LLVM  3.7.0
SeparateConstOffsetFromGEP.cpp
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1 //===-- SeparateConstOffsetFromGEP.cpp - ------------------------*- 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 // Loop unrolling may create many similar GEPs for array accesses.
11 // e.g., a 2-level loop
12 //
13 // float a[32][32]; // global variable
14 //
15 // for (int i = 0; i < 2; ++i) {
16 // for (int j = 0; j < 2; ++j) {
17 // ...
18 // ... = a[x + i][y + j];
19 // ...
20 // }
21 // }
22 //
23 // will probably be unrolled to:
24 //
25 // gep %a, 0, %x, %y; load
26 // gep %a, 0, %x, %y + 1; load
27 // gep %a, 0, %x + 1, %y; load
28 // gep %a, 0, %x + 1, %y + 1; load
29 //
30 // LLVM's GVN does not use partial redundancy elimination yet, and is thus
31 // unable to reuse (gep %a, 0, %x, %y). As a result, this misoptimization incurs
32 // significant slowdown in targets with limited addressing modes. For instance,
33 // because the PTX target does not support the reg+reg addressing mode, the
34 // NVPTX backend emits PTX code that literally computes the pointer address of
35 // each GEP, wasting tons of registers. It emits the following PTX for the
36 // first load and similar PTX for other loads.
37 //
38 // mov.u32 %r1, %x;
39 // mov.u32 %r2, %y;
40 // mul.wide.u32 %rl2, %r1, 128;
41 // mov.u64 %rl3, a;
42 // add.s64 %rl4, %rl3, %rl2;
43 // mul.wide.u32 %rl5, %r2, 4;
44 // add.s64 %rl6, %rl4, %rl5;
45 // ld.global.f32 %f1, [%rl6];
46 //
47 // To reduce the register pressure, the optimization implemented in this file
48 // merges the common part of a group of GEPs, so we can compute each pointer
49 // address by adding a simple offset to the common part, saving many registers.
50 //
51 // It works by splitting each GEP into a variadic base and a constant offset.
52 // The variadic base can be computed once and reused by multiple GEPs, and the
53 // constant offsets can be nicely folded into the reg+immediate addressing mode
54 // (supported by most targets) without using any extra register.
55 //
56 // For instance, we transform the four GEPs and four loads in the above example
57 // into:
58 //
59 // base = gep a, 0, x, y
60 // load base
61 // laod base + 1 * sizeof(float)
62 // load base + 32 * sizeof(float)
63 // load base + 33 * sizeof(float)
64 //
65 // Given the transformed IR, a backend that supports the reg+immediate
66 // addressing mode can easily fold the pointer arithmetics into the loads. For
67 // example, the NVPTX backend can easily fold the pointer arithmetics into the
68 // ld.global.f32 instructions, and the resultant PTX uses much fewer registers.
69 //
70 // mov.u32 %r1, %tid.x;
71 // mov.u32 %r2, %tid.y;
72 // mul.wide.u32 %rl2, %r1, 128;
73 // mov.u64 %rl3, a;
74 // add.s64 %rl4, %rl3, %rl2;
75 // mul.wide.u32 %rl5, %r2, 4;
76 // add.s64 %rl6, %rl4, %rl5;
77 // ld.global.f32 %f1, [%rl6]; // so far the same as unoptimized PTX
78 // ld.global.f32 %f2, [%rl6+4]; // much better
79 // ld.global.f32 %f3, [%rl6+128]; // much better
80 // ld.global.f32 %f4, [%rl6+132]; // much better
81 //
82 // Another improvement enabled by the LowerGEP flag is to lower a GEP with
83 // multiple indices to either multiple GEPs with a single index or arithmetic
84 // operations (depending on whether the target uses alias analysis in codegen).
85 // Such transformation can have following benefits:
86 // (1) It can always extract constants in the indices of structure type.
87 // (2) After such Lowering, there are more optimization opportunities such as
88 // CSE, LICM and CGP.
89 //
90 // E.g. The following GEPs have multiple indices:
91 // BB1:
92 // %p = getelementptr [10 x %struct]* %ptr, i64 %i, i64 %j1, i32 3
93 // load %p
94 // ...
95 // BB2:
96 // %p2 = getelementptr [10 x %struct]* %ptr, i64 %i, i64 %j1, i32 2
97 // load %p2
98 // ...
99 //
100 // We can not do CSE for to the common part related to index "i64 %i". Lowering
101 // GEPs can achieve such goals.
102 // If the target does not use alias analysis in codegen, this pass will
103 // lower a GEP with multiple indices into arithmetic operations:
104 // BB1:
105 // %1 = ptrtoint [10 x %struct]* %ptr to i64 ; CSE opportunity
106 // %2 = mul i64 %i, length_of_10xstruct ; CSE opportunity
107 // %3 = add i64 %1, %2 ; CSE opportunity
108 // %4 = mul i64 %j1, length_of_struct
109 // %5 = add i64 %3, %4
110 // %6 = add i64 %3, struct_field_3 ; Constant offset
111 // %p = inttoptr i64 %6 to i32*
112 // load %p
113 // ...
114 // BB2:
115 // %7 = ptrtoint [10 x %struct]* %ptr to i64 ; CSE opportunity
116 // %8 = mul i64 %i, length_of_10xstruct ; CSE opportunity
117 // %9 = add i64 %7, %8 ; CSE opportunity
118 // %10 = mul i64 %j2, length_of_struct
119 // %11 = add i64 %9, %10
120 // %12 = add i64 %11, struct_field_2 ; Constant offset
121 // %p = inttoptr i64 %12 to i32*
122 // load %p2
123 // ...
124 //
125 // If the target uses alias analysis in codegen, this pass will lower a GEP
126 // with multiple indices into multiple GEPs with a single index:
127 // BB1:
128 // %1 = bitcast [10 x %struct]* %ptr to i8* ; CSE opportunity
129 // %2 = mul i64 %i, length_of_10xstruct ; CSE opportunity
130 // %3 = getelementptr i8* %1, i64 %2 ; CSE opportunity
131 // %4 = mul i64 %j1, length_of_struct
132 // %5 = getelementptr i8* %3, i64 %4
133 // %6 = getelementptr i8* %5, struct_field_3 ; Constant offset
134 // %p = bitcast i8* %6 to i32*
135 // load %p
136 // ...
137 // BB2:
138 // %7 = bitcast [10 x %struct]* %ptr to i8* ; CSE opportunity
139 // %8 = mul i64 %i, length_of_10xstruct ; CSE opportunity
140 // %9 = getelementptr i8* %7, i64 %8 ; CSE opportunity
141 // %10 = mul i64 %j2, length_of_struct
142 // %11 = getelementptr i8* %9, i64 %10
143 // %12 = getelementptr i8* %11, struct_field_2 ; Constant offset
144 // %p2 = bitcast i8* %12 to i32*
145 // load %p2
146 // ...
147 //
148 // Lowering GEPs can also benefit other passes such as LICM and CGP.
149 // LICM (Loop Invariant Code Motion) can not hoist/sink a GEP of multiple
150 // indices if one of the index is variant. If we lower such GEP into invariant
151 // parts and variant parts, LICM can hoist/sink those invariant parts.
152 // CGP (CodeGen Prepare) tries to sink address calculations that match the
153 // target's addressing modes. A GEP with multiple indices may not match and will
154 // not be sunk. If we lower such GEP into smaller parts, CGP may sink some of
155 // them. So we end up with a better addressing mode.
156 //
157 //===----------------------------------------------------------------------===//
158 
161 #include "llvm/IR/Constants.h"
162 #include "llvm/IR/DataLayout.h"
163 #include "llvm/IR/Dominators.h"
164 #include "llvm/IR/Instructions.h"
165 #include "llvm/IR/LLVMContext.h"
166 #include "llvm/IR/Module.h"
167 #include "llvm/IR/Operator.h"
170 #include "llvm/Transforms/Scalar.h"
174 #include "llvm/IR/IRBuilder.h"
175 
176 using namespace llvm;
177 
179  "disable-separate-const-offset-from-gep", cl::init(false),
180  cl::desc("Do not separate the constant offset from a GEP instruction"),
181  cl::Hidden);
182 // Setting this flag may emit false positives when the input module already
183 // contains dead instructions. Therefore, we set it only in unit tests that are
184 // free of dead code.
185 static cl::opt<bool>
186  VerifyNoDeadCode("reassociate-geps-verify-no-dead-code", cl::init(false),
187  cl::desc("Verify this pass produces no dead code"),
188  cl::Hidden);
189 
190 namespace {
191 
192 /// \brief A helper class for separating a constant offset from a GEP index.
193 ///
194 /// In real programs, a GEP index may be more complicated than a simple addition
195 /// of something and a constant integer which can be trivially splitted. For
196 /// example, to split ((a << 3) | 5) + b, we need to search deeper for the
197 /// constant offset, so that we can separate the index to (a << 3) + b and 5.
198 ///
199 /// Therefore, this class looks into the expression that computes a given GEP
200 /// index, and tries to find a constant integer that can be hoisted to the
201 /// outermost level of the expression as an addition. Not every constant in an
202 /// expression can jump out. e.g., we cannot transform (b * (a + 5)) to (b * a +
203 /// 5); nor can we transform (3 * (a + 5)) to (3 * a + 5), however in this case,
204 /// -instcombine probably already optimized (3 * (a + 5)) to (3 * a + 15).
205 class ConstantOffsetExtractor {
206 public:
207  /// Extracts a constant offset from the given GEP index. It returns the
208  /// new index representing the remainder (equal to the original index minus
209  /// the constant offset), or nullptr if we cannot extract a constant offset.
210  /// \p Idx The given GEP index
211  /// \p GEP The given GEP
212  /// \p UserChainTail Outputs the tail of UserChain so that we can
213  /// garbage-collect unused instructions in UserChain.
214  static Value *Extract(Value *Idx, GetElementPtrInst *GEP,
215  User *&UserChainTail, const DominatorTree *DT);
216  /// Looks for a constant offset from the given GEP index without extracting
217  /// it. It returns the numeric value of the extracted constant offset (0 if
218  /// failed). The meaning of the arguments are the same as Extract.
219  static int64_t Find(Value *Idx, GetElementPtrInst *GEP,
220  const DominatorTree *DT);
221 
222 private:
223  ConstantOffsetExtractor(Instruction *InsertionPt, const DominatorTree *DT)
224  : IP(InsertionPt), DL(InsertionPt->getModule()->getDataLayout()), DT(DT) {
225  }
226  /// Searches the expression that computes V for a non-zero constant C s.t.
227  /// V can be reassociated into the form V' + C. If the searching is
228  /// successful, returns C and update UserChain as a def-use chain from C to V;
229  /// otherwise, UserChain is empty.
230  ///
231  /// \p V The given expression
232  /// \p SignExtended Whether V will be sign-extended in the computation of the
233  /// GEP index
234  /// \p ZeroExtended Whether V will be zero-extended in the computation of the
235  /// GEP index
236  /// \p NonNegative Whether V is guaranteed to be non-negative. For example,
237  /// an index of an inbounds GEP is guaranteed to be
238  /// non-negative. Levaraging this, we can better split
239  /// inbounds GEPs.
240  APInt find(Value *V, bool SignExtended, bool ZeroExtended, bool NonNegative);
241  /// A helper function to look into both operands of a binary operator.
242  APInt findInEitherOperand(BinaryOperator *BO, bool SignExtended,
243  bool ZeroExtended);
244  /// After finding the constant offset C from the GEP index I, we build a new
245  /// index I' s.t. I' + C = I. This function builds and returns the new
246  /// index I' according to UserChain produced by function "find".
247  ///
248  /// The building conceptually takes two steps:
249  /// 1) iteratively distribute s/zext towards the leaves of the expression tree
250  /// that computes I
251  /// 2) reassociate the expression tree to the form I' + C.
252  ///
253  /// For example, to extract the 5 from sext(a + (b + 5)), we first distribute
254  /// sext to a, b and 5 so that we have
255  /// sext(a) + (sext(b) + 5).
256  /// Then, we reassociate it to
257  /// (sext(a) + sext(b)) + 5.
258  /// Given this form, we know I' is sext(a) + sext(b).
259  Value *rebuildWithoutConstOffset();
260  /// After the first step of rebuilding the GEP index without the constant
261  /// offset, distribute s/zext to the operands of all operators in UserChain.
262  /// e.g., zext(sext(a + (b + 5)) (assuming no overflow) =>
263  /// zext(sext(a)) + (zext(sext(b)) + zext(sext(5))).
264  ///
265  /// The function also updates UserChain to point to new subexpressions after
266  /// distributing s/zext. e.g., the old UserChain of the above example is
267  /// 5 -> b + 5 -> a + (b + 5) -> sext(...) -> zext(sext(...)),
268  /// and the new UserChain is
269  /// zext(sext(5)) -> zext(sext(b)) + zext(sext(5)) ->
270  /// zext(sext(a)) + (zext(sext(b)) + zext(sext(5))
271  ///
272  /// \p ChainIndex The index to UserChain. ChainIndex is initially
273  /// UserChain.size() - 1, and is decremented during
274  /// the recursion.
275  Value *distributeExtsAndCloneChain(unsigned ChainIndex);
276  /// Reassociates the GEP index to the form I' + C and returns I'.
277  Value *removeConstOffset(unsigned ChainIndex);
278  /// A helper function to apply ExtInsts, a list of s/zext, to value V.
279  /// e.g., if ExtInsts = [sext i32 to i64, zext i16 to i32], this function
280  /// returns "sext i32 (zext i16 V to i32) to i64".
281  Value *applyExts(Value *V);
282 
283  /// A helper function that returns whether we can trace into the operands
284  /// of binary operator BO for a constant offset.
285  ///
286  /// \p SignExtended Whether BO is surrounded by sext
287  /// \p ZeroExtended Whether BO is surrounded by zext
288  /// \p NonNegative Whether BO is known to be non-negative, e.g., an in-bound
289  /// array index.
290  bool CanTraceInto(bool SignExtended, bool ZeroExtended, BinaryOperator *BO,
291  bool NonNegative);
292 
293  /// The path from the constant offset to the old GEP index. e.g., if the GEP
294  /// index is "a * b + (c + 5)". After running function find, UserChain[0] will
295  /// be the constant 5, UserChain[1] will be the subexpression "c + 5", and
296  /// UserChain[2] will be the entire expression "a * b + (c + 5)".
297  ///
298  /// This path helps to rebuild the new GEP index.
299  SmallVector<User *, 8> UserChain;
300  /// A data structure used in rebuildWithoutConstOffset. Contains all
301  /// sext/zext instructions along UserChain.
303  Instruction *IP; /// Insertion position of cloned instructions.
304  const DataLayout &DL;
305  const DominatorTree *DT;
306 };
307 
308 /// \brief A pass that tries to split every GEP in the function into a variadic
309 /// base and a constant offset. It is a FunctionPass because searching for the
310 /// constant offset may inspect other basic blocks.
311 class SeparateConstOffsetFromGEP : public FunctionPass {
312 public:
313  static char ID;
314  SeparateConstOffsetFromGEP(const TargetMachine *TM = nullptr,
315  bool LowerGEP = false)
316  : FunctionPass(ID), DL(nullptr), DT(nullptr), TM(TM), LowerGEP(LowerGEP) {
318  }
319 
320  void getAnalysisUsage(AnalysisUsage &AU) const override {
323  AU.setPreservesCFG();
324  }
325 
326  bool doInitialization(Module &M) override {
327  DL = &M.getDataLayout();
328  return false;
329  }
330  bool runOnFunction(Function &F) override;
331 
332 private:
333  /// Tries to split the given GEP into a variadic base and a constant offset,
334  /// and returns true if the splitting succeeds.
335  bool splitGEP(GetElementPtrInst *GEP);
336  /// Lower a GEP with multiple indices into multiple GEPs with a single index.
337  /// Function splitGEP already split the original GEP into a variadic part and
338  /// a constant offset (i.e., AccumulativeByteOffset). This function lowers the
339  /// variadic part into a set of GEPs with a single index and applies
340  /// AccumulativeByteOffset to it.
341  /// \p Variadic The variadic part of the original GEP.
342  /// \p AccumulativeByteOffset The constant offset.
343  void lowerToSingleIndexGEPs(GetElementPtrInst *Variadic,
344  int64_t AccumulativeByteOffset);
345  /// Lower a GEP with multiple indices into ptrtoint+arithmetics+inttoptr form.
346  /// Function splitGEP already split the original GEP into a variadic part and
347  /// a constant offset (i.e., AccumulativeByteOffset). This function lowers the
348  /// variadic part into a set of arithmetic operations and applies
349  /// AccumulativeByteOffset to it.
350  /// \p Variadic The variadic part of the original GEP.
351  /// \p AccumulativeByteOffset The constant offset.
352  void lowerToArithmetics(GetElementPtrInst *Variadic,
353  int64_t AccumulativeByteOffset);
354  /// Finds the constant offset within each index and accumulates them. If
355  /// LowerGEP is true, it finds in indices of both sequential and structure
356  /// types, otherwise it only finds in sequential indices. The output
357  /// NeedsExtraction indicates whether we successfully find a non-zero constant
358  /// offset.
359  int64_t accumulateByteOffset(GetElementPtrInst *GEP, bool &NeedsExtraction);
360  /// Canonicalize array indices to pointer-size integers. This helps to
361  /// simplify the logic of splitting a GEP. For example, if a + b is a
362  /// pointer-size integer, we have
363  /// gep base, a + b = gep (gep base, a), b
364  /// However, this equality may not hold if the size of a + b is smaller than
365  /// the pointer size, because LLVM conceptually sign-extends GEP indices to
366  /// pointer size before computing the address
367  /// (http://llvm.org/docs/LangRef.html#id181).
368  ///
369  /// This canonicalization is very likely already done in clang and
370  /// instcombine. Therefore, the program will probably remain the same.
371  ///
372  /// Returns true if the module changes.
373  ///
374  /// Verified in @i32_add in split-gep.ll
375  bool canonicalizeArrayIndicesToPointerSize(GetElementPtrInst *GEP);
376  /// Verify F is free of dead code.
377  void verifyNoDeadCode(Function &F);
378 
379  const DataLayout *DL;
380  const DominatorTree *DT;
381  const TargetMachine *TM;
382  /// Whether to lower a GEP with multiple indices into arithmetic operations or
383  /// multiple GEPs with a single index.
384  bool LowerGEP;
385 };
386 } // anonymous namespace
387 
390  SeparateConstOffsetFromGEP, "separate-const-offset-from-gep",
391  "Split GEPs to a variadic base and a constant offset for better CSE", false,
392  false)
396  SeparateConstOffsetFromGEP, "separate-const-offset-from-gep",
397  "Split GEPs to a variadic base and a constant offset for better CSE", false,
398  false)
399 
400 FunctionPass *
402  bool LowerGEP) {
403  return new SeparateConstOffsetFromGEP(TM, LowerGEP);
404 }
405 
406 bool ConstantOffsetExtractor::CanTraceInto(bool SignExtended,
407  bool ZeroExtended,
408  BinaryOperator *BO,
409  bool NonNegative) {
410  // We only consider ADD, SUB and OR, because a non-zero constant found in
411  // expressions composed of these operations can be easily hoisted as a
412  // constant offset by reassociation.
413  if (BO->getOpcode() != Instruction::Add &&
414  BO->getOpcode() != Instruction::Sub &&
415  BO->getOpcode() != Instruction::Or) {
416  return false;
417  }
418 
419  Value *LHS = BO->getOperand(0), *RHS = BO->getOperand(1);
420  // Do not trace into "or" unless it is equivalent to "add". If LHS and RHS
421  // don't have common bits, (LHS | RHS) is equivalent to (LHS + RHS).
422  if (BO->getOpcode() == Instruction::Or &&
423  !haveNoCommonBitsSet(LHS, RHS, DL, nullptr, BO, DT))
424  return false;
425 
426  // In addition, tracing into BO requires that its surrounding s/zext (if
427  // any) is distributable to both operands.
428  //
429  // Suppose BO = A op B.
430  // SignExtended | ZeroExtended | Distributable?
431  // --------------+--------------+----------------------------------
432  // 0 | 0 | true because no s/zext exists
433  // 0 | 1 | zext(BO) == zext(A) op zext(B)
434  // 1 | 0 | sext(BO) == sext(A) op sext(B)
435  // 1 | 1 | zext(sext(BO)) ==
436  // | | zext(sext(A)) op zext(sext(B))
437  if (BO->getOpcode() == Instruction::Add && !ZeroExtended && NonNegative) {
438  // If a + b >= 0 and (a >= 0 or b >= 0), then
439  // sext(a + b) = sext(a) + sext(b)
440  // even if the addition is not marked nsw.
441  //
442  // Leveraging this invarient, we can trace into an sext'ed inbound GEP
443  // index if the constant offset is non-negative.
444  //
445  // Verified in @sext_add in split-gep.ll.
446  if (ConstantInt *ConstLHS = dyn_cast<ConstantInt>(LHS)) {
447  if (!ConstLHS->isNegative())
448  return true;
449  }
450  if (ConstantInt *ConstRHS = dyn_cast<ConstantInt>(RHS)) {
451  if (!ConstRHS->isNegative())
452  return true;
453  }
454  }
455 
456  // sext (add/sub nsw A, B) == add/sub nsw (sext A), (sext B)
457  // zext (add/sub nuw A, B) == add/sub nuw (zext A), (zext B)
458  if (BO->getOpcode() == Instruction::Add ||
459  BO->getOpcode() == Instruction::Sub) {
460  if (SignExtended && !BO->hasNoSignedWrap())
461  return false;
462  if (ZeroExtended && !BO->hasNoUnsignedWrap())
463  return false;
464  }
465 
466  return true;
467 }
468 
469 APInt ConstantOffsetExtractor::findInEitherOperand(BinaryOperator *BO,
470  bool SignExtended,
471  bool ZeroExtended) {
472  // BO being non-negative does not shed light on whether its operands are
473  // non-negative. Clear the NonNegative flag here.
474  APInt ConstantOffset = find(BO->getOperand(0), SignExtended, ZeroExtended,
475  /* NonNegative */ false);
476  // If we found a constant offset in the left operand, stop and return that.
477  // This shortcut might cause us to miss opportunities of combining the
478  // constant offsets in both operands, e.g., (a + 4) + (b + 5) => (a + b) + 9.
479  // However, such cases are probably already handled by -instcombine,
480  // given this pass runs after the standard optimizations.
481  if (ConstantOffset != 0) return ConstantOffset;
482  ConstantOffset = find(BO->getOperand(1), SignExtended, ZeroExtended,
483  /* NonNegative */ false);
484  // If U is a sub operator, negate the constant offset found in the right
485  // operand.
486  if (BO->getOpcode() == Instruction::Sub)
487  ConstantOffset = -ConstantOffset;
488  return ConstantOffset;
489 }
490 
491 APInt ConstantOffsetExtractor::find(Value *V, bool SignExtended,
492  bool ZeroExtended, bool NonNegative) {
493  // TODO(jingyue): We could trace into integer/pointer casts, such as
494  // inttoptr, ptrtoint, bitcast, and addrspacecast. We choose to handle only
495  // integers because it gives good enough results for our benchmarks.
496  unsigned BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
497 
498  // We cannot do much with Values that are not a User, such as an Argument.
499  User *U = dyn_cast<User>(V);
500  if (U == nullptr) return APInt(BitWidth, 0);
501 
502  APInt ConstantOffset(BitWidth, 0);
503  if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
504  // Hooray, we found it!
505  ConstantOffset = CI->getValue();
506  } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(V)) {
507  // Trace into subexpressions for more hoisting opportunities.
508  if (CanTraceInto(SignExtended, ZeroExtended, BO, NonNegative))
509  ConstantOffset = findInEitherOperand(BO, SignExtended, ZeroExtended);
510  } else if (isa<SExtInst>(V)) {
511  ConstantOffset = find(U->getOperand(0), /* SignExtended */ true,
512  ZeroExtended, NonNegative).sext(BitWidth);
513  } else if (isa<ZExtInst>(V)) {
514  // As an optimization, we can clear the SignExtended flag because
515  // sext(zext(a)) = zext(a). Verified in @sext_zext in split-gep.ll.
516  //
517  // Clear the NonNegative flag, because zext(a) >= 0 does not imply a >= 0.
518  ConstantOffset =
519  find(U->getOperand(0), /* SignExtended */ false,
520  /* ZeroExtended */ true, /* NonNegative */ false).zext(BitWidth);
521  }
522 
523  // If we found a non-zero constant offset, add it to the path for
524  // rebuildWithoutConstOffset. Zero is a valid constant offset, but doesn't
525  // help this optimization.
526  if (ConstantOffset != 0)
527  UserChain.push_back(U);
528  return ConstantOffset;
529 }
530 
531 Value *ConstantOffsetExtractor::applyExts(Value *V) {
532  Value *Current = V;
533  // ExtInsts is built in the use-def order. Therefore, we apply them to V
534  // in the reversed order.
535  for (auto I = ExtInsts.rbegin(), E = ExtInsts.rend(); I != E; ++I) {
536  if (Constant *C = dyn_cast<Constant>(Current)) {
537  // If Current is a constant, apply s/zext using ConstantExpr::getCast.
538  // ConstantExpr::getCast emits a ConstantInt if C is a ConstantInt.
539  Current = ConstantExpr::getCast((*I)->getOpcode(), C, (*I)->getType());
540  } else {
541  Instruction *Ext = (*I)->clone();
542  Ext->setOperand(0, Current);
543  Ext->insertBefore(IP);
544  Current = Ext;
545  }
546  }
547  return Current;
548 }
549 
550 Value *ConstantOffsetExtractor::rebuildWithoutConstOffset() {
551  distributeExtsAndCloneChain(UserChain.size() - 1);
552  // Remove all nullptrs (used to be s/zext) from UserChain.
553  unsigned NewSize = 0;
554  for (auto I = UserChain.begin(), E = UserChain.end(); I != E; ++I) {
555  if (*I != nullptr) {
556  UserChain[NewSize] = *I;
557  NewSize++;
558  }
559  }
560  UserChain.resize(NewSize);
561  return removeConstOffset(UserChain.size() - 1);
562 }
563 
564 Value *
565 ConstantOffsetExtractor::distributeExtsAndCloneChain(unsigned ChainIndex) {
566  User *U = UserChain[ChainIndex];
567  if (ChainIndex == 0) {
568  assert(isa<ConstantInt>(U));
569  // If U is a ConstantInt, applyExts will return a ConstantInt as well.
570  return UserChain[ChainIndex] = cast<ConstantInt>(applyExts(U));
571  }
572 
573  if (CastInst *Cast = dyn_cast<CastInst>(U)) {
574  assert((isa<SExtInst>(Cast) || isa<ZExtInst>(Cast)) &&
575  "We only traced into two types of CastInst: sext and zext");
576  ExtInsts.push_back(Cast);
577  UserChain[ChainIndex] = nullptr;
578  return distributeExtsAndCloneChain(ChainIndex - 1);
579  }
580 
581  // Function find only trace into BinaryOperator and CastInst.
582  BinaryOperator *BO = cast<BinaryOperator>(U);
583  // OpNo = which operand of BO is UserChain[ChainIndex - 1]
584  unsigned OpNo = (BO->getOperand(0) == UserChain[ChainIndex - 1] ? 0 : 1);
585  Value *TheOther = applyExts(BO->getOperand(1 - OpNo));
586  Value *NextInChain = distributeExtsAndCloneChain(ChainIndex - 1);
587 
588  BinaryOperator *NewBO = nullptr;
589  if (OpNo == 0) {
590  NewBO = BinaryOperator::Create(BO->getOpcode(), NextInChain, TheOther,
591  BO->getName(), IP);
592  } else {
593  NewBO = BinaryOperator::Create(BO->getOpcode(), TheOther, NextInChain,
594  BO->getName(), IP);
595  }
596  return UserChain[ChainIndex] = NewBO;
597 }
598 
599 Value *ConstantOffsetExtractor::removeConstOffset(unsigned ChainIndex) {
600  if (ChainIndex == 0) {
601  assert(isa<ConstantInt>(UserChain[ChainIndex]));
602  return ConstantInt::getNullValue(UserChain[ChainIndex]->getType());
603  }
604 
605  BinaryOperator *BO = cast<BinaryOperator>(UserChain[ChainIndex]);
606  assert(BO->getNumUses() <= 1 &&
607  "distributeExtsAndCloneChain clones each BinaryOperator in "
608  "UserChain, so no one should be used more than "
609  "once");
610 
611  unsigned OpNo = (BO->getOperand(0) == UserChain[ChainIndex - 1] ? 0 : 1);
612  assert(BO->getOperand(OpNo) == UserChain[ChainIndex - 1]);
613  Value *NextInChain = removeConstOffset(ChainIndex - 1);
614  Value *TheOther = BO->getOperand(1 - OpNo);
615 
616  // If NextInChain is 0 and not the LHS of a sub, we can simplify the
617  // sub-expression to be just TheOther.
618  if (ConstantInt *CI = dyn_cast<ConstantInt>(NextInChain)) {
619  if (CI->isZero() && !(BO->getOpcode() == Instruction::Sub && OpNo == 0))
620  return TheOther;
621  }
622 
623  BinaryOperator::BinaryOps NewOp = BO->getOpcode();
624  if (BO->getOpcode() == Instruction::Or) {
625  // Rebuild "or" as "add", because "or" may be invalid for the new
626  // epxression.
627  //
628  // For instance, given
629  // a | (b + 5) where a and b + 5 have no common bits,
630  // we can extract 5 as the constant offset.
631  //
632  // However, reusing the "or" in the new index would give us
633  // (a | b) + 5
634  // which does not equal a | (b + 5).
635  //
636  // Replacing the "or" with "add" is fine, because
637  // a | (b + 5) = a + (b + 5) = (a + b) + 5
638  NewOp = Instruction::Add;
639  }
640 
641  BinaryOperator *NewBO;
642  if (OpNo == 0) {
643  NewBO = BinaryOperator::Create(NewOp, NextInChain, TheOther, "", IP);
644  } else {
645  NewBO = BinaryOperator::Create(NewOp, TheOther, NextInChain, "", IP);
646  }
647  NewBO->takeName(BO);
648  return NewBO;
649 }
650 
651 Value *ConstantOffsetExtractor::Extract(Value *Idx, GetElementPtrInst *GEP,
652  User *&UserChainTail,
653  const DominatorTree *DT) {
654  ConstantOffsetExtractor Extractor(GEP, DT);
655  // Find a non-zero constant offset first.
656  APInt ConstantOffset =
657  Extractor.find(Idx, /* SignExtended */ false, /* ZeroExtended */ false,
658  GEP->isInBounds());
659  if (ConstantOffset == 0) {
660  UserChainTail = nullptr;
661  return nullptr;
662  }
663  // Separates the constant offset from the GEP index.
664  Value *IdxWithoutConstOffset = Extractor.rebuildWithoutConstOffset();
665  UserChainTail = Extractor.UserChain.back();
666  return IdxWithoutConstOffset;
667 }
668 
670  const DominatorTree *DT) {
671  // If Idx is an index of an inbound GEP, Idx is guaranteed to be non-negative.
672  return ConstantOffsetExtractor(GEP, DT)
673  .find(Idx, /* SignExtended */ false, /* ZeroExtended */ false,
674  GEP->isInBounds())
675  .getSExtValue();
676 }
677 
678 bool SeparateConstOffsetFromGEP::canonicalizeArrayIndicesToPointerSize(
679  GetElementPtrInst *GEP) {
680  bool Changed = false;
681  Type *IntPtrTy = DL->getIntPtrType(GEP->getType());
682  gep_type_iterator GTI = gep_type_begin(*GEP);
683  for (User::op_iterator I = GEP->op_begin() + 1, E = GEP->op_end();
684  I != E; ++I, ++GTI) {
685  // Skip struct member indices which must be i32.
686  if (isa<SequentialType>(*GTI)) {
687  if ((*I)->getType() != IntPtrTy) {
688  *I = CastInst::CreateIntegerCast(*I, IntPtrTy, true, "idxprom", GEP);
689  Changed = true;
690  }
691  }
692  }
693  return Changed;
694 }
695 
696 int64_t
697 SeparateConstOffsetFromGEP::accumulateByteOffset(GetElementPtrInst *GEP,
698  bool &NeedsExtraction) {
699  NeedsExtraction = false;
700  int64_t AccumulativeByteOffset = 0;
701  gep_type_iterator GTI = gep_type_begin(*GEP);
702  for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I, ++GTI) {
703  if (isa<SequentialType>(*GTI)) {
704  // Tries to extract a constant offset from this GEP index.
705  int64_t ConstantOffset =
707  if (ConstantOffset != 0) {
708  NeedsExtraction = true;
709  // A GEP may have multiple indices. We accumulate the extracted
710  // constant offset to a byte offset, and later offset the remainder of
711  // the original GEP with this byte offset.
712  AccumulativeByteOffset +=
713  ConstantOffset * DL->getTypeAllocSize(GTI.getIndexedType());
714  }
715  } else if (LowerGEP) {
716  StructType *StTy = cast<StructType>(*GTI);
717  uint64_t Field = cast<ConstantInt>(GEP->getOperand(I))->getZExtValue();
718  // Skip field 0 as the offset is always 0.
719  if (Field != 0) {
720  NeedsExtraction = true;
721  AccumulativeByteOffset +=
722  DL->getStructLayout(StTy)->getElementOffset(Field);
723  }
724  }
725  }
726  return AccumulativeByteOffset;
727 }
728 
729 void SeparateConstOffsetFromGEP::lowerToSingleIndexGEPs(
730  GetElementPtrInst *Variadic, int64_t AccumulativeByteOffset) {
731  IRBuilder<> Builder(Variadic);
732  Type *IntPtrTy = DL->getIntPtrType(Variadic->getType());
733 
734  Type *I8PtrTy =
735  Builder.getInt8PtrTy(Variadic->getType()->getPointerAddressSpace());
736  Value *ResultPtr = Variadic->getOperand(0);
737  if (ResultPtr->getType() != I8PtrTy)
738  ResultPtr = Builder.CreateBitCast(ResultPtr, I8PtrTy);
739 
740  gep_type_iterator GTI = gep_type_begin(*Variadic);
741  // Create an ugly GEP for each sequential index. We don't create GEPs for
742  // structure indices, as they are accumulated in the constant offset index.
743  for (unsigned I = 1, E = Variadic->getNumOperands(); I != E; ++I, ++GTI) {
744  if (isa<SequentialType>(*GTI)) {
745  Value *Idx = Variadic->getOperand(I);
746  // Skip zero indices.
747  if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx))
748  if (CI->isZero())
749  continue;
750 
751  APInt ElementSize = APInt(IntPtrTy->getIntegerBitWidth(),
752  DL->getTypeAllocSize(GTI.getIndexedType()));
753  // Scale the index by element size.
754  if (ElementSize != 1) {
755  if (ElementSize.isPowerOf2()) {
756  Idx = Builder.CreateShl(
757  Idx, ConstantInt::get(IntPtrTy, ElementSize.logBase2()));
758  } else {
759  Idx = Builder.CreateMul(Idx, ConstantInt::get(IntPtrTy, ElementSize));
760  }
761  }
762  // Create an ugly GEP with a single index for each index.
763  ResultPtr =
764  Builder.CreateGEP(Builder.getInt8Ty(), ResultPtr, Idx, "uglygep");
765  }
766  }
767 
768  // Create a GEP with the constant offset index.
769  if (AccumulativeByteOffset != 0) {
770  Value *Offset = ConstantInt::get(IntPtrTy, AccumulativeByteOffset);
771  ResultPtr =
772  Builder.CreateGEP(Builder.getInt8Ty(), ResultPtr, Offset, "uglygep");
773  }
774  if (ResultPtr->getType() != Variadic->getType())
775  ResultPtr = Builder.CreateBitCast(ResultPtr, Variadic->getType());
776 
777  Variadic->replaceAllUsesWith(ResultPtr);
778  Variadic->eraseFromParent();
779 }
780 
781 void
782 SeparateConstOffsetFromGEP::lowerToArithmetics(GetElementPtrInst *Variadic,
783  int64_t AccumulativeByteOffset) {
784  IRBuilder<> Builder(Variadic);
785  Type *IntPtrTy = DL->getIntPtrType(Variadic->getType());
786 
787  Value *ResultPtr = Builder.CreatePtrToInt(Variadic->getOperand(0), IntPtrTy);
788  gep_type_iterator GTI = gep_type_begin(*Variadic);
789  // Create ADD/SHL/MUL arithmetic operations for each sequential indices. We
790  // don't create arithmetics for structure indices, as they are accumulated
791  // in the constant offset index.
792  for (unsigned I = 1, E = Variadic->getNumOperands(); I != E; ++I, ++GTI) {
793  if (isa<SequentialType>(*GTI)) {
794  Value *Idx = Variadic->getOperand(I);
795  // Skip zero indices.
796  if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx))
797  if (CI->isZero())
798  continue;
799 
800  APInt ElementSize = APInt(IntPtrTy->getIntegerBitWidth(),
801  DL->getTypeAllocSize(GTI.getIndexedType()));
802  // Scale the index by element size.
803  if (ElementSize != 1) {
804  if (ElementSize.isPowerOf2()) {
805  Idx = Builder.CreateShl(
806  Idx, ConstantInt::get(IntPtrTy, ElementSize.logBase2()));
807  } else {
808  Idx = Builder.CreateMul(Idx, ConstantInt::get(IntPtrTy, ElementSize));
809  }
810  }
811  // Create an ADD for each index.
812  ResultPtr = Builder.CreateAdd(ResultPtr, Idx);
813  }
814  }
815 
816  // Create an ADD for the constant offset index.
817  if (AccumulativeByteOffset != 0) {
818  ResultPtr = Builder.CreateAdd(
819  ResultPtr, ConstantInt::get(IntPtrTy, AccumulativeByteOffset));
820  }
821 
822  ResultPtr = Builder.CreateIntToPtr(ResultPtr, Variadic->getType());
823  Variadic->replaceAllUsesWith(ResultPtr);
824  Variadic->eraseFromParent();
825 }
826 
827 bool SeparateConstOffsetFromGEP::splitGEP(GetElementPtrInst *GEP) {
828  // Skip vector GEPs.
829  if (GEP->getType()->isVectorTy())
830  return false;
831 
832  // The backend can already nicely handle the case where all indices are
833  // constant.
834  if (GEP->hasAllConstantIndices())
835  return false;
836 
837  bool Changed = canonicalizeArrayIndicesToPointerSize(GEP);
838 
839  bool NeedsExtraction;
840  int64_t AccumulativeByteOffset = accumulateByteOffset(GEP, NeedsExtraction);
841 
842  if (!NeedsExtraction)
843  return Changed;
844  // If LowerGEP is disabled, before really splitting the GEP, check whether the
845  // backend supports the addressing mode we are about to produce. If no, this
846  // splitting probably won't be beneficial.
847  // If LowerGEP is enabled, even the extracted constant offset can not match
848  // the addressing mode, we can still do optimizations to other lowered parts
849  // of variable indices. Therefore, we don't check for addressing modes in that
850  // case.
851  if (!LowerGEP) {
852  TargetTransformInfo &TTI =
853  getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
854  *GEP->getParent()->getParent());
855  unsigned AddrSpace = GEP->getPointerAddressSpace();
856  if (!TTI.isLegalAddressingMode(GEP->getType()->getElementType(),
857  /*BaseGV=*/nullptr, AccumulativeByteOffset,
858  /*HasBaseReg=*/true, /*Scale=*/0,
859  AddrSpace)) {
860  return Changed;
861  }
862  }
863 
864  // Remove the constant offset in each sequential index. The resultant GEP
865  // computes the variadic base.
866  // Notice that we don't remove struct field indices here. If LowerGEP is
867  // disabled, a structure index is not accumulated and we still use the old
868  // one. If LowerGEP is enabled, a structure index is accumulated in the
869  // constant offset. LowerToSingleIndexGEPs or lowerToArithmetics will later
870  // handle the constant offset and won't need a new structure index.
871  gep_type_iterator GTI = gep_type_begin(*GEP);
872  for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I, ++GTI) {
873  if (isa<SequentialType>(*GTI)) {
874  // Splits this GEP index into a variadic part and a constant offset, and
875  // uses the variadic part as the new index.
876  Value *OldIdx = GEP->getOperand(I);
877  User *UserChainTail;
878  Value *NewIdx =
879  ConstantOffsetExtractor::Extract(OldIdx, GEP, UserChainTail, DT);
880  if (NewIdx != nullptr) {
881  // Switches to the index with the constant offset removed.
882  GEP->setOperand(I, NewIdx);
883  // After switching to the new index, we can garbage-collect UserChain
884  // and the old index if they are not used.
887  }
888  }
889  }
890 
891  // Clear the inbounds attribute because the new index may be off-bound.
892  // e.g.,
893  //
894  // b = add i64 a, 5
895  // addr = gep inbounds float* p, i64 b
896  //
897  // is transformed to:
898  //
899  // addr2 = gep float* p, i64 a
900  // addr = gep float* addr2, i64 5
901  //
902  // If a is -4, although the old index b is in bounds, the new index a is
903  // off-bound. http://llvm.org/docs/LangRef.html#id181 says "if the
904  // inbounds keyword is not present, the offsets are added to the base
905  // address with silently-wrapping two's complement arithmetic".
906  // Therefore, the final code will be a semantically equivalent.
907  //
908  // TODO(jingyue): do some range analysis to keep as many inbounds as
909  // possible. GEPs with inbounds are more friendly to alias analysis.
910  GEP->setIsInBounds(false);
911 
912  // Lowers a GEP to either GEPs with a single index or arithmetic operations.
913  if (LowerGEP) {
914  // As currently BasicAA does not analyze ptrtoint/inttoptr, do not lower to
915  // arithmetic operations if the target uses alias analysis in codegen.
916  if (TM && TM->getSubtargetImpl(*GEP->getParent()->getParent())->useAA())
917  lowerToSingleIndexGEPs(GEP, AccumulativeByteOffset);
918  else
919  lowerToArithmetics(GEP, AccumulativeByteOffset);
920  return true;
921  }
922 
923  // No need to create another GEP if the accumulative byte offset is 0.
924  if (AccumulativeByteOffset == 0)
925  return true;
926 
927  // Offsets the base with the accumulative byte offset.
928  //
929  // %gep ; the base
930  // ... %gep ...
931  //
932  // => add the offset
933  //
934  // %gep2 ; clone of %gep
935  // %new.gep = gep %gep2, <offset / sizeof(*%gep)>
936  // %gep ; will be removed
937  // ... %gep ...
938  //
939  // => replace all uses of %gep with %new.gep and remove %gep
940  //
941  // %gep2 ; clone of %gep
942  // %new.gep = gep %gep2, <offset / sizeof(*%gep)>
943  // ... %new.gep ...
944  //
945  // If AccumulativeByteOffset is not a multiple of sizeof(*%gep), we emit an
946  // uglygep (http://llvm.org/docs/GetElementPtr.html#what-s-an-uglygep):
947  // bitcast %gep2 to i8*, add the offset, and bitcast the result back to the
948  // type of %gep.
949  //
950  // %gep2 ; clone of %gep
951  // %0 = bitcast %gep2 to i8*
952  // %uglygep = gep %0, <offset>
953  // %new.gep = bitcast %uglygep to <type of %gep>
954  // ... %new.gep ...
955  Instruction *NewGEP = GEP->clone();
956  NewGEP->insertBefore(GEP);
957 
958  // Per ANSI C standard, signed / unsigned = unsigned and signed % unsigned =
959  // unsigned.. Therefore, we cast ElementTypeSizeOfGEP to signed because it is
960  // used with unsigned integers later.
961  int64_t ElementTypeSizeOfGEP = static_cast<int64_t>(
962  DL->getTypeAllocSize(GEP->getType()->getElementType()));
963  Type *IntPtrTy = DL->getIntPtrType(GEP->getType());
964  if (AccumulativeByteOffset % ElementTypeSizeOfGEP == 0) {
965  // Very likely. As long as %gep is natually aligned, the byte offset we
966  // extracted should be a multiple of sizeof(*%gep).
967  int64_t Index = AccumulativeByteOffset / ElementTypeSizeOfGEP;
968  NewGEP = GetElementPtrInst::Create(GEP->getResultElementType(), NewGEP,
969  ConstantInt::get(IntPtrTy, Index, true),
970  GEP->getName(), GEP);
971  } else {
972  // Unlikely but possible. For example,
973  // #pragma pack(1)
974  // struct S {
975  // int a[3];
976  // int64 b[8];
977  // };
978  // #pragma pack()
979  //
980  // Suppose the gep before extraction is &s[i + 1].b[j + 3]. After
981  // extraction, it becomes &s[i].b[j] and AccumulativeByteOffset is
982  // sizeof(S) + 3 * sizeof(int64) = 100, which is not a multiple of
983  // sizeof(int64).
984  //
985  // Emit an uglygep in this case.
986  Type *I8PtrTy = Type::getInt8PtrTy(GEP->getContext(),
987  GEP->getPointerAddressSpace());
988  NewGEP = new BitCastInst(NewGEP, I8PtrTy, "", GEP);
989  NewGEP = GetElementPtrInst::Create(
990  Type::getInt8Ty(GEP->getContext()), NewGEP,
991  ConstantInt::get(IntPtrTy, AccumulativeByteOffset, true), "uglygep",
992  GEP);
993  if (GEP->getType() != I8PtrTy)
994  NewGEP = new BitCastInst(NewGEP, GEP->getType(), GEP->getName(), GEP);
995  }
996 
997  GEP->replaceAllUsesWith(NewGEP);
998  GEP->eraseFromParent();
999 
1000  return true;
1001 }
1002 
1003 bool SeparateConstOffsetFromGEP::runOnFunction(Function &F) {
1004  if (skipOptnoneFunction(F))
1005  return false;
1006 
1008  return false;
1009 
1010  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
1011 
1012  bool Changed = false;
1013  for (Function::iterator B = F.begin(), BE = F.end(); B != BE; ++B) {
1014  for (BasicBlock::iterator I = B->begin(), IE = B->end(); I != IE; ) {
1015  if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I++)) {
1016  Changed |= splitGEP(GEP);
1017  }
1018  // No need to split GEP ConstantExprs because all its indices are constant
1019  // already.
1020  }
1021  }
1022 
1023  if (VerifyNoDeadCode)
1024  verifyNoDeadCode(F);
1025 
1026  return Changed;
1027 }
1028 
1029 void SeparateConstOffsetFromGEP::verifyNoDeadCode(Function &F) {
1030  for (auto &B : F) {
1031  for (auto &I : B) {
1032  if (isInstructionTriviallyDead(&I)) {
1033  std::string ErrMessage;
1034  raw_string_ostream RSO(ErrMessage);
1035  RSO << "Dead instruction detected!\n" << I << "\n";
1036  llvm_unreachable(RSO.str().c_str());
1037  }
1038  }
1039  }
1040 }
static unsigned getBitWidth(Type *Ty, const DataLayout &DL)
Returns the bitwidth of the given scalar or pointer type (if unknown returns 0).
INITIALIZE_PASS_BEGIN(SeparateConstOffsetFromGEP,"separate-const-offset-from-gep","Split GEPs to a variadic base and a constant offset for better CSE", false, false) INITIALIZE_PASS_END(SeparateConstOffsetFromGEP
iplist< Instruction >::iterator eraseFromParent()
eraseFromParent - This method unlinks 'this' from the containing basic block and deletes it...
Definition: Instruction.cpp:70
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:104
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:114
iterator end()
Definition: Function.h:459
unsigned getNumOperands() const
Definition: User.h:138
unsigned getPointerAddressSpace() const
Returns the address space of the pointer operand.
Definition: Instructions.h:976
static cl::opt< bool > VerifyNoDeadCode("reassociate-geps-verify-no-dead-code", cl::init(false), cl::desc("Verify this pass produces no dead code"), cl::Hidden)
bool haveNoCommonBitsSet(Value *LHS, Value *RHS, const DataLayout &DL, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr)
Returns true if LHS and RHS have no common bits set.
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:111
F(f)
FunctionType * getType(LLVMContext &Context, ID id, ArrayRef< Type * > Tys=None)
Return the function type for an intrinsic.
Definition: Function.cpp:822
Hexagon Common GEP
unsigned getPointerAddressSpace() const
Get the address space of this pointer or pointer vector type.
Definition: Type.cpp:216
op_iterator op_begin()
Definition: User.h:183
static Constant * getNullValue(Type *Ty)
Definition: Constants.cpp:178
StringRef getName() const
Return a constant reference to the value's name.
Definition: Value.cpp:188
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:70
This is the base class for all instructions that perform data casts.
Definition: InstrTypes.h:389
StructType - Class to represent struct types.
Definition: DerivedTypes.h:191
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
Definition: ErrorHandling.h:98
A Use represents the edge between a Value definition and its users.
Definition: Use.h:69
void setIsInBounds(bool b=true)
setIsInBounds - Set or clear the inbounds flag on this GEP instruction.
#define INITIALIZE_PASS_END(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:75
separate const offset from Split GEPs to a variadic base and a constant offset for better CSE
This provides a uniform API for creating instructions and inserting them into a basic block: either a...
Definition: IRBuilder.h:517
Instruction * clone() const
clone() - Create a copy of 'this' instruction that is identical in all ways except the following: ...
This class represents a no-op cast from one type to another.
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:351
void takeName(Value *V)
Transfer the name from V to this value.
Definition: Value.cpp:256
iterator begin()
Definition: Function.h:457
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:67
Type * getElementType() const
Definition: DerivedTypes.h:323
void initializeSeparateConstOffsetFromGEPPass(PassRegistry &)
bool isInBounds() const
isInBounds - Determine whether the GEP has the inbounds flag.
GetElementPtrInst - an instruction for type-safe pointer arithmetic to access elements of arrays and ...
Definition: Instructions.h:830
bool isLegalAddressingMode(Type *Ty, GlobalValue *BaseGV, int64_t BaseOffset, bool HasBaseReg, int64_t Scale, unsigned AddrSpace=0) const
Return true if the addressing mode represented by AM is legal for this target, for a load/store of th...
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:325
Wrapper pass for TargetTransformInfo.
FunctionPass * createSeparateConstOffsetFromGEPPass(const TargetMachine *TM=nullptr, bool LowerGEP=false)
void insertBefore(Instruction *InsertPos)
Insert an unlinked instruction into a basic block immediately before the specified instruction...
Definition: Instruction.cpp:76
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
bool isVectorTy() const
isVectorTy - True if this is an instance of VectorType.
Definition: Type.h:226
This is an important base class in LLVM.
Definition: Constant.h:41
static const SubtargetFeatureKV * Find(StringRef S, ArrayRef< SubtargetFeatureKV > A)
Find KV in array using binary search.
This file contains the declarations for the subclasses of Constant, which represent the different fla...
APInt Or(const APInt &LHS, const APInt &RHS)
Bitwise OR function for APInt.
Definition: APInt.h:1895
Represent the analysis usage information of a pass.
op_iterator op_end()
Definition: User.h:185
static cl::opt< bool > DisableSeparateConstOffsetFromGEP("disable-separate-const-offset-from-gep", cl::init(false), cl::desc("Do not separate the constant offset from a GEP instruction"), cl::Hidden)
for(unsigned i=0, e=MI->getNumOperands();i!=e;++i)
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:294
Value * getOperand(unsigned i) const
Definition: User.h:118
bool RecursivelyDeleteTriviallyDeadInstructions(Value *V, const TargetLibraryInfo *TLI=nullptr)
RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a trivially dead instruction...
Definition: Local.cpp:340
bool hasAllConstantIndices() const
hasAllConstantIndices - Return true if all of the indices of this GEP are constant integers...
LLVMContext & getContext() const
All values hold a context through their type.
Definition: Value.cpp:519
static PointerType * getInt8PtrTy(LLVMContext &C, unsigned AS=0)
Definition: Type.cpp:283
bool hasNoSignedWrap() const
Determine whether the no signed wrap flag is set.
bool isPowerOf2() const
Check if this APInt's value is a power of two greater than zero.
Definition: APInt.h:386
static GetElementPtrInst * Create(Type *PointeeType, Value *Ptr, ArrayRef< Value * > IdxList, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
Definition: Instructions.h:854
BinaryOps getOpcode() const
Definition: InstrTypes.h:323
static CastInst * CreateIntegerCast(Value *S, Type *Ty, bool isSigned, const Twine &Name="", Instruction *InsertBefore=nullptr)
Create a ZExt, BitCast, or Trunc for int -> int casts.
unsigned getIntegerBitWidth() const
Definition: Type.cpp:176
This is the shared class of boolean and integer constants.
Definition: Constants.h:47
This pass provides access to the codegen interfaces that are needed for IR-level transformations.
unsigned logBase2() const
Definition: APInt.h:1521
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:861
Module.h This file contains the declarations for the Module class.
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:222
SequentialType * getType() const
Definition: Instructions.h:922
static Constant * get(Type *Ty, uint64_t V, bool isSigned=false)
If Ty is a vector type, return a Constant with a splat of the given value.
Definition: Constants.cpp:582
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:263
void setOperand(unsigned i, Value *Val)
Definition: User.h:122
Class for arbitrary precision integers.
Definition: APInt.h:73
static BinaryOperator * Create(BinaryOps Op, Value *S1, Value *S2, const Twine &Name=Twine(), Instruction *InsertBefore=nullptr)
Construct a binary instruction, given the opcode and the two operands.
static Constant * getCast(unsigned ops, Constant *C, Type *Ty, bool OnlyIfReduced=false)
Convenience function for getting a Cast operation.
Definition: Constants.cpp:1591
LLVM_ATTRIBUTE_UNUSED_RESULT std::enable_if< !is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:285
const DataLayout & getDataLayout() const
Get the data layout for the module's target platform.
Definition: Module.cpp:372
#define I(x, y, z)
Definition: MD5.cpp:54
separate const offset from gep
A raw_ostream that writes to an std::string.
Definition: raw_ostream.h:465
aarch64 promote const
bool isInstructionTriviallyDead(Instruction *I, const TargetLibraryInfo *TLI=nullptr)
isInstructionTriviallyDead - Return true if the result produced by the instruction is not used...
Definition: Local.cpp:282
LLVM Value Representation.
Definition: Value.h:69
bool hasNoUnsignedWrap() const
Determine whether the no unsigned wrap flag is set.
Primary interface to the complete machine description for the target machine.
C - The default llvm calling convention, compatible with C.
Definition: CallingConv.h:34
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:203
This pass exposes codegen information to IR-level passes.
unsigned getNumUses() const
This method computes the number of uses of this Value.
Definition: Value.cpp:134
static void Split(std::vector< std::string > &V, StringRef S)
Split - Splits a string of comma separated items in to a vector of strings.
separate const offset from Split GEPs to a variadic base and a constant offset for better false
static IntegerType * getInt8Ty(LLVMContext &C)
Definition: Type.cpp:237
const BasicBlock * getParent() const
Definition: Instruction.h:72
Type * getResultElementType() const
Definition: Instructions.h:931
gep_type_iterator gep_type_begin(const User *GEP)