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1 : //===- llvm/Analysis/ValueTracking.h - Walk computations --------*- C++ -*-===//
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 contains routines that help analyze properties that chains of
11 : // computations have.
12 : //
13 : //===----------------------------------------------------------------------===//
14 :
15 : #ifndef LLVM_ANALYSIS_VALUETRACKING_H
16 : #define LLVM_ANALYSIS_VALUETRACKING_H
17 :
18 : #include "llvm/ADT/ArrayRef.h"
19 : #include "llvm/ADT/Optional.h"
20 : #include "llvm/IR/CallSite.h"
21 : #include "llvm/IR/Constants.h"
22 : #include "llvm/IR/Instruction.h"
23 : #include "llvm/IR/Intrinsics.h"
24 : #include <cassert>
25 : #include <cstdint>
26 :
27 : namespace llvm {
28 :
29 : class AddOperator;
30 : class APInt;
31 : class AssumptionCache;
32 : class DataLayout;
33 : class DominatorTree;
34 : class GEPOperator;
35 : class IntrinsicInst;
36 : struct KnownBits;
37 : class Loop;
38 : class LoopInfo;
39 : class MDNode;
40 : class OptimizationRemarkEmitter;
41 : class StringRef;
42 : class TargetLibraryInfo;
43 : class Value;
44 :
45 : /// Determine which bits of V are known to be either zero or one and return
46 : /// them in the KnownZero/KnownOne bit sets.
47 : ///
48 : /// This function is defined on values with integer type, values with pointer
49 : /// type, and vectors of integers. In the case
50 : /// where V is a vector, the known zero and known one values are the
51 : /// same width as the vector element, and the bit is set only if it is true
52 : /// for all of the elements in the vector.
53 : void computeKnownBits(const Value *V, KnownBits &Known,
54 : const DataLayout &DL, unsigned Depth = 0,
55 : AssumptionCache *AC = nullptr,
56 : const Instruction *CxtI = nullptr,
57 : const DominatorTree *DT = nullptr,
58 : OptimizationRemarkEmitter *ORE = nullptr,
59 : bool UseInstrInfo = true);
60 :
61 : /// Returns the known bits rather than passing by reference.
62 : KnownBits computeKnownBits(const Value *V, const DataLayout &DL,
63 : unsigned Depth = 0, AssumptionCache *AC = nullptr,
64 : const Instruction *CxtI = nullptr,
65 : const DominatorTree *DT = nullptr,
66 : OptimizationRemarkEmitter *ORE = nullptr,
67 : bool UseInstrInfo = true);
68 :
69 : /// Compute known bits from the range metadata.
70 : /// \p KnownZero the set of bits that are known to be zero
71 : /// \p KnownOne the set of bits that are known to be one
72 : void computeKnownBitsFromRangeMetadata(const MDNode &Ranges,
73 : KnownBits &Known);
74 :
75 : /// Return true if LHS and RHS have no common bits set.
76 : bool haveNoCommonBitsSet(const Value *LHS, const Value *RHS,
77 : const DataLayout &DL,
78 : AssumptionCache *AC = nullptr,
79 : const Instruction *CxtI = nullptr,
80 : const DominatorTree *DT = nullptr,
81 : bool UseInstrInfo = true);
82 :
83 : /// Return true if the given value is known to have exactly one bit set when
84 : /// defined. For vectors return true if every element is known to be a power
85 : /// of two when defined. Supports values with integer or pointer type and
86 : /// vectors of integers. If 'OrZero' is set, then return true if the given
87 : /// value is either a power of two or zero.
88 : bool isKnownToBeAPowerOfTwo(const Value *V, const DataLayout &DL,
89 : bool OrZero = false, unsigned Depth = 0,
90 : AssumptionCache *AC = nullptr,
91 : const Instruction *CxtI = nullptr,
92 : const DominatorTree *DT = nullptr,
93 : bool UseInstrInfo = true);
94 :
95 : bool isOnlyUsedInZeroEqualityComparison(const Instruction *CxtI);
96 :
97 : /// Return true if the given value is known to be non-zero when defined. For
98 : /// vectors, return true if every element is known to be non-zero when
99 : /// defined. For pointers, if the context instruction and dominator tree are
100 : /// specified, perform context-sensitive analysis and return true if the
101 : /// pointer couldn't possibly be null at the specified instruction.
102 : /// Supports values with integer or pointer type and vectors of integers.
103 : bool isKnownNonZero(const Value *V, const DataLayout &DL, unsigned Depth = 0,
104 : AssumptionCache *AC = nullptr,
105 : const Instruction *CxtI = nullptr,
106 : const DominatorTree *DT = nullptr,
107 : bool UseInstrInfo = true);
108 :
109 : /// Return true if the two given values are negation.
110 : /// Currently can recoginze Value pair:
111 : /// 1: <X, Y> if X = sub (0, Y) or Y = sub (0, X)
112 : /// 2: <X, Y> if X = sub (A, B) and Y = sub (B, A)
113 : bool isKnownNegation(const Value *X, const Value *Y, bool NeedNSW = false);
114 :
115 : /// Returns true if the give value is known to be non-negative.
116 : bool isKnownNonNegative(const Value *V, const DataLayout &DL,
117 : unsigned Depth = 0,
118 : AssumptionCache *AC = nullptr,
119 : const Instruction *CxtI = nullptr,
120 : const DominatorTree *DT = nullptr,
121 : bool UseInstrInfo = true);
122 :
123 : /// Returns true if the given value is known be positive (i.e. non-negative
124 : /// and non-zero).
125 : bool isKnownPositive(const Value *V, const DataLayout &DL, unsigned Depth = 0,
126 : AssumptionCache *AC = nullptr,
127 : const Instruction *CxtI = nullptr,
128 : const DominatorTree *DT = nullptr,
129 : bool UseInstrInfo = true);
130 :
131 : /// Returns true if the given value is known be negative (i.e. non-positive
132 : /// and non-zero).
133 : bool isKnownNegative(const Value *V, const DataLayout &DL, unsigned Depth = 0,
134 : AssumptionCache *AC = nullptr,
135 : const Instruction *CxtI = nullptr,
136 : const DominatorTree *DT = nullptr,
137 : bool UseInstrInfo = true);
138 :
139 : /// Return true if the given values are known to be non-equal when defined.
140 : /// Supports scalar integer types only.
141 : bool isKnownNonEqual(const Value *V1, const Value *V2, const DataLayout &DL,
142 : AssumptionCache *AC = nullptr,
143 : const Instruction *CxtI = nullptr,
144 : const DominatorTree *DT = nullptr,
145 : bool UseInstrInfo = true);
146 :
147 : /// Return true if 'V & Mask' is known to be zero. We use this predicate to
148 : /// simplify operations downstream. Mask is known to be zero for bits that V
149 : /// cannot have.
150 : ///
151 : /// This function is defined on values with integer type, values with pointer
152 : /// type, and vectors of integers. In the case
153 : /// where V is a vector, the mask, known zero, and known one values are the
154 : /// same width as the vector element, and the bit is set only if it is true
155 : /// for all of the elements in the vector.
156 : bool MaskedValueIsZero(const Value *V, const APInt &Mask,
157 : const DataLayout &DL,
158 : unsigned Depth = 0, AssumptionCache *AC = nullptr,
159 : const Instruction *CxtI = nullptr,
160 : const DominatorTree *DT = nullptr,
161 : bool UseInstrInfo = true);
162 :
163 : /// Return the number of times the sign bit of the register is replicated into
164 : /// the other bits. We know that at least 1 bit is always equal to the sign
165 : /// bit (itself), but other cases can give us information. For example,
166 : /// immediately after an "ashr X, 2", we know that the top 3 bits are all
167 : /// equal to each other, so we return 3. For vectors, return the number of
168 : /// sign bits for the vector element with the mininum number of known sign
169 : /// bits.
170 : unsigned ComputeNumSignBits(const Value *Op, const DataLayout &DL,
171 : unsigned Depth = 0, AssumptionCache *AC = nullptr,
172 : const Instruction *CxtI = nullptr,
173 : const DominatorTree *DT = nullptr,
174 : bool UseInstrInfo = true);
175 :
176 : /// This function computes the integer multiple of Base that equals V. If
177 : /// successful, it returns true and returns the multiple in Multiple. If
178 : /// unsuccessful, it returns false. Also, if V can be simplified to an
179 : /// integer, then the simplified V is returned in Val. Look through sext only
180 : /// if LookThroughSExt=true.
181 : bool ComputeMultiple(Value *V, unsigned Base, Value *&Multiple,
182 : bool LookThroughSExt = false,
183 : unsigned Depth = 0);
184 :
185 : /// Map a call instruction to an intrinsic ID. Libcalls which have equivalent
186 : /// intrinsics are treated as-if they were intrinsics.
187 : Intrinsic::ID getIntrinsicForCallSite(ImmutableCallSite ICS,
188 : const TargetLibraryInfo *TLI);
189 :
190 : /// Return true if we can prove that the specified FP value is never equal to
191 : /// -0.0.
192 : bool CannotBeNegativeZero(const Value *V, const TargetLibraryInfo *TLI,
193 : unsigned Depth = 0);
194 :
195 : /// Return true if we can prove that the specified FP value is either NaN or
196 : /// never less than -0.0.
197 : ///
198 : /// NaN --> true
199 : /// +0 --> true
200 : /// -0 --> true
201 : /// x > +0 --> true
202 : /// x < -0 --> false
203 : bool CannotBeOrderedLessThanZero(const Value *V, const TargetLibraryInfo *TLI);
204 :
205 : /// Return true if the floating-point scalar value is not a NaN or if the
206 : /// floating-point vector value has no NaN elements. Return false if a value
207 : /// could ever be NaN.
208 : bool isKnownNeverNaN(const Value *V, const TargetLibraryInfo *TLI,
209 : unsigned Depth = 0);
210 :
211 : /// Return true if we can prove that the specified FP value's sign bit is 0.
212 : ///
213 : /// NaN --> true/false (depending on the NaN's sign bit)
214 : /// +0 --> true
215 : /// -0 --> false
216 : /// x > +0 --> true
217 : /// x < -0 --> false
218 : bool SignBitMustBeZero(const Value *V, const TargetLibraryInfo *TLI);
219 :
220 : /// If the specified value can be set by repeating the same byte in memory,
221 : /// return the i8 value that it is represented with. This is true for all i8
222 : /// values obviously, but is also true for i32 0, i32 -1, i16 0xF0F0, double
223 : /// 0.0 etc. If the value can't be handled with a repeated byte store (e.g.
224 : /// i16 0x1234), return null. If the value is entirely undef and padding,
225 : /// return undef.
226 : Value *isBytewiseValue(Value *V);
227 :
228 : /// Given an aggregrate and an sequence of indices, see if the scalar value
229 : /// indexed is already around as a register, for example if it were inserted
230 : /// directly into the aggregrate.
231 : ///
232 : /// If InsertBefore is not null, this function will duplicate (modified)
233 : /// insertvalues when a part of a nested struct is extracted.
234 : Value *FindInsertedValue(Value *V,
235 : ArrayRef<unsigned> idx_range,
236 : Instruction *InsertBefore = nullptr);
237 :
238 : /// Analyze the specified pointer to see if it can be expressed as a base
239 : /// pointer plus a constant offset. Return the base and offset to the caller.
240 : Value *GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset,
241 : const DataLayout &DL);
242 : inline const Value *GetPointerBaseWithConstantOffset(const Value *Ptr,
243 : int64_t &Offset,
244 : const DataLayout &DL) {
245 41992 : return GetPointerBaseWithConstantOffset(const_cast<Value *>(Ptr), Offset,
246 : DL);
247 : }
248 :
249 : /// Returns true if the GEP is based on a pointer to a string (array of
250 : // \p CharSize integers) and is indexing into this string.
251 : bool isGEPBasedOnPointerToString(const GEPOperator *GEP,
252 : unsigned CharSize = 8);
253 :
254 : /// Represents offset+length into a ConstantDataArray.
255 : struct ConstantDataArraySlice {
256 : /// ConstantDataArray pointer. nullptr indicates a zeroinitializer (a valid
257 : /// initializer, it just doesn't fit the ConstantDataArray interface).
258 : const ConstantDataArray *Array;
259 :
260 : /// Slice starts at this Offset.
261 : uint64_t Offset;
262 :
263 : /// Length of the slice.
264 : uint64_t Length;
265 :
266 : /// Moves the Offset and adjusts Length accordingly.
267 0 : void move(uint64_t Delta) {
268 : assert(Delta < Length);
269 1207 : Offset += Delta;
270 1207 : Length -= Delta;
271 0 : }
272 :
273 : /// Convenience accessor for elements in the slice.
274 0 : uint64_t operator[](unsigned I) const {
275 4292 : return Array==nullptr ? 0 : Array->getElementAsInteger(I + Offset);
276 : }
277 : };
278 :
279 : /// Returns true if the value \p V is a pointer into a ConstantDataArray.
280 : /// If successful \p Slice will point to a ConstantDataArray info object
281 : /// with an appropriate offset.
282 : bool getConstantDataArrayInfo(const Value *V, ConstantDataArraySlice &Slice,
283 : unsigned ElementSize, uint64_t Offset = 0);
284 :
285 : /// This function computes the length of a null-terminated C string pointed to
286 : /// by V. If successful, it returns true and returns the string in Str. If
287 : /// unsuccessful, it returns false. This does not include the trailing null
288 : /// character by default. If TrimAtNul is set to false, then this returns any
289 : /// trailing null characters as well as any other characters that come after
290 : /// it.
291 : bool getConstantStringInfo(const Value *V, StringRef &Str,
292 : uint64_t Offset = 0, bool TrimAtNul = true);
293 :
294 : /// If we can compute the length of the string pointed to by the specified
295 : /// pointer, return 'len+1'. If we can't, return 0.
296 : uint64_t GetStringLength(const Value *V, unsigned CharSize = 8);
297 :
298 : /// This function returns call pointer argument that is considered the same by
299 : /// aliasing rules. You CAN'T use it to replace one value with another.
300 : const Value *getArgumentAliasingToReturnedPointer(ImmutableCallSite CS);
301 614042 : inline Value *getArgumentAliasingToReturnedPointer(CallSite CS) {
302 : return const_cast<Value *>(
303 614042 : getArgumentAliasingToReturnedPointer(ImmutableCallSite(CS)));
304 : }
305 :
306 : // {launder,strip}.invariant.group returns pointer that aliases its argument,
307 : // and it only captures pointer by returning it.
308 : // These intrinsics are not marked as nocapture, because returning is
309 : // considered as capture. The arguments are not marked as returned neither,
310 : // because it would make it useless.
311 : bool isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(
312 : ImmutableCallSite CS);
313 :
314 : /// This method strips off any GEP address adjustments and pointer casts from
315 : /// the specified value, returning the original object being addressed. Note
316 : /// that the returned value has pointer type if the specified value does. If
317 : /// the MaxLookup value is non-zero, it limits the number of instructions to
318 : /// be stripped off.
319 : Value *GetUnderlyingObject(Value *V, const DataLayout &DL,
320 : unsigned MaxLookup = 6);
321 : inline const Value *GetUnderlyingObject(const Value *V, const DataLayout &DL,
322 : unsigned MaxLookup = 6) {
323 104602952 : return GetUnderlyingObject(const_cast<Value *>(V), DL, MaxLookup);
324 : }
325 :
326 : /// This method is similar to GetUnderlyingObject except that it can
327 : /// look through phi and select instructions and return multiple objects.
328 : ///
329 : /// If LoopInfo is passed, loop phis are further analyzed. If a pointer
330 : /// accesses different objects in each iteration, we don't look through the
331 : /// phi node. E.g. consider this loop nest:
332 : ///
333 : /// int **A;
334 : /// for (i)
335 : /// for (j) {
336 : /// A[i][j] = A[i-1][j] * B[j]
337 : /// }
338 : ///
339 : /// This is transformed by Load-PRE to stash away A[i] for the next iteration
340 : /// of the outer loop:
341 : ///
342 : /// Curr = A[0]; // Prev_0
343 : /// for (i: 1..N) {
344 : /// Prev = Curr; // Prev = PHI (Prev_0, Curr)
345 : /// Curr = A[i];
346 : /// for (j: 0..N) {
347 : /// Curr[j] = Prev[j] * B[j]
348 : /// }
349 : /// }
350 : ///
351 : /// Since A[i] and A[i-1] are independent pointers, getUnderlyingObjects
352 : /// should not assume that Curr and Prev share the same underlying object thus
353 : /// it shouldn't look through the phi above.
354 : void GetUnderlyingObjects(Value *V, SmallVectorImpl<Value *> &Objects,
355 : const DataLayout &DL, LoopInfo *LI = nullptr,
356 : unsigned MaxLookup = 6);
357 :
358 : /// This is a wrapper around GetUnderlyingObjects and adds support for basic
359 : /// ptrtoint+arithmetic+inttoptr sequences.
360 : bool getUnderlyingObjectsForCodeGen(const Value *V,
361 : SmallVectorImpl<Value *> &Objects,
362 : const DataLayout &DL);
363 :
364 : /// Return true if the only users of this pointer are lifetime markers.
365 : bool onlyUsedByLifetimeMarkers(const Value *V);
366 :
367 : /// Return true if the instruction does not have any effects besides
368 : /// calculating the result and does not have undefined behavior.
369 : ///
370 : /// This method never returns true for an instruction that returns true for
371 : /// mayHaveSideEffects; however, this method also does some other checks in
372 : /// addition. It checks for undefined behavior, like dividing by zero or
373 : /// loading from an invalid pointer (but not for undefined results, like a
374 : /// shift with a shift amount larger than the width of the result). It checks
375 : /// for malloc and alloca because speculatively executing them might cause a
376 : /// memory leak. It also returns false for instructions related to control
377 : /// flow, specifically terminators and PHI nodes.
378 : ///
379 : /// If the CtxI is specified this method performs context-sensitive analysis
380 : /// and returns true if it is safe to execute the instruction immediately
381 : /// before the CtxI.
382 : ///
383 : /// If the CtxI is NOT specified this method only looks at the instruction
384 : /// itself and its operands, so if this method returns true, it is safe to
385 : /// move the instruction as long as the correct dominance relationships for
386 : /// the operands and users hold.
387 : ///
388 : /// This method can return true for instructions that read memory;
389 : /// for such instructions, moving them may change the resulting value.
390 : bool isSafeToSpeculativelyExecute(const Value *V,
391 : const Instruction *CtxI = nullptr,
392 : const DominatorTree *DT = nullptr);
393 :
394 : /// Returns true if the result or effects of the given instructions \p I
395 : /// depend on or influence global memory.
396 : /// Memory dependence arises for example if the instruction reads from
397 : /// memory or may produce effects or undefined behaviour. Memory dependent
398 : /// instructions generally cannot be reorderd with respect to other memory
399 : /// dependent instructions or moved into non-dominated basic blocks.
400 : /// Instructions which just compute a value based on the values of their
401 : /// operands are not memory dependent.
402 : bool mayBeMemoryDependent(const Instruction &I);
403 :
404 : /// Return true if it is an intrinsic that cannot be speculated but also
405 : /// cannot trap.
406 : bool isAssumeLikeIntrinsic(const Instruction *I);
407 :
408 : /// Return true if it is valid to use the assumptions provided by an
409 : /// assume intrinsic, I, at the point in the control-flow identified by the
410 : /// context instruction, CxtI.
411 : bool isValidAssumeForContext(const Instruction *I, const Instruction *CxtI,
412 : const DominatorTree *DT = nullptr);
413 :
414 : enum class OverflowResult { AlwaysOverflows, MayOverflow, NeverOverflows };
415 :
416 : OverflowResult computeOverflowForUnsignedMul(const Value *LHS,
417 : const Value *RHS,
418 : const DataLayout &DL,
419 : AssumptionCache *AC,
420 : const Instruction *CxtI,
421 : const DominatorTree *DT,
422 : bool UseInstrInfo = true);
423 : OverflowResult computeOverflowForSignedMul(const Value *LHS, const Value *RHS,
424 : const DataLayout &DL,
425 : AssumptionCache *AC,
426 : const Instruction *CxtI,
427 : const DominatorTree *DT,
428 : bool UseInstrInfo = true);
429 : OverflowResult computeOverflowForUnsignedAdd(const Value *LHS,
430 : const Value *RHS,
431 : const DataLayout &DL,
432 : AssumptionCache *AC,
433 : const Instruction *CxtI,
434 : const DominatorTree *DT,
435 : bool UseInstrInfo = true);
436 : OverflowResult computeOverflowForSignedAdd(const Value *LHS, const Value *RHS,
437 : const DataLayout &DL,
438 : AssumptionCache *AC = nullptr,
439 : const Instruction *CxtI = nullptr,
440 : const DominatorTree *DT = nullptr);
441 : /// This version also leverages the sign bit of Add if known.
442 : OverflowResult computeOverflowForSignedAdd(const AddOperator *Add,
443 : const DataLayout &DL,
444 : AssumptionCache *AC = nullptr,
445 : const Instruction *CxtI = nullptr,
446 : const DominatorTree *DT = nullptr);
447 : OverflowResult computeOverflowForUnsignedSub(const Value *LHS, const Value *RHS,
448 : const DataLayout &DL,
449 : AssumptionCache *AC,
450 : const Instruction *CxtI,
451 : const DominatorTree *DT);
452 : OverflowResult computeOverflowForSignedSub(const Value *LHS, const Value *RHS,
453 : const DataLayout &DL,
454 : AssumptionCache *AC,
455 : const Instruction *CxtI,
456 : const DominatorTree *DT);
457 :
458 : /// Returns true if the arithmetic part of the \p II 's result is
459 : /// used only along the paths control dependent on the computation
460 : /// not overflowing, \p II being an <op>.with.overflow intrinsic.
461 : bool isOverflowIntrinsicNoWrap(const IntrinsicInst *II,
462 : const DominatorTree &DT);
463 :
464 : /// Return true if this function can prove that the instruction I will
465 : /// always transfer execution to one of its successors (including the next
466 : /// instruction that follows within a basic block). E.g. this is not
467 : /// guaranteed for function calls that could loop infinitely.
468 : ///
469 : /// In other words, this function returns false for instructions that may
470 : /// transfer execution or fail to transfer execution in a way that is not
471 : /// captured in the CFG nor in the sequence of instructions within a basic
472 : /// block.
473 : ///
474 : /// Undefined behavior is assumed not to happen, so e.g. division is
475 : /// guaranteed to transfer execution to the following instruction even
476 : /// though division by zero might cause undefined behavior.
477 : bool isGuaranteedToTransferExecutionToSuccessor(const Instruction *I);
478 :
479 : /// Returns true if this block does not contain a potential implicit exit.
480 : /// This is equivelent to saying that all instructions within the basic block
481 : /// are guaranteed to transfer execution to their successor within the basic
482 : /// block. This has the same assumptions w.r.t. undefined behavior as the
483 : /// instruction variant of this function.
484 : bool isGuaranteedToTransferExecutionToSuccessor(const BasicBlock *BB);
485 :
486 : /// Return true if this function can prove that the instruction I
487 : /// is executed for every iteration of the loop L.
488 : ///
489 : /// Note that this currently only considers the loop header.
490 : bool isGuaranteedToExecuteForEveryIteration(const Instruction *I,
491 : const Loop *L);
492 :
493 : /// Return true if this function can prove that I is guaranteed to yield
494 : /// full-poison (all bits poison) if at least one of its operands are
495 : /// full-poison (all bits poison).
496 : ///
497 : /// The exact rules for how poison propagates through instructions have
498 : /// not been settled as of 2015-07-10, so this function is conservative
499 : /// and only considers poison to be propagated in uncontroversial
500 : /// cases. There is no attempt to track values that may be only partially
501 : /// poison.
502 : bool propagatesFullPoison(const Instruction *I);
503 :
504 : /// Return either nullptr or an operand of I such that I will trigger
505 : /// undefined behavior if I is executed and that operand has a full-poison
506 : /// value (all bits poison).
507 : const Value *getGuaranteedNonFullPoisonOp(const Instruction *I);
508 :
509 : /// Return true if this function can prove that if PoisonI is executed
510 : /// and yields a full-poison value (all bits poison), then that will
511 : /// trigger undefined behavior.
512 : ///
513 : /// Note that this currently only considers the basic block that is
514 : /// the parent of I.
515 : bool programUndefinedIfFullPoison(const Instruction *PoisonI);
516 :
517 : /// Specific patterns of select instructions we can match.
518 : enum SelectPatternFlavor {
519 : SPF_UNKNOWN = 0,
520 : SPF_SMIN, /// Signed minimum
521 : SPF_UMIN, /// Unsigned minimum
522 : SPF_SMAX, /// Signed maximum
523 : SPF_UMAX, /// Unsigned maximum
524 : SPF_FMINNUM, /// Floating point minnum
525 : SPF_FMAXNUM, /// Floating point maxnum
526 : SPF_ABS, /// Absolute value
527 : SPF_NABS /// Negated absolute value
528 : };
529 :
530 : /// Behavior when a floating point min/max is given one NaN and one
531 : /// non-NaN as input.
532 : enum SelectPatternNaNBehavior {
533 : SPNB_NA = 0, /// NaN behavior not applicable.
534 : SPNB_RETURNS_NAN, /// Given one NaN input, returns the NaN.
535 : SPNB_RETURNS_OTHER, /// Given one NaN input, returns the non-NaN.
536 : SPNB_RETURNS_ANY /// Given one NaN input, can return either (or
537 : /// it has been determined that no operands can
538 : /// be NaN).
539 : };
540 :
541 : struct SelectPatternResult {
542 : SelectPatternFlavor Flavor;
543 : SelectPatternNaNBehavior NaNBehavior; /// Only applicable if Flavor is
544 : /// SPF_FMINNUM or SPF_FMAXNUM.
545 : bool Ordered; /// When implementing this min/max pattern as
546 : /// fcmp; select, does the fcmp have to be
547 : /// ordered?
548 :
549 : /// Return true if \p SPF is a min or a max pattern.
550 : static bool isMinOrMax(SelectPatternFlavor SPF) {
551 369148 : return SPF != SPF_UNKNOWN && SPF != SPF_ABS && SPF != SPF_NABS;
552 : }
553 : };
554 :
555 : /// Pattern match integer [SU]MIN, [SU]MAX and ABS idioms, returning the kind
556 : /// and providing the out parameter results if we successfully match.
557 : ///
558 : /// For ABS/NABS, LHS will be set to the input to the abs idiom. RHS will be
559 : /// the negation instruction from the idiom.
560 : ///
561 : /// If CastOp is not nullptr, also match MIN/MAX idioms where the type does
562 : /// not match that of the original select. If this is the case, the cast
563 : /// operation (one of Trunc,SExt,Zext) that must be done to transform the
564 : /// type of LHS and RHS into the type of V is returned in CastOp.
565 : ///
566 : /// For example:
567 : /// %1 = icmp slt i32 %a, i32 4
568 : /// %2 = sext i32 %a to i64
569 : /// %3 = select i1 %1, i64 %2, i64 4
570 : ///
571 : /// -> LHS = %a, RHS = i32 4, *CastOp = Instruction::SExt
572 : ///
573 : SelectPatternResult matchSelectPattern(Value *V, Value *&LHS, Value *&RHS,
574 : Instruction::CastOps *CastOp = nullptr,
575 : unsigned Depth = 0);
576 : inline SelectPatternResult
577 0 : matchSelectPattern(const Value *V, const Value *&LHS, const Value *&RHS,
578 : Instruction::CastOps *CastOp = nullptr) {
579 0 : Value *L = const_cast<Value*>(LHS);
580 0 : Value *R = const_cast<Value*>(RHS);
581 0 : auto Result = matchSelectPattern(const_cast<Value*>(V), L, R);
582 0 : LHS = L;
583 0 : RHS = R;
584 0 : return Result;
585 : }
586 :
587 : /// Return the canonical comparison predicate for the specified
588 : /// minimum/maximum flavor.
589 : CmpInst::Predicate getMinMaxPred(SelectPatternFlavor SPF,
590 : bool Ordered = false);
591 :
592 : /// Return the inverse minimum/maximum flavor of the specified flavor.
593 : /// For example, signed minimum is the inverse of signed maximum.
594 : SelectPatternFlavor getInverseMinMaxFlavor(SelectPatternFlavor SPF);
595 :
596 : /// Return the canonical inverse comparison predicate for the specified
597 : /// minimum/maximum flavor.
598 : CmpInst::Predicate getInverseMinMaxPred(SelectPatternFlavor SPF);
599 :
600 : /// Return true if RHS is known to be implied true by LHS. Return false if
601 : /// RHS is known to be implied false by LHS. Otherwise, return None if no
602 : /// implication can be made.
603 : /// A & B must be i1 (boolean) values or a vector of such values. Note that
604 : /// the truth table for implication is the same as <=u on i1 values (but not
605 : /// <=s!). The truth table for both is:
606 : /// | T | F (B)
607 : /// T | T | F
608 : /// F | T | T
609 : /// (A)
610 : Optional<bool> isImpliedCondition(const Value *LHS, const Value *RHS,
611 : const DataLayout &DL, bool LHSIsTrue = true,
612 : unsigned Depth = 0);
613 : } // end namespace llvm
614 :
615 : #endif // LLVM_ANALYSIS_VALUETRACKING_H
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