521 if (StructType *STy = GTI.getStructTypeOrNull()) {
522 Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
523 } else {
524 uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
525 Offset += Size*CI->getSExtValue();
526 }
527 } else {
528 // Found our variable index.
529 break;
530 }
531 }
532
533 // If there are no variable indices, we must have a constant offset, just
534 // evaluate it the general way.
535 if (i == e) return nullptr;
536
537 Value *VariableIdx = GEP->getOperand(i);
538 // Determine the scale factor of the variable element. For example, this is
539 // 4 if the variable index is into an array of i32.
540 uint64_t VariableScale = DL.getTypeAllocSize(GTI.getIndexedType());
541
542 // Verify that there are no other variable indices. If so, emit the hard way.
543 for (++i, ++GTI; i != e; ++i, ++GTI) {
544 ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i));
545 if (!CI) return nullptr;
546
547 // Compute the aggregate offset of constant indices.
548 if (CI->isZero()) continue;
549
550 // Handle a struct index, which adds its field offset to the pointer.
551 if (StructType *STy = GTI.getStructTypeOrNull()) {
552 Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
553 } else {
554 uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
555 Offset += Size*CI->getSExtValue();
556 }
557 }
558
559 // Okay, we know we have a single variable index, which must be a
560 // pointer/array/vector index. If there is no offset, life is simple, return
561 // the index.
562 Type *IntPtrTy = DL.getIntPtrType(GEP->getOperand(0)->getType());
563 unsigned IntPtrWidth = IntPtrTy->getIntegerBitWidth();
564 if (Offset == 0) {
565 // Cast to intptrty in case a truncation occurs. If an extension is needed,
566 // we don't need to bother extending: the extension won't affect where the
567 // computation crosses zero.
568 if (VariableIdx->getType()->getPrimitiveSizeInBits() > IntPtrWidth) {
569 VariableIdx = IC.Builder->CreateTrunc(VariableIdx, IntPtrTy);
570 }
571 return VariableIdx;
572 }
573
574 // Otherwise, there is an index. The computation we will do will be modulo
575 // the pointer size, so get it.
576 uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
577
578 Offset &= PtrSizeMask;
579 VariableScale &= PtrSizeMask;
580
581 // To do this transformation, any constant index must be a multiple of the
582 // variable scale factor. For example, we can evaluate "12 + 4*i" as "3 + i",
583 // but we can't evaluate "10 + 3*i" in terms of i. Check that the offset is a
584 // multiple of the variable scale.
585 int64_t NewOffs = Offset / (int64_t)VariableScale;
586 if (Offset != NewOffs*(int64_t)VariableScale)
587 return nullptr;
588
589 // Okay, we can do this evaluation. Start by converting the index to intptr.
590 if (VariableIdx->getType() != IntPtrTy)
591 VariableIdx = IC.Builder->CreateIntCast(VariableIdx, IntPtrTy,
592 true /*Signed*/);
593 Constant *OffsetVal = ConstantInt::get(IntPtrTy, NewOffs);
594 return IC.Builder->CreateAdd(VariableIdx, OffsetVal, "offset");
595}
596
597/// Returns true if we can rewrite Start as a GEP with pointer Base
598/// and some integer offset. The nodes that need to be re-written
599/// for this transformation will be added to Explored.
600static bool canRewriteGEPAsOffset(Value *Start, Value *Base,
601 const DataLayout &DL,
602 SetVector<Value *> &Explored) {
603 SmallVector<Value *, 16> WorkList(1, Start);
604 Explored.insert(Base);
605
606 // The following traversal gives us an order which can be used
607 // when doing the final transformation. Since in the final
608 // transformation we create the PHI replacement instructions first,
609 // we don't have to get them in any particular order.
610 //
611 // However, for other instructions we will have to traverse the
612 // operands of an instruction first, which means that we have to
613 // do a post-order traversal.
614 while (!WorkList.empty()) {
615 SetVector<PHINode *> PHIs;
616
617 while (!WorkList.empty()) {
618 if (Explored.size() >= 100)
619 return false;
620
621 Value *V = WorkList.back();
622
623 if (Explored.count(V) != 0) {
624 WorkList.pop_back();
625 continue;
626 }
627
628 if (!isa<IntToPtrInst>(V) && !isa<PtrToIntInst>(V) &&
629 !isa<GetElementPtrInst>(V) && !isa<PHINode>(V))
630 // We've found some value that we can't explore which is different from
631 // the base. Therefore we can't do this transformation.
632 return false;
633
634 if (isa<IntToPtrInst>(V) || isa<PtrToIntInst>(V)) {
635 auto *CI = dyn_cast<CastInst>(V);
636 if (!CI->isNoopCast(DL))
637 return false;
638
639 if (Explored.count(CI->getOperand(0)) == 0)
640 WorkList.push_back(CI->getOperand(0));
641 }
642
643 if (auto *GEP = dyn_cast<GEPOperator>(V)) {
644 // We're limiting the GEP to having one index. This will preserve
645 // the original pointer type. We could handle more cases in the
646 // future.
647 if (GEP->getNumIndices() != 1 || !GEP->isInBounds() ||
648 GEP->getType() != Start->getType())
649 return false;
650
651 if (Explored.count(GEP->getOperand(0)) == 0)
652 WorkList.push_back(GEP->getOperand(0));
653 }
654
655 if (WorkList.back() == V) {
656 WorkList.pop_back();
657 // We've finished visiting this node, mark it as such.
658 Explored.insert(V);
659 }
660
661 if (auto *PN = dyn_cast<PHINode>(V)) {
662 // We cannot transform PHIs on unsplittable basic blocks.
663 if (isa<CatchSwitchInst>(PN->getParent()->getTerminator()))
664 return false;
665 Explored.insert(PN);
666 PHIs.insert(PN);
667 }
668 }
669
670 // Explore the PHI nodes further.
671 for (auto *PN : PHIs)
672 for (Value *Op : PN->incoming_values())
673 if (Explored.count(Op) == 0)
674 WorkList.push_back(Op);
675 }
676
677 // Make sure that we can do this. Since we can't insert GEPs in a basic
678 // block before a PHI node, we can't easily do this transformation if
679 // we have PHI node users of transformed instructions.
680 for (Value *Val : Explored) {
681 for (Value *Use : Val->uses()) {
682
683 auto *PHI = dyn_cast<PHINode>(Use);
684 auto *Inst = dyn_cast<Instruction>(Val);
685
686 if (Inst == Base || Inst == PHI || !Inst || !PHI ||
687 Explored.count(PHI) == 0)
688 continue;
689
690 if (PHI->getParent() == Inst->getParent())
691 return false;
692 }
693 }
694 return true;
695}
696
697// Sets the appropriate insert point on Builder where we can add
698// a replacement Instruction for V (if that is possible).
699static void setInsertionPoint(IRBuilder<> &Builder, Value *V,
700 bool Before = true) {
701 if (auto *PHI = dyn_cast<PHINode>(V)) {
702 Builder.SetInsertPoint(&*PHI->getParent()->getFirstInsertionPt());
703 return;
704 }
705 if (auto *I = dyn_cast<Instruction>(V)) {
706 if (!Before)
707 I = &*std::next(I->getIterator());
708 Builder.SetInsertPoint(I);
709 return;
710 }
711 if (auto *A = dyn_cast<Argument>(V)) {
712 // Set the insertion point in the entry block.
713 BasicBlock &Entry = A->getParent()->getEntryBlock();
714 Builder.SetInsertPoint(&*Entry.getFirstInsertionPt());
715 return;
716 }
717 // Otherwise, this is a constant and we don't need to set a new
718 // insertion point.
719 assert(isa<Constant>(V) && "Setting insertion point for unknown value!")((isa<Constant>(V) && "Setting insertion point for unknown value!"
) ? static_cast<void> (0) : __assert_fail ("isa<Constant>(V) && \"Setting insertion point for unknown value!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 719, __PRETTY_FUNCTION__))
;
720}
721
722/// Returns a re-written value of Start as an indexed GEP using Base as a
723/// pointer.
724static Value *rewriteGEPAsOffset(Value *Start, Value *Base,
725 const DataLayout &DL,
726 SetVector<Value *> &Explored) {
727 // Perform all the substitutions. This is a bit tricky because we can
728 // have cycles in our use-def chains.
729 // 1. Create the PHI nodes without any incoming values.
730 // 2. Create all the other values.
731 // 3. Add the edges for the PHI nodes.
732 // 4. Emit GEPs to get the original pointers.
733 // 5. Remove the original instructions.
734 Type *IndexType = IntegerType::get(
735 Base->getContext(), DL.getPointerTypeSizeInBits(Start->getType()));
736
737 DenseMap<Value *, Value *> NewInsts;
738 NewInsts[Base] = ConstantInt::getNullValue(IndexType);
739
740 // Create the new PHI nodes, without adding any incoming values.
741 for (Value *Val : Explored) {
742 if (Val == Base)
743 continue;
744 // Create empty phi nodes. This avoids cyclic dependencies when creating
745 // the remaining instructions.
746 if (auto *PHI = dyn_cast<PHINode>(Val))
747 NewInsts[PHI] = PHINode::Create(IndexType, PHI->getNumIncomingValues(),
748 PHI->getName() + ".idx", PHI);
749 }
750 IRBuilder<> Builder(Base->getContext());
751
752 // Create all the other instructions.
753 for (Value *Val : Explored) {
754
755 if (NewInsts.find(Val) != NewInsts.end())
756 continue;
757
758 if (auto *CI = dyn_cast<CastInst>(Val)) {
759 NewInsts[CI] = NewInsts[CI->getOperand(0)];
760 continue;
761 }
762 if (auto *GEP = dyn_cast<GEPOperator>(Val)) {
763 Value *Index = NewInsts[GEP->getOperand(1)] ? NewInsts[GEP->getOperand(1)]
764 : GEP->getOperand(1);
765 setInsertionPoint(Builder, GEP);
766 // Indices might need to be sign extended. GEPs will magically do
767 // this, but we need to do it ourselves here.
768 if (Index->getType()->getScalarSizeInBits() !=
769 NewInsts[GEP->getOperand(0)]->getType()->getScalarSizeInBits()) {
770 Index = Builder.CreateSExtOrTrunc(
771 Index, NewInsts[GEP->getOperand(0)]->getType(),
772 GEP->getOperand(0)->getName() + ".sext");
773 }
774
775 auto *Op = NewInsts[GEP->getOperand(0)];
776 if (isa<ConstantInt>(Op) && dyn_cast<ConstantInt>(Op)->isZero())
777 NewInsts[GEP] = Index;
778 else
779 NewInsts[GEP] = Builder.CreateNSWAdd(
780 Op, Index, GEP->getOperand(0)->getName() + ".add");
781 continue;
782 }
783 if (isa<PHINode>(Val))
784 continue;
785
786 llvm_unreachable("Unexpected instruction type")::llvm::llvm_unreachable_internal("Unexpected instruction type"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 786)
;
787 }
788
789 // Add the incoming values to the PHI nodes.
790 for (Value *Val : Explored) {
791 if (Val == Base)
792 continue;
793 // All the instructions have been created, we can now add edges to the
794 // phi nodes.
795 if (auto *PHI = dyn_cast<PHINode>(Val)) {
796 PHINode *NewPhi = static_cast<PHINode *>(NewInsts[PHI]);
797 for (unsigned I = 0, E = PHI->getNumIncomingValues(); I < E; ++I) {
798 Value *NewIncoming = PHI->getIncomingValue(I);
799
800 if (NewInsts.find(NewIncoming) != NewInsts.end())
801 NewIncoming = NewInsts[NewIncoming];
802
803 NewPhi->addIncoming(NewIncoming, PHI->getIncomingBlock(I));
804 }
805 }
806 }
807
808 for (Value *Val : Explored) {
809 if (Val == Base)
810 continue;
811
812 // Depending on the type, for external users we have to emit
813 // a GEP or a GEP + ptrtoint.
814 setInsertionPoint(Builder, Val, false);
815
816 // If required, create an inttoptr instruction for Base.
817 Value *NewBase = Base;
818 if (!Base->getType()->isPointerTy())
819 NewBase = Builder.CreateBitOrPointerCast(Base, Start->getType(),
820 Start->getName() + "to.ptr");
821
822 Value *GEP = Builder.CreateInBoundsGEP(
823 Start->getType()->getPointerElementType(), NewBase,
824 makeArrayRef(NewInsts[Val]), Val->getName() + ".ptr");
825
826 if (!Val->getType()->isPointerTy()) {
827 Value *Cast = Builder.CreatePointerCast(GEP, Val->getType(),
828 Val->getName() + ".conv");
829 GEP = Cast;
830 }
831 Val->replaceAllUsesWith(GEP);
832 }
833
834 return NewInsts[Start];
835}
836
837/// Looks through GEPs, IntToPtrInsts and PtrToIntInsts in order to express
838/// the input Value as a constant indexed GEP. Returns a pair containing
839/// the GEPs Pointer and Index.
840static std::pair<Value *, Value *>
841getAsConstantIndexedAddress(Value *V, const DataLayout &DL) {
842 Type *IndexType = IntegerType::get(V->getContext(),
843 DL.getPointerTypeSizeInBits(V->getType()));
844
845 Constant *Index = ConstantInt::getNullValue(IndexType);
846 while (true) {
847 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
848 // We accept only inbouds GEPs here to exclude the possibility of
849 // overflow.
850 if (!GEP->isInBounds())
851 break;
852 if (GEP->hasAllConstantIndices() && GEP->getNumIndices() == 1 &&
853 GEP->getType() == V->getType()) {
854 V = GEP->getOperand(0);
855 Constant *GEPIndex = static_cast<Constant *>(GEP->getOperand(1));
856 Index = ConstantExpr::getAdd(
857 Index, ConstantExpr::getSExtOrBitCast(GEPIndex, IndexType));
858 continue;
859 }
860 break;
861 }
862 if (auto *CI = dyn_cast<IntToPtrInst>(V)) {
863 if (!CI->isNoopCast(DL))
864 break;
865 V = CI->getOperand(0);
866 continue;
867 }
868 if (auto *CI = dyn_cast<PtrToIntInst>(V)) {
869 if (!CI->isNoopCast(DL))
870 break;
871 V = CI->getOperand(0);
872 continue;
873 }
874 break;
875 }
876 return {V, Index};
877}
878
879/// Converts (CMP GEPLHS, RHS) if this change would make RHS a constant.
880/// We can look through PHIs, GEPs and casts in order to determine a common base
881/// between GEPLHS and RHS.
882static Instruction *transformToIndexedCompare(GEPOperator *GEPLHS, Value *RHS,
883 ICmpInst::Predicate Cond,
884 const DataLayout &DL) {
885 if (!GEPLHS->hasAllConstantIndices())
886 return nullptr;
887
888 // Make sure the pointers have the same type.
889 if (GEPLHS->getType() != RHS->getType())
890 return nullptr;
891
892 Value *PtrBase, *Index;
893 std::tie(PtrBase, Index) = getAsConstantIndexedAddress(GEPLHS, DL);
894
895 // The set of nodes that will take part in this transformation.
896 SetVector<Value *> Nodes;
897
898 if (!canRewriteGEPAsOffset(RHS, PtrBase, DL, Nodes))
899 return nullptr;
900
901 // We know we can re-write this as
902 // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2)
903 // Since we've only looked through inbouds GEPs we know that we
904 // can't have overflow on either side. We can therefore re-write
905 // this as:
906 // OFFSET1 cmp OFFSET2
907 Value *NewRHS = rewriteGEPAsOffset(RHS, PtrBase, DL, Nodes);
908
909 // RewriteGEPAsOffset has replaced RHS and all of its uses with a re-written
910 // GEP having PtrBase as the pointer base, and has returned in NewRHS the
911 // offset. Since Index is the offset of LHS to the base pointer, we will now
912 // compare the offsets instead of comparing the pointers.
913 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Index, NewRHS);
914}
915
916/// Fold comparisons between a GEP instruction and something else. At this point
917/// we know that the GEP is on the LHS of the comparison.
918Instruction *InstCombiner::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
919 ICmpInst::Predicate Cond,
920 Instruction &I) {
921 // Don't transform signed compares of GEPs into index compares. Even if the
922 // GEP is inbounds, the final add of the base pointer can have signed overflow
923 // and would change the result of the icmp.
924 // e.g. "&foo[0] <s &foo[1]" can't be folded to "true" because "foo" could be
925 // the maximum signed value for the pointer type.
926 if (ICmpInst::isSigned(Cond))
927 return nullptr;
928
929 // Look through bitcasts and addrspacecasts. We do not however want to remove
930 // 0 GEPs.
931 if (!isa<GetElementPtrInst>(RHS))
932 RHS = RHS->stripPointerCasts();
933
934 Value *PtrBase = GEPLHS->getOperand(0);
935 if (PtrBase == RHS && GEPLHS->isInBounds()) {
936 // ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0).
937 // This transformation (ignoring the base and scales) is valid because we
938 // know pointers can't overflow since the gep is inbounds. See if we can
939 // output an optimized form.
940 Value *Offset = evaluateGEPOffsetExpression(GEPLHS, *this, DL);
941
942 // If not, synthesize the offset the hard way.
943 if (!Offset)
944 Offset = EmitGEPOffset(GEPLHS);
945 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset,
946 Constant::getNullValue(Offset->getType()));
947 } else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) {
948 // If the base pointers are different, but the indices are the same, just
949 // compare the base pointer.
950 if (PtrBase != GEPRHS->getOperand(0)) {
951 bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands();
952 IndicesTheSame &= GEPLHS->getOperand(0)->getType() ==
953 GEPRHS->getOperand(0)->getType();
954 if (IndicesTheSame)
955 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
956 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
957 IndicesTheSame = false;
958 break;
959 }
960
961 // If all indices are the same, just compare the base pointers.
962 if (IndicesTheSame)
963 return new ICmpInst(Cond, GEPLHS->getOperand(0), GEPRHS->getOperand(0));
964
965 // If we're comparing GEPs with two base pointers that only differ in type
966 // and both GEPs have only constant indices or just one use, then fold
967 // the compare with the adjusted indices.
968 if (GEPLHS->isInBounds() && GEPRHS->isInBounds() &&
969 (GEPLHS->hasAllConstantIndices() || GEPLHS->hasOneUse()) &&
970 (GEPRHS->hasAllConstantIndices() || GEPRHS->hasOneUse()) &&
971 PtrBase->stripPointerCasts() ==
972 GEPRHS->getOperand(0)->stripPointerCasts()) {
973 Value *LOffset = EmitGEPOffset(GEPLHS);
974 Value *ROffset = EmitGEPOffset(GEPRHS);
975
976 // If we looked through an addrspacecast between different sized address
977 // spaces, the LHS and RHS pointers are different sized
978 // integers. Truncate to the smaller one.
979 Type *LHSIndexTy = LOffset->getType();
980 Type *RHSIndexTy = ROffset->getType();
981 if (LHSIndexTy != RHSIndexTy) {
982 if (LHSIndexTy->getPrimitiveSizeInBits() <
983 RHSIndexTy->getPrimitiveSizeInBits()) {
984 ROffset = Builder->CreateTrunc(ROffset, LHSIndexTy);
985 } else
986 LOffset = Builder->CreateTrunc(LOffset, RHSIndexTy);
987 }
988
989 Value *Cmp = Builder->CreateICmp(ICmpInst::getSignedPredicate(Cond),
990 LOffset, ROffset);
991 return replaceInstUsesWith(I, Cmp);
992 }
993
994 // Otherwise, the base pointers are different and the indices are
995 // different. Try convert this to an indexed compare by looking through
996 // PHIs/casts.
997 return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
998 }
999
1000 // If one of the GEPs has all zero indices, recurse.
1001 if (GEPLHS->hasAllZeroIndices())
1002 return foldGEPICmp(GEPRHS, GEPLHS->getOperand(0),
1003 ICmpInst::getSwappedPredicate(Cond), I);
1004
1005 // If the other GEP has all zero indices, recurse.
1006 if (GEPRHS->hasAllZeroIndices())
1007 return foldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I);
1008
1009 bool GEPsInBounds = GEPLHS->isInBounds() && GEPRHS->isInBounds();
1010 if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) {
1011 // If the GEPs only differ by one index, compare it.
1012 unsigned NumDifferences = 0; // Keep track of # differences.
1013 unsigned DiffOperand = 0; // The operand that differs.
1014 for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
1015 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
1016 if (GEPLHS->getOperand(i)->getType()->getPrimitiveSizeInBits() !=
1017 GEPRHS->getOperand(i)->getType()->getPrimitiveSizeInBits()) {
1018 // Irreconcilable differences.
1019 NumDifferences = 2;
1020 break;
1021 } else {
1022 if (NumDifferences++) break;
1023 DiffOperand = i;
1024 }
1025 }
1026
1027 if (NumDifferences == 0) // SAME GEP?
1028 return replaceInstUsesWith(I, // No comparison is needed here.
1029 Builder->getInt1(ICmpInst::isTrueWhenEqual(Cond)));
1030
1031 else if (NumDifferences == 1 && GEPsInBounds) {
1032 Value *LHSV = GEPLHS->getOperand(DiffOperand);
1033 Value *RHSV = GEPRHS->getOperand(DiffOperand);
1034 // Make sure we do a signed comparison here.
1035 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), LHSV, RHSV);
1036 }
1037 }
1038
1039 // Only lower this if the icmp is the only user of the GEP or if we expect
1040 // the result to fold to a constant!
1041 if (GEPsInBounds && (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) &&
1042 (isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) {
1043 // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2)
1044 Value *L = EmitGEPOffset(GEPLHS);
1045 Value *R = EmitGEPOffset(GEPRHS);
1046 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R);
1047 }
1048 }
1049
1050 // Try convert this to an indexed compare by looking through PHIs/casts as a
1051 // last resort.
1052 return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
1053}
1054
1055Instruction *InstCombiner::foldAllocaCmp(ICmpInst &ICI,
1056 const AllocaInst *Alloca,
1057 const Value *Other) {
1058 assert(ICI.isEquality() && "Cannot fold non-equality comparison.")((ICI.isEquality() && "Cannot fold non-equality comparison."
) ? static_cast<void> (0) : __assert_fail ("ICI.isEquality() && \"Cannot fold non-equality comparison.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 1058, __PRETTY_FUNCTION__))
;
1059
1060 // It would be tempting to fold away comparisons between allocas and any
1061 // pointer not based on that alloca (e.g. an argument). However, even
1062 // though such pointers cannot alias, they can still compare equal.
1063 //
1064 // But LLVM doesn't specify where allocas get their memory, so if the alloca
1065 // doesn't escape we can argue that it's impossible to guess its value, and we
1066 // can therefore act as if any such guesses are wrong.
1067 //
1068 // The code below checks that the alloca doesn't escape, and that it's only
1069 // used in a comparison once (the current instruction). The
1070 // single-comparison-use condition ensures that we're trivially folding all
1071 // comparisons against the alloca consistently, and avoids the risk of
1072 // erroneously folding a comparison of the pointer with itself.
1073
1074 unsigned MaxIter = 32; // Break cycles and bound to constant-time.
1075
1076 SmallVector<const Use *, 32> Worklist;
1077 for (const Use &U : Alloca->uses()) {
1078 if (Worklist.size() >= MaxIter)
1079 return nullptr;
1080 Worklist.push_back(&U);
1081 }
1082
1083 unsigned NumCmps = 0;
1084 while (!Worklist.empty()) {
1085 assert(Worklist.size() <= MaxIter)((Worklist.size() <= MaxIter) ? static_cast<void> (0
) : __assert_fail ("Worklist.size() <= MaxIter", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 1085, __PRETTY_FUNCTION__))
;
1086 const Use *U = Worklist.pop_back_val();
1087 const Value *V = U->getUser();
1088 --MaxIter;
1089
1090 if (isa<BitCastInst>(V) || isa<GetElementPtrInst>(V) || isa<PHINode>(V) ||
1091 isa<SelectInst>(V)) {
1092 // Track the uses.
1093 } else if (isa<LoadInst>(V)) {
1094 // Loading from the pointer doesn't escape it.
1095 continue;
1096 } else if (const auto *SI = dyn_cast<StoreInst>(V)) {
1097 // Storing *to* the pointer is fine, but storing the pointer escapes it.
1098 if (SI->getValueOperand() == U->get())
1099 return nullptr;
1100 continue;
1101 } else if (isa<ICmpInst>(V)) {
1102 if (NumCmps++)
1103 return nullptr; // Found more than one cmp.
1104 continue;
1105 } else if (const auto *Intrin = dyn_cast<IntrinsicInst>(V)) {
1106 switch (Intrin->getIntrinsicID()) {
1107 // These intrinsics don't escape or compare the pointer. Memset is safe
1108 // because we don't allow ptrtoint. Memcpy and memmove are safe because
1109 // we don't allow stores, so src cannot point to V.
1110 case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
1111 case Intrinsic::dbg_declare: case Intrinsic::dbg_value:
1112 case Intrinsic::memcpy: case Intrinsic::memmove: case Intrinsic::memset:
1113 continue;
1114 default:
1115 return nullptr;
1116 }
1117 } else {
1118 return nullptr;
1119 }
1120 for (const Use &U : V->uses()) {
1121 if (Worklist.size() >= MaxIter)
1122 return nullptr;
1123 Worklist.push_back(&U);
1124 }
1125 }
1126
1127 Type *CmpTy = CmpInst::makeCmpResultType(Other->getType());
1128 return replaceInstUsesWith(
1129 ICI,
1130 ConstantInt::get(CmpTy, !CmpInst::isTrueWhenEqual(ICI.getPredicate())));
1131}
1132
1133/// Fold "icmp pred (X+CI), X".
1134Instruction *InstCombiner::foldICmpAddOpConst(Instruction &ICI,
1135 Value *X, ConstantInt *CI,
1136 ICmpInst::Predicate Pred) {
1137 // From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0,
1138 // so the values can never be equal. Similarly for all other "or equals"
1139 // operators.
1140
1141 // (X+1) <u X --> X >u (MAXUINT-1) --> X == 255
1142 // (X+2) <u X --> X >u (MAXUINT-2) --> X > 253
1143 // (X+MAXUINT) <u X --> X >u (MAXUINT-MAXUINT) --> X != 0
1144 if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
1145 Value *R =
1146 ConstantExpr::getSub(ConstantInt::getAllOnesValue(CI->getType()), CI);
1147 return new ICmpInst(ICmpInst::ICMP_UGT, X, R);
1148 }
1149
1150 // (X+1) >u X --> X <u (0-1) --> X != 255
1151 // (X+2) >u X --> X <u (0-2) --> X <u 254
1152 // (X+MAXUINT) >u X --> X <u (0-MAXUINT) --> X <u 1 --> X == 0
1153 if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE)
1154 return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantExpr::getNeg(CI));
1155
1156 unsigned BitWidth = CI->getType()->getPrimitiveSizeInBits();
1157 ConstantInt *SMax = ConstantInt::get(X->getContext(),
1158 APInt::getSignedMaxValue(BitWidth));
1159
1160 // (X+ 1) <s X --> X >s (MAXSINT-1) --> X == 127
1161 // (X+ 2) <s X --> X >s (MAXSINT-2) --> X >s 125
1162 // (X+MAXSINT) <s X --> X >s (MAXSINT-MAXSINT) --> X >s 0
1163 // (X+MINSINT) <s X --> X >s (MAXSINT-MINSINT) --> X >s -1
1164 // (X+ -2) <s X --> X >s (MAXSINT- -2) --> X >s 126
1165 // (X+ -1) <s X --> X >s (MAXSINT- -1) --> X != 127
1166 if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
1167 return new ICmpInst(ICmpInst::ICMP_SGT, X, ConstantExpr::getSub(SMax, CI));
1168
1169 // (X+ 1) >s X --> X <s (MAXSINT-(1-1)) --> X != 127
1170 // (X+ 2) >s X --> X <s (MAXSINT-(2-1)) --> X <s 126
1171 // (X+MAXSINT) >s X --> X <s (MAXSINT-(MAXSINT-1)) --> X <s 1
1172 // (X+MINSINT) >s X --> X <s (MAXSINT-(MINSINT-1)) --> X <s -2
1173 // (X+ -2) >s X --> X <s (MAXSINT-(-2-1)) --> X <s -126
1174 // (X+ -1) >s X --> X <s (MAXSINT-(-1-1)) --> X == -128
1175
1176 assert(Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)((Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE) ?
static_cast<void> (0) : __assert_fail ("Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 1176, __PRETTY_FUNCTION__))
;
1177 Constant *C = Builder->getInt(CI->getValue()-1);
1178 return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantExpr::getSub(SMax, C));
1179}
1180
1181/// Handle "(icmp eq/ne (ashr/lshr AP2, A), AP1)" ->
1182/// (icmp eq/ne A, Log2(AP2/AP1)) ->
1183/// (icmp eq/ne A, Log2(AP2) - Log2(AP1)).
1184Instruction *InstCombiner::foldICmpShrConstConst(ICmpInst &I, Value *A,
1185 const APInt &AP1,
1186 const APInt &AP2) {
1187 assert(I.isEquality() && "Cannot fold icmp gt/lt")((I.isEquality() && "Cannot fold icmp gt/lt") ? static_cast
<void> (0) : __assert_fail ("I.isEquality() && \"Cannot fold icmp gt/lt\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 1187, __PRETTY_FUNCTION__))
;
1188
1189 auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
1190 if (I.getPredicate() == I.ICMP_NE)
1191 Pred = CmpInst::getInversePredicate(Pred);
1192 return new ICmpInst(Pred, LHS, RHS);
1193 };
1194
1195 // Don't bother doing any work for cases which InstSimplify handles.
1196 if (AP2 == 0)
1197 return nullptr;
1198
1199 bool IsAShr = isa<AShrOperator>(I.getOperand(0));
1200 if (IsAShr) {
1201 if (AP2.isAllOnesValue())
1202 return nullptr;
1203 if (AP2.isNegative() != AP1.isNegative())
1204 return nullptr;
1205 if (AP2.sgt(AP1))
1206 return nullptr;
1207 }
1208
1209 if (!AP1)
1210 // 'A' must be large enough to shift out the highest set bit.
1211 return getICmp(I.ICMP_UGT, A,
1212 ConstantInt::get(A->getType(), AP2.logBase2()));
1213
1214 if (AP1 == AP2)
1215 return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
1216
1217 int Shift;
1218 if (IsAShr && AP1.isNegative())
1219 Shift = AP1.countLeadingOnes() - AP2.countLeadingOnes();
1220 else
1221 Shift = AP1.countLeadingZeros() - AP2.countLeadingZeros();
1222
1223 if (Shift > 0) {
1224 if (IsAShr && AP1 == AP2.ashr(Shift)) {
1225 // There are multiple solutions if we are comparing against -1 and the LHS
1226 // of the ashr is not a power of two.
1227 if (AP1.isAllOnesValue() && !AP2.isPowerOf2())
1228 return getICmp(I.ICMP_UGE, A, ConstantInt::get(A->getType(), Shift));
1229 return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1230 } else if (AP1 == AP2.lshr(Shift)) {
1231 return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1232 }
1233 }
1234
1235 // Shifting const2 will never be equal to const1.
1236 // FIXME: This should always be handled by InstSimplify?
1237 auto *TorF = ConstantInt::get(I.getType(), I.getPredicate() == I.ICMP_NE);
1238 return replaceInstUsesWith(I, TorF);
1239}
1240
1241/// Handle "(icmp eq/ne (shl AP2, A), AP1)" ->
1242/// (icmp eq/ne A, TrailingZeros(AP1) - TrailingZeros(AP2)).
1243Instruction *InstCombiner::foldICmpShlConstConst(ICmpInst &I, Value *A,
1244 const APInt &AP1,
1245 const APInt &AP2) {
1246 assert(I.isEquality() && "Cannot fold icmp gt/lt")((I.isEquality() && "Cannot fold icmp gt/lt") ? static_cast
<void> (0) : __assert_fail ("I.isEquality() && \"Cannot fold icmp gt/lt\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 1246, __PRETTY_FUNCTION__))
;
1247
1248 auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
1249 if (I.getPredicate() == I.ICMP_NE)
1250 Pred = CmpInst::getInversePredicate(Pred);
1251 return new ICmpInst(Pred, LHS, RHS);
1252 };
1253
1254 // Don't bother doing any work for cases which InstSimplify handles.
1255 if (AP2 == 0)
1256 return nullptr;
1257
1258 unsigned AP2TrailingZeros = AP2.countTrailingZeros();
1259
1260 if (!AP1 && AP2TrailingZeros != 0)
1261 return getICmp(
1262 I.ICMP_UGE, A,
1263 ConstantInt::get(A->getType(), AP2.getBitWidth() - AP2TrailingZeros));
1264
1265 if (AP1 == AP2)
1266 return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
1267
1268 // Get the distance between the lowest bits that are set.
1269 int Shift = AP1.countTrailingZeros() - AP2TrailingZeros;
1270
1271 if (Shift > 0 && AP2.shl(Shift) == AP1)
1272 return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1273
1274 // Shifting const2 will never be equal to const1.
1275 // FIXME: This should always be handled by InstSimplify?
1276 auto *TorF = ConstantInt::get(I.getType(), I.getPredicate() == I.ICMP_NE);
1277 return replaceInstUsesWith(I, TorF);
1278}
1279
1280/// The caller has matched a pattern of the form:
1281/// I = icmp ugt (add (add A, B), CI2), CI1
1282/// If this is of the form:
1283/// sum = a + b
1284/// if (sum+128 >u 255)
1285/// Then replace it with llvm.sadd.with.overflow.i8.
1286///
1287static Instruction *processUGT_ADDCST_ADD(ICmpInst &I, Value *A, Value *B,
1288 ConstantInt *CI2, ConstantInt *CI1,
1289 InstCombiner &IC) {
1290 // The transformation we're trying to do here is to transform this into an
1291 // llvm.sadd.with.overflow. To do this, we have to replace the original add
1292 // with a narrower add, and discard the add-with-constant that is part of the
1293 // range check (if we can't eliminate it, this isn't profitable).
1294
1295 // In order to eliminate the add-with-constant, the compare can be its only
1296 // use.
1297 Instruction *AddWithCst = cast<Instruction>(I.getOperand(0));
1298 if (!AddWithCst->hasOneUse())
1299 return nullptr;
1300
1301 // If CI2 is 2^7, 2^15, 2^31, then it might be an sadd.with.overflow.
1302 if (!CI2->getValue().isPowerOf2())
1303 return nullptr;
1304 unsigned NewWidth = CI2->getValue().countTrailingZeros();
1305 if (NewWidth != 7 && NewWidth != 15 && NewWidth != 31)
1306 return nullptr;
1307
1308 // The width of the new add formed is 1 more than the bias.
1309 ++NewWidth;
1310
1311 // Check to see that CI1 is an all-ones value with NewWidth bits.
1312 if (CI1->getBitWidth() == NewWidth ||
1313 CI1->getValue() != APInt::getLowBitsSet(CI1->getBitWidth(), NewWidth))
1314 return nullptr;
1315
1316 // This is only really a signed overflow check if the inputs have been
1317 // sign-extended; check for that condition. For example, if CI2 is 2^31 and
1318 // the operands of the add are 64 bits wide, we need at least 33 sign bits.
1319 unsigned NeededSignBits = CI1->getBitWidth() - NewWidth + 1;
1320 if (IC.ComputeNumSignBits(A, 0, &I) < NeededSignBits ||
1321 IC.ComputeNumSignBits(B, 0, &I) < NeededSignBits)
1322 return nullptr;
1323
1324 // In order to replace the original add with a narrower
1325 // llvm.sadd.with.overflow, the only uses allowed are the add-with-constant
1326 // and truncates that discard the high bits of the add. Verify that this is
1327 // the case.
1328 Instruction *OrigAdd = cast<Instruction>(AddWithCst->getOperand(0));
1329 for (User *U : OrigAdd->users()) {
1330 if (U == AddWithCst)
1331 continue;
1332
1333 // Only accept truncates for now. We would really like a nice recursive
1334 // predicate like SimplifyDemandedBits, but which goes downwards the use-def
1335 // chain to see which bits of a value are actually demanded. If the
1336 // original add had another add which was then immediately truncated, we
1337 // could still do the transformation.
1338 TruncInst *TI = dyn_cast<TruncInst>(U);
1339 if (!TI || TI->getType()->getPrimitiveSizeInBits() > NewWidth)
1340 return nullptr;
1341 }
1342
1343 // If the pattern matches, truncate the inputs to the narrower type and
1344 // use the sadd_with_overflow intrinsic to efficiently compute both the
1345 // result and the overflow bit.
1346 Type *NewType = IntegerType::get(OrigAdd->getContext(), NewWidth);
1347 Value *F = Intrinsic::getDeclaration(I.getModule(),
1348 Intrinsic::sadd_with_overflow, NewType);
1349
1350 InstCombiner::BuilderTy *Builder = IC.Builder;
1351
1352 // Put the new code above the original add, in case there are any uses of the
1353 // add between the add and the compare.
1354 Builder->SetInsertPoint(OrigAdd);
1355
1356 Value *TruncA = Builder->CreateTrunc(A, NewType, A->getName() + ".trunc");
1357 Value *TruncB = Builder->CreateTrunc(B, NewType, B->getName() + ".trunc");
1358 CallInst *Call = Builder->CreateCall(F, {TruncA, TruncB}, "sadd");
1359 Value *Add = Builder->CreateExtractValue(Call, 0, "sadd.result");
1360 Value *ZExt = Builder->CreateZExt(Add, OrigAdd->getType());
1361
1362 // The inner add was the result of the narrow add, zero extended to the
1363 // wider type. Replace it with the result computed by the intrinsic.
1364 IC.replaceInstUsesWith(*OrigAdd, ZExt);
1365
1366 // The original icmp gets replaced with the overflow value.
1367 return ExtractValueInst::Create(Call, 1, "sadd.overflow");
1368}
1369
1370// Fold icmp Pred X, C.
1371Instruction *InstCombiner::foldICmpWithConstant(ICmpInst &Cmp) {
1372 CmpInst::Predicate Pred = Cmp.getPredicate();
1373 Value *X = Cmp.getOperand(0);
1374
1375 const APInt *C;
1376 if (!match(Cmp.getOperand(1), m_APInt(C)))
1377 return nullptr;
1378
1379 Value *A = nullptr, *B = nullptr;
1380
1381 // Match the following pattern, which is a common idiom when writing
1382 // overflow-safe integer arithmetic functions. The source performs an addition
1383 // in wider type and explicitly checks for overflow using comparisons against
1384 // INT_MIN and INT_MAX. Simplify by using the sadd_with_overflow intrinsic.
1385 //
1386 // TODO: This could probably be generalized to handle other overflow-safe
1387 // operations if we worked out the formulas to compute the appropriate magic
1388 // constants.
1389 //
1390 // sum = a + b
1391 // if (sum+128 >u 255) ... -> llvm.sadd.with.overflow.i8
1392 {
1393 ConstantInt *CI2; // I = icmp ugt (add (add A, B), CI2), CI
1394 if (Pred == ICmpInst::ICMP_UGT &&
1395 match(X, m_Add(m_Add(m_Value(A), m_Value(B)), m_ConstantInt(CI2))))
1396 if (Instruction *Res = processUGT_ADDCST_ADD(
1397 Cmp, A, B, CI2, cast<ConstantInt>(Cmp.getOperand(1)), *this))
1398 return Res;
1399 }
1400
1401 // (icmp sgt smin(PosA, B) 0) -> (icmp sgt B 0)
1402 if (*C == 0 && Pred == ICmpInst::ICMP_SGT) {
1403 SelectPatternResult SPR = matchSelectPattern(X, A, B);
1404 if (SPR.Flavor == SPF_SMIN) {
1405 if (isKnownPositive(A, DL))
1406 return new ICmpInst(Pred, B, Cmp.getOperand(1));
1407 if (isKnownPositive(B, DL))
1408 return new ICmpInst(Pred, A, Cmp.getOperand(1));
1409 }
1410 }
1411
1412 // FIXME: Use m_APInt to allow folds for splat constants.
1413 ConstantInt *CI = dyn_cast<ConstantInt>(Cmp.getOperand(1));
1414 if (!CI)
1415 return nullptr;
1416
1417 // Canonicalize icmp instructions based on dominating conditions.
1418 BasicBlock *Parent = Cmp.getParent();
1419 BasicBlock *Dom = Parent->getSinglePredecessor();
1420 auto *BI = Dom ? dyn_cast<BranchInst>(Dom->getTerminator()) : nullptr;
1421 ICmpInst::Predicate Pred2;
1422 BasicBlock *TrueBB, *FalseBB;
1423 ConstantInt *CI2;
1424 if (BI && match(BI, m_Br(m_ICmp(Pred2, m_Specific(X), m_ConstantInt(CI2)),
1425 TrueBB, FalseBB)) &&
1426 TrueBB != FalseBB) {
1427 ConstantRange CR =
1428 ConstantRange::makeAllowedICmpRegion(Pred, CI->getValue());
1429 ConstantRange DominatingCR =
1430 (Parent == TrueBB)
1431 ? ConstantRange::makeExactICmpRegion(Pred2, CI2->getValue())
1432 : ConstantRange::makeExactICmpRegion(
1433 CmpInst::getInversePredicate(Pred2), CI2->getValue());
1434 ConstantRange Intersection = DominatingCR.intersectWith(CR);
1435 ConstantRange Difference = DominatingCR.difference(CR);
1436 if (Intersection.isEmptySet())
1437 return replaceInstUsesWith(Cmp, Builder->getFalse());
1438 if (Difference.isEmptySet())
1439 return replaceInstUsesWith(Cmp, Builder->getTrue());
1440
1441 // If this is a normal comparison, it demands all bits. If it is a sign
1442 // bit comparison, it only demands the sign bit.
1443 bool UnusedBit;
1444 bool IsSignBit = isSignBitCheck(Pred, CI->getValue(), UnusedBit);
1445
1446 // Canonicalizing a sign bit comparison that gets used in a branch,
1447 // pessimizes codegen by generating branch on zero instruction instead
1448 // of a test and branch. So we avoid canonicalizing in such situations
1449 // because test and branch instruction has better branch displacement
1450 // than compare and branch instruction.
1451 if (!isBranchOnSignBitCheck(Cmp, IsSignBit) && !Cmp.isEquality()) {
1452 if (auto *AI = Intersection.getSingleElement())
1453 return new ICmpInst(ICmpInst::ICMP_EQ, X, Builder->getInt(*AI));
1454 if (auto *AD = Difference.getSingleElement())
1455 return new ICmpInst(ICmpInst::ICMP_NE, X, Builder->getInt(*AD));
1456 }
1457 }
1458
1459 return nullptr;
1460}
1461
1462/// Fold icmp (trunc X, Y), C.
1463Instruction *InstCombiner::foldICmpTruncConstant(ICmpInst &Cmp,
1464 Instruction *Trunc,
1465 const APInt *C) {
1466 ICmpInst::Predicate Pred = Cmp.getPredicate();
1467 Value *X = Trunc->getOperand(0);
1468 if (*C == 1 && C->getBitWidth() > 1) {
1469 // icmp slt trunc(signum(V)) 1 --> icmp slt V, 1
1470 Value *V = nullptr;
1471 if (Pred == ICmpInst::ICMP_SLT && match(X, m_Signum(m_Value(V))))
1472 return new ICmpInst(ICmpInst::ICMP_SLT, V,
1473 ConstantInt::get(V->getType(), 1));
1474 }
1475
1476 if (Cmp.isEquality() && Trunc->hasOneUse()) {
1477 // Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|highbits if all
1478 // of the high bits truncated out of x are known.
1479 unsigned DstBits = Trunc->getType()->getScalarSizeInBits(),
1480 SrcBits = X->getType()->getScalarSizeInBits();
1481 KnownBits Known(SrcBits);
1482 computeKnownBits(X, Known, 0, &Cmp);
1483
1484 // If all the high bits are known, we can do this xform.
1485 if ((Known.Zero | Known.One).countLeadingOnes() >= SrcBits - DstBits) {
1486 // Pull in the high bits from known-ones set.
1487 APInt NewRHS = C->zext(SrcBits);
1488 NewRHS |= Known.One & APInt::getHighBitsSet(SrcBits, SrcBits - DstBits);
1489 return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), NewRHS));
1490 }
1491 }
1492
1493 return nullptr;
1494}
1495
1496/// Fold icmp (xor X, Y), C.
1497Instruction *InstCombiner::foldICmpXorConstant(ICmpInst &Cmp,
1498 BinaryOperator *Xor,
1499 const APInt *C) {
1500 Value *X = Xor->getOperand(0);
1501 Value *Y = Xor->getOperand(1);
1502 const APInt *XorC;
1503 if (!match(Y, m_APInt(XorC)))
1504 return nullptr;
1505
1506 // If this is a comparison that tests the signbit (X < 0) or (x > -1),
1507 // fold the xor.
1508 ICmpInst::Predicate Pred = Cmp.getPredicate();
1509 if ((Pred == ICmpInst::ICMP_SLT && *C == 0) ||
1510 (Pred == ICmpInst::ICMP_SGT && C->isAllOnesValue())) {
1511
1512 // If the sign bit of the XorCst is not set, there is no change to
1513 // the operation, just stop using the Xor.
1514 if (!XorC->isNegative()) {
1515 Cmp.setOperand(0, X);
1516 Worklist.Add(Xor);
1517 return &Cmp;
1518 }
1519
1520 // Was the old condition true if the operand is positive?
1521 bool isTrueIfPositive = Pred == ICmpInst::ICMP_SGT;
1522
1523 // If so, the new one isn't.
1524 isTrueIfPositive ^= true;
1525
1526 Constant *CmpConstant = cast<Constant>(Cmp.getOperand(1));
1527 if (isTrueIfPositive)
1528 return new ICmpInst(ICmpInst::ICMP_SGT, X, SubOne(CmpConstant));
1529 else
1530 return new ICmpInst(ICmpInst::ICMP_SLT, X, AddOne(CmpConstant));
1531 }
1532
1533 if (Xor->hasOneUse()) {
1534 // (icmp u/s (xor X SignMask), C) -> (icmp s/u X, (xor C SignMask))
1535 if (!Cmp.isEquality() && XorC->isSignMask()) {
1536 Pred = Cmp.isSigned() ? Cmp.getUnsignedPredicate()
1537 : Cmp.getSignedPredicate();
1538 return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), *C ^ *XorC));
1539 }
1540
1541 // (icmp u/s (xor X ~SignMask), C) -> (icmp s/u X, (xor C ~SignMask))
1542 if (!Cmp.isEquality() && XorC->isMaxSignedValue()) {
1543 Pred = Cmp.isSigned() ? Cmp.getUnsignedPredicate()
1544 : Cmp.getSignedPredicate();
1545 Pred = Cmp.getSwappedPredicate(Pred);
1546 return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), *C ^ *XorC));
1547 }
1548 }
1549
1550 // (icmp ugt (xor X, C), ~C) -> (icmp ult X, C)
1551 // iff -C is a power of 2
1552 if (Pred == ICmpInst::ICMP_UGT && *XorC == ~(*C) && (*C + 1).isPowerOf2())
1553 return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
1554
1555 // (icmp ult (xor X, C), -C) -> (icmp uge X, C)
1556 // iff -C is a power of 2
1557 if (Pred == ICmpInst::ICMP_ULT && *XorC == -(*C) && C->isPowerOf2())
1558 return new ICmpInst(ICmpInst::ICMP_UGE, X, Y);
1559
1560 return nullptr;
1561}
1562
1563/// Fold icmp (and (sh X, Y), C2), C1.
1564Instruction *InstCombiner::foldICmpAndShift(ICmpInst &Cmp, BinaryOperator *And,
1565 const APInt *C1, const APInt *C2) {
1566 BinaryOperator *Shift = dyn_cast<BinaryOperator>(And->getOperand(0));
1567 if (!Shift || !Shift->isShift())
1568 return nullptr;
1569
1570 // If this is: (X >> C3) & C2 != C1 (where any shift and any compare could
1571 // exist), turn it into (X & (C2 << C3)) != (C1 << C3). This happens a LOT in
1572 // code produced by the clang front-end, for bitfield access.
1573 // This seemingly simple opportunity to fold away a shift turns out to be
1574 // rather complicated. See PR17827 for details.
1575 unsigned ShiftOpcode = Shift->getOpcode();
1576 bool IsShl = ShiftOpcode == Instruction::Shl;
1577 const APInt *C3;
1578 if (match(Shift->getOperand(1), m_APInt(C3))) {
1579 bool CanFold = false;
1580 if (ShiftOpcode == Instruction::AShr) {
1581 // There may be some constraints that make this possible, but nothing
1582 // simple has been discovered yet.
1583 CanFold = false;
1584 } else if (ShiftOpcode == Instruction::Shl) {
1585 // For a left shift, we can fold if the comparison is not signed. We can
1586 // also fold a signed comparison if the mask value and comparison value
1587 // are not negative. These constraints may not be obvious, but we can
1588 // prove that they are correct using an SMT solver.
1589 if (!Cmp.isSigned() || (!C2->isNegative() && !C1->isNegative()))
1590 CanFold = true;
1591 } else if (ShiftOpcode == Instruction::LShr) {
1592 // For a logical right shift, we can fold if the comparison is not signed.
1593 // We can also fold a signed comparison if the shifted mask value and the
1594 // shifted comparison value are not negative. These constraints may not be
1595 // obvious, but we can prove that they are correct using an SMT solver.
1596 if (!Cmp.isSigned() ||
1597 (!C2->shl(*C3).isNegative() && !C1->shl(*C3).isNegative()))
1598 CanFold = true;
1599 }
1600
1601 if (CanFold) {
1602 APInt NewCst = IsShl ? C1->lshr(*C3) : C1->shl(*C3);
1603 APInt SameAsC1 = IsShl ? NewCst.shl(*C3) : NewCst.lshr(*C3);
1604 // Check to see if we are shifting out any of the bits being compared.
1605 if (SameAsC1 != *C1) {
1606 // If we shifted bits out, the fold is not going to work out. As a
1607 // special case, check to see if this means that the result is always
1608 // true or false now.
1609 if (Cmp.getPredicate() == ICmpInst::ICMP_EQ)
1610 return replaceInstUsesWith(Cmp, ConstantInt::getFalse(Cmp.getType()));
1611 if (Cmp.getPredicate() == ICmpInst::ICMP_NE)
1612 return replaceInstUsesWith(Cmp, ConstantInt::getTrue(Cmp.getType()));
1613 } else {
1614 Cmp.setOperand(1, ConstantInt::get(And->getType(), NewCst));
1615 APInt NewAndCst = IsShl ? C2->lshr(*C3) : C2->shl(*C3);
1616 And->setOperand(1, ConstantInt::get(And->getType(), NewAndCst));
1617 And->setOperand(0, Shift->getOperand(0));
1618 Worklist.Add(Shift); // Shift is dead.
1619 return &Cmp;
1620 }
1621 }
1622 }
1623
1624 // Turn ((X >> Y) & C2) == 0 into (X & (C2 << Y)) == 0. The latter is
1625 // preferable because it allows the C2 << Y expression to be hoisted out of a
1626 // loop if Y is invariant and X is not.
1627 if (Shift->hasOneUse() && *C1 == 0 && Cmp.isEquality() &&
1628 !Shift->isArithmeticShift() && !isa<Constant>(Shift->getOperand(0))) {
1629 // Compute C2 << Y.
1630 Value *NewShift =
1631 IsShl ? Builder->CreateLShr(And->getOperand(1), Shift->getOperand(1))
1632 : Builder->CreateShl(And->getOperand(1), Shift->getOperand(1));
1633
1634 // Compute X & (C2 << Y).
1635 Value *NewAnd = Builder->CreateAnd(Shift->getOperand(0), NewShift);
1636 Cmp.setOperand(0, NewAnd);
1637 return &Cmp;
1638 }
1639
1640 return nullptr;
1641}
1642
1643/// Fold icmp (and X, C2), C1.
1644Instruction *InstCombiner::foldICmpAndConstConst(ICmpInst &Cmp,
1645 BinaryOperator *And,
1646 const APInt *C1) {
1647 const APInt *C2;
1648 if (!match(And->getOperand(1), m_APInt(C2)))
1649 return nullptr;
1650
1651 if (!And->hasOneUse() || !And->getOperand(0)->hasOneUse())
1652 return nullptr;
1653
1654 // If the LHS is an 'and' of a truncate and we can widen the and/compare to
1655 // the input width without changing the value produced, eliminate the cast:
1656 //
1657 // icmp (and (trunc W), C2), C1 -> icmp (and W, C2'), C1'
1658 //
1659 // We can do this transformation if the constants do not have their sign bits
1660 // set or if it is an equality comparison. Extending a relational comparison
1661 // when we're checking the sign bit would not work.
1662 Value *W;
1663 if (match(And->getOperand(0), m_Trunc(m_Value(W))) &&
1664 (Cmp.isEquality() || (!C1->isNegative() && !C2->isNegative()))) {
1665 // TODO: Is this a good transform for vectors? Wider types may reduce
1666 // throughput. Should this transform be limited (even for scalars) by using
1667 // shouldChangeType()?
1668 if (!Cmp.getType()->isVectorTy()) {
1669 Type *WideType = W->getType();
1670 unsigned WideScalarBits = WideType->getScalarSizeInBits();
1671 Constant *ZextC1 = ConstantInt::get(WideType, C1->zext(WideScalarBits));
1672 Constant *ZextC2 = ConstantInt::get(WideType, C2->zext(WideScalarBits));
1673 Value *NewAnd = Builder->CreateAnd(W, ZextC2, And->getName());
1674 return new ICmpInst(Cmp.getPredicate(), NewAnd, ZextC1);
1675 }
1676 }
1677
1678 if (Instruction *I = foldICmpAndShift(Cmp, And, C1, C2))
1679 return I;
1680
1681 // (icmp pred (and (or (lshr A, B), A), 1), 0) -->
1682 // (icmp pred (and A, (or (shl 1, B), 1), 0))
1683 //
1684 // iff pred isn't signed
1685 if (!Cmp.isSigned() && *C1 == 0 && match(And->getOperand(1), m_One())) {
1686 Constant *One = cast<Constant>(And->getOperand(1));
1687 Value *Or = And->getOperand(0);
1688 Value *A, *B, *LShr;
1689 if (match(Or, m_Or(m_Value(LShr), m_Value(A))) &&
1690 match(LShr, m_LShr(m_Specific(A), m_Value(B)))) {
1691 unsigned UsesRemoved = 0;
1692 if (And->hasOneUse())
1693 ++UsesRemoved;
1694 if (Or->hasOneUse())
1695 ++UsesRemoved;
1696 if (LShr->hasOneUse())
1697 ++UsesRemoved;
1698
1699 // Compute A & ((1 << B) | 1)
1700 Value *NewOr = nullptr;
1701 if (auto *C = dyn_cast<Constant>(B)) {
1702 if (UsesRemoved >= 1)
1703 NewOr = ConstantExpr::getOr(ConstantExpr::getNUWShl(One, C), One);
1704 } else {
1705 if (UsesRemoved >= 3)
1706 NewOr = Builder->CreateOr(Builder->CreateShl(One, B, LShr->getName(),
1707 /*HasNUW=*/true),
1708 One, Or->getName());
1709 }
1710 if (NewOr) {
1711 Value *NewAnd = Builder->CreateAnd(A, NewOr, And->getName());
1712 Cmp.setOperand(0, NewAnd);
1713 return &Cmp;
1714 }
1715 }
1716 }
1717
1718 // (X & C2) > C1 --> (X & C2) != 0, if any bit set in (X & C2) will produce a
1719 // result greater than C1.
1720 unsigned NumTZ = C2->countTrailingZeros();
1721 if (Cmp.getPredicate() == ICmpInst::ICMP_UGT && NumTZ < C2->getBitWidth() &&
1722 APInt::getOneBitSet(C2->getBitWidth(), NumTZ).ugt(*C1)) {
1723 Constant *Zero = Constant::getNullValue(And->getType());
1724 return new ICmpInst(ICmpInst::ICMP_NE, And, Zero);
1725 }
1726
1727 return nullptr;
1728}
1729
1730/// Fold icmp (and X, Y), C.
1731Instruction *InstCombiner::foldICmpAndConstant(ICmpInst &Cmp,
1732 BinaryOperator *And,
1733 const APInt *C) {
1734 if (Instruction *I = foldICmpAndConstConst(Cmp, And, C))
1735 return I;
1736
1737 // TODO: These all require that Y is constant too, so refactor with the above.
1738
1739 // Try to optimize things like "A[i] & 42 == 0" to index computations.
1740 Value *X = And->getOperand(0);
1741 Value *Y = And->getOperand(1);
1742 if (auto *LI = dyn_cast<LoadInst>(X))
1743 if (auto *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0)))
1744 if (auto *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
1745 if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
1746 !LI->isVolatile() && isa<ConstantInt>(Y)) {
1747 ConstantInt *C2 = cast<ConstantInt>(Y);
1748 if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, Cmp, C2))
1749 return Res;
1750 }
1751
1752 if (!Cmp.isEquality())
1753 return nullptr;
1754
1755 // X & -C == -C -> X > u ~C
1756 // X & -C != -C -> X <= u ~C
1757 // iff C is a power of 2
1758 if (Cmp.getOperand(1) == Y && (-(*C)).isPowerOf2()) {
1759 auto NewPred = Cmp.getPredicate() == CmpInst::ICMP_EQ ? CmpInst::ICMP_UGT
1760 : CmpInst::ICMP_ULE;
1761 return new ICmpInst(NewPred, X, SubOne(cast<Constant>(Cmp.getOperand(1))));
1762 }
1763
1764 // (X & C2) == 0 -> (trunc X) >= 0
1765 // (X & C2) != 0 -> (trunc X) < 0
1766 // iff C2 is a power of 2 and it masks the sign bit of a legal integer type.
1767 const APInt *C2;
1768 if (And->hasOneUse() && *C == 0 && match(Y, m_APInt(C2))) {
1769 int32_t ExactLogBase2 = C2->exactLogBase2();
1770 if (ExactLogBase2 != -1 && DL.isLegalInteger(ExactLogBase2 + 1)) {
1771 Type *NTy = IntegerType::get(Cmp.getContext(), ExactLogBase2 + 1);
1772 if (And->getType()->isVectorTy())
1773 NTy = VectorType::get(NTy, And->getType()->getVectorNumElements());
1774 Value *Trunc = Builder->CreateTrunc(X, NTy);
1775 auto NewPred = Cmp.getPredicate() == CmpInst::ICMP_EQ ? CmpInst::ICMP_SGE
1776 : CmpInst::ICMP_SLT;
1777 return new ICmpInst(NewPred, Trunc, Constant::getNullValue(NTy));
1778 }
1779 }
1780
1781 return nullptr;
1782}
1783
1784/// Fold icmp (or X, Y), C.
1785Instruction *InstCombiner::foldICmpOrConstant(ICmpInst &Cmp, BinaryOperator *Or,
1786 const APInt *C) {
1787 ICmpInst::Predicate Pred = Cmp.getPredicate();
1788 if (*C == 1) {
1789 // icmp slt signum(V) 1 --> icmp slt V, 1
1790 Value *V = nullptr;
1791 if (Pred == ICmpInst::ICMP_SLT && match(Or, m_Signum(m_Value(V))))
1792 return new ICmpInst(ICmpInst::ICMP_SLT, V,
1793 ConstantInt::get(V->getType(), 1));
1794 }
1795
1796 // X | C == C --> X <=u C
1797 // X | C != C --> X >u C
1798 // iff C+1 is a power of 2 (C is a bitmask of the low bits)
1799 if (Cmp.isEquality() && Cmp.getOperand(1) == Or->getOperand(1) &&
1800 (*C + 1).isPowerOf2()) {
1801 Pred = (Pred == CmpInst::ICMP_EQ) ? CmpInst::ICMP_ULE : CmpInst::ICMP_UGT;
1802 return new ICmpInst(Pred, Or->getOperand(0), Or->getOperand(1));
1803 }
1804
1805 if (!Cmp.isEquality() || *C != 0 || !Or->hasOneUse())
1806 return nullptr;
1807
1808 Value *P, *Q;
1809 if (match(Or, m_Or(m_PtrToInt(m_Value(P)), m_PtrToInt(m_Value(Q))))) {
1810 // Simplify icmp eq (or (ptrtoint P), (ptrtoint Q)), 0
1811 // -> and (icmp eq P, null), (icmp eq Q, null).
1812 Value *CmpP =
1813 Builder->CreateICmp(Pred, P, ConstantInt::getNullValue(P->getType()));
1814 Value *CmpQ =
1815 Builder->CreateICmp(Pred, Q, ConstantInt::getNullValue(Q->getType()));
1816 auto LogicOpc = Pred == ICmpInst::Predicate::ICMP_EQ ? Instruction::And
1817 : Instruction::Or;
1818 return BinaryOperator::Create(LogicOpc, CmpP, CmpQ);
1819 }
1820
1821 return nullptr;
1822}
1823
1824/// Fold icmp (mul X, Y), C.
1825Instruction *InstCombiner::foldICmpMulConstant(ICmpInst &Cmp,
1826 BinaryOperator *Mul,
1827 const APInt *C) {
1828 const APInt *MulC;
1829 if (!match(Mul->getOperand(1), m_APInt(MulC)))
1830 return nullptr;
1831
1832 // If this is a test of the sign bit and the multiply is sign-preserving with
1833 // a constant operand, use the multiply LHS operand instead.
1834 ICmpInst::Predicate Pred = Cmp.getPredicate();
1835 if (isSignTest(Pred, *C) && Mul->hasNoSignedWrap()) {
1836 if (MulC->isNegative())
1837 Pred = ICmpInst::getSwappedPredicate(Pred);
1838 return new ICmpInst(Pred, Mul->getOperand(0),
1839 Constant::getNullValue(Mul->getType()));
1840 }
1841
1842 return nullptr;
1843}
1844
1845/// Fold icmp (shl 1, Y), C.
1846static Instruction *foldICmpShlOne(ICmpInst &Cmp, Instruction *Shl,
1847 const APInt *C) {
1848 Value *Y;
1849 if (!match(Shl, m_Shl(m_One(), m_Value(Y))))
1850 return nullptr;
1851
1852 Type *ShiftType = Shl->getType();
1853 uint32_t TypeBits = C->getBitWidth();
1854 bool CIsPowerOf2 = C->isPowerOf2();
1855 ICmpInst::Predicate Pred = Cmp.getPredicate();
1856 if (Cmp.isUnsigned()) {
1857 // (1 << Y) pred C -> Y pred Log2(C)
1858 if (!CIsPowerOf2) {
1859 // (1 << Y) < 30 -> Y <= 4
1860 // (1 << Y) <= 30 -> Y <= 4
1861 // (1 << Y) >= 30 -> Y > 4
1862 // (1 << Y) > 30 -> Y > 4
1863 if (Pred == ICmpInst::ICMP_ULT)
1864 Pred = ICmpInst::ICMP_ULE;
1865 else if (Pred == ICmpInst::ICMP_UGE)
1866 Pred = ICmpInst::ICMP_UGT;
1867 }
1868
1869 // (1 << Y) >= 2147483648 -> Y >= 31 -> Y == 31
1870 // (1 << Y) < 2147483648 -> Y < 31 -> Y != 31
1871 unsigned CLog2 = C->logBase2();
1872 if (CLog2 == TypeBits - 1) {
1873 if (Pred == ICmpInst::ICMP_UGE)
1874 Pred = ICmpInst::ICMP_EQ;
1875 else if (Pred == ICmpInst::ICMP_ULT)
1876 Pred = ICmpInst::ICMP_NE;
1877 }
1878 return new ICmpInst(Pred, Y, ConstantInt::get(ShiftType, CLog2));
1879 } else if (Cmp.isSigned()) {
1880 Constant *BitWidthMinusOne = ConstantInt::get(ShiftType, TypeBits - 1);
1881 if (C->isAllOnesValue()) {
1882 // (1 << Y) <= -1 -> Y == 31
1883 if (Pred == ICmpInst::ICMP_SLE)
1884 return new ICmpInst(ICmpInst::ICMP_EQ, Y, BitWidthMinusOne);
1885
1886 // (1 << Y) > -1 -> Y != 31
1887 if (Pred == ICmpInst::ICMP_SGT)
1888 return new ICmpInst(ICmpInst::ICMP_NE, Y, BitWidthMinusOne);
1889 } else if (!(*C)) {
1890 // (1 << Y) < 0 -> Y == 31
1891 // (1 << Y) <= 0 -> Y == 31
1892 if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
1893 return new ICmpInst(ICmpInst::ICMP_EQ, Y, BitWidthMinusOne);
1894
1895 // (1 << Y) >= 0 -> Y != 31
1896 // (1 << Y) > 0 -> Y != 31
1897 if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)
1898 return new ICmpInst(ICmpInst::ICMP_NE, Y, BitWidthMinusOne);
1899 }
1900 } else if (Cmp.isEquality() && CIsPowerOf2) {
1901 return new ICmpInst(Pred, Y, ConstantInt::get(ShiftType, C->logBase2()));
1902 }
1903
1904 return nullptr;
1905}
1906
1907/// Fold icmp (shl X, Y), C.
1908Instruction *InstCombiner::foldICmpShlConstant(ICmpInst &Cmp,
1909 BinaryOperator *Shl,
1910 const APInt *C) {
1911 const APInt *ShiftVal;
1912 if (Cmp.isEquality() && match(Shl->getOperand(0), m_APInt(ShiftVal)))
1913 return foldICmpShlConstConst(Cmp, Shl->getOperand(1), *C, *ShiftVal);
1914
1915 const APInt *ShiftAmt;
1916 if (!match(Shl->getOperand(1), m_APInt(ShiftAmt)))
1917 return foldICmpShlOne(Cmp, Shl, C);
1918
1919 // Check that the shift amount is in range. If not, don't perform undefined
1920 // shifts. When the shift is visited, it will be simplified.
1921 unsigned TypeBits = C->getBitWidth();
1922 if (ShiftAmt->uge(TypeBits))
1923 return nullptr;
1924
1925 ICmpInst::Predicate Pred = Cmp.getPredicate();
1926 Value *X = Shl->getOperand(0);
1927 Type *ShType = Shl->getType();
1928
1929 // NSW guarantees that we are only shifting out sign bits from the high bits,
1930 // so we can ASHR the compare constant without needing a mask and eliminate
1931 // the shift.
1932 if (Shl->hasNoSignedWrap()) {
1933 if (Pred == ICmpInst::ICMP_SGT) {
1934 // icmp Pred (shl nsw X, ShiftAmt), C --> icmp Pred X, (C >>s ShiftAmt)
1935 APInt ShiftedC = C->ashr(*ShiftAmt);
1936 return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1937 }
1938 if (Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) {
1939 // This is the same code as the SGT case, but assert the pre-condition
1940 // that is needed for this to work with equality predicates.
1941 assert(C->ashr(*ShiftAmt).shl(*ShiftAmt) == *C &&((C->ashr(*ShiftAmt).shl(*ShiftAmt) == *C && "Compare known true or false was not folded"
) ? static_cast<void> (0) : __assert_fail ("C->ashr(*ShiftAmt).shl(*ShiftAmt) == *C && \"Compare known true or false was not folded\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 1942, __PRETTY_FUNCTION__))
1942 "Compare known true or false was not folded")((C->ashr(*ShiftAmt).shl(*ShiftAmt) == *C && "Compare known true or false was not folded"
) ? static_cast<void> (0) : __assert_fail ("C->ashr(*ShiftAmt).shl(*ShiftAmt) == *C && \"Compare known true or false was not folded\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 1942, __PRETTY_FUNCTION__))
;
1943 APInt ShiftedC = C->ashr(*ShiftAmt);
1944 return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1945 }
1946 if (Pred == ICmpInst::ICMP_SLT) {
1947 // SLE is the same as above, but SLE is canonicalized to SLT, so convert:
1948 // (X << S) <=s C is equiv to X <=s (C >> S) for all C
1949 // (X << S) <s (C + 1) is equiv to X <s (C >> S) + 1 if C <s SMAX
1950 // (X << S) <s C is equiv to X <s ((C - 1) >> S) + 1 if C >s SMIN
1951 assert(!C->isMinSignedValue() && "Unexpected icmp slt")((!C->isMinSignedValue() && "Unexpected icmp slt")
? static_cast<void> (0) : __assert_fail ("!C->isMinSignedValue() && \"Unexpected icmp slt\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 1951, __PRETTY_FUNCTION__))
;
1952 APInt ShiftedC = (*C - 1).ashr(*ShiftAmt) + 1;
1953 return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1954 }
1955 // If this is a signed comparison to 0 and the shift is sign preserving,
1956 // use the shift LHS operand instead; isSignTest may change 'Pred', so only
1957 // do that if we're sure to not continue on in this function.
1958 if (isSignTest(Pred, *C))
1959 return new ICmpInst(Pred, X, Constant::getNullValue(ShType));
1960 }
1961
1962 // NUW guarantees that we are only shifting out zero bits from the high bits,
1963 // so we can LSHR the compare constant without needing a mask and eliminate
1964 // the shift.
1965 if (Shl->hasNoUnsignedWrap()) {
1966 if (Pred == ICmpInst::ICMP_UGT) {
1967 // icmp Pred (shl nuw X, ShiftAmt), C --> icmp Pred X, (C >>u ShiftAmt)
1968 APInt ShiftedC = C->lshr(*ShiftAmt);
1969 return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1970 }
1971 if (Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) {
1972 // This is the same code as the UGT case, but assert the pre-condition
1973 // that is needed for this to work with equality predicates.
1974 assert(C->lshr(*ShiftAmt).shl(*ShiftAmt) == *C &&((C->lshr(*ShiftAmt).shl(*ShiftAmt) == *C && "Compare known true or false was not folded"
) ? static_cast<void> (0) : __assert_fail ("C->lshr(*ShiftAmt).shl(*ShiftAmt) == *C && \"Compare known true or false was not folded\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 1975, __PRETTY_FUNCTION__))
1975 "Compare known true or false was not folded")((C->lshr(*ShiftAmt).shl(*ShiftAmt) == *C && "Compare known true or false was not folded"
) ? static_cast<void> (0) : __assert_fail ("C->lshr(*ShiftAmt).shl(*ShiftAmt) == *C && \"Compare known true or false was not folded\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 1975, __PRETTY_FUNCTION__))
;
1976 APInt ShiftedC = C->lshr(*ShiftAmt);
1977 return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1978 }
1979 if (Pred == ICmpInst::ICMP_ULT) {
1980 // ULE is the same as above, but ULE is canonicalized to ULT, so convert:
1981 // (X << S) <=u C is equiv to X <=u (C >> S) for all C
1982 // (X << S) <u (C + 1) is equiv to X <u (C >> S) + 1 if C <u ~0u
1983 // (X << S) <u C is equiv to X <u ((C - 1) >> S) + 1 if C >u 0
1984 assert(C->ugt(0) && "ult 0 should have been eliminated")((C->ugt(0) && "ult 0 should have been eliminated"
) ? static_cast<void> (0) : __assert_fail ("C->ugt(0) && \"ult 0 should have been eliminated\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 1984, __PRETTY_FUNCTION__))
;
1985 APInt ShiftedC = (*C - 1).lshr(*ShiftAmt) + 1;
1986 return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1987 }
1988 }
1989
1990 if (Cmp.isEquality() && Shl->hasOneUse()) {
1991 // Strength-reduce the shift into an 'and'.
1992 Constant *Mask = ConstantInt::get(
1993 ShType,
1994 APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt->getZExtValue()));
1995 Value *And = Builder->CreateAnd(X, Mask, Shl->getName() + ".mask");
1996 Constant *LShrC = ConstantInt::get(ShType, C->lshr(*ShiftAmt));
1997 return new ICmpInst(Pred, And, LShrC);
1998 }
1999
2000 // Otherwise, if this is a comparison of the sign bit, simplify to and/test.
2001 bool TrueIfSigned = false;
2002 if (Shl->hasOneUse() && isSignBitCheck(Pred, *C, TrueIfSigned)) {
2003 // (X << 31) <s 0 --> (X & 1) != 0
2004 Constant *Mask = ConstantInt::get(
2005 ShType,
2006 APInt::getOneBitSet(TypeBits, TypeBits - ShiftAmt->getZExtValue() - 1));
2007 Value *And = Builder->CreateAnd(X, Mask, Shl->getName() + ".mask");
2008 return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ,
2009 And, Constant::getNullValue(ShType));
2010 }
2011
2012 // Transform (icmp pred iM (shl iM %v, N), C)
2013 // -> (icmp pred i(M-N) (trunc %v iM to i(M-N)), (trunc (C>>N))
2014 // Transform the shl to a trunc if (trunc (C>>N)) has no loss and M-N.
2015 // This enables us to get rid of the shift in favor of a trunc that may be
2016 // free on the target. It has the additional benefit of comparing to a
2017 // smaller constant that may be more target-friendly.
2018 unsigned Amt = ShiftAmt->getLimitedValue(TypeBits - 1);
2019 if (Shl->hasOneUse() && Amt != 0 && C->countTrailingZeros() >= Amt &&
2020 DL.isLegalInteger(TypeBits - Amt)) {
2021 Type *TruncTy = IntegerType::get(Cmp.getContext(), TypeBits - Amt);
2022 if (ShType->isVectorTy())
2023 TruncTy = VectorType::get(TruncTy, ShType->getVectorNumElements());
2024 Constant *NewC =
2025 ConstantInt::get(TruncTy, C->ashr(*ShiftAmt).trunc(TypeBits - Amt));
2026 return new ICmpInst(Pred, Builder->CreateTrunc(X, TruncTy), NewC);
2027 }
2028
2029 return nullptr;
2030}
2031
2032/// Fold icmp ({al}shr X, Y), C.
2033Instruction *InstCombiner::foldICmpShrConstant(ICmpInst &Cmp,
2034 BinaryOperator *Shr,
2035 const APInt *C) {
2036 // An exact shr only shifts out zero bits, so:
2037 // icmp eq/ne (shr X, Y), 0 --> icmp eq/ne X, 0
2038 Value *X = Shr->getOperand(0);
2039 CmpInst::Predicate Pred = Cmp.getPredicate();
2040 if (Cmp.isEquality() && Shr->isExact() && Shr->hasOneUse() && *C == 0)
2041 return new ICmpInst(Pred, X, Cmp.getOperand(1));
2042
2043 const APInt *ShiftVal;
2044 if (Cmp.isEquality() && match(Shr->getOperand(0), m_APInt(ShiftVal)))
2045 return foldICmpShrConstConst(Cmp, Shr->getOperand(1), *C, *ShiftVal);
2046
2047 const APInt *ShiftAmt;
2048 if (!match(Shr->getOperand(1), m_APInt(ShiftAmt)))
2049 return nullptr;
2050
2051 // Check that the shift amount is in range. If not, don't perform undefined
2052 // shifts. When the shift is visited it will be simplified.
2053 unsigned TypeBits = C->getBitWidth();
2054 unsigned ShAmtVal = ShiftAmt->getLimitedValue(TypeBits);
2055 if (ShAmtVal >= TypeBits || ShAmtVal == 0)
2056 return nullptr;
2057
2058 bool IsAShr = Shr->getOpcode() == Instruction::AShr;
2059 if (!Cmp.isEquality()) {
2060 // If we have an unsigned comparison and an ashr, we can't simplify this.
2061 // Similarly for signed comparisons with lshr.
2062 if (Cmp.isSigned() != IsAShr)
2063 return nullptr;
2064
2065 // Otherwise, all lshr and most exact ashr's are equivalent to a udiv/sdiv
2066 // by a power of 2. Since we already have logic to simplify these,
2067 // transform to div and then simplify the resultant comparison.
2068 if (IsAShr && (!Shr->isExact() || ShAmtVal == TypeBits - 1))
2069 return nullptr;
2070
2071 // Revisit the shift (to delete it).
2072 Worklist.Add(Shr);
2073
2074 Constant *DivCst = ConstantInt::get(
2075 Shr->getType(), APInt::getOneBitSet(TypeBits, ShAmtVal));
2076
2077 Value *Tmp = IsAShr ? Builder->CreateSDiv(X, DivCst, "", Shr->isExact())
2078 : Builder->CreateUDiv(X, DivCst, "", Shr->isExact());
2079
2080 Cmp.setOperand(0, Tmp);
2081
2082 // If the builder folded the binop, just return it.
2083 BinaryOperator *TheDiv = dyn_cast<BinaryOperator>(Tmp);
2084 if (!TheDiv)
2085 return &Cmp;
2086
2087 // Otherwise, fold this div/compare.
2088 assert(TheDiv->getOpcode() == Instruction::SDiv ||((TheDiv->getOpcode() == Instruction::SDiv || TheDiv->getOpcode
() == Instruction::UDiv) ? static_cast<void> (0) : __assert_fail
("TheDiv->getOpcode() == Instruction::SDiv || TheDiv->getOpcode() == Instruction::UDiv"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 2089, __PRETTY_FUNCTION__))
2089 TheDiv->getOpcode() == Instruction::UDiv)((TheDiv->getOpcode() == Instruction::SDiv || TheDiv->getOpcode
() == Instruction::UDiv) ? static_cast<void> (0) : __assert_fail
("TheDiv->getOpcode() == Instruction::SDiv || TheDiv->getOpcode() == Instruction::UDiv"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 2089, __PRETTY_FUNCTION__))
;
2090
2091 Instruction *Res = foldICmpDivConstant(Cmp, TheDiv, C);
2092 assert(Res && "This div/cst should have folded!")((Res && "This div/cst should have folded!") ? static_cast
<void> (0) : __assert_fail ("Res && \"This div/cst should have folded!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 2092, __PRETTY_FUNCTION__))
;
2093 return Res;
2094 }
2095
2096 // Handle equality comparisons of shift-by-constant.
2097
2098 // If the comparison constant changes with the shift, the comparison cannot
2099 // succeed (bits of the comparison constant cannot match the shifted value).
2100 // This should be known by InstSimplify and already be folded to true/false.
2101 assert(((IsAShr && C->shl(ShAmtVal).ashr(ShAmtVal) == *C) ||((((IsAShr && C->shl(ShAmtVal).ashr(ShAmtVal) == *
C) || (!IsAShr && C->shl(ShAmtVal).lshr(ShAmtVal) ==
*C)) && "Expected icmp+shr simplify did not occur.")
? static_cast<void> (0) : __assert_fail ("((IsAShr && C->shl(ShAmtVal).ashr(ShAmtVal) == *C) || (!IsAShr && C->shl(ShAmtVal).lshr(ShAmtVal) == *C)) && \"Expected icmp+shr simplify did not occur.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 2103, __PRETTY_FUNCTION__))
2102 (!IsAShr && C->shl(ShAmtVal).lshr(ShAmtVal) == *C)) &&((((IsAShr && C->shl(ShAmtVal).ashr(ShAmtVal) == *
C) || (!IsAShr && C->shl(ShAmtVal).lshr(ShAmtVal) ==
*C)) && "Expected icmp+shr simplify did not occur.")
? static_cast<void> (0) : __assert_fail ("((IsAShr && C->shl(ShAmtVal).ashr(ShAmtVal) == *C) || (!IsAShr && C->shl(ShAmtVal).lshr(ShAmtVal) == *C)) && \"Expected icmp+shr simplify did not occur.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 2103, __PRETTY_FUNCTION__))
2103 "Expected icmp+shr simplify did not occur.")((((IsAShr && C->shl(ShAmtVal).ashr(ShAmtVal) == *
C) || (!IsAShr && C->shl(ShAmtVal).lshr(ShAmtVal) ==
*C)) && "Expected icmp+shr simplify did not occur.")
? static_cast<void> (0) : __assert_fail ("((IsAShr && C->shl(ShAmtVal).ashr(ShAmtVal) == *C) || (!IsAShr && C->shl(ShAmtVal).lshr(ShAmtVal) == *C)) && \"Expected icmp+shr simplify did not occur.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 2103, __PRETTY_FUNCTION__))
;
2104
2105 // Check if the bits shifted out are known to be zero. If so, we can compare
2106 // against the unshifted value:
2107 // (X & 4) >> 1 == 2 --> (X & 4) == 4.
2108 Constant *ShiftedCmpRHS = ConstantInt::get(Shr->getType(), *C << ShAmtVal);
2109 if (Shr->hasOneUse()) {
2110 if (Shr->isExact())
2111 return new ICmpInst(Pred, X, ShiftedCmpRHS);
2112
2113 // Otherwise strength reduce the shift into an 'and'.
2114 APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal));
2115 Constant *Mask = ConstantInt::get(Shr->getType(), Val);
2116 Value *And = Builder->CreateAnd(X, Mask, Shr->getName() + ".mask");
2117 return new ICmpInst(Pred, And, ShiftedCmpRHS);
2118 }
2119
2120 return nullptr;
2121}
2122
2123/// Fold icmp (udiv X, Y), C.
2124Instruction *InstCombiner::foldICmpUDivConstant(ICmpInst &Cmp,
2125 BinaryOperator *UDiv,
2126 const APInt *C) {
2127 const APInt *C2;
2128 if (!match(UDiv->getOperand(0), m_APInt(C2)))
2129 return nullptr;
2130
2131 assert(C2 != 0 && "udiv 0, X should have been simplified already.")((C2 != 0 && "udiv 0, X should have been simplified already."
) ? static_cast<void> (0) : __assert_fail ("C2 != 0 && \"udiv 0, X should have been simplified already.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 2131, __PRETTY_FUNCTION__))
;
2132
2133 // (icmp ugt (udiv C2, Y), C) -> (icmp ule Y, C2/(C+1))
2134 Value *Y = UDiv->getOperand(1);
2135 if (Cmp.getPredicate() == ICmpInst::ICMP_UGT) {
2136 assert(!C->isMaxValue() &&((!C->isMaxValue() && "icmp ugt X, UINT_MAX should have been simplified already."
) ? static_cast<void> (0) : __assert_fail ("!C->isMaxValue() && \"icmp ugt X, UINT_MAX should have been simplified already.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 2137, __PRETTY_FUNCTION__))
2137 "icmp ugt X, UINT_MAX should have been simplified already.")((!C->isMaxValue() && "icmp ugt X, UINT_MAX should have been simplified already."
) ? static_cast<void> (0) : __assert_fail ("!C->isMaxValue() && \"icmp ugt X, UINT_MAX should have been simplified already.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 2137, __PRETTY_FUNCTION__))
;
2138 return new ICmpInst(ICmpInst::ICMP_ULE, Y,
2139 ConstantInt::get(Y->getType(), C2->udiv(*C + 1)));
2140 }
2141
2142 // (icmp ult (udiv C2, Y), C) -> (icmp ugt Y, C2/C)
2143 if (Cmp.getPredicate() == ICmpInst::ICMP_ULT) {
2144 assert(C != 0 && "icmp ult X, 0 should have been simplified already.")((C != 0 && "icmp ult X, 0 should have been simplified already."
) ? static_cast<void> (0) : __assert_fail ("C != 0 && \"icmp ult X, 0 should have been simplified already.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 2144, __PRETTY_FUNCTION__))
;
2145 return new ICmpInst(ICmpInst::ICMP_UGT, Y,
2146 ConstantInt::get(Y->getType(), C2->udiv(*C)));
2147 }
2148
2149 return nullptr;
2150}
2151
2152/// Fold icmp ({su}div X, Y), C.
2153Instruction *InstCombiner::foldICmpDivConstant(ICmpInst &Cmp,
2154 BinaryOperator *Div,
2155 const APInt *C) {
2156 // Fold: icmp pred ([us]div X, C2), C -> range test
2157 // Fold this div into the comparison, producing a range check.
2158 // Determine, based on the divide type, what the range is being
2159 // checked. If there is an overflow on the low or high side, remember
2160 // it, otherwise compute the range [low, hi) bounding the new value.
2161 // See: InsertRangeTest above for the kinds of replacements possible.
2162 const APInt *C2;
2163 if (!match(Div->getOperand(1), m_APInt(C2)))
1
Taking false branch
2164 return nullptr;
2165
2166 // FIXME: If the operand types don't match the type of the divide
2167 // then don't attempt this transform. The code below doesn't have the
2168 // logic to deal with a signed divide and an unsigned compare (and
2169 // vice versa). This is because (x /s C2) <s C produces different
2170 // results than (x /s C2) <u C or (x /u C2) <s C or even
2171 // (x /u C2) <u C. Simply casting the operands and result won't
2172 // work. :( The if statement below tests that condition and bails
2173 // if it finds it.
2174 bool DivIsSigned = Div->getOpcode() == Instruction::SDiv;
2
Assuming the condition is true
2175 if (!Cmp.isEquality() && DivIsSigned != Cmp.isSigned())
2176 return nullptr;
2177
2178 // The ProdOV computation fails on divide by 0 and divide by -1. Cases with
2179 // INT_MIN will also fail if the divisor is 1. Although folds of all these
2180 // division-by-constant cases should be present, we can not assert that they
2181 // have happened before we reach this icmp instruction.
2182 if (*C2 == 0 || *C2 == 1 || (DivIsSigned && C2->isAllOnesValue()))
3
Taking false branch
2183 return nullptr;
2184
2185 // TODO: We could do all of the computations below using APInt.
2186 Constant *CmpRHS = cast<Constant>(Cmp.getOperand(1));
2187 Constant *DivRHS = cast<Constant>(Div->getOperand(1));
2188
2189 // Compute Prod = CmpRHS * DivRHS. We are essentially solving an equation of
2190 // form X / C2 = C. We solve for X by multiplying C2 (DivRHS) and C (CmpRHS).
2191 // By solving for X, we can turn this into a range check instead of computing
2192 // a divide.
2193 Constant *Prod = ConstantExpr::getMul(CmpRHS, DivRHS);
2194
2195 // Determine if the product overflows by seeing if the product is not equal to
2196 // the divide. Make sure we do the same kind of divide as in the LHS
2197 // instruction that we're folding.
2198 bool ProdOV = (DivIsSigned ? ConstantExpr::getSDiv(Prod, DivRHS)
4
'?' condition is true
5
Assuming the condition is false
2199 : ConstantExpr::getUDiv(Prod, DivRHS)) != CmpRHS;
2200
2201 ICmpInst::Predicate Pred = Cmp.getPredicate();
2202
2203 // If the division is known to be exact, then there is no remainder from the
2204 // divide, so the covered range size is unit, otherwise it is the divisor.
2205 Constant *RangeSize =
2206 Div->isExact() ? ConstantInt::get(Div->getType(), 1) : DivRHS;
6
Assuming the condition is false
7
'?' condition is false
2207
2208 // Figure out the interval that is being checked. For example, a comparison
2209 // like "X /u 5 == 0" is really checking that X is in the interval [0, 5).
2210 // Compute this interval based on the constants involved and the signedness of
2211 // the compare/divide. This computes a half-open interval, keeping track of
2212 // whether either value in the interval overflows. After analysis each
2213 // overflow variable is set to 0 if it's corresponding bound variable is valid
2214 // -1 if overflowed off the bottom end, or +1 if overflowed off the top end.
2215 int LoOverflow = 0, HiOverflow = 0;
2216 Constant *LoBound = nullptr, *HiBound = nullptr;
8
'LoBound' initialized to a null pointer value
2217
2218 if (!DivIsSigned) { // udiv
9
Taking false branch
2219 // e.g. X/5 op 3 --> [15, 20)
2220 LoBound = Prod;
2221 HiOverflow = LoOverflow = ProdOV;
2222 if (!HiOverflow) {
2223 // If this is not an exact divide, then many values in the range collapse
2224 // to the same result value.
2225 HiOverflow = addWithOverflow(HiBound, LoBound, RangeSize, false);
2226 }
2227 } else if (C2->isStrictlyPositive()) { // Divisor is > 0.
10
Taking false branch
2228 if (*C == 0) { // (X / pos) op 0
2229 // Can't overflow. e.g. X/2 op 0 --> [-1, 2)
2230 LoBound = ConstantExpr::getNeg(SubOne(RangeSize));
2231 HiBound = RangeSize;
2232 } else if (C->isStrictlyPositive()) { // (X / pos) op pos
2233 LoBound = Prod; // e.g. X/5 op 3 --> [15, 20)
2234 HiOverflow = LoOverflow = ProdOV;
2235 if (!HiOverflow)
2236 HiOverflow = addWithOverflow(HiBound, Prod, RangeSize, true);
2237 } else { // (X / pos) op neg
2238 // e.g. X/5 op -3 --> [-15-4, -15+1) --> [-19, -14)
2239 HiBound = AddOne(Prod);
2240 LoOverflow = HiOverflow = ProdOV ? -1 : 0;
2241 if (!LoOverflow) {
2242 Constant *DivNeg = ConstantExpr::getNeg(RangeSize);
2243 LoOverflow = addWithOverflow(LoBound, HiBound, DivNeg, true) ? -1 : 0;
2244 }
2245 }
2246 } else if (C2->isNegative()) { // Divisor is < 0.
11
Taking false branch
2247 if (Div->isExact())
2248 RangeSize = ConstantExpr::getNeg(RangeSize);
2249 if (*C == 0) { // (X / neg) op 0
2250 // e.g. X/-5 op 0 --> [-4, 5)
2251 LoBound = AddOne(RangeSize);
2252 HiBound = ConstantExpr::getNeg(RangeSize);
2253 if (HiBound == DivRHS) { // -INTMIN = INTMIN
2254 HiOverflow = 1; // [INTMIN+1, overflow)
2255 HiBound = nullptr; // e.g. X/INTMIN = 0 --> X > INTMIN
2256 }
2257 } else if (C->isStrictlyPositive()) { // (X / neg) op pos
2258 // e.g. X/-5 op 3 --> [-19, -14)
2259 HiBound = AddOne(Prod);
2260 HiOverflow = LoOverflow = ProdOV ? -1 : 0;
2261 if (!LoOverflow)
2262 LoOverflow = addWithOverflow(LoBound, HiBound, RangeSize, true) ? -1:0;
2263 } else { // (X / neg) op neg
2264 LoBound = Prod; // e.g. X/-5 op -3 --> [15, 20)
2265 LoOverflow = HiOverflow = ProdOV;
2266 if (!HiOverflow)
2267 HiOverflow = subWithOverflow(HiBound, Prod, RangeSize, true);
2268 }
2269
2270 // Dividing by a negative swaps the condition. LT <-> GT
2271 Pred = ICmpInst::getSwappedPredicate(Pred);
2272 }
2273
2274 Value *X = Div->getOperand(0);
2275 switch (Pred) {
12
Control jumps to 'case ICMP_NE:' at line 2289
2276 default: llvm_unreachable("Unhandled icmp opcode!")::llvm::llvm_unreachable_internal("Unhandled icmp opcode!", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 2276)
;
2277 case ICmpInst::ICMP_EQ:
2278 if (LoOverflow && HiOverflow)
2279 return replaceInstUsesWith(Cmp, Builder->getFalse());
2280 if (HiOverflow)
2281 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
2282 ICmpInst::ICMP_UGE, X, LoBound);
2283 if (LoOverflow)
2284 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
2285 ICmpInst::ICMP_ULT, X, HiBound);
2286 return replaceInstUsesWith(
2287 Cmp, insertRangeTest(X, LoBound->getUniqueInteger(),
2288 HiBound->getUniqueInteger(), DivIsSigned, true));
2289 case ICmpInst::ICMP_NE:
2290 if (LoOverflow && HiOverflow)
2291 return replaceInstUsesWith(Cmp, Builder->getTrue());
2292 if (HiOverflow)
13
Taking false branch
2293 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
2294 ICmpInst::ICMP_ULT, X, LoBound);
2295 if (LoOverflow)
14
Taking false branch
2296 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
2297 ICmpInst::ICMP_UGE, X, HiBound);
2298 return replaceInstUsesWith(Cmp,
2299 insertRangeTest(X, LoBound->getUniqueInteger(),
15
Called C++ object pointer is null
2300 HiBound->getUniqueInteger(),
2301 DivIsSigned, false));
2302 case ICmpInst::ICMP_ULT:
2303 case ICmpInst::ICMP_SLT:
2304 if (LoOverflow == +1) // Low bound is greater than input range.
2305 return replaceInstUsesWith(Cmp, Builder->getTrue());
2306 if (LoOverflow == -1) // Low bound is less than input range.
2307 return replaceInstUsesWith(Cmp, Builder->getFalse());
2308 return new ICmpInst(Pred, X, LoBound);
2309 case ICmpInst::ICMP_UGT:
2310 case ICmpInst::ICMP_SGT:
2311 if (HiOverflow == +1) // High bound greater than input range.
2312 return replaceInstUsesWith(Cmp, Builder->getFalse());
2313 if (HiOverflow == -1) // High bound less than input range.
2314 return replaceInstUsesWith(Cmp, Builder->getTrue());
2315 if (Pred == ICmpInst::ICMP_UGT)
2316 return new ICmpInst(ICmpInst::ICMP_UGE, X, HiBound);
2317 return new ICmpInst(ICmpInst::ICMP_SGE, X, HiBound);
2318 }
2319
2320 return nullptr;
2321}
2322
2323/// Fold icmp (sub X, Y), C.
2324Instruction *InstCombiner::foldICmpSubConstant(ICmpInst &Cmp,
2325 BinaryOperator *Sub,
2326 const APInt *C) {
2327 Value *X = Sub->getOperand(0), *Y = Sub->getOperand(1);
2328 ICmpInst::Predicate Pred = Cmp.getPredicate();
2329
2330 // The following transforms are only worth it if the only user of the subtract
2331 // is the icmp.
2332 if (!Sub->hasOneUse())
2333 return nullptr;
2334
2335 if (Sub->hasNoSignedWrap()) {
2336 // (icmp sgt (sub nsw X, Y), -1) -> (icmp sge X, Y)
2337 if (Pred == ICmpInst::ICMP_SGT && C->isAllOnesValue())
2338 return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
2339
2340 // (icmp sgt (sub nsw X, Y), 0) -> (icmp sgt X, Y)
2341 if (Pred == ICmpInst::ICMP_SGT && *C == 0)
2342 return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
2343
2344 // (icmp slt (sub nsw X, Y), 0) -> (icmp slt X, Y)
2345 if (Pred == ICmpInst::ICMP_SLT && *C == 0)
2346 return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
2347
2348 // (icmp slt (sub nsw X, Y), 1) -> (icmp sle X, Y)
2349 if (Pred == ICmpInst::ICMP_SLT && *C == 1)
2350 return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
2351 }
2352
2353 const APInt *C2;
2354 if (!match(X, m_APInt(C2)))
2355 return nullptr;
2356
2357 // C2 - Y <u C -> (Y | (C - 1)) == C2
2358 // iff (C2 & (C - 1)) == C - 1 and C is a power of 2
2359 if (Pred == ICmpInst::ICMP_ULT && C->isPowerOf2() &&
2360 (*C2 & (*C - 1)) == (*C - 1))
2361 return new ICmpInst(ICmpInst::ICMP_EQ, Builder->CreateOr(Y, *C - 1), X);
2362
2363 // C2 - Y >u C -> (Y | C) != C2
2364 // iff C2 & C == C and C + 1 is a power of 2
2365 if (Pred == ICmpInst::ICMP_UGT && (*C + 1).isPowerOf2() && (*C2 & *C) == *C)
2366 return new ICmpInst(ICmpInst::ICMP_NE, Builder->CreateOr(Y, *C), X);
2367
2368 return nullptr;
2369}
2370
2371/// Fold icmp (add X, Y), C.
2372Instruction *InstCombiner::foldICmpAddConstant(ICmpInst &Cmp,
2373 BinaryOperator *Add,
2374 const APInt *C) {
2375 Value *Y = Add->getOperand(1);
2376 const APInt *C2;
2377 if (Cmp.isEquality() || !match(Y, m_APInt(C2)))
2378 return nullptr;
2379
2380 // Fold icmp pred (add X, C2), C.
2381 Value *X = Add->getOperand(0);
2382 Type *Ty = Add->getType();
2383 CmpInst::Predicate Pred = Cmp.getPredicate();
2384
2385 // If the add does not wrap, we can always adjust the compare by subtracting
2386 // the constants. Equality comparisons are handled elsewhere. SGE/SLE are
2387 // canonicalized to SGT/SLT.
2388 if (Add->hasNoSignedWrap() &&
2389 (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SLT)) {
2390 bool Overflow;
2391 APInt NewC = C->ssub_ov(*C2, Overflow);
2392 // If there is overflow, the result must be true or false.
2393 // TODO: Can we assert there is no overflow because InstSimplify always
2394 // handles those cases?
2395 if (!Overflow)
2396 // icmp Pred (add nsw X, C2), C --> icmp Pred X, (C - C2)
2397 return new ICmpInst(Pred, X, ConstantInt::get(Ty, NewC));
2398 }
2399
2400 auto CR = ConstantRange::makeExactICmpRegion(Pred, *C).subtract(*C2);
2401 const APInt &Upper = CR.getUpper();
2402 const APInt &Lower = CR.getLower();
2403 if (Cmp.isSigned()) {
2404 if (Lower.isSignMask())
2405 return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantInt::get(Ty, Upper));
2406 if (Upper.isSignMask())
2407 return new ICmpInst(ICmpInst::ICMP_SGE, X, ConstantInt::get(Ty, Lower));
2408 } else {
2409 if (Lower.isMinValue())
2410 return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantInt::get(Ty, Upper));
2411 if (Upper.isMinValue())
2412 return new ICmpInst(ICmpInst::ICMP_UGE, X, ConstantInt::get(Ty, Lower));
2413 }
2414
2415 if (!Add->hasOneUse())
2416 return nullptr;
2417
2418 // X+C <u C2 -> (X & -C2) == C
2419 // iff C & (C2-1) == 0
2420 // C2 is a power of 2
2421 if (Pred == ICmpInst::ICMP_ULT && C->isPowerOf2() && (*C2 & (*C - 1)) == 0)
2422 return new ICmpInst(ICmpInst::ICMP_EQ, Builder->CreateAnd(X, -(*C)),
2423 ConstantExpr::getNeg(cast<Constant>(Y)));
2424
2425 // X+C >u C2 -> (X & ~C2) != C
2426 // iff C & C2 == 0
2427 // C2+1 is a power of 2
2428 if (Pred == ICmpInst::ICMP_UGT && (*C + 1).isPowerOf2() && (*C2 & *C) == 0)
2429 return new ICmpInst(ICmpInst::ICMP_NE, Builder->CreateAnd(X, ~(*C)),
2430 ConstantExpr::getNeg(cast<Constant>(Y)));
2431
2432 return nullptr;
2433}
2434
2435/// Try to fold integer comparisons with a constant operand: icmp Pred X, C
2436/// where X is some kind of instruction.
2437Instruction *InstCombiner::foldICmpInstWithConstant(ICmpInst &Cmp) {
2438 const APInt *C;
2439 if (!match(Cmp.getOperand(1), m_APInt(C)))
2440 return nullptr;
2441
2442 BinaryOperator *BO;
2443 if (match(Cmp.getOperand(0), m_BinOp(BO))) {
2444 switch (BO->getOpcode()) {
2445 case Instruction::Xor:
2446 if (Instruction *I = foldICmpXorConstant(Cmp, BO, C))
2447 return I;
2448 break;
2449 case Instruction::And:
2450 if (Instruction *I = foldICmpAndConstant(Cmp, BO, C))
2451 return I;
2452 break;
2453 case Instruction::Or:
2454 if (Instruction *I = foldICmpOrConstant(Cmp, BO, C))
2455 return I;
2456 break;
2457 case Instruction::Mul:
2458 if (Instruction *I = foldICmpMulConstant(Cmp, BO, C))
2459 return I;
2460 break;
2461 case Instruction::Shl:
2462 if (Instruction *I = foldICmpShlConstant(Cmp, BO, C))
2463 return I;
2464 break;
2465 case Instruction::LShr:
2466 case Instruction::AShr:
2467 if (Instruction *I = foldICmpShrConstant(Cmp, BO, C))
2468 return I;
2469 break;
2470 case Instruction::UDiv:
2471 if (Instruction *I = foldICmpUDivConstant(Cmp, BO, C))
2472 return I;
2473 LLVM_FALLTHROUGH[[clang::fallthrough]];
2474 case Instruction::SDiv:
2475 if (Instruction *I = foldICmpDivConstant(Cmp, BO, C))
2476 return I;
2477 break;
2478 case Instruction::Sub:
2479 if (Instruction *I = foldICmpSubConstant(Cmp, BO, C))
2480 return I;
2481 break;
2482 case Instruction::Add:
2483 if (Instruction *I = foldICmpAddConstant(Cmp, BO, C))
2484 return I;
2485 break;
2486 default:
2487 break;
2488 }
2489 // TODO: These folds could be refactored to be part of the above calls.
2490 if (Instruction *I = foldICmpBinOpEqualityWithConstant(Cmp, BO, C))
2491 return I;
2492 }
2493
2494 Instruction *LHSI;
2495 if (match(Cmp.getOperand(0), m_Instruction(LHSI)) &&
2496 LHSI->getOpcode() == Instruction::Trunc)
2497 if (Instruction *I = foldICmpTruncConstant(Cmp, LHSI, C))
2498 return I;
2499
2500 if (Instruction *I = foldICmpIntrinsicWithConstant(Cmp, C))
2501 return I;
2502
2503 return nullptr;
2504}
2505
2506/// Fold an icmp equality instruction with binary operator LHS and constant RHS:
2507/// icmp eq/ne BO, C.
2508Instruction *InstCombiner::foldICmpBinOpEqualityWithConstant(ICmpInst &Cmp,
2509 BinaryOperator *BO,
2510 const APInt *C) {
2511 // TODO: Some of these folds could work with arbitrary constants, but this
2512 // function is limited to scalar and vector splat constants.
2513 if (!Cmp.isEquality())
2514 return nullptr;
2515
2516 ICmpInst::Predicate Pred = Cmp.getPredicate();
2517 bool isICMP_NE = Pred == ICmpInst::ICMP_NE;
2518 Constant *RHS = cast<Constant>(Cmp.getOperand(1));
2519 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
2520
2521 switch (BO->getOpcode()) {
2522 case Instruction::SRem:
2523 // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
2524 if (*C == 0 && BO->hasOneUse()) {
2525 const APInt *BOC;
2526 if (match(BOp1, m_APInt(BOC)) && BOC->sgt(1) && BOC->isPowerOf2()) {
2527 Value *NewRem = Builder->CreateURem(BOp0, BOp1, BO->getName());
2528 return new ICmpInst(Pred, NewRem,
2529 Constant::getNullValue(BO->getType()));
2530 }
2531 }
2532 break;
2533 case Instruction::Add: {
2534 // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
2535 const APInt *BOC;
2536 if (match(BOp1, m_APInt(BOC))) {
2537 if (BO->hasOneUse()) {
2538 Constant *SubC = ConstantExpr::getSub(RHS, cast<Constant>(BOp1));
2539 return new ICmpInst(Pred, BOp0, SubC);
2540 }
2541 } else if (*C == 0) {
2542 // Replace ((add A, B) != 0) with (A != -B) if A or B is
2543 // efficiently invertible, or if the add has just this one use.
2544 if (Value *NegVal = dyn_castNegVal(BOp1))
2545 return new ICmpInst(Pred, BOp0, NegVal);
2546 if (Value *NegVal = dyn_castNegVal(BOp0))
2547 return new ICmpInst(Pred, NegVal, BOp1);
2548 if (BO->hasOneUse()) {
2549 Value *Neg = Builder->CreateNeg(BOp1);
2550 Neg->takeName(BO);
2551 return new ICmpInst(Pred, BOp0, Neg);
2552 }
2553 }
2554 break;
2555 }
2556 case Instruction::Xor:
2557 if (BO->hasOneUse()) {
2558 if (Constant *BOC = dyn_cast<Constant>(BOp1)) {
2559 // For the xor case, we can xor two constants together, eliminating
2560 // the explicit xor.
2561 return new ICmpInst(Pred, BOp0, ConstantExpr::getXor(RHS, BOC));
2562 } else if (*C == 0) {
2563 // Replace ((xor A, B) != 0) with (A != B)
2564 return new ICmpInst(Pred, BOp0, BOp1);
2565 }
2566 }
2567 break;
2568 case Instruction::Sub:
2569 if (BO->hasOneUse()) {
2570 const APInt *BOC;
2571 if (match(BOp0, m_APInt(BOC))) {
2572 // Replace ((sub BOC, B) != C) with (B != BOC-C).
2573 Constant *SubC = ConstantExpr::getSub(cast<Constant>(BOp0), RHS);
2574 return new ICmpInst(Pred, BOp1, SubC);
2575 } else if (*C == 0) {
2576 // Replace ((sub A, B) != 0) with (A != B).
2577 return new ICmpInst(Pred, BOp0, BOp1);
2578 }
2579 }
2580 break;
2581 case Instruction::Or: {
2582 const APInt *BOC;
2583 if (match(BOp1, m_APInt(BOC)) && BO->hasOneUse() && RHS->isAllOnesValue()) {
2584 // Comparing if all bits outside of a constant mask are set?
2585 // Replace (X | C) == -1 with (X & ~C) == ~C.
2586 // This removes the -1 constant.
2587 Constant *NotBOC = ConstantExpr::getNot(cast<Constant>(BOp1));
2588 Value *And = Builder->CreateAnd(BOp0, NotBOC);
2589 return new ICmpInst(Pred, And, NotBOC);
2590 }
2591 break;
2592 }
2593 case Instruction::And: {
2594 const APInt *BOC;
2595 if (match(BOp1, m_APInt(BOC))) {
2596 // If we have ((X & C) == C), turn it into ((X & C) != 0).
2597 if (C == BOC && C->isPowerOf2())
2598 return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE,
2599 BO, Constant::getNullValue(RHS->getType()));
2600
2601 // Don't perform the following transforms if the AND has multiple uses
2602 if (!BO->hasOneUse())
2603 break;
2604
2605 // Replace (and X, (1 << size(X)-1) != 0) with x s< 0
2606 if (BOC->isSignMask()) {
2607 Constant *Zero = Constant::getNullValue(BOp0->getType());
2608 auto NewPred = isICMP_NE ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
2609 return new ICmpInst(NewPred, BOp0, Zero);
2610 }
2611
2612 // ((X & ~7) == 0) --> X < 8
2613 if (*C == 0 && (~(*BOC) + 1).isPowerOf2()) {
2614 Constant *NegBOC = ConstantExpr::getNeg(cast<Constant>(BOp1));
2615 auto NewPred = isICMP_NE ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
2616 return new ICmpInst(NewPred, BOp0, NegBOC);
2617 }
2618 }
2619 break;
2620 }
2621 case Instruction::Mul:
2622 if (*C == 0 && BO->hasNoSignedWrap()) {
2623 const APInt *BOC;
2624 if (match(BOp1, m_APInt(BOC)) && *BOC != 0) {
2625 // The trivial case (mul X, 0) is handled by InstSimplify.
2626 // General case : (mul X, C) != 0 iff X != 0
2627 // (mul X, C) == 0 iff X == 0
2628 return new ICmpInst(Pred, BOp0, Constant::getNullValue(RHS->getType()));
2629 }
2630 }
2631 break;
2632 case Instruction::UDiv:
2633 if (*C == 0) {
2634 // (icmp eq/ne (udiv A, B), 0) -> (icmp ugt/ule i32 B, A)
2635 auto NewPred = isICMP_NE ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_UGT;
2636 return new ICmpInst(NewPred, BOp1, BOp0);
2637 }
2638 break;
2639 default:
2640 break;
2641 }
2642 return nullptr;
2643}
2644
2645/// Fold an icmp with LLVM intrinsic and constant operand: icmp Pred II, C.
2646Instruction *InstCombiner::foldICmpIntrinsicWithConstant(ICmpInst &Cmp,
2647 const APInt *C) {
2648 IntrinsicInst *II = dyn_cast<IntrinsicInst>(Cmp.getOperand(0));
2649 if (!II || !Cmp.isEquality())
2650 return nullptr;
2651
2652 // Handle icmp {eq|ne} <intrinsic>, intcst.
2653 switch (II->getIntrinsicID()) {
2654 case Intrinsic::bswap:
2655 Worklist.Add(II);
2656 Cmp.setOperand(0, II->getArgOperand(0));
2657 Cmp.setOperand(1, Builder->getInt(C->byteSwap()));
2658 return &Cmp;
2659 case Intrinsic::ctlz:
2660 case Intrinsic::cttz:
2661 // ctz(A) == bitwidth(A) -> A == 0 and likewise for !=
2662 if (*C == C->getBitWidth()) {
2663 Worklist.Add(II);
2664 Cmp.setOperand(0, II->getArgOperand(0));
2665 Cmp.setOperand(1, ConstantInt::getNullValue(II->getType()));
2666 return &Cmp;
2667 }
2668 break;
2669 case Intrinsic::ctpop: {
2670 // popcount(A) == 0 -> A == 0 and likewise for !=
2671 // popcount(A) == bitwidth(A) -> A == -1 and likewise for !=
2672 bool IsZero = *C == 0;
2673 if (IsZero || *C == C->getBitWidth()) {
2674 Worklist.Add(II);
2675 Cmp.setOperand(0, II->getArgOperand(0));
2676 auto *NewOp = IsZero ? Constant::getNullValue(II->getType())
2677 : Constant::getAllOnesValue(II->getType());
2678 Cmp.setOperand(1, NewOp);
2679 return &Cmp;
2680 }
2681 break;
2682 }
2683 default:
2684 break;
2685 }
2686 return nullptr;
2687}
2688
2689/// Handle icmp with constant (but not simple integer constant) RHS.
2690Instruction *InstCombiner::foldICmpInstWithConstantNotInt(ICmpInst &I) {
2691 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2692 Constant *RHSC = dyn_cast<Constant>(Op1);
2693 Instruction *LHSI = dyn_cast<Instruction>(Op0);
2694 if (!RHSC || !LHSI)
2695 return nullptr;
2696
2697 switch (LHSI->getOpcode()) {
2698 case Instruction::GetElementPtr:
2699 // icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null
2700 if (RHSC->isNullValue() &&
2701 cast<GetElementPtrInst>(LHSI)->hasAllZeroIndices())
2702 return new ICmpInst(
2703 I.getPredicate(), LHSI->getOperand(0),
2704 Constant::getNullValue(LHSI->getOperand(0)->getType()));
2705 break;
2706 case Instruction::PHI:
2707 // Only fold icmp into the PHI if the phi and icmp are in the same
2708 // block. If in the same block, we're encouraging jump threading. If
2709 // not, we are just pessimizing the code by making an i1 phi.
2710 if (LHSI->getParent() == I.getParent())
2711 if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
2712 return NV;
2713 break;
2714 case Instruction::Select: {
2715 // If either operand of the select is a constant, we can fold the
2716 // comparison into the select arms, which will cause one to be
2717 // constant folded and the select turned into a bitwise or.
2718 Value *Op1 = nullptr, *Op2 = nullptr;
2719 ConstantInt *CI = nullptr;
2720 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
2721 Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2722 CI = dyn_cast<ConstantInt>(Op1);
2723 }
2724 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
2725 Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2726 CI = dyn_cast<ConstantInt>(Op2);
2727 }
2728
2729 // We only want to perform this transformation if it will not lead to
2730 // additional code. This is true if either both sides of the select
2731 // fold to a constant (in which case the icmp is replaced with a select
2732 // which will usually simplify) or this is the only user of the
2733 // select (in which case we are trading a select+icmp for a simpler
2734 // select+icmp) or all uses of the select can be replaced based on
2735 // dominance information ("Global cases").
2736 bool Transform = false;
2737 if (Op1 && Op2)
2738 Transform = true;
2739 else if (Op1 || Op2) {
2740 // Local case
2741 if (LHSI->hasOneUse())
2742 Transform = true;
2743 // Global cases
2744 else if (CI && !CI->isZero())
2745 // When Op1 is constant try replacing select with second operand.
2746 // Otherwise Op2 is constant and try replacing select with first
2747 // operand.
2748 Transform =
2749 replacedSelectWithOperand(cast<SelectInst>(LHSI), &I, Op1 ? 2 : 1);
2750 }
2751 if (Transform) {
2752 if (!Op1)
2753 Op1 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(1), RHSC,
2754 I.getName());
2755 if (!Op2)
2756 Op2 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(2), RHSC,
2757 I.getName());
2758 return SelectInst::Create(LHSI->getOperand(0), Op1, Op2);
2759 }
2760 break;
2761 }
2762 case Instruction::IntToPtr:
2763 // icmp pred inttoptr(X), null -> icmp pred X, 0
2764 if (RHSC->isNullValue() &&
2765 DL.getIntPtrType(RHSC->getType()) == LHSI->getOperand(0)->getType())
2766 return new ICmpInst(
2767 I.getPredicate(), LHSI->getOperand(0),
2768 Constant::getNullValue(LHSI->getOperand(0)->getType()));
2769 break;
2770
2771 case Instruction::Load:
2772 // Try to optimize things like "A[i] > 4" to index computations.
2773 if (GetElementPtrInst *GEP =
2774 dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
2775 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
2776 if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
2777 !cast<LoadInst>(LHSI)->isVolatile())
2778 if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
2779 return Res;
2780 }
2781 break;
2782 }
2783
2784 return nullptr;
2785}
2786
2787/// Try to fold icmp (binop), X or icmp X, (binop).
2788Instruction *InstCombiner::foldICmpBinOp(ICmpInst &I) {
2789 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2790
2791 // Special logic for binary operators.
2792 BinaryOperator *BO0 = dyn_cast<BinaryOperator>(Op0);
2793 BinaryOperator *BO1 = dyn_cast<BinaryOperator>(Op1);
2794 if (!BO0 && !BO1)
2795 return nullptr;
2796
2797 CmpInst::Predicate Pred = I.getPredicate();
2798 bool NoOp0WrapProblem = false, NoOp1WrapProblem = false;
2799 if (BO0 && isa<OverflowingBinaryOperator>(BO0))
2800 NoOp0WrapProblem =
2801 ICmpInst::isEquality(Pred) ||
2802 (CmpInst::isUnsigned(Pred) && BO0->hasNoUnsignedWrap()) ||
2803 (CmpInst::isSigned(Pred) && BO0->hasNoSignedWrap());
2804 if (BO1 && isa<OverflowingBinaryOperator>(BO1))
2805 NoOp1WrapProblem =
2806 ICmpInst::isEquality(Pred) ||
2807 (CmpInst::isUnsigned(Pred) && BO1->hasNoUnsignedWrap()) ||
2808 (CmpInst::isSigned(Pred) && BO1->hasNoSignedWrap());
2809
2810 // Analyze the case when either Op0 or Op1 is an add instruction.
2811 // Op0 = A + B (or A and B are null); Op1 = C + D (or C and D are null).
2812 Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr;
2813 if (BO0 && BO0->getOpcode() == Instruction::Add) {
2814 A = BO0->getOperand(0);
2815 B = BO0->getOperand(1);
2816 }
2817 if (BO1 && BO1->getOpcode() == Instruction::Add) {
2818 C = BO1->getOperand(0);
2819 D = BO1->getOperand(1);
2820 }
2821
2822 // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow.
2823 if ((A == Op1 || B == Op1) && NoOp0WrapProblem)
2824 return new ICmpInst(Pred, A == Op1 ? B : A,
2825 Constant::getNullValue(Op1->getType()));
2826
2827 // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow.
2828 if ((C == Op0 || D == Op0) && NoOp1WrapProblem)
2829 return new ICmpInst(Pred, Constant::getNullValue(Op0->getType()),
2830 C == Op0 ? D : C);
2831
2832 // icmp (X+Y), (X+Z) -> icmp Y, Z for equalities or if there is no overflow.
2833 if (A && C && (A == C || A == D || B == C || B == D) && NoOp0WrapProblem &&
2834 NoOp1WrapProblem &&
2835 // Try not to increase register pressure.
2836 BO0->hasOneUse() && BO1->hasOneUse()) {
2837 // Determine Y and Z in the form icmp (X+Y), (X+Z).
2838 Value *Y, *Z;
2839 if (A == C) {
2840 // C + B == C + D -> B == D
2841 Y = B;
2842 Z = D;
2843 } else if (A == D) {
2844 // D + B == C + D -> B == C
2845 Y = B;
2846 Z = C;
2847 } else if (B == C) {
2848 // A + C == C + D -> A == D
2849 Y = A;
2850 Z = D;
2851 } else {
2852 assert(B == D)((B == D) ? static_cast<void> (0) : __assert_fail ("B == D"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 2852, __PRETTY_FUNCTION__))
;
2853 // A + D == C + D -> A == C
2854 Y = A;
2855 Z = C;
2856 }
2857 return new ICmpInst(Pred, Y, Z);
2858 }
2859
2860 // icmp slt (X + -1), Y -> icmp sle X, Y
2861 if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLT &&
2862 match(B, m_AllOnes()))
2863 return new ICmpInst(CmpInst::ICMP_SLE, A, Op1);
2864
2865 // icmp sge (X + -1), Y -> icmp sgt X, Y
2866 if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGE &&
2867 match(B, m_AllOnes()))
2868 return new ICmpInst(CmpInst::ICMP_SGT, A, Op1);
2869
2870 // icmp sle (X + 1), Y -> icmp slt X, Y
2871 if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLE && match(B, m_One()))
2872 return new ICmpInst(CmpInst::ICMP_SLT, A, Op1);
2873
2874 // icmp sgt (X + 1), Y -> icmp sge X, Y
2875 if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGT && match(B, m_One()))
2876 return new ICmpInst(CmpInst::ICMP_SGE, A, Op1);
2877
2878 // icmp sgt X, (Y + -1) -> icmp sge X, Y
2879 if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGT &&
2880 match(D, m_AllOnes()))
2881 return new ICmpInst(CmpInst::ICMP_SGE, Op0, C);
2882
2883 // icmp sle X, (Y + -1) -> icmp slt X, Y
2884 if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLE &&
2885 match(D, m_AllOnes()))
2886 return new ICmpInst(CmpInst::ICMP_SLT, Op0, C);
2887
2888 // icmp sge X, (Y + 1) -> icmp sgt X, Y
2889 if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGE && match(D, m_One()))
2890 return new ICmpInst(CmpInst::ICMP_SGT, Op0, C);
2891
2892 // icmp slt X, (Y + 1) -> icmp sle X, Y
2893 if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLT && match(D, m_One()))
2894 return new ICmpInst(CmpInst::ICMP_SLE, Op0, C);
2895
2896 // TODO: The subtraction-related identities shown below also hold, but
2897 // canonicalization from (X -nuw 1) to (X + -1) means that the combinations
2898 // wouldn't happen even if they were implemented.
2899 //
2900 // icmp ult (X - 1), Y -> icmp ule X, Y
2901 // icmp uge (X - 1), Y -> icmp ugt X, Y
2902 // icmp ugt X, (Y - 1) -> icmp uge X, Y
2903 // icmp ule X, (Y - 1) -> icmp ult X, Y
2904
2905 // icmp ule (X + 1), Y -> icmp ult X, Y
2906 if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_ULE && match(B, m_One()))
2907 return new ICmpInst(CmpInst::ICMP_ULT, A, Op1);
2908
2909 // icmp ugt (X + 1), Y -> icmp uge X, Y
2910 if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_UGT && match(B, m_One()))
2911 return new ICmpInst(CmpInst::ICMP_UGE, A, Op1);
2912
2913 // icmp uge X, (Y + 1) -> icmp ugt X, Y
2914 if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_UGE && match(D, m_One()))
2915 return new ICmpInst(CmpInst::ICMP_UGT, Op0, C);
2916
2917 // icmp ult X, (Y + 1) -> icmp ule X, Y
2918 if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_ULT && match(D, m_One()))
2919 return new ICmpInst(CmpInst::ICMP_ULE, Op0, C);
2920
2921 // if C1 has greater magnitude than C2:
2922 // icmp (X + C1), (Y + C2) -> icmp (X + C3), Y
2923 // s.t. C3 = C1 - C2
2924 //
2925 // if C2 has greater magnitude than C1:
2926 // icmp (X + C1), (Y + C2) -> icmp X, (Y + C3)
2927 // s.t. C3 = C2 - C1
2928 if (A && C && NoOp0WrapProblem && NoOp1WrapProblem &&
2929 (BO0->hasOneUse() || BO1->hasOneUse()) && !I.isUnsigned())
2930 if (ConstantInt *C1 = dyn_cast<ConstantInt>(B))
2931 if (ConstantInt *C2 = dyn_cast<ConstantInt>(D)) {
2932 const APInt &AP1 = C1->getValue();
2933 const APInt &AP2 = C2->getValue();
2934 if (AP1.isNegative() == AP2.isNegative()) {
2935 APInt AP1Abs = C1->getValue().abs();
2936 APInt AP2Abs = C2->getValue().abs();
2937 if (AP1Abs.uge(AP2Abs)) {
2938 ConstantInt *C3 = Builder->getInt(AP1 - AP2);
2939 Value *NewAdd = Builder->CreateNSWAdd(A, C3);
2940 return new ICmpInst(Pred, NewAdd, C);
2941 } else {
2942 ConstantInt *C3 = Builder->getInt(AP2 - AP1);
2943 Value *NewAdd = Builder->CreateNSWAdd(C, C3);
2944 return new ICmpInst(Pred, A, NewAdd);
2945 }
2946 }
2947 }
2948
2949 // Analyze the case when either Op0 or Op1 is a sub instruction.
2950 // Op0 = A - B (or A and B are null); Op1 = C - D (or C and D are null).
2951 A = nullptr;
2952 B = nullptr;
2953 C = nullptr;
2954 D = nullptr;
2955 if (BO0 && BO0->getOpcode() == Instruction::Sub) {
2956 A = BO0->getOperand(0);
2957 B = BO0->getOperand(1);
2958 }
2959 if (BO1 && BO1->getOpcode() == Instruction::Sub) {
2960 C = BO1->getOperand(0);
2961 D = BO1->getOperand(1);
2962 }
2963
2964 // icmp (X-Y), X -> icmp 0, Y for equalities or if there is no overflow.
2965 if (A == Op1 && NoOp0WrapProblem)
2966 return new ICmpInst(Pred, Constant::getNullValue(Op1->getType()), B);
2967
2968 // icmp X, (X-Y) -> icmp Y, 0 for equalities or if there is no overflow.
2969 if (C == Op0 && NoOp1WrapProblem)
2970 return new ICmpInst(Pred, D, Constant::getNullValue(Op0->getType()));
2971
2972 // icmp (Y-X), (Z-X) -> icmp Y, Z for equalities or if there is no overflow.
2973 if (B && D && B == D && NoOp0WrapProblem && NoOp1WrapProblem &&
2974 // Try not to increase register pressure.
2975 BO0->hasOneUse() && BO1->hasOneUse())
2976 return new ICmpInst(Pred, A, C);
2977
2978 // icmp (X-Y), (X-Z) -> icmp Z, Y for equalities or if there is no overflow.
2979 if (A && C && A == C && NoOp0WrapProblem && NoOp1WrapProblem &&
2980 // Try not to increase register pressure.
2981 BO0->hasOneUse() && BO1->hasOneUse())
2982 return new ICmpInst(Pred, D, B);
2983
2984 // icmp (0-X) < cst --> x > -cst
2985 if (NoOp0WrapProblem && ICmpInst::isSigned(Pred)) {
2986 Value *X;
2987 if (match(BO0, m_Neg(m_Value(X))))
2988 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(Op1))
2989 if (!RHSC->isMinValue(/*isSigned=*/true))
2990 return new ICmpInst(I.getSwappedPredicate(), X,
2991 ConstantExpr::getNeg(RHSC));
2992 }
2993
2994 BinaryOperator *SRem = nullptr;
2995 // icmp (srem X, Y), Y
2996 if (BO0 && BO0->getOpcode() == Instruction::SRem && Op1 == BO0->getOperand(1))
2997 SRem = BO0;
2998 // icmp Y, (srem X, Y)
2999 else if (BO1 && BO1->getOpcode() == Instruction::SRem &&
3000 Op0 == BO1->getOperand(1))
3001 SRem = BO1;
3002 if (SRem) {
3003 // We don't check hasOneUse to avoid increasing register pressure because
3004 // the value we use is the same value this instruction was already using.
3005 switch (SRem == BO0 ? ICmpInst::getSwappedPredicate(Pred) : Pred) {
3006 default:
3007 break;
3008 case ICmpInst::ICMP_EQ:
3009 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
3010 case ICmpInst::ICMP_NE:
3011 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
3012 case ICmpInst::ICMP_SGT:
3013 case ICmpInst::ICMP_SGE:
3014 return new ICmpInst(ICmpInst::ICMP_SGT, SRem->getOperand(1),
3015 Constant::getAllOnesValue(SRem->getType()));
3016 case ICmpInst::ICMP_SLT:
3017 case ICmpInst::ICMP_SLE:
3018 return new ICmpInst(ICmpInst::ICMP_SLT, SRem->getOperand(1),
3019 Constant::getNullValue(SRem->getType()));
3020 }
3021 }
3022
3023 if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() && BO0->hasOneUse() &&
3024 BO1->hasOneUse() && BO0->getOperand(1) == BO1->getOperand(1)) {
3025 switch (BO0->getOpcode()) {
3026 default:
3027 break;
3028 case Instruction::Add:
3029 case Instruction::Sub:
3030 case Instruction::Xor:
3031 if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b
3032 return new ICmpInst(I.getPredicate(), BO0->getOperand(0),
3033 BO1->getOperand(0));
3034 // icmp u/s (a ^ signmask), (b ^ signmask) --> icmp s/u a, b
3035 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO0->getOperand(1))) {
3036 if (CI->getValue().isSignMask()) {
3037 ICmpInst::Predicate Pred =
3038 I.isSigned() ? I.getUnsignedPredicate() : I.getSignedPredicate();
3039 return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3040 }
3041
3042 if (BO0->getOpcode() == Instruction::Xor && CI->isMaxValue(true)) {
3043 ICmpInst::Predicate Pred =
3044 I.isSigned() ? I.getUnsignedPredicate() : I.getSignedPredicate();
3045 Pred = I.getSwappedPredicate(Pred);
3046 return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3047 }
3048 }
3049 break;
3050 case Instruction::Mul:
3051 if (!I.isEquality())
3052 break;
3053
3054 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO0->getOperand(1))) {
3055 // a * Cst icmp eq/ne b * Cst --> a & Mask icmp b & Mask
3056 // Mask = -1 >> count-trailing-zeros(Cst).
3057 if (!CI->isZero() && !CI->isOne()) {
3058 const APInt &AP = CI->getValue();
3059 ConstantInt *Mask = ConstantInt::get(
3060 I.getContext(),
3061 APInt::getLowBitsSet(AP.getBitWidth(),
3062 AP.getBitWidth() - AP.countTrailingZeros()));
3063 Value *And1 = Builder->CreateAnd(BO0->getOperand(0), Mask);
3064 Value *And2 = Builder->CreateAnd(BO1->getOperand(0), Mask);
3065 return new ICmpInst(I.getPredicate(), And1, And2);
3066 }
3067 }
3068 break;
3069 case Instruction::UDiv:
3070 case Instruction::LShr:
3071 if (I.isSigned())
3072 break;
3073 LLVM_FALLTHROUGH[[clang::fallthrough]];
3074 case Instruction::SDiv:
3075 case Instruction::AShr:
3076 if (!BO0->isExact() || !BO1->isExact())
3077 break;
3078 return new ICmpInst(I.getPredicate(), BO0->getOperand(0),
3079 BO1->getOperand(0));
3080 case Instruction::Shl: {
3081 bool NUW = BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap();
3082 bool NSW = BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap();
3083 if (!NUW && !NSW)
3084 break;
3085 if (!NSW && I.isSigned())
3086 break;
3087 return new ICmpInst(I.getPredicate(), BO0->getOperand(0),
3088 BO1->getOperand(0));
3089 }
3090 }
3091 }
3092
3093 if (BO0) {
3094 // Transform A & (L - 1) `ult` L --> L != 0
3095 auto LSubOne = m_Add(m_Specific(Op1), m_AllOnes());
3096 auto BitwiseAnd =
3097 m_CombineOr(m_And(m_Value(), LSubOne), m_And(LSubOne, m_Value()));
3098
3099 if (match(BO0, BitwiseAnd) && I.getPredicate() == ICmpInst::ICMP_ULT) {
3100 auto *Zero = Constant::getNullValue(BO0->getType());
3101 return new ICmpInst(ICmpInst::ICMP_NE, Op1, Zero);
3102 }
3103 }
3104
3105 return nullptr;
3106}
3107
3108/// Fold icmp Pred min|max(X, Y), X.
3109static Instruction *foldICmpWithMinMax(ICmpInst &Cmp) {
3110 ICmpInst::Predicate Pred = Cmp.getPredicate();
3111 Value *Op0 = Cmp.getOperand(0);
3112 Value *X = Cmp.getOperand(1);
3113
3114 // Canonicalize minimum or maximum operand to LHS of the icmp.
3115 if (match(X, m_c_SMin(m_Specific(Op0), m_Value())) ||
3116 match(X, m_c_SMax(m_Specific(Op0), m_Value())) ||
3117 match(X, m_c_UMin(m_Specific(Op0), m_Value())) ||
3118 match(X, m_c_UMax(m_Specific(Op0), m_Value()))) {
3119 std::swap(Op0, X);
3120 Pred = Cmp.getSwappedPredicate();
3121 }
3122
3123 Value *Y;
3124 if (match(Op0, m_c_SMin(m_Specific(X), m_Value(Y)))) {
3125 // smin(X, Y) == X --> X s<= Y
3126 // smin(X, Y) s>= X --> X s<= Y
3127 if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SGE)
3128 return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
3129
3130 // smin(X, Y) != X --> X s> Y
3131 // smin(X, Y) s< X --> X s> Y
3132 if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SLT)
3133 return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
3134
3135 // These cases should be handled in InstSimplify:
3136 // smin(X, Y) s<= X --> true
3137 // smin(X, Y) s> X --> false
3138 return nullptr;
3139 }
3140
3141 if (match(Op0, m_c_SMax(m_Specific(X), m_Value(Y)))) {
3142 // smax(X, Y) == X --> X s>= Y
3143 // smax(X, Y) s<= X --> X s>= Y
3144 if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SLE)
3145 return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
3146
3147 // smax(X, Y) != X --> X s< Y
3148 // smax(X, Y) s> X --> X s< Y
3149 if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SGT)
3150 return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
3151
3152 // These cases should be handled in InstSimplify:
3153 // smax(X, Y) s>= X --> true
3154 // smax(X, Y) s< X --> false
3155 return nullptr;
3156 }
3157
3158 if (match(Op0, m_c_UMin(m_Specific(X), m_Value(Y)))) {
3159 // umin(X, Y) == X --> X u<= Y
3160 // umin(X, Y) u>= X --> X u<= Y
3161 if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_UGE)
3162 return new ICmpInst(ICmpInst::ICMP_ULE, X, Y);
3163
3164 // umin(X, Y) != X --> X u> Y
3165 // umin(X, Y) u< X --> X u> Y
3166 if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_ULT)
3167 return new ICmpInst(ICmpInst::ICMP_UGT, X, Y);
3168
3169 // These cases should be handled in InstSimplify:
3170 // umin(X, Y) u<= X --> true
3171 // umin(X, Y) u> X --> false
3172 return nullptr;
3173 }
3174
3175 if (match(Op0, m_c_UMax(m_Specific(X), m_Value(Y)))) {
3176 // umax(X, Y) == X --> X u>= Y
3177 // umax(X, Y) u<= X --> X u>= Y
3178 if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_ULE)
3179 return new ICmpInst(ICmpInst::ICMP_UGE, X, Y);
3180
3181 // umax(X, Y) != X --> X u< Y
3182 // umax(X, Y) u> X --> X u< Y
3183 if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_UGT)
3184 return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
3185
3186 // These cases should be handled in InstSimplify:
3187 // umax(X, Y) u>= X --> true
3188 // umax(X, Y) u< X --> false
3189 return nullptr;
3190 }
3191
3192 return nullptr;
3193}
3194
3195Instruction *InstCombiner::foldICmpEquality(ICmpInst &I) {
3196 if (!I.isEquality())
3197 return nullptr;
3198
3199 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
3200 Value *A, *B, *C, *D;
3201 if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
3202 if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0
3203 Value *OtherVal = A == Op1 ? B : A;
3204 return new ICmpInst(I.getPredicate(), OtherVal,
3205 Constant::getNullValue(A->getType()));
3206 }
3207
3208 if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) {
3209 // A^c1 == C^c2 --> A == C^(c1^c2)
3210 ConstantInt *C1, *C2;
3211 if (match(B, m_ConstantInt(C1)) && match(D, m_ConstantInt(C2)) &&
3212 Op1->hasOneUse()) {
3213 Constant *NC = Builder->getInt(C1->getValue() ^ C2->getValue());
3214 Value *Xor = Builder->CreateXor(C, NC);
3215 return new ICmpInst(I.getPredicate(), A, Xor);
3216 }
3217
3218 // A^B == A^D -> B == D
3219 if (A == C)
3220 return new ICmpInst(I.getPredicate(), B, D);
3221 if (A == D)
3222 return new ICmpInst(I.getPredicate(), B, C);
3223 if (B == C)
3224 return new ICmpInst(I.getPredicate(), A, D);
3225 if (B == D)
3226 return new ICmpInst(I.getPredicate(), A, C);
3227 }
3228 }
3229
3230 if (match(Op1, m_Xor(m_Value(A), m_Value(B))) && (A == Op0 || B == Op0)) {
3231 // A == (A^B) -> B == 0
3232 Value *OtherVal = A == Op0 ? B : A;
3233 return new ICmpInst(I.getPredicate(), OtherVal,
3234 Constant::getNullValue(A->getType()));
3235 }
3236
3237 // (X&Z) == (Y&Z) -> (X^Y) & Z == 0
3238 if (match(Op0, m_OneUse(m_And(m_Value(A), m_Value(B)))) &&
3239 match(Op1, m_OneUse(m_And(m_Value(C), m_Value(D))))) {
3240 Value *X = nullptr, *Y = nullptr, *Z = nullptr;
3241
3242 if (A == C) {
3243 X = B;
3244 Y = D;
3245 Z = A;
3246 } else if (A == D) {
3247 X = B;
3248 Y = C;
3249 Z = A;
3250 } else if (B == C) {
3251 X = A;
3252 Y = D;
3253 Z = B;
3254 } else if (B == D) {
3255 X = A;
3256 Y = C;
3257 Z = B;
3258 }
3259
3260 if (X) { // Build (X^Y) & Z
3261 Op1 = Builder->CreateXor(X, Y);
3262 Op1 = Builder->CreateAnd(Op1, Z);
3263 I.setOperand(0, Op1);
3264 I.setOperand(1, Constant::getNullValue(Op1->getType()));
3265 return &I;
3266 }
3267 }
3268
3269 // Transform (zext A) == (B & (1<<X)-1) --> A == (trunc B)
3270 // and (B & (1<<X)-1) == (zext A) --> A == (trunc B)
3271 ConstantInt *Cst1;
3272 if ((Op0->hasOneUse() && match(Op0, m_ZExt(m_Value(A))) &&
3273 match(Op1, m_And(m_Value(B), m_ConstantInt(Cst1)))) ||
3274 (Op1->hasOneUse() && match(Op0, m_And(m_Value(B), m_ConstantInt(Cst1))) &&
3275 match(Op1, m_ZExt(m_Value(A))))) {
3276 APInt Pow2 = Cst1->getValue() + 1;
3277 if (Pow2.isPowerOf2() && isa<IntegerType>(A->getType()) &&
3278 Pow2.logBase2() == cast<IntegerType>(A->getType())->getBitWidth())
3279 return new ICmpInst(I.getPredicate(), A,
3280 Builder->CreateTrunc(B, A->getType()));
3281 }
3282
3283 // (A >> C) == (B >> C) --> (A^B) u< (1 << C)
3284 // For lshr and ashr pairs.
3285 if ((match(Op0, m_OneUse(m_LShr(m_Value(A), m_ConstantInt(Cst1)))) &&
3286 match(Op1, m_OneUse(m_LShr(m_Value(B), m_Specific(Cst1))))) ||
3287 (match(Op0, m_OneUse(m_AShr(m_Value(A), m_ConstantInt(Cst1)))) &&
3288 match(Op1, m_OneUse(m_AShr(m_Value(B), m_Specific(Cst1)))))) {
3289 unsigned TypeBits = Cst1->getBitWidth();
3290 unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
3291 if (ShAmt < TypeBits && ShAmt != 0) {
3292 ICmpInst::Predicate Pred = I.getPredicate() == ICmpInst::ICMP_NE
3293 ? ICmpInst::ICMP_UGE
3294 : ICmpInst::ICMP_ULT;
3295 Value *Xor = Builder->CreateXor(A, B, I.getName() + ".unshifted");
3296 APInt CmpVal = APInt::getOneBitSet(TypeBits, ShAmt);
3297 return new ICmpInst(Pred, Xor, Builder->getInt(CmpVal));
3298 }
3299 }
3300
3301 // (A << C) == (B << C) --> ((A^B) & (~0U >> C)) == 0
3302 if (match(Op0, m_OneUse(m_Shl(m_Value(A), m_ConstantInt(Cst1)))) &&
3303 match(Op1, m_OneUse(m_Shl(m_Value(B), m_Specific(Cst1))))) {
3304 unsigned TypeBits = Cst1->getBitWidth();
3305 unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
3306 if (ShAmt < TypeBits && ShAmt != 0) {
3307 Value *Xor = Builder->CreateXor(A, B, I.getName() + ".unshifted");
3308 APInt AndVal = APInt::getLowBitsSet(TypeBits, TypeBits - ShAmt);
3309 Value *And = Builder->CreateAnd(Xor, Builder->getInt(AndVal),
3310 I.getName() + ".mask");
3311 return new ICmpInst(I.getPredicate(), And,
3312 Constant::getNullValue(Cst1->getType()));
3313 }
3314 }
3315
3316 // Transform "icmp eq (trunc (lshr(X, cst1)), cst" to
3317 // "icmp (and X, mask), cst"
3318 uint64_t ShAmt = 0;
3319 if (Op0->hasOneUse() &&
3320 match(Op0, m_Trunc(m_OneUse(m_LShr(m_Value(A), m_ConstantInt(ShAmt))))) &&
3321 match(Op1, m_ConstantInt(Cst1)) &&
3322 // Only do this when A has multiple uses. This is most important to do
3323 // when it exposes other optimizations.
3324 !A->hasOneUse()) {
3325 unsigned ASize = cast<IntegerType>(A->getType())->getPrimitiveSizeInBits();
3326
3327 if (ShAmt < ASize) {
3328 APInt MaskV =
3329 APInt::getLowBitsSet(ASize, Op0->getType()->getPrimitiveSizeInBits());
3330 MaskV <<= ShAmt;
3331
3332 APInt CmpV = Cst1->getValue().zext(ASize);
3333 CmpV <<= ShAmt;
3334
3335 Value *Mask = Builder->CreateAnd(A, Builder->getInt(MaskV));
3336 return new ICmpInst(I.getPredicate(), Mask, Builder->getInt(CmpV));
3337 }
3338 }
3339
3340 return nullptr;
3341}
3342
3343/// Handle icmp (cast x to y), (cast/cst). We only handle extending casts so
3344/// far.
3345Instruction *InstCombiner::foldICmpWithCastAndCast(ICmpInst &ICmp) {
3346 const CastInst *LHSCI = cast<CastInst>(ICmp.getOperand(0));
3347 Value *LHSCIOp = LHSCI->getOperand(0);
3348 Type *SrcTy = LHSCIOp->getType();
3349 Type *DestTy = LHSCI->getType();
3350 Value *RHSCIOp;
3351
3352 // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
3353 // integer type is the same size as the pointer type.
3354 if (LHSCI->getOpcode() == Instruction::PtrToInt &&
3355 DL.getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth()) {
3356 Value *RHSOp = nullptr;
3357 if (auto *RHSC = dyn_cast<PtrToIntOperator>(ICmp.getOperand(1))) {
3358 Value *RHSCIOp = RHSC->getOperand(0);
3359 if (RHSCIOp->getType()->getPointerAddressSpace() ==
3360 LHSCIOp->getType()->getPointerAddressSpace()) {
3361 RHSOp = RHSC->getOperand(0);
3362 // If the pointer types don't match, insert a bitcast.
3363 if (LHSCIOp->getType() != RHSOp->getType())
3364 RHSOp = Builder->CreateBitCast(RHSOp, LHSCIOp->getType());
3365 }
3366 } else if (auto *RHSC = dyn_cast<Constant>(ICmp.getOperand(1))) {
3367 RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy);
3368 }
3369
3370 if (RHSOp)
3371 return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSOp);
3372 }
3373
3374 // The code below only handles extension cast instructions, so far.
3375 // Enforce this.
3376 if (LHSCI->getOpcode() != Instruction::ZExt &&
3377 LHSCI->getOpcode() != Instruction::SExt)
3378 return nullptr;
3379
3380 bool isSignedExt = LHSCI->getOpcode() == Instruction::SExt;
3381 bool isSignedCmp = ICmp.isSigned();
3382
3383 if (auto *CI = dyn_cast<CastInst>(ICmp.getOperand(1))) {
3384 // Not an extension from the same type?
3385 RHSCIOp = CI->getOperand(0);
3386 if (RHSCIOp->getType() != LHSCIOp->getType())
3387 return nullptr;
3388
3389 // If the signedness of the two casts doesn't agree (i.e. one is a sext
3390 // and the other is a zext), then we can't handle this.
3391 if (CI->getOpcode() != LHSCI->getOpcode())
3392 return nullptr;
3393
3394 // Deal with equality cases early.
3395 if (ICmp.isEquality())
3396 return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSCIOp);
3397
3398 // A signed comparison of sign extended values simplifies into a
3399 // signed comparison.
3400 if (isSignedCmp && isSignedExt)
3401 return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSCIOp);
3402
3403 // The other three cases all fold into an unsigned comparison.
3404 return new ICmpInst(ICmp.getUnsignedPredicate(), LHSCIOp, RHSCIOp);
3405 }
3406
3407 // If we aren't dealing with a constant on the RHS, exit early.
3408 auto *C = dyn_cast<Constant>(ICmp.getOperand(1));
3409 if (!C)
3410 return nullptr;
3411
3412 // Compute the constant that would happen if we truncated to SrcTy then
3413 // re-extended to DestTy.
3414 Constant *Res1 = ConstantExpr::getTrunc(C, SrcTy);
3415 Constant *Res2 = ConstantExpr::getCast(LHSCI->getOpcode(), Res1, DestTy);
3416
3417 // If the re-extended constant didn't change...
3418 if (Res2 == C) {
3419 // Deal with equality cases early.
3420 if (ICmp.isEquality())
3421 return new ICmpInst(ICmp.getPredicate(), LHSCIOp, Res1);
3422
3423 // A signed comparison of sign extended values simplifies into a
3424 // signed comparison.
3425 if (isSignedExt && isSignedCmp)
3426 return new ICmpInst(ICmp.getPredicate(), LHSCIOp, Res1);
3427
3428 // The other three cases all fold into an unsigned comparison.
3429 return new ICmpInst(ICmp.getUnsignedPredicate(), LHSCIOp, Res1);
3430 }
3431
3432 // The re-extended constant changed, partly changed (in the case of a vector),
3433 // or could not be determined to be equal (in the case of a constant
3434 // expression), so the constant cannot be represented in the shorter type.
3435 // Consequently, we cannot emit a simple comparison.
3436 // All the cases that fold to true or false will have already been handled
3437 // by SimplifyICmpInst, so only deal with the tricky case.
3438
3439 if (isSignedCmp || !isSignedExt || !isa<ConstantInt>(C))
3440 return nullptr;
3441
3442 // Evaluate the comparison for LT (we invert for GT below). LE and GE cases
3443 // should have been folded away previously and not enter in here.
3444
3445 // We're performing an unsigned comp with a sign extended value.
3446 // This is true if the input is >= 0. [aka >s -1]
3447 Constant *NegOne = Constant::getAllOnesValue(SrcTy);
3448 Value *Result = Builder->CreateICmpSGT(LHSCIOp, NegOne, ICmp.getName());
3449
3450 // Finally, return the value computed.
3451 if (ICmp.getPredicate() == ICmpInst::ICMP_ULT)
3452 return replaceInstUsesWith(ICmp, Result);
3453
3454 assert(ICmp.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!")((ICmp.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!"
) ? static_cast<void> (0) : __assert_fail ("ICmp.getPredicate() == ICmpInst::ICMP_UGT && \"ICmp should be folded!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 3454, __PRETTY_FUNCTION__))
;
3455 return BinaryOperator::CreateNot(Result);
3456}
3457
3458bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
3459 Value *RHS, Instruction &OrigI,
3460 Value *&Result, Constant *&Overflow) {
3461 if (OrigI.isCommutative() && isa<Constant>(LHS) && !isa<Constant>(RHS))
3462 std::swap(LHS, RHS);
3463
3464 auto SetResult = [&](Value *OpResult, Constant *OverflowVal, bool ReuseName) {
3465 Result = OpResult;
3466 Overflow = OverflowVal;
3467 if (ReuseName)
3468 Result->takeName(&OrigI);
3469 return true;
3470 };
3471
3472 // If the overflow check was an add followed by a compare, the insertion point
3473 // may be pointing to the compare. We want to insert the new instructions
3474 // before the add in case there are uses of the add between the add and the
3475 // compare.
3476 Builder->SetInsertPoint(&OrigI);
3477
3478 switch (OCF) {
3479 case OCF_INVALID:
3480 llvm_unreachable("bad overflow check kind!")::llvm::llvm_unreachable_internal("bad overflow check kind!",
"/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 3480)
;
3481
3482 case OCF_UNSIGNED_ADD: {
3483 OverflowResult OR = computeOverflowForUnsignedAdd(LHS, RHS, &OrigI);
3484 if (OR == OverflowResult::NeverOverflows)
3485 return SetResult(Builder->CreateNUWAdd(LHS, RHS), Builder->getFalse(),
3486 true);
3487
3488 if (OR == OverflowResult::AlwaysOverflows)
3489 return SetResult(Builder->CreateAdd(LHS, RHS), Builder->getTrue(), true);
3490
3491 // Fall through uadd into sadd
3492 LLVM_FALLTHROUGH[[clang::fallthrough]];
3493 }
3494 case OCF_SIGNED_ADD: {
3495 // X + 0 -> {X, false}
3496 if (match(RHS, m_Zero()))
3497 return SetResult(LHS, Builder->getFalse(), false);
3498
3499 // We can strength reduce this signed add into a regular add if we can prove
3500 // that it will never overflow.
3501 if (OCF == OCF_SIGNED_ADD)
3502 if (WillNotOverflowSignedAdd(LHS, RHS, OrigI))
3503 return SetResult(Builder->CreateNSWAdd(LHS, RHS), Builder->getFalse(),
3504 true);
3505 break;
3506 }
3507
3508 case OCF_UNSIGNED_SUB:
3509 case OCF_SIGNED_SUB: {
3510 // X - 0 -> {X, false}
3511 if (match(RHS, m_Zero()))
3512 return SetResult(LHS, Builder->getFalse(), false);
3513
3514 if (OCF == OCF_SIGNED_SUB) {
3515 if (WillNotOverflowSignedSub(LHS, RHS, OrigI))
3516 return SetResult(Builder->CreateNSWSub(LHS, RHS), Builder->getFalse(),
3517 true);
3518 } else {
3519 if (WillNotOverflowUnsignedSub(LHS, RHS, OrigI))
3520 return SetResult(Builder->CreateNUWSub(LHS, RHS), Builder->getFalse(),
3521 true);
3522 }
3523 break;
3524 }
3525
3526 case OCF_UNSIGNED_MUL: {
3527 OverflowResult OR = computeOverflowForUnsignedMul(LHS, RHS, &OrigI);
3528 if (OR == OverflowResult::NeverOverflows)
3529 return SetResult(Builder->CreateNUWMul(LHS, RHS), Builder->getFalse(),
3530 true);
3531 if (OR == OverflowResult::AlwaysOverflows)
3532 return SetResult(Builder->CreateMul(LHS, RHS), Builder->getTrue(), true);
3533 LLVM_FALLTHROUGH[[clang::fallthrough]];
3534 }
3535 case OCF_SIGNED_MUL:
3536 // X * undef -> undef
3537 if (isa<UndefValue>(RHS))
3538 return SetResult(RHS, UndefValue::get(Builder->getInt1Ty()), false);
3539
3540 // X * 0 -> {0, false}
3541 if (match(RHS, m_Zero()))
3542 return SetResult(RHS, Builder->getFalse(), false);
3543
3544 // X * 1 -> {X, false}
3545 if (match(RHS, m_One()))
3546 return SetResult(LHS, Builder->getFalse(), false);
3547
3548 if (OCF == OCF_SIGNED_MUL)
3549 if (WillNotOverflowSignedMul(LHS, RHS, OrigI))
3550 return SetResult(Builder->CreateNSWMul(LHS, RHS), Builder->getFalse(),
3551 true);
3552 break;
3553 }
3554
3555 return false;
3556}
3557
3558/// \brief Recognize and process idiom involving test for multiplication
3559/// overflow.
3560///
3561/// The caller has matched a pattern of the form:
3562/// I = cmp u (mul(zext A, zext B), V
3563/// The function checks if this is a test for overflow and if so replaces
3564/// multiplication with call to 'mul.with.overflow' intrinsic.
3565///
3566/// \param I Compare instruction.
3567/// \param MulVal Result of 'mult' instruction. It is one of the arguments of
3568/// the compare instruction. Must be of integer type.
3569/// \param OtherVal The other argument of compare instruction.
3570/// \returns Instruction which must replace the compare instruction, NULL if no
3571/// replacement required.
3572static Instruction *processUMulZExtIdiom(ICmpInst &I, Value *MulVal,
3573 Value *OtherVal, InstCombiner &IC) {
3574 // Don't bother doing this transformation for pointers, don't do it for
3575 // vectors.
3576 if (!isa<IntegerType>(MulVal->getType()))
3577 return nullptr;
3578
3579 assert(I.getOperand(0) == MulVal || I.getOperand(1) == MulVal)((I.getOperand(0) == MulVal || I.getOperand(1) == MulVal) ? static_cast
<void> (0) : __assert_fail ("I.getOperand(0) == MulVal || I.getOperand(1) == MulVal"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 3579, __PRETTY_FUNCTION__))
;
3580 assert(I.getOperand(0) == OtherVal || I.getOperand(1) == OtherVal)((I.getOperand(0) == OtherVal || I.getOperand(1) == OtherVal)
? static_cast<void> (0) : __assert_fail ("I.getOperand(0) == OtherVal || I.getOperand(1) == OtherVal"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 3580, __PRETTY_FUNCTION__))
;
3581 auto *MulInstr = dyn_cast<Instruction>(MulVal);
3582 if (!MulInstr)
3583 return nullptr;
3584 assert(MulInstr->getOpcode() == Instruction::Mul)((MulInstr->getOpcode() == Instruction::Mul) ? static_cast
<void> (0) : __assert_fail ("MulInstr->getOpcode() == Instruction::Mul"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 3584, __PRETTY_FUNCTION__))
;
3585
3586 auto *LHS = cast<ZExtOperator>(MulInstr->getOperand(0)),
3587 *RHS = cast<ZExtOperator>(MulInstr->getOperand(1));
3588 assert(LHS->getOpcode() == Instruction::ZExt)((LHS->getOpcode() == Instruction::ZExt) ? static_cast<
void> (0) : __assert_fail ("LHS->getOpcode() == Instruction::ZExt"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 3588, __PRETTY_FUNCTION__))
;
3589 assert(RHS->getOpcode() == Instruction::ZExt)((RHS->getOpcode() == Instruction::ZExt) ? static_cast<
void> (0) : __assert_fail ("RHS->getOpcode() == Instruction::ZExt"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 3589, __PRETTY_FUNCTION__))
;
3590 Value *A = LHS->getOperand(0), *B = RHS->getOperand(0);
3591
3592 // Calculate type and width of the result produced by mul.with.overflow.
3593 Type *TyA = A->getType(), *TyB = B->getType();
3594 unsigned WidthA = TyA->getPrimitiveSizeInBits(),
3595 WidthB = TyB->getPrimitiveSizeInBits();
3596 unsigned MulWidth;
3597 Type *MulType;
3598 if (WidthB > WidthA) {
3599 MulWidth = WidthB;
3600 MulType = TyB;
3601 } else {
3602 MulWidth = WidthA;
3603 MulType = TyA;
3604 }
3605
3606 // In order to replace the original mul with a narrower mul.with.overflow,
3607 // all uses must ignore upper bits of the product. The number of used low
3608 // bits must be not greater than the width of mul.with.overflow.
3609 if (MulVal->hasNUsesOrMore(2))
3610 for (User *U : MulVal->users()) {
3611 if (U == &I)
3612 continue;
3613 if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
3614 // Check if truncation ignores bits above MulWidth.
3615 unsigned TruncWidth = TI->getType()->getPrimitiveSizeInBits();
3616 if (TruncWidth > MulWidth)
3617 return nullptr;
3618 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
3619 // Check if AND ignores bits above MulWidth.
3620 if (BO->getOpcode() != Instruction::And)
3621 return nullptr;
3622 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1))) {
3623 const APInt &CVal = CI->getValue();
3624 if (CVal.getBitWidth() - CVal.countLeadingZeros() > MulWidth)
3625 return nullptr;
3626 }
3627 } else {
3628 // Other uses prohibit this transformation.
3629 return nullptr;
3630 }
3631 }
3632
3633 // Recognize patterns
3634 switch (I.getPredicate()) {
3635 case ICmpInst::ICMP_EQ:
3636 case ICmpInst::ICMP_NE:
3637 // Recognize pattern:
3638 // mulval = mul(zext A, zext B)
3639 // cmp eq/neq mulval, zext trunc mulval
3640 if (ZExtInst *Zext = dyn_cast<ZExtInst>(OtherVal))
3641 if (Zext->hasOneUse()) {
3642 Value *ZextArg = Zext->getOperand(0);
3643 if (TruncInst *Trunc = dyn_cast<TruncInst>(ZextArg))
3644 if (Trunc->getType()->getPrimitiveSizeInBits() == MulWidth)
3645 break; //Recognized
3646 }
3647
3648 // Recognize pattern:
3649 // mulval = mul(zext A, zext B)
3650 // cmp eq/neq mulval, and(mulval, mask), mask selects low MulWidth bits.
3651 ConstantInt *CI;
3652 Value *ValToMask;
3653 if (match(OtherVal, m_And(m_Value(ValToMask), m_ConstantInt(CI)))) {
3654 if (ValToMask != MulVal)
3655 return nullptr;
3656 const APInt &CVal = CI->getValue() + 1;
3657 if (CVal.isPowerOf2()) {
3658 unsigned MaskWidth = CVal.logBase2();
3659 if (MaskWidth == MulWidth)
3660 break; // Recognized
3661 }
3662 }
3663 return nullptr;
3664
3665 case ICmpInst::ICMP_UGT:
3666 // Recognize pattern:
3667 // mulval = mul(zext A, zext B)
3668 // cmp ugt mulval, max
3669 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3670 APInt MaxVal = APInt::getMaxValue(MulWidth);
3671 MaxVal = MaxVal.zext(CI->getBitWidth());
3672 if (MaxVal.eq(CI->getValue()))
3673 break; // Recognized
3674 }
3675 return nullptr;
3676
3677 case ICmpInst::ICMP_UGE:
3678 // Recognize pattern:
3679 // mulval = mul(zext A, zext B)
3680 // cmp uge mulval, max+1
3681 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3682 APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
3683 if (MaxVal.eq(CI->getValue()))
3684 break; // Recognized
3685 }
3686 return nullptr;
3687
3688 case ICmpInst::ICMP_ULE:
3689 // Recognize pattern:
3690 // mulval = mul(zext A, zext B)
3691 // cmp ule mulval, max
3692 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3693 APInt MaxVal = APInt::getMaxValue(MulWidth);
3694 MaxVal = MaxVal.zext(CI->getBitWidth());
3695 if (MaxVal.eq(CI->getValue()))
3696 break; // Recognized
3697 }
3698 return nullptr;
3699
3700 case ICmpInst::ICMP_ULT:
3701 // Recognize pattern:
3702 // mulval = mul(zext A, zext B)
3703 // cmp ule mulval, max + 1
3704 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3705 APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
3706 if (MaxVal.eq(CI->getValue()))
3707 break; // Recognized
3708 }
3709 return nullptr;
3710
3711 default:
3712 return nullptr;
3713 }
3714
3715 InstCombiner::BuilderTy *Builder = IC.Builder;
3716 Builder->SetInsertPoint(MulInstr);
3717
3718 // Replace: mul(zext A, zext B) --> mul.with.overflow(A, B)
3719 Value *MulA = A, *MulB = B;
3720 if (WidthA < MulWidth)
3721 MulA = Builder->CreateZExt(A, MulType);
3722 if (WidthB < MulWidth)
3723 MulB = Builder->CreateZExt(B, MulType);
3724 Value *F = Intrinsic::getDeclaration(I.getModule(),
3725 Intrinsic::umul_with_overflow, MulType);
3726 CallInst *Call = Builder->CreateCall(F, {MulA, MulB}, "umul");
3727 IC.Worklist.Add(MulInstr);
3728
3729 // If there are uses of mul result other than the comparison, we know that
3730 // they are truncation or binary AND. Change them to use result of
3731 // mul.with.overflow and adjust properly mask/size.
3732 if (MulVal->hasNUsesOrMore(2)) {
3733 Value *Mul = Builder->CreateExtractValue(Call, 0, "umul.value");
3734 for (User *U : MulVal->users()) {
3735 if (U == &I || U == OtherVal)
3736 continue;
3737 if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
3738 if (TI->getType()->getPrimitiveSizeInBits() == MulWidth)
3739 IC.replaceInstUsesWith(*TI, Mul);
3740 else
3741 TI->setOperand(0, Mul);
3742 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
3743 assert(BO->getOpcode() == Instruction::And)((BO->getOpcode() == Instruction::And) ? static_cast<void
> (0) : __assert_fail ("BO->getOpcode() == Instruction::And"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 3743, __PRETTY_FUNCTION__))
;
3744 // Replace (mul & mask) --> zext (mul.with.overflow & short_mask)
3745 ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1));
3746 APInt ShortMask = CI->getValue().trunc(MulWidth);
3747 Value *ShortAnd = Builder->CreateAnd(Mul, ShortMask);
3748 Instruction *Zext =
3749 cast<Instruction>(Builder->CreateZExt(ShortAnd, BO->getType()));
3750 IC.Worklist.Add(Zext);
3751 IC.replaceInstUsesWith(*BO, Zext);
3752 } else {
3753 llvm_unreachable("Unexpected Binary operation")::llvm::llvm_unreachable_internal("Unexpected Binary operation"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 3753)
;
3754 }
3755 IC.Worklist.Add(cast<Instruction>(U));
3756 }
3757 }
3758 if (isa<Instruction>(OtherVal))
3759 IC.Worklist.Add(cast<Instruction>(OtherVal));
3760
3761 // The original icmp gets replaced with the overflow value, maybe inverted
3762 // depending on predicate.
3763 bool Inverse = false;
3764 switch (I.getPredicate()) {
3765 case ICmpInst::ICMP_NE:
3766 break;
3767 case ICmpInst::ICMP_EQ:
3768 Inverse = true;
3769 break;
3770 case ICmpInst::ICMP_UGT:
3771 case ICmpInst::ICMP_UGE:
3772 if (I.getOperand(0) == MulVal)
3773 break;
3774 Inverse = true;
3775 break;
3776 case ICmpInst::ICMP_ULT:
3777 case ICmpInst::ICMP_ULE:
3778 if (I.getOperand(1) == MulVal)
3779 break;
3780 Inverse = true;
3781 break;
3782 default:
3783 llvm_unreachable("Unexpected predicate")::llvm::llvm_unreachable_internal("Unexpected predicate", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 3783)
;
3784 }
3785 if (Inverse) {
3786 Value *Res = Builder->CreateExtractValue(Call, 1);
3787 return BinaryOperator::CreateNot(Res);
3788 }
3789
3790 return ExtractValueInst::Create(Call, 1);
3791}
3792
3793/// When performing a comparison against a constant, it is possible that not all
3794/// the bits in the LHS are demanded. This helper method computes the mask that
3795/// IS demanded.
3796static APInt getDemandedBitsLHSMask(ICmpInst &I, unsigned BitWidth,
3797 bool isSignCheck) {
3798 if (isSignCheck)
3799 return APInt::getSignMask(BitWidth);
3800
3801 ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand(1));
3802 if (!CI) return APInt::getAllOnesValue(BitWidth);
3803 const APInt &RHS = CI->getValue();
3804
3805 switch (I.getPredicate()) {
3806 // For a UGT comparison, we don't care about any bits that
3807 // correspond to the trailing ones of the comparand. The value of these
3808 // bits doesn't impact the outcome of the comparison, because any value
3809 // greater than the RHS must differ in a bit higher than these due to carry.
3810 case ICmpInst::ICMP_UGT: {
3811 unsigned trailingOnes = RHS.countTrailingOnes();
3812 return APInt::getBitsSetFrom(BitWidth, trailingOnes);
3813 }
3814
3815 // Similarly, for a ULT comparison, we don't care about the trailing zeros.
3816 // Any value less than the RHS must differ in a higher bit because of carries.
3817 case ICmpInst::ICMP_ULT: {
3818 unsigned trailingZeros = RHS.countTrailingZeros();
3819 return APInt::getBitsSetFrom(BitWidth, trailingZeros);
3820 }
3821
3822 default:
3823 return APInt::getAllOnesValue(BitWidth);
3824 }
3825}
3826
3827/// \brief Check if the order of \p Op0 and \p Op1 as operand in an ICmpInst
3828/// should be swapped.
3829/// The decision is based on how many times these two operands are reused
3830/// as subtract operands and their positions in those instructions.
3831/// The rational is that several architectures use the same instruction for
3832/// both subtract and cmp, thus it is better if the order of those operands
3833/// match.
3834/// \return true if Op0 and Op1 should be swapped.
3835static bool swapMayExposeCSEOpportunities(const Value * Op0,
3836 const Value * Op1) {
3837 // Filter out pointer value as those cannot appears directly in subtract.
3838 // FIXME: we may want to go through inttoptrs or bitcasts.
3839 if (Op0->getType()->isPointerTy())
3840 return false;
3841 // Count every uses of both Op0 and Op1 in a subtract.
3842 // Each time Op0 is the first operand, count -1: swapping is bad, the
3843 // subtract has already the same layout as the compare.
3844 // Each time Op0 is the second operand, count +1: swapping is good, the
3845 // subtract has a different layout as the compare.
3846 // At the end, if the benefit is greater than 0, Op0 should come second to
3847 // expose more CSE opportunities.
3848 int GlobalSwapBenefits = 0;
3849 for (const User *U : Op0->users()) {
3850 const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(U);
3851 if (!BinOp || BinOp->getOpcode() != Instruction::Sub)
3852 continue;
3853 // If Op0 is the first argument, this is not beneficial to swap the
3854 // arguments.
3855 int LocalSwapBenefits = -1;
3856 unsigned Op1Idx = 1;
3857 if (BinOp->getOperand(Op1Idx) == Op0) {
3858 Op1Idx = 0;
3859 LocalSwapBenefits = 1;
3860 }
3861 if (BinOp->getOperand(Op1Idx) != Op1)
3862 continue;
3863 GlobalSwapBenefits += LocalSwapBenefits;
3864 }
3865 return GlobalSwapBenefits > 0;
3866}
3867
3868/// \brief Check that one use is in the same block as the definition and all
3869/// other uses are in blocks dominated by a given block.
3870///
3871/// \param DI Definition
3872/// \param UI Use
3873/// \param DB Block that must dominate all uses of \p DI outside
3874/// the parent block
3875/// \return true when \p UI is the only use of \p DI in the parent block
3876/// and all other uses of \p DI are in blocks dominated by \p DB.
3877///
3878bool InstCombiner::dominatesAllUses(const Instruction *DI,
3879 const Instruction *UI,
3880 const BasicBlock *DB) const {
3881 assert(DI && UI && "Instruction not defined\n")((DI && UI && "Instruction not defined\n") ? static_cast
<void> (0) : __assert_fail ("DI && UI && \"Instruction not defined\\n\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 3881, __PRETTY_FUNCTION__))
;
3882 // Ignore incomplete definitions.
3883 if (!DI->getParent())
3884 return false;
3885 // DI and UI must be in the same block.
3886 if (DI->getParent() != UI->getParent())
3887 return false;
3888 // Protect from self-referencing blocks.
3889 if (DI->getParent() == DB)
3890 return false;
3891 for (const User *U : DI->users()) {
3892 auto *Usr = cast<Instruction>(U);
3893 if (Usr != UI && !DT.dominates(DB, Usr->getParent()))
3894 return false;
3895 }
3896 return true;
3897}
3898
3899/// Return true when the instruction sequence within a block is select-cmp-br.
3900static bool isChainSelectCmpBranch(const SelectInst *SI) {
3901 const BasicBlock *BB = SI->getParent();
3902 if (!BB)
3903 return false;
3904 auto *BI = dyn_cast_or_null<BranchInst>(BB->getTerminator());
3905 if (!BI || BI->getNumSuccessors() != 2)
3906 return false;
3907 auto *IC = dyn_cast<ICmpInst>(BI->getCondition());
3908 if (!IC || (IC->getOperand(0) != SI && IC->getOperand(1) != SI))
3909 return false;
3910 return true;
3911}
3912
3913/// \brief True when a select result is replaced by one of its operands
3914/// in select-icmp sequence. This will eventually result in the elimination
3915/// of the select.
3916///
3917/// \param SI Select instruction
3918/// \param Icmp Compare instruction
3919/// \param SIOpd Operand that replaces the select
3920///
3921/// Notes:
3922/// - The replacement is global and requires dominator information
3923/// - The caller is responsible for the actual replacement
3924///
3925/// Example:
3926///
3927/// entry:
3928/// %4 = select i1 %3, %C* %0, %C* null
3929/// %5 = icmp eq %C* %4, null
3930/// br i1 %5, label %9, label %7
3931/// ...
3932/// ; <label>:7 ; preds = %entry
3933/// %8 = getelementptr inbounds %C* %4, i64 0, i32 0
3934/// ...
3935///
3936/// can be transformed to
3937///
3938/// %5 = icmp eq %C* %0, null
3939/// %6 = select i1 %3, i1 %5, i1 true
3940/// br i1 %6, label %9, label %7
3941/// ...
3942/// ; <label>:7 ; preds = %entry
3943/// %8 = getelementptr inbounds %C* %0, i64 0, i32 0 // replace by %0!
3944///
3945/// Similar when the first operand of the select is a constant or/and
3946/// the compare is for not equal rather than equal.
3947///
3948/// NOTE: The function is only called when the select and compare constants
3949/// are equal, the optimization can work only for EQ predicates. This is not a
3950/// major restriction since a NE compare should be 'normalized' to an equal
3951/// compare, which usually happens in the combiner and test case
3952/// select-cmp-br.ll checks for it.
3953bool InstCombiner::replacedSelectWithOperand(SelectInst *SI,
3954 const ICmpInst *Icmp,
3955 const unsigned SIOpd) {
3956 assert((SIOpd == 1 || SIOpd == 2) && "Invalid select operand!")(((SIOpd == 1 || SIOpd == 2) && "Invalid select operand!"
) ? static_cast<void> (0) : __assert_fail ("(SIOpd == 1 || SIOpd == 2) && \"Invalid select operand!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 3956, __PRETTY_FUNCTION__))
;
3957 if (isChainSelectCmpBranch(SI) && Icmp->getPredicate() == ICmpInst::ICMP_EQ) {
3958 BasicBlock *Succ = SI->getParent()->getTerminator()->getSuccessor(1);
3959 // The check for the single predecessor is not the best that can be
3960 // done. But it protects efficiently against cases like when SI's
3961 // home block has two successors, Succ and Succ1, and Succ1 predecessor
3962 // of Succ. Then SI can't be replaced by SIOpd because the use that gets
3963 // replaced can be reached on either path. So the uniqueness check
3964 // guarantees that the path all uses of SI (outside SI's parent) are on
3965 // is disjoint from all other paths out of SI. But that information
3966 // is more expensive to compute, and the trade-off here is in favor
3967 // of compile-time. It should also be noticed that we check for a single
3968 // predecessor and not only uniqueness. This to handle the situation when
3969 // Succ and Succ1 points to the same basic block.
3970 if (Succ->getSinglePredecessor() && dominatesAllUses(SI, Icmp, Succ)) {
3971 NumSel++;
3972 SI->replaceUsesOutsideBlock(SI->getOperand(SIOpd), SI->getParent());
3973 return true;
3974 }
3975 }
3976 return false;
3977}
3978
3979/// Try to fold the comparison based on range information we can get by checking
3980/// whether bits are known to be zero or one in the inputs.
3981Instruction *InstCombiner::foldICmpUsingKnownBits(ICmpInst &I) {
3982 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
3983 Type *Ty = Op0->getType();
3984 ICmpInst::Predicate Pred = I.getPredicate();
3985
3986 // Get scalar or pointer size.
3987 unsigned BitWidth = Ty->isIntOrIntVectorTy()
3988 ? Ty->getScalarSizeInBits()
3989 : DL.getTypeSizeInBits(Ty->getScalarType());
3990
3991 if (!BitWidth)
3992 return nullptr;
3993
3994 // If this is a normal comparison, it demands all bits. If it is a sign bit
3995 // comparison, it only demands the sign bit.
3996 bool IsSignBit = false;
3997 const APInt *CmpC;
3998 if (match(Op1, m_APInt(CmpC))) {
3999 bool UnusedBit;
4000 IsSignBit = isSignBitCheck(Pred, *CmpC, UnusedBit);
4001 }
4002
4003 KnownBits Op0Known(BitWidth);
4004 KnownBits Op1Known(BitWidth);
4005
4006 if (SimplifyDemandedBits(&I, 0,
4007 getDemandedBitsLHSMask(I, BitWidth, IsSignBit),
4008 Op0Known, 0))
4009 return &I;
4010
4011 if (SimplifyDemandedBits(&I, 1, APInt::getAllOnesValue(BitWidth),
4012 Op1Known, 0))
4013 return &I;
4014
4015 // Given the known and unknown bits, compute a range that the LHS could be
4016 // in. Compute the Min, Max and RHS values based on the known bits. For the
4017 // EQ and NE we use unsigned values.
4018 APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0);
4019 APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0);
4020 if (I.isSigned()) {
4021 computeSignedMinMaxValuesFromKnownBits(Op0Known, Op0Min, Op0Max);
4022 computeSignedMinMaxValuesFromKnownBits(Op1Known, Op1Min, Op1Max);
4023 } else {
4024 computeUnsignedMinMaxValuesFromKnownBits(Op0Known, Op0Min, Op0Max);
4025 computeUnsignedMinMaxValuesFromKnownBits(Op1Known, Op1Min, Op1Max);
4026 }
4027
4028 // If Min and Max are known to be the same, then SimplifyDemandedBits
4029 // figured out that the LHS is a constant. Constant fold this now, so that
4030 // code below can assume that Min != Max.
4031 if (!isa<Constant>(Op0) && Op0Min == Op0Max)
4032 return new ICmpInst(Pred, ConstantInt::get(Op0->getType(), Op0Min), Op1);
4033 if (!isa<Constant>(Op1) && Op1Min == Op1Max)
4034 return new ICmpInst(Pred, Op0, ConstantInt::get(Op1->getType(), Op1Min));
4035
4036 // Based on the range information we know about the LHS, see if we can
4037 // simplify this comparison. For example, (x&4) < 8 is always true.
4038 switch (Pred) {
4039 default:
4040 llvm_unreachable("Unknown icmp opcode!")::llvm::llvm_unreachable_internal("Unknown icmp opcode!", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 4040)
;
4041 case ICmpInst::ICMP_EQ:
4042 case ICmpInst::ICMP_NE: {
4043 if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) {
4044 return Pred == CmpInst::ICMP_EQ
4045 ? replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()))
4046 : replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4047 }
4048
4049 // If all bits are known zero except for one, then we know at most one bit
4050 // is set. If the comparison is against zero, then this is a check to see if
4051 // *that* bit is set.
4052 APInt Op0KnownZeroInverted = ~Op0Known.Zero;
4053 if (~Op1Known.Zero == 0) {
4054 // If the LHS is an AND with the same constant, look through it.
4055 Value *LHS = nullptr;
4056 const APInt *LHSC;
4057 if (!match(Op0, m_And(m_Value(LHS), m_APInt(LHSC))) ||
4058 *LHSC != Op0KnownZeroInverted)
4059 LHS = Op0;
4060
4061 Value *X;
4062 if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
4063 APInt ValToCheck = Op0KnownZeroInverted;
4064 Type *XTy = X->getType();
4065 if (ValToCheck.isPowerOf2()) {
4066 // ((1 << X) & 8) == 0 -> X != 3
4067 // ((1 << X) & 8) != 0 -> X == 3
4068 auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
4069 auto NewPred = ICmpInst::getInversePredicate(Pred);
4070 return new ICmpInst(NewPred, X, CmpC);
4071 } else if ((++ValToCheck).isPowerOf2()) {
4072 // ((1 << X) & 7) == 0 -> X >= 3
4073 // ((1 << X) & 7) != 0 -> X < 3
4074 auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
4075 auto NewPred =
4076 Pred == CmpInst::ICMP_EQ ? CmpInst::ICMP_UGE : CmpInst::ICMP_ULT;
4077 return new ICmpInst(NewPred, X, CmpC);
4078 }
4079 }
4080
4081 // Check if the LHS is 8 >>u x and the result is a power of 2 like 1.
4082 const APInt *CI;
4083 if (Op0KnownZeroInverted == 1 &&
4084 match(LHS, m_LShr(m_Power2(CI), m_Value(X)))) {
4085 // ((8 >>u X) & 1) == 0 -> X != 3
4086 // ((8 >>u X) & 1) != 0 -> X == 3
4087 unsigned CmpVal = CI->countTrailingZeros();
4088 auto NewPred = ICmpInst::getInversePredicate(Pred);
4089 return new ICmpInst(NewPred, X, ConstantInt::get(X->getType(), CmpVal));
4090 }
4091 }
4092 break;
4093 }
4094 case ICmpInst::ICMP_ULT: {
4095 if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B)
4096 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4097 if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B)
4098 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4099 if (Op1Min == Op0Max) // A <u B -> A != B if max(A) == min(B)
4100 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4101
4102 const APInt *CmpC;
4103 if (match(Op1, m_APInt(CmpC))) {
4104 // A <u C -> A == C-1 if min(A)+1 == C
4105 if (Op1Max == Op0Min + 1) {
4106 Constant *CMinus1 = ConstantInt::get(Op0->getType(), *CmpC - 1);
4107 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, CMinus1);
4108 }
4109 }
4110 break;
4111 }
4112 case ICmpInst::ICMP_UGT: {
4113 if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B)
4114 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4115
4116 if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B)
4117 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4118
4119 if (Op1Max == Op0Min) // A >u B -> A != B if min(A) == max(B)
4120 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4121
4122 const APInt *CmpC;
4123 if (match(Op1, m_APInt(CmpC))) {
4124 // A >u C -> A == C+1 if max(a)-1 == C
4125 if (*CmpC == Op0Max - 1)
4126 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4127 ConstantInt::get(Op1->getType(), *CmpC + 1));
4128 }
4129 break;
4130 }
4131 case ICmpInst::ICMP_SLT:
4132 if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C)
4133 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4134 if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C)
4135 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4136 if (Op1Min == Op0Max) // A <s B -> A != B if max(A) == min(B)
4137 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4138 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
4139 if (Op1Max == Op0Min + 1) // A <s C -> A == C-1 if min(A)+1 == C
4140 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4141 Builder->getInt(CI->getValue() - 1));
4142 }
4143 break;
4144 case ICmpInst::ICMP_SGT:
4145 if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B)
4146 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4147 if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B)
4148 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4149
4150 if (Op1Max == Op0Min) // A >s B -> A != B if min(A) == max(B)
4151 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4152 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
4153 if (Op1Min == Op0Max - 1) // A >s C -> A == C+1 if max(A)-1 == C
4154 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4155 Builder->getInt(CI->getValue() + 1));
4156 }
4157 break;
4158 case ICmpInst::ICMP_SGE:
4159 assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!")((!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!"
) ? static_cast<void> (0) : __assert_fail ("!isa<ConstantInt>(Op1) && \"ICMP_SGE with ConstantInt not folded!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 4159, __PRETTY_FUNCTION__))
;
4160 if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B)
4161 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4162 if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B)
4163 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4164 break;
4165 case ICmpInst::ICMP_SLE:
4166 assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!")((!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!"
) ? static_cast<void> (0) : __assert_fail ("!isa<ConstantInt>(Op1) && \"ICMP_SLE with ConstantInt not folded!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 4166, __PRETTY_FUNCTION__))
;
4167 if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B)
4168 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4169 if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B)
4170 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4171 break;
4172 case ICmpInst::ICMP_UGE:
4173 assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!")((!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!"
) ? static_cast<void> (0) : __assert_fail ("!isa<ConstantInt>(Op1) && \"ICMP_UGE with ConstantInt not folded!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 4173, __PRETTY_FUNCTION__))
;
4174 if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B)
4175 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4176 if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B)
4177 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4178 break;
4179 case ICmpInst::ICMP_ULE:
4180 assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!")((!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!"
) ? static_cast<void> (0) : __assert_fail ("!isa<ConstantInt>(Op1) && \"ICMP_ULE with ConstantInt not folded!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 4180, __PRETTY_FUNCTION__))
;
4181 if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B)
4182 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4183 if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B)
4184 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4185 break;
4186 }
4187
4188 // Turn a signed comparison into an unsigned one if both operands are known to
4189 // have the same sign.
4190 if (I.isSigned() &&
4191 ((Op0Known.Zero.isNegative() && Op1Known.Zero.isNegative()) ||
4192 (Op0Known.One.isNegative() && Op1Known.One.isNegative())))
4193 return new ICmpInst(I.getUnsignedPredicate(), Op0, Op1);
4194
4195 return nullptr;
4196}
4197
4198/// If we have an icmp le or icmp ge instruction with a constant operand, turn
4199/// it into the appropriate icmp lt or icmp gt instruction. This transform
4200/// allows them to be folded in visitICmpInst.
4201static ICmpInst *canonicalizeCmpWithConstant(ICmpInst &I) {
4202 ICmpInst::Predicate Pred = I.getPredicate();
4203 if (Pred != ICmpInst::ICMP_SLE && Pred != ICmpInst::ICMP_SGE &&
4204 Pred != ICmpInst::ICMP_ULE && Pred != ICmpInst::ICMP_UGE)
4205 return nullptr;
4206
4207 Value *Op0 = I.getOperand(0);
4208 Value *Op1 = I.getOperand(1);
4209 auto *Op1C = dyn_cast<Constant>(Op1);
4210 if (!Op1C)
4211 return nullptr;
4212
4213 // Check if the constant operand can be safely incremented/decremented without
4214 // overflowing/underflowing. For scalars, SimplifyICmpInst has already handled
4215 // the edge cases for us, so we just assert on them. For vectors, we must
4216 // handle the edge cases.
4217 Type *Op1Type = Op1->getType();
4218 bool IsSigned = I.isSigned();
4219 bool IsLE = (Pred == ICmpInst::ICMP_SLE || Pred == ICmpInst::ICMP_ULE);
4220 auto *CI = dyn_cast<ConstantInt>(Op1C);
4221 if (CI) {
4222 // A <= MAX -> TRUE ; A >= MIN -> TRUE
4223 assert(IsLE ? !CI->isMaxValue(IsSigned) : !CI->isMinValue(IsSigned))((IsLE ? !CI->isMaxValue(IsSigned) : !CI->isMinValue(IsSigned
)) ? static_cast<void> (0) : __assert_fail ("IsLE ? !CI->isMaxValue(IsSigned) : !CI->isMinValue(IsSigned)"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 4223, __PRETTY_FUNCTION__))
;
4224 } else if (Op1Type->isVectorTy()) {
4225 // TODO? If the edge cases for vectors were guaranteed to be handled as they
4226 // are for scalar, we could remove the min/max checks. However, to do that,
4227 // we would have to use insertelement/shufflevector to replace edge values.
4228 unsigned NumElts = Op1Type->getVectorNumElements();
4229 for (unsigned i = 0; i != NumElts; ++i) {
4230 Constant *Elt = Op1C->getAggregateElement(i);
4231 if (!Elt)
4232 return nullptr;
4233
4234 if (isa<UndefValue>(Elt))
4235 continue;
4236
4237 // Bail out if we can't determine if this constant is min/max or if we
4238 // know that this constant is min/max.
4239 auto *CI = dyn_cast<ConstantInt>(Elt);
4240 if (!CI || (IsLE ? CI->isMaxValue(IsSigned) : CI->isMinValue(IsSigned)))
4241 return nullptr;
4242 }
4243 } else {
4244 // ConstantExpr?
4245 return nullptr;
4246 }
4247
4248 // Increment or decrement the constant and set the new comparison predicate:
4249 // ULE -> ULT ; UGE -> UGT ; SLE -> SLT ; SGE -> SGT
4250 Constant *OneOrNegOne = ConstantInt::get(Op1Type, IsLE ? 1 : -1, true);
4251 CmpInst::Predicate NewPred = IsLE ? ICmpInst::ICMP_ULT: ICmpInst::ICMP_UGT;
4252 NewPred = IsSigned ? ICmpInst::getSignedPredicate(NewPred) : NewPred;
4253 return new ICmpInst(NewPred, Op0, ConstantExpr::getAdd(Op1C, OneOrNegOne));
4254}
4255
4256Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
4257 bool Changed = false;
4258 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4259 unsigned Op0Cplxity = getComplexity(Op0);
4260 unsigned Op1Cplxity = getComplexity(Op1);
4261
4262 /// Orders the operands of the compare so that they are listed from most
4263 /// complex to least complex. This puts constants before unary operators,
4264 /// before binary operators.
4265 if (Op0Cplxity < Op1Cplxity ||
4266 (Op0Cplxity == Op1Cplxity && swapMayExposeCSEOpportunities(Op0, Op1))) {
4267 I.swapOperands();
4268 std::swap(Op0, Op1);
4269 Changed = true;
4270 }
4271
4272 if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1,
4273 SQ.getWithInstruction(&I)))
4274 return replaceInstUsesWith(I, V);
4275
4276 // comparing -val or val with non-zero is the same as just comparing val
4277 // ie, abs(val) != 0 -> val != 0
4278 if (I.getPredicate() == ICmpInst::ICMP_NE && match(Op1, m_Zero())) {
4279 Value *Cond, *SelectTrue, *SelectFalse;
4280 if (match(Op0, m_Select(m_Value(Cond), m_Value(SelectTrue),
4281 m_Value(SelectFalse)))) {
4282 if (Value *V = dyn_castNegVal(SelectTrue)) {
4283 if (V == SelectFalse)
4284 return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
4285 }
4286 else if (Value *V = dyn_castNegVal(SelectFalse)) {
4287 if (V == SelectTrue)
4288 return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
4289 }
4290 }
4291 }
4292
4293 Type *Ty = Op0->getType();
4294
4295 // icmp's with boolean values can always be turned into bitwise operations
4296 if (Ty->getScalarType()->isIntegerTy(1)) {
4297 switch (I.getPredicate()) {
4298 default: llvm_unreachable("Invalid icmp instruction!")::llvm::llvm_unreachable_internal("Invalid icmp instruction!"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 4298)
;
4299 case ICmpInst::ICMP_EQ: { // icmp eq i1 A, B -> ~(A^B)
4300 Value *Xor = Builder->CreateXor(Op0, Op1, I.getName() + "tmp");
4301 return BinaryOperator::CreateNot(Xor);
4302 }
4303 case ICmpInst::ICMP_NE: // icmp ne i1 A, B -> A^B
4304 return BinaryOperator::CreateXor(Op0, Op1);
4305
4306 case ICmpInst::ICMP_UGT:
4307 std::swap(Op0, Op1); // Change icmp ugt -> icmp ult
4308 LLVM_FALLTHROUGH[[clang::fallthrough]];
4309 case ICmpInst::ICMP_ULT:{ // icmp ult i1 A, B -> ~A & B
4310 Value *Not = Builder->CreateNot(Op0, I.getName() + "tmp");
4311 return BinaryOperator::CreateAnd(Not, Op1);
4312 }
4313 case ICmpInst::ICMP_SGT:
4314 std::swap(Op0, Op1); // Change icmp sgt -> icmp slt
4315 LLVM_FALLTHROUGH[[clang::fallthrough]];
4316 case ICmpInst::ICMP_SLT: { // icmp slt i1 A, B -> A & ~B
4317 Value *Not = Builder->CreateNot(Op1, I.getName() + "tmp");
4318 return BinaryOperator::CreateAnd(Not, Op0);
4319 }
4320 case ICmpInst::ICMP_UGE:
4321 std::swap(Op0, Op1); // Change icmp uge -> icmp ule
4322 LLVM_FALLTHROUGH[[clang::fallthrough]];
4323 case ICmpInst::ICMP_ULE: { // icmp ule i1 A, B -> ~A | B
4324 Value *Not = Builder->CreateNot(Op0, I.getName() + "tmp");
4325 return BinaryOperator::CreateOr(Not, Op1);
4326 }
4327 case ICmpInst::ICMP_SGE:
4328 std::swap(Op0, Op1); // Change icmp sge -> icmp sle
4329 LLVM_FALLTHROUGH[[clang::fallthrough]];
4330 case ICmpInst::ICMP_SLE: { // icmp sle i1 A, B -> A | ~B
4331 Value *Not = Builder->CreateNot(Op1, I.getName() + "tmp");
4332 return BinaryOperator::CreateOr(Not, Op0);
4333 }
4334 }
4335 }
4336
4337 if (ICmpInst *NewICmp = canonicalizeCmpWithConstant(I))
4338 return NewICmp;
4339
4340 if (Instruction *Res = foldICmpWithConstant(I))
4341 return Res;
4342
4343 if (Instruction *Res = foldICmpUsingKnownBits(I))
4344 return Res;
4345
4346 // Test if the ICmpInst instruction is used exclusively by a select as
4347 // part of a minimum or maximum operation. If so, refrain from doing
4348 // any other folding. This helps out other analyses which understand
4349 // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
4350 // and CodeGen. And in this case, at least one of the comparison
4351 // operands has at least one user besides the compare (the select),
4352 // which would often largely negate the benefit of folding anyway.
4353 if (I.hasOneUse())
4354 if (SelectInst *SI = dyn_cast<SelectInst>(*I.user_begin()))
4355 if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) ||
4356 (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1))
4357 return nullptr;
4358
4359 // FIXME: We only do this after checking for min/max to prevent infinite
4360 // looping caused by a reverse canonicalization of these patterns for min/max.
4361 // FIXME: The organization of folds is a mess. These would naturally go into
4362 // canonicalizeCmpWithConstant(), but we can't move all of the above folds
4363 // down here after the min/max restriction.
4364 ICmpInst::Predicate Pred = I.getPredicate();
4365 const APInt *C;
4366 if (match(Op1, m_APInt(C))) {
4367 // For i32: x >u 2147483647 -> x <s 0 -> true if sign bit set
4368 if (Pred == ICmpInst::ICMP_UGT && C->isMaxSignedValue()) {
4369 Constant *Zero = Constant::getNullValue(Op0->getType());
4370 return new ICmpInst(ICmpInst::ICMP_SLT, Op0, Zero);
4371 }
4372
4373 // For i32: x <u 2147483648 -> x >s -1 -> true if sign bit clear
4374 if (Pred == ICmpInst::ICMP_ULT && C->isMinSignedValue()) {
4375 Constant *AllOnes = Constant::getAllOnesValue(Op0->getType());
4376 return new ICmpInst(ICmpInst::ICMP_SGT, Op0, AllOnes);
4377 }
4378 }
4379
4380 if (Instruction *Res = foldICmpInstWithConstant(I))
4381 return Res;
4382
4383 if (Instruction *Res = foldICmpInstWithConstantNotInt(I))
4384 return Res;
4385
4386 // If we can optimize a 'icmp GEP, P' or 'icmp P, GEP', do so now.
4387 if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op0))
4388 if (Instruction *NI = foldGEPICmp(GEP, Op1, I.getPredicate(), I))
4389 return NI;
4390 if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op1))
4391 if (Instruction *NI = foldGEPICmp(GEP, Op0,
4392 ICmpInst::getSwappedPredicate(I.getPredicate()), I))
4393 return NI;
4394
4395 // Try to optimize equality comparisons against alloca-based pointers.
4396 if (Op0->getType()->isPointerTy() && I.isEquality()) {
4397 assert(Op1->getType()->isPointerTy() && "Comparing pointer with non-pointer?")((Op1->getType()->isPointerTy() && "Comparing pointer with non-pointer?"
) ? static_cast<void> (0) : __assert_fail ("Op1->getType()->isPointerTy() && \"Comparing pointer with non-pointer?\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 4397, __PRETTY_FUNCTION__))
;
4398 if (auto *Alloca = dyn_cast<AllocaInst>(GetUnderlyingObject(Op0, DL)))
4399 if (Instruction *New = foldAllocaCmp(I, Alloca, Op1))
4400 return New;
4401 if (auto *Alloca = dyn_cast<AllocaInst>(GetUnderlyingObject(Op1, DL)))
4402 if (Instruction *New = foldAllocaCmp(I, Alloca, Op0))
4403 return New;
4404 }
4405
4406 // Test to see if the operands of the icmp are casted versions of other
4407 // values. If the ptr->ptr cast can be stripped off both arguments, we do so
4408 // now.
4409 if (BitCastInst *CI = dyn_cast<BitCastInst>(Op0)) {
4410 if (Op0->getType()->isPointerTy() &&
4411 (isa<Constant>(Op1) || isa<BitCastInst>(Op1))) {
4412 // We keep moving the cast from the left operand over to the right
4413 // operand, where it can often be eliminated completely.
4414 Op0 = CI->getOperand(0);
4415
4416 // If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast
4417 // so eliminate it as well.
4418 if (BitCastInst *CI2 = dyn_cast<BitCastInst>(Op1))
4419 Op1 = CI2->getOperand(0);
4420
4421 // If Op1 is a constant, we can fold the cast into the constant.
4422 if (Op0->getType() != Op1->getType()) {
4423 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
4424 Op1 = ConstantExpr::getBitCast(Op1C, Op0->getType());
4425 } else {
4426 // Otherwise, cast the RHS right before the icmp
4427 Op1 = Builder->CreateBitCast(Op1, Op0->getType());
4428 }
4429 }
4430 return new ICmpInst(I.getPredicate(), Op0, Op1);
4431 }
4432 }
4433
4434 if (isa<CastInst>(Op0)) {
4435 // Handle the special case of: icmp (cast bool to X), <cst>
4436 // This comes up when you have code like
4437 // int X = A < B;
4438 // if (X) ...
4439 // For generality, we handle any zero-extension of any operand comparison
4440 // with a constant or another cast from the same type.
4441 if (isa<Constant>(Op1) || isa<CastInst>(Op1))
4442 if (Instruction *R = foldICmpWithCastAndCast(I))
4443 return R;
4444 }
4445
4446 if (Instruction *Res = foldICmpBinOp(I))
4447 return Res;
4448
4449 if (Instruction *Res = foldICmpWithMinMax(I))
4450 return Res;
4451
4452 {
4453 Value *A, *B;
4454 // Transform (A & ~B) == 0 --> (A & B) != 0
4455 // and (A & ~B) != 0 --> (A & B) == 0
4456 // if A is a power of 2.
4457 if (match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) &&
4458 match(Op1, m_Zero()) &&
4459 isKnownToBeAPowerOfTwo(A, DL, false, 0, &AC, &I, &DT) && I.isEquality())
4460 return new ICmpInst(I.getInversePredicate(),
4461 Builder->CreateAnd(A, B),
4462 Op1);
4463
4464 // ~x < ~y --> y < x
4465 // ~x < cst --> ~cst < x
4466 if (match(Op0, m_Not(m_Value(A)))) {
4467 if (match(Op1, m_Not(m_Value(B))))
4468 return new ICmpInst(I.getPredicate(), B, A);
4469 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(Op1))
4470 return new ICmpInst(I.getPredicate(), ConstantExpr::getNot(RHSC), A);
4471 }
4472
4473 Instruction *AddI = nullptr;
4474 if (match(&I, m_UAddWithOverflow(m_Value(A), m_Value(B),
4475 m_Instruction(AddI))) &&
4476 isa<IntegerType>(A->getType())) {
4477 Value *Result;
4478 Constant *Overflow;
4479 if (OptimizeOverflowCheck(OCF_UNSIGNED_ADD, A, B, *AddI, Result,
4480 Overflow)) {
4481 replaceInstUsesWith(*AddI, Result);
4482 return replaceInstUsesWith(I, Overflow);
4483 }
4484 }
4485
4486 // (zext a) * (zext b) --> llvm.umul.with.overflow.
4487 if (match(Op0, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
4488 if (Instruction *R = processUMulZExtIdiom(I, Op0, Op1, *this))
4489 return R;
4490 }
4491 if (match(Op1, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
4492 if (Instruction *R = processUMulZExtIdiom(I, Op1, Op0, *this))
4493 return R;
4494 }
4495 }
4496
4497 if (Instruction *Res = foldICmpEquality(I))
4498 return Res;
4499
4500 // The 'cmpxchg' instruction returns an aggregate containing the old value and
4501 // an i1 which indicates whether or not we successfully did the swap.
4502 //
4503 // Replace comparisons between the old value and the expected value with the
4504 // indicator that 'cmpxchg' returns.
4505 //
4506 // N.B. This transform is only valid when the 'cmpxchg' is not permitted to
4507 // spuriously fail. In those cases, the old value may equal the expected
4508 // value but it is possible for the swap to not occur.
4509 if (I.getPredicate() == ICmpInst::ICMP_EQ)
4510 if (auto *EVI = dyn_cast<ExtractValueInst>(Op0))
4511 if (auto *ACXI = dyn_cast<AtomicCmpXchgInst>(EVI->getAggregateOperand()))
4512 if (EVI->getIndices()[0] == 0 && ACXI->getCompareOperand() == Op1 &&
4513 !ACXI->isWeak())
4514 return ExtractValueInst::Create(ACXI, 1);
4515
4516 {
4517 Value *X; ConstantInt *Cst;
4518 // icmp X+Cst, X
4519 if (match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op1 == X)
4520 return foldICmpAddOpConst(I, X, Cst, I.getPredicate());
4521
4522 // icmp X, X+Cst
4523 if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X)
4524 return foldICmpAddOpConst(I, X, Cst, I.getSwappedPredicate());
4525 }
4526 return Changed ? &I : nullptr;
4527}
4528
4529/// Fold fcmp ([us]itofp x, cst) if possible.
4530Instruction *InstCombiner::foldFCmpIntToFPConst(FCmpInst &I, Instruction *LHSI,
4531 Constant *RHSC) {
4532 if (!isa<ConstantFP>(RHSC)) return nullptr;
4533 const APFloat &RHS = cast<ConstantFP>(RHSC)->getValueAPF();
4534
4535 // Get the width of the mantissa. We don't want to hack on conversions that
4536 // might lose information from the integer, e.g. "i64 -> float"
4537 int MantissaWidth = LHSI->getType()->getFPMantissaWidth();
4538 if (MantissaWidth == -1) return nullptr; // Unknown.
4539
4540 IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType());
4541
4542 bool LHSUnsigned = isa<UIToFPInst>(LHSI);
4543
4544 if (I.isEquality()) {
4545 FCmpInst::Predicate P = I.getPredicate();
4546 bool IsExact = false;
4547 APSInt RHSCvt(IntTy->getBitWidth(), LHSUnsigned);
4548 RHS.convertToInteger(RHSCvt, APFloat::rmNearestTiesToEven, &IsExact);
4549
4550 // If the floating point constant isn't an integer value, we know if we will
4551 // ever compare equal / not equal to it.
4552 if (!IsExact) {
4553 // TODO: Can never be -0.0 and other non-representable values
4554 APFloat RHSRoundInt(RHS);
4555 RHSRoundInt.roundToIntegral(APFloat::rmNearestTiesToEven);
4556 if (RHS.compare(RHSRoundInt) != APFloat::cmpEqual) {
4557 if (P == FCmpInst::FCMP_OEQ || P == FCmpInst::FCMP_UEQ)
4558 return replaceInstUsesWith(I, Builder->getFalse());
4559
4560 assert(P == FCmpInst::FCMP_ONE || P == FCmpInst::FCMP_UNE)((P == FCmpInst::FCMP_ONE || P == FCmpInst::FCMP_UNE) ? static_cast
<void> (0) : __assert_fail ("P == FCmpInst::FCMP_ONE || P == FCmpInst::FCMP_UNE"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 4560, __PRETTY_FUNCTION__))
;
4561 return replaceInstUsesWith(I, Builder->getTrue());
4562 }
4563 }
4564
4565 // TODO: If the constant is exactly representable, is it always OK to do
4566 // equality compares as integer?
4567 }
4568
4569 // Check to see that the input is converted from an integer type that is small
4570 // enough that preserves all bits. TODO: check here for "known" sign bits.
4571 // This would allow us to handle (fptosi (x >>s 62) to float) if x is i64 f.e.
4572 unsigned InputSize = IntTy->getScalarSizeInBits();
4573
4574 // Following test does NOT adjust InputSize downwards for signed inputs,
4575 // because the most negative value still requires all the mantissa bits
4576 // to distinguish it from one less than that value.
4577 if ((int)InputSize > MantissaWidth) {
4578 // Conversion would lose accuracy. Check if loss can impact comparison.
4579 int Exp = ilogb(RHS);
4580 if (Exp == APFloat::IEK_Inf) {
4581 int MaxExponent = ilogb(APFloat::getLargest(RHS.getSemantics()));
4582 if (MaxExponent < (int)InputSize - !LHSUnsigned)
4583 // Conversion could create infinity.
4584 return nullptr;
4585 } else {
4586 // Note that if RHS is zero or NaN, then Exp is negative
4587 // and first condition is trivially false.
4588 if (MantissaWidth <= Exp && Exp <= (int)InputSize - !LHSUnsigned)
4589 // Conversion could affect comparison.
4590 return nullptr;
4591 }
4592 }
4593
4594 // Otherwise, we can potentially simplify the comparison. We know that it
4595 // will always come through as an integer value and we know the constant is
4596 // not a NAN (it would have been previously simplified).
4597 assert(!RHS.isNaN() && "NaN comparison not already folded!")((!RHS.isNaN() && "NaN comparison not already folded!"
) ? static_cast<void> (0) : __assert_fail ("!RHS.isNaN() && \"NaN comparison not already folded!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 4597, __PRETTY_FUNCTION__))
;
4598
4599 ICmpInst::Predicate Pred;
4600 switch (I.getPredicate()) {
4601 default: llvm_unreachable("Unexpected predicate!")::llvm::llvm_unreachable_internal("Unexpected predicate!", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 4601)
;
4602 case FCmpInst::FCMP_UEQ:
4603 case FCmpInst::FCMP_OEQ:
4604 Pred = ICmpInst::ICMP_EQ;
4605 break;
4606 case FCmpInst::FCMP_UGT:
4607 case FCmpInst::FCMP_OGT:
4608 Pred = LHSUnsigned ? ICmpInst::ICMP_UGT : ICmpInst::ICMP_SGT;
4609 break;
4610 case FCmpInst::FCMP_UGE:
4611 case FCmpInst::FCMP_OGE:
4612 Pred = LHSUnsigned ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_SGE;
4613 break;
4614 case FCmpInst::FCMP_ULT:
4615 case FCmpInst::FCMP_OLT:
4616 Pred = LHSUnsigned ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_SLT;
4617 break;
4618 case FCmpInst::FCMP_ULE:
4619 case FCmpInst::FCMP_OLE:
4620 Pred = LHSUnsigned ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_SLE;
4621 break;
4622 case FCmpInst::FCMP_UNE:
4623 case FCmpInst::FCMP_ONE:
4624 Pred = ICmpInst::ICMP_NE;
4625 break;
4626 case FCmpInst::FCMP_ORD:
4627 return replaceInstUsesWith(I, Builder->getTrue());
4628 case FCmpInst::FCMP_UNO:
4629 return replaceInstUsesWith(I, Builder->getFalse());
4630 }
4631
4632 // Now we know that the APFloat is a normal number, zero or inf.
4633
4634 // See if the FP constant is too large for the integer. For example,
4635 // comparing an i8 to 300.0.
4636 unsigned IntWidth = IntTy->getScalarSizeInBits();
4637
4638 if (!LHSUnsigned) {
4639 // If the RHS value is > SignedMax, fold the comparison. This handles +INF
4640 // and large values.
4641 APFloat SMax(RHS.getSemantics());
4642 SMax.convertFromAPInt(APInt::getSignedMaxValue(IntWidth), true,
4643 APFloat::rmNearestTiesToEven);
4644 if (SMax.compare(RHS) == APFloat::cmpLessThan) { // smax < 13123.0
4645 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SLT ||
4646 Pred == ICmpInst::ICMP_SLE)
4647 return replaceInstUsesWith(I, Builder->getTrue());
4648 return replaceInstUsesWith(I, Builder->getFalse());
4649 }
4650 } else {
4651 // If the RHS value is > UnsignedMax, fold the comparison. This handles
4652 // +INF and large values.
4653 APFloat UMax(RHS.getSemantics());
4654 UMax.convertFromAPInt(APInt::getMaxValue(IntWidth), false,
4655 APFloat::rmNearestTiesToEven);
4656 if (UMax.compare(RHS) == APFloat::cmpLessThan) { // umax < 13123.0
4657 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_ULT ||
4658 Pred == ICmpInst::ICMP_ULE)
4659 return replaceInstUsesWith(I, Builder->getTrue());
4660 return replaceInstUsesWith(I, Builder->getFalse());
4661 }
4662 }
4663
4664 if (!LHSUnsigned) {
4665 // See if the RHS value is < SignedMin.
4666 APFloat SMin(RHS.getSemantics());
4667 SMin.convertFromAPInt(APInt::getSignedMinValue(IntWidth), true,
4668 APFloat::rmNearestTiesToEven);
4669 if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // smin > 12312.0
4670 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT ||
4671 Pred == ICmpInst::ICMP_SGE)
4672 return replaceInstUsesWith(I, Builder->getTrue());
4673 return replaceInstUsesWith(I, Builder->getFalse());
4674 }
4675 } else {
4676 // See if the RHS value is < UnsignedMin.
4677 APFloat SMin(RHS.getSemantics());
4678 SMin.convertFromAPInt(APInt::getMinValue(IntWidth), true,
4679 APFloat::rmNearestTiesToEven);
4680 if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // umin > 12312.0
4681 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_UGT ||
4682 Pred == ICmpInst::ICMP_UGE)
4683 return replaceInstUsesWith(I, Builder->getTrue());
4684 return replaceInstUsesWith(I, Builder->getFalse());
4685 }
4686 }
4687
4688 // Okay, now we know that the FP constant fits in the range [SMIN, SMAX] or
4689 // [0, UMAX], but it may still be fractional. See if it is fractional by
4690 // casting the FP value to the integer value and back, checking for equality.
4691 // Don't do this for zero, because -0.0 is not fractional.
4692 Constant *RHSInt = LHSUnsigned
4693 ? ConstantExpr::getFPToUI(RHSC, IntTy)
4694 : ConstantExpr::getFPToSI(RHSC, IntTy);
4695 if (!RHS.isZero()) {
4696 bool Equal = LHSUnsigned
4697 ? ConstantExpr::getUIToFP(RHSInt, RHSC->getType()) == RHSC
4698 : ConstantExpr::getSIToFP(RHSInt, RHSC->getType()) == RHSC;
4699 if (!Equal) {
4700 // If we had a comparison against a fractional value, we have to adjust
4701 // the compare predicate and sometimes the value. RHSC is rounded towards
4702 // zero at this point.
4703 switch (Pred) {
4704 default: llvm_unreachable("Unexpected integer comparison!")::llvm::llvm_unreachable_internal("Unexpected integer comparison!"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 4704)
;
4705 case ICmpInst::ICMP_NE: // (float)int != 4.4 --> true
4706 return replaceInstUsesWith(I, Builder->getTrue());
4707 case ICmpInst::ICMP_EQ: // (float)int == 4.4 --> false
4708 return replaceInstUsesWith(I, Builder->getFalse());
4709 case ICmpInst::ICMP_ULE:
4710 // (float)int <= 4.4 --> int <= 4
4711 // (float)int <= -4.4 --> false
4712 if (RHS.isNegative())
4713 return replaceInstUsesWith(I, Builder->getFalse());
4714 break;
4715 case ICmpInst::ICMP_SLE:
4716 // (float)int <= 4.4 --> int <= 4
4717 // (float)int <= -4.4 --> int < -4
4718 if (RHS.isNegative())
4719 Pred = ICmpInst::ICMP_SLT;
4720 break;
4721 case ICmpInst::ICMP_ULT:
4722 // (float)int < -4.4 --> false
4723 // (float)int < 4.4 --> int <= 4
4724 if (RHS.isNegative())
4725 return replaceInstUsesWith(I, Builder->getFalse());
4726 Pred = ICmpInst::ICMP_ULE;
4727 break;
4728 case ICmpInst::ICMP_SLT:
4729 // (float)int < -4.4 --> int < -4
4730 // (float)int < 4.4 --> int <= 4
4731 if (!RHS.isNegative())
4732 Pred = ICmpInst::ICMP_SLE;
4733 break;
4734 case ICmpInst::ICMP_UGT:
4735 // (float)int > 4.4 --> int > 4
4736 // (float)int > -4.4 --> true
4737 if (RHS.isNegative())
4738 return replaceInstUsesWith(I, Builder->getTrue());
4739 break;
4740 case ICmpInst::ICMP_SGT:
4741 // (float)int > 4.4 --> int > 4
4742 // (float)int > -4.4 --> int >= -4
4743 if (RHS.isNegative())
4744 Pred = ICmpInst::ICMP_SGE;
4745 break;
4746 case ICmpInst::ICMP_UGE:
4747 // (float)int >= -4.4 --> true
4748 // (float)int >= 4.4 --> int > 4
4749 if (RHS.isNegative())
4750 return replaceInstUsesWith(I, Builder->getTrue());
4751 Pred = ICmpInst::ICMP_UGT;
4752 break;
4753 case ICmpInst::ICMP_SGE:
4754 // (float)int >= -4.4 --> int >= -4
4755 // (float)int >= 4.4 --> int > 4
4756 if (!RHS.isNegative())
4757 Pred = ICmpInst::ICMP_SGT;
4758 break;
4759 }
4760 }
4761 }
4762
4763 // Lower this FP comparison into an appropriate integer version of the
4764 // comparison.
4765 return new ICmpInst(Pred, LHSI->getOperand(0), RHSInt);
4766}
4767
4768Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
4769 bool Changed = false;
4770
4771 /// Orders the operands of the compare so that they are listed from most
4772 /// complex to least complex. This puts constants before unary operators,
4773 /// before binary operators.
4774 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1))) {
4775 I.swapOperands();
4776 Changed = true;
4777 }
4778
4779 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4780
4781 if (Value *V =
4782 SimplifyFCmpInst(I.getPredicate(), Op0, Op1, I.getFastMathFlags(),
4783 SQ.getWithInstruction(&I)))
4784 return replaceInstUsesWith(I, V);
4785
4786 // Simplify 'fcmp pred X, X'
4787 if (Op0 == Op1) {
4788 switch (I.getPredicate()) {
4789 default: llvm_unreachable("Unknown predicate!")::llvm::llvm_unreachable_internal("Unknown predicate!", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 4789)
;
4790 case FCmpInst::FCMP_UNO: // True if unordered: isnan(X) | isnan(Y)
4791 case FCmpInst::FCMP_ULT: // True if unordered or less than
4792 case FCmpInst::FCMP_UGT: // True if unordered or greater than
4793 case FCmpInst::FCMP_UNE: // True if unordered or not equal
4794 // Canonicalize these to be 'fcmp uno %X, 0.0'.
4795 I.setPredicate(FCmpInst::FCMP_UNO);
4796 I.setOperand(1, Constant::getNullValue(Op0->getType()));
4797 return &I;
4798
4799 case FCmpInst::FCMP_ORD: // True if ordered (no nans)
4800 case FCmpInst::FCMP_OEQ: // True if ordered and equal
4801 case FCmpInst::FCMP_OGE: // True if ordered and greater than or equal
4802 case FCmpInst::FCMP_OLE: // True if ordered and less than or equal
4803 // Canonicalize these to be 'fcmp ord %X, 0.0'.
4804 I.setPredicate(FCmpInst::FCMP_ORD);
4805 I.setOperand(1, Constant::getNullValue(Op0->getType()));
4806 return &I;
4807 }
4808 }
4809
4810 // Test if the FCmpInst instruction is used exclusively by a select as
4811 // part of a minimum or maximum operation. If so, refrain from doing
4812 // any other folding. This helps out other analyses which understand
4813 // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
4814 // and CodeGen. And in this case, at least one of the comparison
4815 // operands has at least one user besides the compare (the select),
4816 // which would often largely negate the benefit of folding anyway.
4817 if (I.hasOneUse())
4818 if (SelectInst *SI = dyn_cast<SelectInst>(*I.user_begin()))
4819 if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) ||
4820 (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1))
4821 return nullptr;
4822
4823 // Handle fcmp with constant RHS
4824 if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
4825 if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
4826 switch (LHSI->getOpcode()) {
4827 case Instruction::FPExt: {
4828 // fcmp (fpext x), C -> fcmp x, (fptrunc C) if fptrunc is lossless
4829 FPExtInst *LHSExt = cast<FPExtInst>(LHSI);
4830 ConstantFP *RHSF = dyn_cast<ConstantFP>(RHSC);
4831 if (!RHSF)
4832 break;
4833
4834 const fltSemantics *Sem;
4835 // FIXME: This shouldn't be here.
4836 if (LHSExt->getSrcTy()->isHalfTy())
4837 Sem = &APFloat::IEEEhalf();
4838 else if (LHSExt->getSrcTy()->isFloatTy())
4839 Sem = &APFloat::IEEEsingle();
4840 else if (LHSExt->getSrcTy()->isDoubleTy())
4841 Sem = &APFloat::IEEEdouble();
4842 else if (LHSExt->getSrcTy()->isFP128Ty())
4843 Sem = &APFloat::IEEEquad();
4844 else if (LHSExt->getSrcTy()->isX86_FP80Ty())
4845 Sem = &APFloat::x87DoubleExtended();
4846 else if (LHSExt->getSrcTy()->isPPC_FP128Ty())
4847 Sem = &APFloat::PPCDoubleDouble();
4848 else
4849 break;
4850
4851 bool Lossy;
4852 APFloat F = RHSF->getValueAPF();
4853 F.convert(*Sem, APFloat::rmNearestTiesToEven, &Lossy);
4854
4855 // Avoid lossy conversions and denormals. Zero is a special case
4856 // that's OK to convert.
4857 APFloat Fabs = F;
4858 Fabs.clearSign();
4859 if (!Lossy &&
4860 ((Fabs.compare(APFloat::getSmallestNormalized(*Sem)) !=
4861 APFloat::cmpLessThan) || Fabs.isZero()))
4862
4863 return new FCmpInst(I.getPredicate(), LHSExt->getOperand(0),
4864 ConstantFP::get(RHSC->getContext(), F));
4865 break;
4866 }
4867 case Instruction::PHI:
4868 // Only fold fcmp into the PHI if the phi and fcmp are in the same
4869 // block. If in the same block, we're encouraging jump threading. If
4870 // not, we are just pessimizing the code by making an i1 phi.
4871 if (LHSI->getParent() == I.getParent())
4872 if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
4873 return NV;
4874 break;
4875 case Instruction::SIToFP:
4876 case Instruction::UIToFP:
4877 if (Instruction *NV = foldFCmpIntToFPConst(I, LHSI, RHSC))
4878 return NV;
4879 break;
4880 case Instruction::FSub: {
4881 // fcmp pred (fneg x), C -> fcmp swap(pred) x, -C
4882 Value *Op;
4883 if (match(LHSI, m_FNeg(m_Value(Op))))
4884 return new FCmpInst(I.getSwappedPredicate(), Op,
4885 ConstantExpr::getFNeg(RHSC));
4886 break;
4887 }
4888 case Instruction::Load:
4889 if (GetElementPtrInst *GEP =
4890 dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
4891 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
4892 if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
4893 !cast<LoadInst>(LHSI)->isVolatile())
4894 if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
4895 return Res;
4896 }
4897 break;
4898 case Instruction::Call: {
4899 if (!RHSC->isNullValue())
4900 break;
4901
4902 CallInst *CI = cast<CallInst>(LHSI);
4903 Intrinsic::ID IID = getIntrinsicForCallSite(CI, &TLI);
4904 if (IID != Intrinsic::fabs)
4905 break;
4906
4907 // Various optimization for fabs compared with zero.
4908 switch (I.getPredicate()) {
4909 default:
4910 break;
4911 // fabs(x) < 0 --> false
4912 case FCmpInst::FCMP_OLT:
4913 llvm_unreachable("handled by SimplifyFCmpInst")::llvm::llvm_unreachable_internal("handled by SimplifyFCmpInst"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn301769/lib/Transforms/InstCombine/InstCombineCompares.cpp"
, 4913)
;
4914 // fabs(x) > 0 --> x != 0
4915 case FCmpInst::FCMP_OGT:
4916 return new FCmpInst(FCmpInst::FCMP_ONE, CI->getArgOperand(0), RHSC);
4917 // fabs(x) <= 0 --> x == 0
4918 case FCmpInst::FCMP_OLE:
4919 return new FCmpInst(FCmpInst::FCMP_OEQ, CI->getArgOperand(0), RHSC);
4920 // fabs(x) >= 0 --> !isnan(x)
4921 case FCmpInst::FCMP_OGE:
4922 return new FCmpInst(FCmpInst::FCMP_ORD, CI->getArgOperand(0), RHSC);
4923 // fabs(x) == 0 --> x == 0
4924 // fabs(x) != 0 --> x != 0
4925 case FCmpInst::FCMP_OEQ:
4926 case FCmpInst::FCMP_UEQ:
4927 case FCmpInst::FCMP_ONE:
4928 case FCmpInst::FCMP_UNE:
4929 return new FCmpInst(I.getPredicate(), CI->getArgOperand(0), RHSC);
4930 }
4931 }
4932 }
4933 }
4934
4935 // fcmp pred (fneg x), (fneg y) -> fcmp swap(pred) x, y
4936 Value *X, *Y;
4937 if (match(Op0, m_FNeg(m_Value(X))) && match(Op1, m_FNeg(m_Value(Y))))
4938 return new FCmpInst(I.getSwappedPredicate(), X, Y);
4939
4940 // fcmp (fpext x), (fpext y) -> fcmp x, y
4941 if (FPExtInst *LHSExt = dyn_cast<FPExtInst>(Op0))
4942 if (FPExtInst *RHSExt = dyn_cast<FPExtInst>(Op1))
4943 if (LHSExt->getSrcTy() == RHSExt->getSrcTy())
4944 return new FCmpInst(I.getPredicate(), LHSExt->getOperand(0),
4945 RHSExt->getOperand(0));
4946
4947 return Changed ? &I : nullptr;
4948}