1//===- SeparateConstOffsetFromGEP.cpp -------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// Loop unrolling may create many similar GEPs for array accesses.
10// e.g., a 2-level loop
11//
12// float a[32][32]; // global variable
13//
14// for (int i = 0; i < 2; ++i) {
15// for (int j = 0; j < 2; ++j) {
16// ...
17// ... = a[x + i][y + j];
18// ...
19// }
20// }
21//
22// will probably be unrolled to:
23//
24// gep %a, 0, %x, %y; load
25// gep %a, 0, %x, %y + 1; load
26// gep %a, 0, %x + 1, %y; load
27// gep %a, 0, %x + 1, %y + 1; load
28//
29// LLVM's GVN does not use partial redundancy elimination yet, and is thus
30// unable to reuse (gep %a, 0, %x, %y). As a result, this misoptimization incurs
31// significant slowdown in targets with limited addressing modes. For instance,
32// because the PTX target does not support the reg+reg addressing mode, the
33// NVPTX backend emits PTX code that literally computes the pointer address of
34// each GEP, wasting tons of registers. It emits the following PTX for the
35// first load and similar PTX for other loads.
36//
37// mov.u32 %r1, %x;
38// mov.u32 %r2, %y;
39// mul.wide.u32 %rl2, %r1, 128;
40// mov.u64 %rl3, a;
41// add.s64 %rl4, %rl3, %rl2;
42// mul.wide.u32 %rl5, %r2, 4;
43// add.s64 %rl6, %rl4, %rl5;
44// ld.global.f32 %f1, [%rl6];
45//
46// To reduce the register pressure, the optimization implemented in this file
47// merges the common part of a group of GEPs, so we can compute each pointer
48// address by adding a simple offset to the common part, saving many registers.
49//
50// It works by splitting each GEP into a variadic base and a constant offset.
51// The variadic base can be computed once and reused by multiple GEPs, and the
52// constant offsets can be nicely folded into the reg+immediate addressing mode
53// (supported by most targets) without using any extra register.
54//
55// For instance, we transform the four GEPs and four loads in the above example
56// into:
57//
58// base = gep a, 0, x, y
59// load base
60// load base + 1 * sizeof(float)
61// load base + 32 * sizeof(float)
62// load base + 33 * sizeof(float)
63//
64// Given the transformed IR, a backend that supports the reg+immediate
65// addressing mode can easily fold the pointer arithmetics into the loads. For
66// example, the NVPTX backend can easily fold the pointer arithmetics into the
67// ld.global.f32 instructions, and the resultant PTX uses much fewer registers.
68//
69// mov.u32 %r1, %tid.x;
70// mov.u32 %r2, %tid.y;
71// mul.wide.u32 %rl2, %r1, 128;
72// mov.u64 %rl3, a;
73// add.s64 %rl4, %rl3, %rl2;
74// mul.wide.u32 %rl5, %r2, 4;
75// add.s64 %rl6, %rl4, %rl5;
76// ld.global.f32 %f1, [%rl6]; // so far the same as unoptimized PTX
77// ld.global.f32 %f2, [%rl6+4]; // much better
78// ld.global.f32 %f3, [%rl6+128]; // much better
79// ld.global.f32 %f4, [%rl6+132]; // much better
80//
81// Another improvement enabled by the LowerGEP flag is to lower a GEP with
82// multiple indices to multiple GEPs with a single index.
83// Such transformation can have following benefits:
84// (1) It can always extract constants in the indices of structure type.
85// (2) After such Lowering, there are more optimization opportunities such as
86// CSE, LICM and CGP.
87//
88// E.g. The following GEPs have multiple indices:
89// BB1:
90// %p = getelementptr [10 x %struct], ptr %ptr, i64 %i, i64 %j1, i32 3
91// load %p
92// ...
93// BB2:
94// %p2 = getelementptr [10 x %struct], ptr %ptr, i64 %i, i64 %j1, i32 2
95// load %p2
96// ...
97//
98// We can not do CSE to the common part related to index "i64 %i". Lowering
99// GEPs can achieve such goals.
100//
101// This pass will lower a GEP with multiple indices into multiple GEPs with a
102// single index:
103// BB1:
104// %2 = mul i64 %i, length_of_10xstruct ; CSE opportunity
105// %3 = getelementptr i8, ptr %ptr, i64 %2 ; CSE opportunity
106// %4 = mul i64 %j1, length_of_struct
107// %5 = getelementptr i8, ptr %3, i64 %4
108// %p = getelementptr i8, ptr %5, struct_field_3 ; Constant offset
109// load %p
110// ...
111// BB2:
112// %8 = mul i64 %i, length_of_10xstruct ; CSE opportunity
113// %9 = getelementptr i8, ptr %ptr, i64 %8 ; CSE opportunity
114// %10 = mul i64 %j2, length_of_struct
115// %11 = getelementptr i8, ptr %9, i64 %10
116// %p2 = getelementptr i8, ptr %11, struct_field_2 ; Constant offset
117// load %p2
118// ...
119//
120// Lowering GEPs can also benefit other passes such as LICM and CGP.
121// LICM (Loop Invariant Code Motion) can not hoist/sink a GEP of multiple
122// indices if one of the index is variant. If we lower such GEP into invariant
123// parts and variant parts, LICM can hoist/sink those invariant parts.
124// CGP (CodeGen Prepare) tries to sink address calculations that match the
125// target's addressing modes. A GEP with multiple indices may not match and will
126// not be sunk. If we lower such GEP into smaller parts, CGP may sink some of
127// them. So we end up with a better addressing mode.
128//
129//===----------------------------------------------------------------------===//
130
131#include "llvm/Transforms/Scalar/SeparateConstOffsetFromGEP.h"
132#include "llvm/ADT/APInt.h"
133#include "llvm/ADT/DenseMap.h"
134#include "llvm/ADT/DepthFirstIterator.h"
135#include "llvm/ADT/SmallVector.h"
136#include "llvm/Analysis/LoopInfo.h"
137#include "llvm/Analysis/MemoryBuiltins.h"
138#include "llvm/Analysis/TargetLibraryInfo.h"
139#include "llvm/Analysis/TargetTransformInfo.h"
140#include "llvm/Analysis/ValueTracking.h"
141#include "llvm/IR/BasicBlock.h"
142#include "llvm/IR/Constant.h"
143#include "llvm/IR/Constants.h"
144#include "llvm/IR/DataLayout.h"
145#include "llvm/IR/DerivedTypes.h"
146#include "llvm/IR/Dominators.h"
147#include "llvm/IR/Function.h"
148#include "llvm/IR/GetElementPtrTypeIterator.h"
149#include "llvm/IR/IRBuilder.h"
150#include "llvm/IR/InstrTypes.h"
151#include "llvm/IR/Instruction.h"
152#include "llvm/IR/Instructions.h"
153#include "llvm/IR/Module.h"
154#include "llvm/IR/PassManager.h"
155#include "llvm/IR/PatternMatch.h"
156#include "llvm/IR/Type.h"
157#include "llvm/IR/User.h"
158#include "llvm/IR/Value.h"
159#include "llvm/InitializePasses.h"
160#include "llvm/Pass.h"
161#include "llvm/Support/Casting.h"
162#include "llvm/Support/CommandLine.h"
163#include "llvm/Support/ErrorHandling.h"
164#include "llvm/Support/raw_ostream.h"
165#include "llvm/Transforms/Scalar.h"
166#include "llvm/Transforms/Utils/Local.h"
167#include <cassert>
168#include <cstdint>
169#include <string>
170
171using namespace llvm;
172using namespace llvm::PatternMatch;
173
174static cl::opt<bool> DisableSeparateConstOffsetFromGEP(
175 "disable-separate-const-offset-from-gep", cl::init(Val: false),
176 cl::desc("Do not separate the constant offset from a GEP instruction"),
177 cl::Hidden);
178
179// Setting this flag may emit false positives when the input module already
180// contains dead instructions. Therefore, we set it only in unit tests that are
181// free of dead code.
182static cl::opt<bool>
183 VerifyNoDeadCode("reassociate-geps-verify-no-dead-code", cl::init(Val: false),
184 cl::desc("Verify this pass produces no dead code"),
185 cl::Hidden);
186
187namespace {
188
189/// A helper class for separating a constant offset from a GEP index.
190///
191/// In real programs, a GEP index may be more complicated than a simple addition
192/// of something and a constant integer which can be trivially splitted. For
193/// example, to split ((a << 3) | 5) + b, we need to search deeper for the
194/// constant offset, so that we can separate the index to (a << 3) + b and 5.
195///
196/// Therefore, this class looks into the expression that computes a given GEP
197/// index, and tries to find a constant integer that can be hoisted to the
198/// outermost level of the expression as an addition. Not every constant in an
199/// expression can jump out. e.g., we cannot transform (b * (a + 5)) to (b * a +
200/// 5); nor can we transform (3 * (a + 5)) to (3 * a + 5), however in this case,
201/// -instcombine probably already optimized (3 * (a + 5)) to (3 * a + 15).
202class ConstantOffsetExtractor {
203public:
204 /// Extracts a constant offset from the given GEP index. It returns the
205 /// new index representing the remainder (equal to the original index minus
206 /// the constant offset), or nullptr if we cannot extract a constant offset.
207 /// \p Idx The given GEP index
208 /// \p GEP The given GEP
209 /// \p UserChainTail Outputs the tail of UserChain so that we can
210 /// garbage-collect unused instructions in UserChain.
211 /// \p PreservesNUW Outputs whether the extraction allows preserving the
212 /// GEP's nuw flag, if it has one.
213 static Value *Extract(Value *Idx, GetElementPtrInst *GEP,
214 User *&UserChainTail, bool &PreservesNUW);
215
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 APInt Find(Value *Idx, GetElementPtrInst *GEP);
220
221private:
222 ConstantOffsetExtractor(BasicBlock::iterator InsertionPt)
223 : IP(InsertionPt), DL(InsertionPt->getDataLayout()) {}
224
225 /// Searches the expression that computes V for a non-zero constant C s.t.
226 /// V can be reassociated into the form V' + C. If the searching is
227 /// successful, returns C and update UserChain as a def-use chain from C to V;
228 /// otherwise, UserChain is empty.
229 ///
230 /// \p V The given expression
231 /// \p GEP The base GEP instruction, used for determining relevant
232 /// types, flags, and non-negativity needed for safe
233 /// reassociation
234 /// \p Idx The original index of the GEP
235 /// \p SignExtended Whether V will be sign-extended in the computation of
236 /// the GEP index
237 /// \p ZeroExtended Whether V will be zero-extended in the computation of
238 /// the GEP index
239 APInt find(Value *V, GetElementPtrInst *GEP, Value *Idx, bool SignExtended,
240 bool ZeroExtended);
241
242 /// A helper function to look into both operands of a binary operator.
243 APInt findInEitherOperand(BinaryOperator *BO, bool SignExtended,
244 bool ZeroExtended);
245
246 /// After finding the constant offset C from the GEP index I, we build a new
247 /// index I' s.t. I' + C = I. This function builds and returns the new
248 /// index I' according to UserChain produced by function "find".
249 ///
250 /// The building conceptually takes two steps:
251 /// 1) iteratively distribute sext/zext/trunc towards the leaves of the
252 /// expression tree that computes I
253 /// 2) reassociate the expression tree to the form I' + C.
254 ///
255 /// For example, to extract the 5 from sext(a + (b + 5)), we first distribute
256 /// sext to a, b and 5 so that we have
257 /// sext(a) + (sext(b) + 5).
258 /// Then, we reassociate it to
259 /// (sext(a) + sext(b)) + 5.
260 /// Given this form, we know I' is sext(a) + sext(b).
261 Value *rebuildWithoutConstOffset();
262
263 /// After the first step of rebuilding the GEP index without the constant
264 /// offset, distribute sext/zext/trunc to the operands of all operators in
265 /// UserChain. e.g., zext(sext(a + (b + 5)) (assuming no overflow) =>
266 /// zext(sext(a)) + (zext(sext(b)) + zext(sext(5))).
267 ///
268 /// The function also updates UserChain to point to new subexpressions after
269 /// distributing sext/zext/trunc. e.g., the old UserChain of the above example
270 /// is
271 /// 5 -> b + 5 -> a + (b + 5) -> sext(...) -> zext(sext(...)),
272 /// and the new UserChain is
273 /// zext(sext(5)) -> zext(sext(b)) + zext(sext(5)) ->
274 /// zext(sext(a)) + (zext(sext(b)) + zext(sext(5))
275 ///
276 /// \p ChainIndex The index to UserChain. ChainIndex is initially
277 /// UserChain.size() - 1, and is decremented during
278 /// the recursion.
279 Value *distributeCastsAndCloneChain(unsigned ChainIndex);
280
281 /// Reassociates the GEP index to the form I' + C and returns I'.
282 Value *removeConstOffset(unsigned ChainIndex);
283
284 /// A helper function to apply CastInsts, a list of sext/zext/trunc, to value
285 /// V. e.g., if CastInsts = [sext i32 to i64, zext i16 to i32], this function
286 /// returns "sext i32 (zext i16 V to i32) to i64".
287 Value *applyCasts(Value *V);
288
289 /// A helper function that returns whether we can trace into the operands
290 /// of binary operator BO for a constant offset.
291 ///
292 /// \p SignExtended Whether BO is surrounded by sext
293 /// \p ZeroExtended Whether BO is surrounded by zext
294 /// \p GEP The base GEP instruction, used for determining relevant
295 /// types and flags needed for safe reassociation.
296 /// \p Idx The original index of the GEP
297 bool canTraceInto(bool SignExtended, bool ZeroExtended, BinaryOperator *BO,
298 GetElementPtrInst *GEP, Value *Idx);
299
300 /// The path from the constant offset to the old GEP index. e.g., if the GEP
301 /// index is "a * b + (c + 5)". After running function find, UserChain[0] will
302 /// be the constant 5, UserChain[1] will be the subexpression "c + 5", and
303 /// UserChain[2] will be the entire expression "a * b + (c + 5)".
304 ///
305 /// This path helps to rebuild the new GEP index.
306 SmallVector<User *, 8> UserChain;
307
308 /// A data structure used in rebuildWithoutConstOffset. Contains all
309 /// sext/zext/trunc instructions along UserChain.
310 SmallVector<CastInst *, 16> CastInsts;
311
312 /// Insertion position of cloned instructions.
313 BasicBlock::iterator IP;
314
315 const DataLayout &DL;
316};
317
318/// A pass that tries to split every GEP in the function into a variadic
319/// base and a constant offset. It is a FunctionPass because searching for the
320/// constant offset may inspect other basic blocks.
321class SeparateConstOffsetFromGEPLegacyPass : public FunctionPass {
322public:
323 static char ID;
324
325 SeparateConstOffsetFromGEPLegacyPass(bool LowerGEP = false)
326 : FunctionPass(ID), LowerGEP(LowerGEP) {
327 initializeSeparateConstOffsetFromGEPLegacyPassPass(
328 *PassRegistry::getPassRegistry());
329 }
330
331 void getAnalysisUsage(AnalysisUsage &AU) const override {
332 AU.addRequired<DominatorTreeWrapperPass>();
333 AU.addRequired<TargetTransformInfoWrapperPass>();
334 AU.addRequired<LoopInfoWrapperPass>();
335 AU.setPreservesCFG();
336 AU.addRequired<TargetLibraryInfoWrapperPass>();
337 }
338
339 bool runOnFunction(Function &F) override;
340
341private:
342 bool LowerGEP;
343};
344
345/// A pass that tries to split every GEP in the function into a variadic
346/// base and a constant offset. It is a FunctionPass because searching for the
347/// constant offset may inspect other basic blocks.
348class SeparateConstOffsetFromGEP {
349public:
350 SeparateConstOffsetFromGEP(
351 DominatorTree *DT, LoopInfo *LI, TargetLibraryInfo *TLI,
352 function_ref<TargetTransformInfo &(Function &)> GetTTI, bool LowerGEP)
353 : DT(DT), LI(LI), TLI(TLI), GetTTI(GetTTI), LowerGEP(LowerGEP) {}
354
355 bool run(Function &F);
356
357private:
358 /// Track the operands of an add or sub.
359 using ExprKey = std::pair<Value *, Value *>;
360
361 /// Create a pair for use as a map key for a commutable operation.
362 static ExprKey createNormalizedCommutablePair(Value *A, Value *B) {
363 if (A < B)
364 return {A, B};
365 return {B, A};
366 }
367
368 /// Tries to split the given GEP into a variadic base and a constant offset,
369 /// and returns true if the splitting succeeds.
370 bool splitGEP(GetElementPtrInst *GEP);
371
372 /// Tries to reorder the given GEP with the GEP that produces the base if
373 /// doing so results in producing a constant offset as the outermost
374 /// index.
375 bool reorderGEP(GetElementPtrInst *GEP, TargetTransformInfo &TTI);
376
377 /// Lower a GEP with multiple indices into multiple GEPs with a single index.
378 /// Function splitGEP already split the original GEP into a variadic part and
379 /// a constant offset (i.e., AccumulativeByteOffset). This function lowers the
380 /// variadic part into a set of GEPs with a single index and applies
381 /// AccumulativeByteOffset to it.
382 /// \p Variadic The variadic part of the original GEP.
383 /// \p AccumulativeByteOffset The constant offset.
384 void lowerToSingleIndexGEPs(GetElementPtrInst *Variadic,
385 const APInt &AccumulativeByteOffset);
386
387 /// Finds the constant offset within each index and accumulates them. If
388 /// LowerGEP is true, it finds in indices of both sequential and structure
389 /// types, otherwise it only finds in sequential indices. The output
390 /// NeedsExtraction indicates whether we successfully find a non-zero constant
391 /// offset.
392 APInt accumulateByteOffset(GetElementPtrInst *GEP, bool &NeedsExtraction);
393
394 /// Canonicalize array indices to pointer-size integers. This helps to
395 /// simplify the logic of splitting a GEP. For example, if a + b is a
396 /// pointer-size integer, we have
397 /// gep base, a + b = gep (gep base, a), b
398 /// However, this equality may not hold if the size of a + b is smaller than
399 /// the pointer size, because LLVM conceptually sign-extends GEP indices to
400 /// pointer size before computing the address
401 /// (http://llvm.org/docs/LangRef.html#id181).
402 ///
403 /// This canonicalization is very likely already done in clang and
404 /// instcombine. Therefore, the program will probably remain the same.
405 ///
406 /// Returns true if the module changes.
407 ///
408 /// Verified in @i32_add in split-gep.ll
409 bool canonicalizeArrayIndicesToIndexSize(GetElementPtrInst *GEP);
410
411 /// Optimize sext(a)+sext(b) to sext(a+b) when a+b can't sign overflow.
412 /// SeparateConstOffsetFromGEP distributes a sext to leaves before extracting
413 /// the constant offset. After extraction, it becomes desirable to reunion the
414 /// distributed sexts. For example,
415 ///
416 /// &a[sext(i +nsw (j +nsw 5)]
417 /// => distribute &a[sext(i) +nsw (sext(j) +nsw 5)]
418 /// => constant extraction &a[sext(i) + sext(j)] + 5
419 /// => reunion &a[sext(i +nsw j)] + 5
420 bool reuniteExts(Function &F);
421
422 /// A helper that reunites sexts in an instruction.
423 bool reuniteExts(Instruction *I);
424
425 /// Find the closest dominator of <Dominatee> that is equivalent to <Key>.
426 Instruction *findClosestMatchingDominator(
427 ExprKey Key, Instruction *Dominatee,
428 DenseMap<ExprKey, SmallVector<Instruction *, 2>> &DominatingExprs);
429
430 /// Verify F is free of dead code.
431 void verifyNoDeadCode(Function &F);
432
433 bool hasMoreThanOneUseInLoop(Value *v, Loop *L);
434
435 // Swap the index operand of two GEP.
436 void swapGEPOperand(GetElementPtrInst *First, GetElementPtrInst *Second);
437
438 // Check if it is safe to swap operand of two GEP.
439 bool isLegalToSwapOperand(GetElementPtrInst *First, GetElementPtrInst *Second,
440 Loop *CurLoop);
441
442 const DataLayout *DL = nullptr;
443 DominatorTree *DT = nullptr;
444 LoopInfo *LI;
445 TargetLibraryInfo *TLI;
446 // Retrieved lazily since not always used.
447 function_ref<TargetTransformInfo &(Function &)> GetTTI;
448
449 /// Whether to lower a GEP with multiple indices into arithmetic operations or
450 /// multiple GEPs with a single index.
451 bool LowerGEP;
452
453 DenseMap<ExprKey, SmallVector<Instruction *, 2>> DominatingAdds;
454 DenseMap<ExprKey, SmallVector<Instruction *, 2>> DominatingSubs;
455};
456
457} // end anonymous namespace
458
459char SeparateConstOffsetFromGEPLegacyPass::ID = 0;
460
461INITIALIZE_PASS_BEGIN(
462 SeparateConstOffsetFromGEPLegacyPass, "separate-const-offset-from-gep",
463 "Split GEPs to a variadic base and a constant offset for better CSE", false,
464 false)
465INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
466INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)
467INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
468INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
469INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
470INITIALIZE_PASS_END(
471 SeparateConstOffsetFromGEPLegacyPass, "separate-const-offset-from-gep",
472 "Split GEPs to a variadic base and a constant offset for better CSE", false,
473 false)
474
475FunctionPass *llvm::createSeparateConstOffsetFromGEPPass(bool LowerGEP) {
476 return new SeparateConstOffsetFromGEPLegacyPass(LowerGEP);
477}
478
479// Checks if it is safe to reorder an add/sext result used in a GEP.
480//
481// An inbounds GEP does not guarantee that the index is non-negative.
482// This helper checks first if the index is known non-negative. If the index is
483// non-negative, the transform is always safe.
484// Second, it checks whether the GEP is inbounds and directly based on a global
485// or an alloca, which are required to prove futher transform validity.
486// If the GEP:
487// - Has a zero offset from the base, the index is non-negative (any negative
488// value would produce poison/UB)
489// - Has ObjectSize < (2^(N-1) - C + 1) * stride, where C is a constant from the
490// add, stride is the element size of Idx, and N is bitwidth of Idx.
491// This is because with this pattern:
492// %add = add iN %val, C
493// %sext = sext iN %add to i64
494// %gep = getelementptr inbounds TYPE, %sext
495// The worst-case is when %val sign-flips to produce the smallest magnitude
496// negative value, at 2^(N-1)-1. In this case, the add/sext is -(2^(N-1)-C+1),
497// and the sext/add is 2^(N-1)+C-1 (2^N difference). The original add/sext
498// only produces a defined GEP when -(2^(N-1)-C+1) is inbounds. So, if
499// ObjectSize < (2^(N-1) - C + 1) * stride, it is impossible for the
500// worst-case sign-flip to be defined.
501// Note that in this case the GEP is not neccesarily non-negative, but any
502// negative results will still produce the same behavior in the reordered
503// version with a defined GEP.
504// This can also work for negative C, but the threshold is instead
505// (2^(N-1)+C)*stride, since the sign-flip is done in reverse and is instead
506// producing a large positive value that still needs to be inbounds to the
507// object size. If C is negative, we cannot make any useful assumptions based
508// on the offset, since it would need to be extremely large.
509static bool canReorderAddSextToGEP(const GetElementPtrInst *GEP,
510 const Value *Idx, const BinaryOperator *Add,
511 const DataLayout &DL) {
512 if (isKnownNonNegative(V: Idx, SQ: DL))
513 return true;
514
515 if (!GEP->isInBounds())
516 return false;
517
518 const Value *Ptr = GEP->getPointerOperand();
519 int64_t Offset = 0;
520 const Value *Base =
521 GetPointerBaseWithConstantOffset(Ptr: const_cast<Value *>(Ptr), Offset, DL);
522
523 // We need one of the operands to be a constant to be able to trace into the
524 // operator.
525 const ConstantInt *CI = dyn_cast<ConstantInt>(Val: Add->getOperand(i_nocapture: 0));
526 if (!CI)
527 CI = dyn_cast<ConstantInt>(Val: Add->getOperand(i_nocapture: 1));
528 if (!CI)
529 return false;
530 // Calculate the threshold
531 APInt Threshold;
532 unsigned N = Add->getType()->getIntegerBitWidth();
533 TypeSize ElemSize = DL.getTypeAllocSize(Ty: GEP->getSourceElementType());
534 if (ElemSize.isScalable())
535 return false;
536 uint64_t Stride = ElemSize.getFixedValue();
537 if (!CI->isNegative()) {
538 // (2^(N-1) - C + 1) * stride
539 Threshold = (APInt::getSignedMinValue(numBits: N).zext(width: 128) -
540 CI->getValue().zextOrTrunc(width: 128) + 1) *
541 APInt(128, Stride);
542 } else {
543 // (2^(N-1) + C) * stride
544 Threshold = (APInt::getSignedMinValue(numBits: N).zext(width: 128) +
545 CI->getValue().sextOrTrunc(width: 128)) *
546 APInt(128, Stride);
547 }
548
549 if (Base && (isa<AllocaInst>(Val: Base) || isa<GlobalObject>(Val: Base)) &&
550 !CI->isNegative()) {
551 // If the offset is zero from an alloca or global, inbounds is sufficient to
552 // prove non-negativity if one add operand is non-negative
553 if (Offset == 0)
554 return true;
555
556 // Check if the Offset < Threshold (positive CI only) otherwise
557 if (Offset < 0)
558 return true;
559 if (APInt(128, (uint64_t)Offset).ult(RHS: Threshold))
560 return true;
561 } else {
562 // If we can't determine the offset from the base object, we can still use
563 // the underlying object and type size constraints
564 Base = getUnderlyingObject(V: Ptr);
565 // Can only prove non-negativity if the base object is known
566 if (!(isa<AllocaInst>(Val: Base) || isa<GlobalObject>(Val: Base)))
567 return false;
568 }
569
570 // Check if the ObjectSize < Threshold (for both positive or negative C)
571 uint64_t ObjSize = 0;
572 if (const auto *AI = dyn_cast<AllocaInst>(Val: Base)) {
573 if (auto AllocSize = AI->getAllocationSize(DL))
574 if (!AllocSize->isScalable())
575 ObjSize = AllocSize->getFixedValue();
576 } else if (const auto *GV = dyn_cast<GlobalVariable>(Val: Base)) {
577 TypeSize GVSize = DL.getTypeAllocSize(Ty: GV->getValueType());
578 if (!GVSize.isScalable())
579 ObjSize = GVSize.getFixedValue();
580 }
581 if (ObjSize > 0 && APInt(128, ObjSize).ult(RHS: Threshold))
582 return true;
583
584 return false;
585}
586
587bool ConstantOffsetExtractor::canTraceInto(bool SignExtended, bool ZeroExtended,
588 BinaryOperator *BO,
589 GetElementPtrInst *GEP, Value *Idx) {
590 // We only consider ADD, SUB and OR, because a non-zero constant found in
591 // expressions composed of these operations can be easily hoisted as a
592 // constant offset by reassociation.
593 if (BO->getOpcode() != Instruction::Add &&
594 BO->getOpcode() != Instruction::Sub &&
595 BO->getOpcode() != Instruction::Or) {
596 return false;
597 }
598
599 // Do not trace into "or" unless it is equivalent to "add nuw nsw".
600 // This is the case if the or's disjoint flag is set.
601 if (BO->getOpcode() == Instruction::Or &&
602 !cast<PossiblyDisjointInst>(Val: BO)->isDisjoint())
603 return false;
604
605 // FIXME: We don't currently support constants from the RHS of subs,
606 // when we are zero-extended, because we need a way to zero-extended
607 // them before they are negated.
608 if (ZeroExtended && !SignExtended && BO->getOpcode() == Instruction::Sub)
609 return false;
610
611 // In addition, tracing into BO requires that its surrounding sext/zext/trunc
612 // (if any) is distributable to both operands.
613 //
614 // Suppose BO = A op B.
615 // SignExtended | ZeroExtended | Distributable?
616 // --------------+--------------+----------------------------------
617 // 0 | 0 | true because no s/zext exists
618 // 0 | 1 | zext(BO) == zext(A) op zext(B)
619 // 1 | 0 | sext(BO) == sext(A) op sext(B)
620 // 1 | 1 | zext(sext(BO)) ==
621 // | | zext(sext(A)) op zext(sext(B))
622 if (BO->getOpcode() == Instruction::Add && !ZeroExtended && GEP) {
623 // If a + b >= 0 and (a >= 0 or b >= 0), then
624 // sext(a + b) = sext(a) + sext(b)
625 // even if the addition is not marked nsw.
626 //
627 // Leveraging this invariant, we can trace into an sext'ed inbound GEP
628 // index under certain conditions (see canReorderAddSextToGEP).
629 //
630 // Verified in @sext_add in split-gep.ll.
631 if (canReorderAddSextToGEP(GEP, Idx, Add: BO, DL))
632 return true;
633 }
634
635 // For a sext(add nuw), allow tracing through when the enclosing GEP is both
636 // inbounds and nuw.
637 bool GEPInboundsNUW =
638 GEP ? (GEP->isInBounds() && GEP->hasNoUnsignedWrap()) : false;
639 if (BO->getOpcode() == Instruction::Add && SignExtended && !ZeroExtended &&
640 GEPInboundsNUW && BO->hasNoUnsignedWrap())
641 return true;
642
643 // sext (add/sub nsw A, B) == add/sub nsw (sext A), (sext B)
644 // zext (add/sub nuw A, B) == add/sub nuw (zext A), (zext B)
645 if (BO->getOpcode() == Instruction::Add ||
646 BO->getOpcode() == Instruction::Sub) {
647 if (SignExtended && !BO->hasNoSignedWrap())
648 return false;
649 if (ZeroExtended && !BO->hasNoUnsignedWrap())
650 return false;
651 }
652
653 return true;
654}
655
656APInt ConstantOffsetExtractor::findInEitherOperand(BinaryOperator *BO,
657 bool SignExtended,
658 bool ZeroExtended) {
659 // Save off the current height of the chain, in case we need to restore it.
660 size_t ChainLength = UserChain.size();
661
662 // BO cannot use information from the base GEP at this point, so clear it.
663 APInt ConstantOffset =
664 find(V: BO->getOperand(i_nocapture: 0), GEP: nullptr, Idx: nullptr, SignExtended, ZeroExtended);
665 // If we found a constant offset in the left operand, stop and return that.
666 // This shortcut might cause us to miss opportunities of combining the
667 // constant offsets in both operands, e.g., (a + 4) + (b + 5) => (a + b) + 9.
668 // However, such cases are probably already handled by -instcombine,
669 // given this pass runs after the standard optimizations.
670 if (ConstantOffset != 0) return ConstantOffset;
671
672 // Reset the chain back to where it was when we started exploring this node,
673 // since visiting the LHS didn't pan out.
674 UserChain.resize(N: ChainLength);
675
676 ConstantOffset =
677 find(V: BO->getOperand(i_nocapture: 1), GEP: nullptr, Idx: nullptr, SignExtended, ZeroExtended);
678 // If U is a sub operator, negate the constant offset found in the right
679 // operand.
680 if (BO->getOpcode() == Instruction::Sub)
681 ConstantOffset = -ConstantOffset;
682
683 // If RHS wasn't a suitable candidate either, reset the chain again.
684 if (ConstantOffset == 0)
685 UserChain.resize(N: ChainLength);
686
687 return ConstantOffset;
688}
689
690APInt ConstantOffsetExtractor::find(Value *V, GetElementPtrInst *GEP,
691 Value *Idx, bool SignExtended,
692 bool ZeroExtended) {
693 // TODO(jingyue): We could trace into integer/pointer casts, such as
694 // inttoptr, ptrtoint, bitcast, and addrspacecast. We choose to handle only
695 // integers because it gives good enough results for our benchmarks.
696 unsigned BitWidth = cast<IntegerType>(Val: V->getType())->getBitWidth();
697
698 // We cannot do much with Values that are not a User, such as an Argument.
699 User *U = dyn_cast<User>(Val: V);
700 if (U == nullptr) return APInt(BitWidth, 0);
701
702 APInt ConstantOffset(BitWidth, 0);
703 if (ConstantInt *CI = dyn_cast<ConstantInt>(Val: V)) {
704 // Hooray, we found it!
705 ConstantOffset = CI->getValue();
706 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Val: V)) {
707 // Trace into subexpressions for more hoisting opportunities.
708 if (canTraceInto(SignExtended, ZeroExtended, BO, GEP, Idx))
709 ConstantOffset = findInEitherOperand(BO, SignExtended, ZeroExtended);
710 } else if (isa<TruncInst>(Val: V)) {
711 ConstantOffset =
712 find(V: U->getOperand(i: 0), GEP, Idx, SignExtended, ZeroExtended)
713 .trunc(width: BitWidth);
714 } else if (isa<SExtInst>(Val: V)) {
715 ConstantOffset =
716 find(V: U->getOperand(i: 0), GEP, Idx, /* SignExtended */ true, ZeroExtended)
717 .sext(width: BitWidth);
718 } else if (isa<ZExtInst>(Val: V)) {
719 // As an optimization, we can clear the SignExtended flag because
720 // sext(zext(a)) = zext(a). Verified in @sext_zext in split-gep.ll.
721 ConstantOffset = find(V: U->getOperand(i: 0), GEP, Idx, /* SignExtended */ false,
722 /* ZeroExtended */ true)
723 .zext(width: BitWidth);
724 }
725
726 // If we found a non-zero constant offset, add it to the path for
727 // rebuildWithoutConstOffset. Zero is a valid constant offset, but doesn't
728 // help this optimization.
729 if (ConstantOffset != 0)
730 UserChain.push_back(Elt: U);
731 return ConstantOffset;
732}
733
734Value *ConstantOffsetExtractor::applyCasts(Value *V) {
735 Value *Current = V;
736 // CastInsts is built in the use-def order. Therefore, we apply them to V
737 // in the reversed order.
738 for (CastInst *I : llvm::reverse(C&: CastInsts)) {
739 if (Constant *C = dyn_cast<Constant>(Val: Current)) {
740 // Try to constant fold the cast.
741 Current = ConstantFoldCastOperand(Opcode: I->getOpcode(), C, DestTy: I->getType(), DL);
742 if (Current)
743 continue;
744 }
745
746 Instruction *Cast = I->clone();
747 Cast->setOperand(i: 0, Val: Current);
748 // In ConstantOffsetExtractor::find we do not analyze nuw/nsw for trunc, so
749 // we assume that it is ok to redistribute trunc over add/sub/or. But for
750 // example (add (trunc nuw A), (trunc nuw B)) is more poisonous than (trunc
751 // nuw (add A, B))). To make such redistributions legal we drop all the
752 // poison generating flags from cloned trunc instructions here.
753 if (isa<TruncInst>(Val: Cast))
754 Cast->dropPoisonGeneratingFlags();
755 Cast->insertBefore(BB&: *IP->getParent(), InsertPos: IP);
756 Current = Cast;
757 }
758 return Current;
759}
760
761Value *ConstantOffsetExtractor::rebuildWithoutConstOffset() {
762 distributeCastsAndCloneChain(ChainIndex: UserChain.size() - 1);
763 // Remove all nullptrs (used to be sext/zext/trunc) from UserChain.
764 unsigned NewSize = 0;
765 for (User *I : UserChain) {
766 if (I != nullptr) {
767 UserChain[NewSize] = I;
768 NewSize++;
769 }
770 }
771 UserChain.resize(N: NewSize);
772 return removeConstOffset(ChainIndex: UserChain.size() - 1);
773}
774
775Value *
776ConstantOffsetExtractor::distributeCastsAndCloneChain(unsigned ChainIndex) {
777 User *U = UserChain[ChainIndex];
778 if (ChainIndex == 0) {
779 assert(isa<ConstantInt>(U));
780 // If U is a ConstantInt, applyCasts will return a ConstantInt as well.
781 return UserChain[ChainIndex] = cast<ConstantInt>(Val: applyCasts(V: U));
782 }
783
784 if (CastInst *Cast = dyn_cast<CastInst>(Val: U)) {
785 assert(
786 (isa<SExtInst>(Cast) || isa<ZExtInst>(Cast) || isa<TruncInst>(Cast)) &&
787 "Only following instructions can be traced: sext, zext & trunc");
788 CastInsts.push_back(Elt: Cast);
789 UserChain[ChainIndex] = nullptr;
790 return distributeCastsAndCloneChain(ChainIndex: ChainIndex - 1);
791 }
792
793 // Function find only trace into BinaryOperator and CastInst.
794 BinaryOperator *BO = cast<BinaryOperator>(Val: U);
795 // OpNo = which operand of BO is UserChain[ChainIndex - 1]
796 unsigned OpNo = (BO->getOperand(i_nocapture: 0) == UserChain[ChainIndex - 1] ? 0 : 1);
797 Value *TheOther = applyCasts(V: BO->getOperand(i_nocapture: 1 - OpNo));
798 Value *NextInChain = distributeCastsAndCloneChain(ChainIndex: ChainIndex - 1);
799
800 BinaryOperator *NewBO = nullptr;
801 if (OpNo == 0) {
802 NewBO = BinaryOperator::Create(Op: BO->getOpcode(), S1: NextInChain, S2: TheOther,
803 Name: BO->getName(), InsertBefore: IP);
804 } else {
805 NewBO = BinaryOperator::Create(Op: BO->getOpcode(), S1: TheOther, S2: NextInChain,
806 Name: BO->getName(), InsertBefore: IP);
807 }
808 return UserChain[ChainIndex] = NewBO;
809}
810
811Value *ConstantOffsetExtractor::removeConstOffset(unsigned ChainIndex) {
812 if (ChainIndex == 0) {
813 assert(isa<ConstantInt>(UserChain[ChainIndex]));
814 return ConstantInt::getNullValue(Ty: UserChain[ChainIndex]->getType());
815 }
816
817 BinaryOperator *BO = cast<BinaryOperator>(Val: UserChain[ChainIndex]);
818 assert((BO->use_empty() || BO->hasOneUse()) &&
819 "distributeCastsAndCloneChain clones each BinaryOperator in "
820 "UserChain, so no one should be used more than "
821 "once");
822
823 unsigned OpNo = (BO->getOperand(i_nocapture: 0) == UserChain[ChainIndex - 1] ? 0 : 1);
824 assert(BO->getOperand(OpNo) == UserChain[ChainIndex - 1]);
825 Value *NextInChain = removeConstOffset(ChainIndex: ChainIndex - 1);
826 Value *TheOther = BO->getOperand(i_nocapture: 1 - OpNo);
827
828 // If NextInChain is 0 and not the LHS of a sub, we can simplify the
829 // sub-expression to be just TheOther.
830 if (ConstantInt *CI = dyn_cast<ConstantInt>(Val: NextInChain)) {
831 if (CI->isZero() && !(BO->getOpcode() == Instruction::Sub && OpNo == 0))
832 return TheOther;
833 }
834
835 BinaryOperator::BinaryOps NewOp = BO->getOpcode();
836 if (BO->getOpcode() == Instruction::Or) {
837 // Rebuild "or" as "add", because "or" may be invalid for the new
838 // expression.
839 //
840 // For instance, given
841 // a | (b + 5) where a and b + 5 have no common bits,
842 // we can extract 5 as the constant offset.
843 //
844 // However, reusing the "or" in the new index would give us
845 // (a | b) + 5
846 // which does not equal a | (b + 5).
847 //
848 // Replacing the "or" with "add" is fine, because
849 // a | (b + 5) = a + (b + 5) = (a + b) + 5
850 NewOp = Instruction::Add;
851 }
852
853 BinaryOperator *NewBO;
854 if (OpNo == 0) {
855 NewBO = BinaryOperator::Create(Op: NewOp, S1: NextInChain, S2: TheOther, Name: "", InsertBefore: IP);
856 } else {
857 NewBO = BinaryOperator::Create(Op: NewOp, S1: TheOther, S2: NextInChain, Name: "", InsertBefore: IP);
858 }
859 NewBO->takeName(V: BO);
860 return NewBO;
861}
862
863/// A helper function to check if reassociating through an entry in the user
864/// chain would invalidate the GEP's nuw flag.
865static bool allowsPreservingNUW(const User *U) {
866 if (const BinaryOperator *BO = dyn_cast<BinaryOperator>(Val: U)) {
867 // Binary operations need to be effectively add nuw.
868 auto Opcode = BO->getOpcode();
869 if (Opcode == BinaryOperator::Or) {
870 // Ors are only considered here if they are disjoint. The addition that
871 // they represent in this case is NUW.
872 assert(cast<PossiblyDisjointInst>(BO)->isDisjoint());
873 return true;
874 }
875 return Opcode == BinaryOperator::Add && BO->hasNoUnsignedWrap();
876 }
877 // UserChain can only contain ConstantInt, CastInst, or BinaryOperator.
878 // Among the possible CastInsts, only trunc without nuw is a problem: If it
879 // is distributed through an add nuw, wrapping may occur:
880 // "add nuw trunc(a), trunc(b)" is more poisonous than "trunc(add nuw a, b)"
881 if (const TruncInst *TI = dyn_cast<TruncInst>(Val: U))
882 return TI->hasNoUnsignedWrap();
883 assert((isa<CastInst>(U) || isa<ConstantInt>(U)) && "Unexpected User.");
884 return true;
885}
886
887Value *ConstantOffsetExtractor::Extract(Value *Idx, GetElementPtrInst *GEP,
888 User *&UserChainTail,
889 bool &PreservesNUW) {
890 ConstantOffsetExtractor Extractor(GEP->getIterator());
891 // Find a non-zero constant offset first.
892 APInt ConstantOffset = Extractor.find(V: Idx, GEP, Idx, /* SignExtended */ false,
893 /* ZeroExtended */ false);
894 if (ConstantOffset == 0) {
895 UserChainTail = nullptr;
896 PreservesNUW = true;
897 return nullptr;
898 }
899
900 PreservesNUW = all_of(Range&: Extractor.UserChain, P: allowsPreservingNUW);
901
902 // Separates the constant offset from the GEP index.
903 Value *IdxWithoutConstOffset = Extractor.rebuildWithoutConstOffset();
904 UserChainTail = Extractor.UserChain.back();
905 return IdxWithoutConstOffset;
906}
907
908APInt ConstantOffsetExtractor::Find(Value *Idx, GetElementPtrInst *GEP) {
909 return ConstantOffsetExtractor(GEP->getIterator())
910 .find(V: Idx, GEP, Idx, /* SignExtended */ false, /* ZeroExtended */ false);
911}
912
913bool SeparateConstOffsetFromGEP::canonicalizeArrayIndicesToIndexSize(
914 GetElementPtrInst *GEP) {
915 bool Changed = false;
916 Type *PtrIdxTy = DL->getIndexType(PtrTy: GEP->getType());
917 gep_type_iterator GTI = gep_type_begin(GEP: *GEP);
918 for (User::op_iterator I = GEP->op_begin() + 1, E = GEP->op_end();
919 I != E; ++I, ++GTI) {
920 // Skip struct member indices which must be i32.
921 if (GTI.isSequential()) {
922 if ((*I)->getType() != PtrIdxTy) {
923 *I = CastInst::CreateIntegerCast(S: *I, Ty: PtrIdxTy, isSigned: true, Name: "idxprom",
924 InsertBefore: GEP->getIterator());
925 Changed = true;
926 }
927 }
928 }
929 return Changed;
930}
931
932APInt SeparateConstOffsetFromGEP::accumulateByteOffset(GetElementPtrInst *GEP,
933 bool &NeedsExtraction) {
934 NeedsExtraction = false;
935 unsigned IdxWidth = DL->getIndexTypeSizeInBits(Ty: GEP->getType());
936 APInt AccumulativeByteOffset(IdxWidth, 0);
937 gep_type_iterator GTI = gep_type_begin(GEP: *GEP);
938 for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I, ++GTI) {
939 if (GTI.isSequential()) {
940 // Constant offsets of scalable types are not really constant.
941 if (GTI.getIndexedType()->isScalableTy())
942 continue;
943
944 // Tries to extract a constant offset from this GEP index.
945 APInt ConstantOffset =
946 ConstantOffsetExtractor::Find(Idx: GEP->getOperand(i_nocapture: I), GEP)
947 .sextOrTrunc(width: IdxWidth);
948 if (ConstantOffset != 0) {
949 NeedsExtraction = true;
950 // A GEP may have multiple indices. We accumulate the extracted
951 // constant offset to a byte offset, and later offset the remainder of
952 // the original GEP with this byte offset.
953 AccumulativeByteOffset +=
954 ConstantOffset * APInt(IdxWidth,
955 GTI.getSequentialElementStride(DL: *DL),
956 /*IsSigned=*/true, /*ImplicitTrunc=*/true);
957 }
958 } else if (LowerGEP) {
959 StructType *StTy = GTI.getStructType();
960 uint64_t Field = cast<ConstantInt>(Val: GEP->getOperand(i_nocapture: I))->getZExtValue();
961 // Skip field 0 as the offset is always 0.
962 if (Field != 0) {
963 NeedsExtraction = true;
964 AccumulativeByteOffset +=
965 APInt(IdxWidth, DL->getStructLayout(Ty: StTy)->getElementOffset(Idx: Field),
966 /*IsSigned=*/true, /*ImplicitTrunc=*/true);
967 }
968 }
969 }
970 return AccumulativeByteOffset;
971}
972
973void SeparateConstOffsetFromGEP::lowerToSingleIndexGEPs(
974 GetElementPtrInst *Variadic, const APInt &AccumulativeByteOffset) {
975 IRBuilder<> Builder(Variadic);
976 Type *PtrIndexTy = DL->getIndexType(PtrTy: Variadic->getType());
977
978 Value *ResultPtr = Variadic->getOperand(i_nocapture: 0);
979 Loop *L = LI->getLoopFor(BB: Variadic->getParent());
980 // Check if the base is not loop invariant or used more than once.
981 bool isSwapCandidate =
982 L && L->isLoopInvariant(V: ResultPtr) &&
983 !hasMoreThanOneUseInLoop(v: ResultPtr, L);
984 Value *FirstResult = nullptr;
985
986 gep_type_iterator GTI = gep_type_begin(GEP: *Variadic);
987 // Create an ugly GEP for each sequential index. We don't create GEPs for
988 // structure indices, as they are accumulated in the constant offset index.
989 for (unsigned I = 1, E = Variadic->getNumOperands(); I != E; ++I, ++GTI) {
990 if (GTI.isSequential()) {
991 Value *Idx = Variadic->getOperand(i_nocapture: I);
992 // Skip zero indices.
993 if (ConstantInt *CI = dyn_cast<ConstantInt>(Val: Idx))
994 if (CI->isZero())
995 continue;
996
997 APInt ElementSize = APInt(PtrIndexTy->getIntegerBitWidth(),
998 GTI.getSequentialElementStride(DL: *DL));
999 // Scale the index by element size.
1000 if (ElementSize != 1) {
1001 if (ElementSize.isPowerOf2()) {
1002 Idx = Builder.CreateShl(
1003 LHS: Idx, RHS: ConstantInt::get(Ty: PtrIndexTy, V: ElementSize.logBase2()));
1004 } else {
1005 Idx =
1006 Builder.CreateMul(LHS: Idx, RHS: ConstantInt::get(Ty: PtrIndexTy, V: ElementSize));
1007 }
1008 }
1009 // Create an ugly GEP with a single index for each index.
1010 ResultPtr = Builder.CreatePtrAdd(Ptr: ResultPtr, Offset: Idx, Name: "uglygep");
1011 if (FirstResult == nullptr)
1012 FirstResult = ResultPtr;
1013 }
1014 }
1015
1016 // Create a GEP with the constant offset index.
1017 if (AccumulativeByteOffset != 0) {
1018 Value *Offset = ConstantInt::get(Ty: PtrIndexTy, V: AccumulativeByteOffset);
1019 ResultPtr = Builder.CreatePtrAdd(Ptr: ResultPtr, Offset, Name: "uglygep");
1020 } else
1021 isSwapCandidate = false;
1022
1023 // If we created a GEP with constant index, and the base is loop invariant,
1024 // then we swap the first one with it, so LICM can move constant GEP out
1025 // later.
1026 auto *FirstGEP = dyn_cast_or_null<GetElementPtrInst>(Val: FirstResult);
1027 auto *SecondGEP = dyn_cast<GetElementPtrInst>(Val: ResultPtr);
1028 if (isSwapCandidate && isLegalToSwapOperand(First: FirstGEP, Second: SecondGEP, CurLoop: L))
1029 swapGEPOperand(First: FirstGEP, Second: SecondGEP);
1030
1031 Variadic->replaceAllUsesWith(V: ResultPtr);
1032 Variadic->eraseFromParent();
1033}
1034
1035bool SeparateConstOffsetFromGEP::reorderGEP(GetElementPtrInst *GEP,
1036 TargetTransformInfo &TTI) {
1037 auto PtrGEP = dyn_cast<GetElementPtrInst>(Val: GEP->getPointerOperand());
1038 if (!PtrGEP)
1039 return false;
1040
1041 bool NestedNeedsExtraction;
1042 APInt NestedByteOffset = accumulateByteOffset(GEP: PtrGEP, NeedsExtraction&: NestedNeedsExtraction);
1043 if (!NestedNeedsExtraction)
1044 return false;
1045
1046 unsigned AddrSpace = PtrGEP->getPointerAddressSpace();
1047 if (!TTI.isLegalAddressingMode(Ty: GEP->getResultElementType(),
1048 /*BaseGV=*/nullptr,
1049 BaseOffset: NestedByteOffset.getSExtValue(),
1050 /*HasBaseReg=*/true, /*Scale=*/0, AddrSpace))
1051 return false;
1052
1053 bool GEPInBounds = GEP->isInBounds();
1054 bool PtrGEPInBounds = PtrGEP->isInBounds();
1055 bool IsChainInBounds = GEPInBounds && PtrGEPInBounds;
1056 if (IsChainInBounds) {
1057 auto IsKnownNonNegative = [this](Value *V) {
1058 return isKnownNonNegative(V, SQ: *DL);
1059 };
1060 IsChainInBounds &= all_of(Range: GEP->indices(), P: IsKnownNonNegative);
1061 if (IsChainInBounds)
1062 IsChainInBounds &= all_of(Range: PtrGEP->indices(), P: IsKnownNonNegative);
1063 }
1064
1065 IRBuilder<> Builder(GEP);
1066 // For trivial GEP chains, we can swap the indices.
1067 Value *NewSrc = Builder.CreateGEP(
1068 Ty: GEP->getSourceElementType(), Ptr: PtrGEP->getPointerOperand(),
1069 IdxList: SmallVector<Value *, 4>(GEP->indices()), Name: "", NW: IsChainInBounds);
1070 Value *NewGEP = Builder.CreateGEP(Ty: PtrGEP->getSourceElementType(), Ptr: NewSrc,
1071 IdxList: SmallVector<Value *, 4>(PtrGEP->indices()),
1072 Name: "", NW: IsChainInBounds);
1073 GEP->replaceAllUsesWith(V: NewGEP);
1074 RecursivelyDeleteTriviallyDeadInstructions(V: GEP);
1075 return true;
1076}
1077
1078bool SeparateConstOffsetFromGEP::splitGEP(GetElementPtrInst *GEP) {
1079 // Skip vector GEPs.
1080 if (GEP->getType()->isVectorTy())
1081 return false;
1082
1083 // If the base of this GEP is a ptradd of a constant, lets pass the constant
1084 // along. This ensures that when we have a chain of GEPs the constant
1085 // offset from each is accumulated.
1086 Value *NewBase;
1087 const APInt *BaseOffset;
1088 bool ExtractBase = match(V: GEP->getPointerOperand(),
1089 P: m_PtrAdd(PointerOp: m_Value(V&: NewBase), OffsetOp: m_APInt(Res&: BaseOffset)));
1090
1091 unsigned IdxWidth = DL->getIndexTypeSizeInBits(Ty: GEP->getType());
1092 APInt BaseByteOffset =
1093 ExtractBase ? BaseOffset->sextOrTrunc(width: IdxWidth) : APInt(IdxWidth, 0);
1094
1095 // The backend can already nicely handle the case where all indices are
1096 // constant.
1097 if (GEP->hasAllConstantIndices() && !ExtractBase)
1098 return false;
1099
1100 bool Changed = canonicalizeArrayIndicesToIndexSize(GEP);
1101
1102 bool NeedsExtraction;
1103 APInt NonBaseByteOffset = accumulateByteOffset(GEP, NeedsExtraction);
1104 APInt AccumulativeByteOffset = BaseByteOffset + NonBaseByteOffset;
1105
1106 TargetTransformInfo &TTI = GetTTI(*GEP->getFunction());
1107
1108 if (!NeedsExtraction && !ExtractBase) {
1109 Changed |= reorderGEP(GEP, TTI);
1110 return Changed;
1111 }
1112
1113 // If LowerGEP is disabled, before really splitting the GEP, check whether the
1114 // backend supports the addressing mode we are about to produce. If no, this
1115 // splitting probably won't be beneficial.
1116 // If LowerGEP is enabled, even the extracted constant offset can not match
1117 // the addressing mode, we can still do optimizations to other lowered parts
1118 // of variable indices. Therefore, we don't check for addressing modes in that
1119 // case.
1120 if (!LowerGEP) {
1121 unsigned AddrSpace = GEP->getPointerAddressSpace();
1122 if (!TTI.isLegalAddressingMode(
1123 Ty: GEP->getResultElementType(),
1124 /*BaseGV=*/nullptr, BaseOffset: AccumulativeByteOffset.getSExtValue(),
1125 /*HasBaseReg=*/true, /*Scale=*/0, AddrSpace)) {
1126 // If the addressing mode was not legal and the base byte offset was not
1127 // 0, it could be a case where the total offset became too large for
1128 // the addressing mode. Try again without extracting the base offset.
1129 if (!ExtractBase)
1130 return Changed;
1131 ExtractBase = false;
1132 BaseByteOffset = APInt(IdxWidth, 0);
1133 AccumulativeByteOffset = NonBaseByteOffset;
1134 if (!TTI.isLegalAddressingMode(
1135 Ty: GEP->getResultElementType(),
1136 /*BaseGV=*/nullptr, BaseOffset: AccumulativeByteOffset.getSExtValue(),
1137 /*HasBaseReg=*/true, /*Scale=*/0, AddrSpace))
1138 return Changed;
1139 // We can proceed with just extracting the other (non-base) offsets.
1140 NeedsExtraction = true;
1141 }
1142 }
1143
1144 // Track information for preserving GEP flags.
1145 bool AllOffsetsNonNegative = AccumulativeByteOffset.isNonNegative();
1146 bool AllNUWPreserved = GEP->hasNoUnsignedWrap();
1147 bool NewGEPInBounds = GEP->isInBounds();
1148 bool NewGEPNUSW = GEP->hasNoUnsignedSignedWrap();
1149
1150 // Remove the constant offset in each sequential index. The resultant GEP
1151 // computes the variadic base.
1152 // Notice that we don't remove struct field indices here. If LowerGEP is
1153 // disabled, a structure index is not accumulated and we still use the old
1154 // one. If LowerGEP is enabled, a structure index is accumulated in the
1155 // constant offset. LowerToSingleIndexGEPs will later handle the constant
1156 // offset and won't need a new structure index.
1157 gep_type_iterator GTI = gep_type_begin(GEP: *GEP);
1158 for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I, ++GTI) {
1159 if (GTI.isSequential()) {
1160 // Constant offsets of scalable types are not really constant.
1161 if (GTI.getIndexedType()->isScalableTy())
1162 continue;
1163
1164 // Splits this GEP index into a variadic part and a constant offset, and
1165 // uses the variadic part as the new index.
1166 Value *Idx = GEP->getOperand(i_nocapture: I);
1167 User *UserChainTail;
1168 bool PreservesNUW;
1169 Value *NewIdx = ConstantOffsetExtractor::Extract(Idx, GEP, UserChainTail,
1170 PreservesNUW);
1171 if (NewIdx != nullptr) {
1172 // Switches to the index with the constant offset removed.
1173 GEP->setOperand(i_nocapture: I, Val_nocapture: NewIdx);
1174 // After switching to the new index, we can garbage-collect UserChain
1175 // and the old index if they are not used.
1176 RecursivelyDeleteTriviallyDeadInstructions(V: UserChainTail);
1177 RecursivelyDeleteTriviallyDeadInstructions(V: Idx);
1178 Idx = NewIdx;
1179 AllNUWPreserved &= PreservesNUW;
1180 }
1181 AllOffsetsNonNegative =
1182 AllOffsetsNonNegative && isKnownNonNegative(V: Idx, SQ: *DL);
1183 }
1184 }
1185 if (ExtractBase) {
1186 GEPOperator *Base = cast<GEPOperator>(Val: GEP->getPointerOperand());
1187 AllNUWPreserved &= Base->hasNoUnsignedWrap();
1188 NewGEPInBounds &= Base->isInBounds();
1189 NewGEPNUSW &= Base->hasNoUnsignedSignedWrap();
1190 AllOffsetsNonNegative &= BaseByteOffset.isNonNegative();
1191
1192 GEP->setOperand(i_nocapture: 0, Val_nocapture: NewBase);
1193 RecursivelyDeleteTriviallyDeadInstructions(V: Base);
1194 }
1195
1196 // Clear the inbounds attribute because the new index may be off-bound.
1197 // e.g.,
1198 //
1199 // b = add i64 a, 5
1200 // addr = gep inbounds float, float* p, i64 b
1201 //
1202 // is transformed to:
1203 //
1204 // addr2 = gep float, float* p, i64 a ; inbounds removed
1205 // addr = gep float, float* addr2, i64 5 ; inbounds removed
1206 //
1207 // If a is -4, although the old index b is in bounds, the new index a is
1208 // off-bound. http://llvm.org/docs/LangRef.html#id181 says "if the
1209 // inbounds keyword is not present, the offsets are added to the base
1210 // address with silently-wrapping two's complement arithmetic".
1211 // Therefore, the final code will be a semantically equivalent.
1212 GEPNoWrapFlags NewGEPFlags = GEPNoWrapFlags::none();
1213
1214 // If the initial GEP was inbounds/nusw and all variable indices and the
1215 // accumulated offsets are non-negative, they can be added in any order and
1216 // the intermediate results are in bounds and don't overflow in a nusw sense.
1217 // So, we can preserve the inbounds/nusw flag for both GEPs.
1218 bool CanPreserveInBoundsNUSW = AllOffsetsNonNegative;
1219
1220 // If the initial GEP was NUW and all operations that we reassociate were NUW
1221 // additions, the resulting GEPs are also NUW.
1222 if (AllNUWPreserved) {
1223 NewGEPFlags |= GEPNoWrapFlags::noUnsignedWrap();
1224 // If the initial GEP additionally had NUSW (or inbounds, which implies
1225 // NUSW), we know that the indices in the initial GEP must all have their
1226 // signbit not set. For indices that are the result of NUW adds, the
1227 // add-operands therefore also don't have their signbit set. Therefore, all
1228 // indices of the resulting GEPs are non-negative -> we can preserve
1229 // the inbounds/nusw flag.
1230 CanPreserveInBoundsNUSW |= NewGEPNUSW;
1231 }
1232
1233 if (CanPreserveInBoundsNUSW) {
1234 if (NewGEPInBounds)
1235 NewGEPFlags |= GEPNoWrapFlags::inBounds();
1236 else if (NewGEPNUSW)
1237 NewGEPFlags |= GEPNoWrapFlags::noUnsignedSignedWrap();
1238 }
1239
1240 GEP->setNoWrapFlags(NewGEPFlags);
1241
1242 // Lowers a GEP to GEPs with a single index.
1243 if (LowerGEP) {
1244 lowerToSingleIndexGEPs(Variadic: GEP, AccumulativeByteOffset);
1245 return true;
1246 }
1247
1248 // No need to create another GEP if the accumulative byte offset is 0.
1249 if (AccumulativeByteOffset == 0)
1250 return true;
1251
1252 // Offsets the base with the accumulative byte offset.
1253 //
1254 // %gep ; the base
1255 // ... %gep ...
1256 //
1257 // => add the offset
1258 //
1259 // %gep2 ; clone of %gep
1260 // %new.gep = gep i8, %gep2, %offset
1261 // %gep ; will be removed
1262 // ... %gep ...
1263 //
1264 // => replace all uses of %gep with %new.gep and remove %gep
1265 //
1266 // %gep2 ; clone of %gep
1267 // %new.gep = gep i8, %gep2, %offset
1268 // ... %new.gep ...
1269 Instruction *NewGEP = GEP->clone();
1270 NewGEP->insertBefore(InsertPos: GEP->getIterator());
1271
1272 Type *PtrIdxTy = DL->getIndexType(PtrTy: GEP->getType());
1273 IRBuilder<> Builder(GEP);
1274 NewGEP = cast<Instruction>(Val: Builder.CreatePtrAdd(
1275 Ptr: NewGEP, Offset: ConstantInt::get(Ty: PtrIdxTy, V: AccumulativeByteOffset),
1276 Name: GEP->getName(), NW: NewGEPFlags));
1277 NewGEP->copyMetadata(SrcInst: *GEP);
1278
1279 GEP->replaceAllUsesWith(V: NewGEP);
1280 GEP->eraseFromParent();
1281
1282 return true;
1283}
1284
1285bool SeparateConstOffsetFromGEPLegacyPass::runOnFunction(Function &F) {
1286 if (skipFunction(F))
1287 return false;
1288 auto *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
1289 auto *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
1290 auto *TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
1291 auto GetTTI = [this](Function &F) -> TargetTransformInfo & {
1292 return this->getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
1293 };
1294 SeparateConstOffsetFromGEP Impl(DT, LI, TLI, GetTTI, LowerGEP);
1295 return Impl.run(F);
1296}
1297
1298bool SeparateConstOffsetFromGEP::run(Function &F) {
1299 if (DisableSeparateConstOffsetFromGEP)
1300 return false;
1301
1302 DL = &F.getDataLayout();
1303 bool Changed = false;
1304
1305 ReversePostOrderTraversal<Function *> RPOT(&F);
1306 for (BasicBlock *B : RPOT) {
1307 if (!DT->isReachableFromEntry(A: B))
1308 continue;
1309
1310 for (Instruction &I : llvm::make_early_inc_range(Range&: *B))
1311 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Val: &I))
1312 Changed |= splitGEP(GEP);
1313 // No need to split GEP ConstantExprs because all its indices are constant
1314 // already.
1315 }
1316
1317 Changed |= reuniteExts(F);
1318
1319 if (VerifyNoDeadCode)
1320 verifyNoDeadCode(F);
1321
1322 return Changed;
1323}
1324
1325Instruction *SeparateConstOffsetFromGEP::findClosestMatchingDominator(
1326 ExprKey Key, Instruction *Dominatee,
1327 DenseMap<ExprKey, SmallVector<Instruction *, 2>> &DominatingExprs) {
1328 auto Pos = DominatingExprs.find(Val: Key);
1329 if (Pos == DominatingExprs.end())
1330 return nullptr;
1331
1332 auto &Candidates = Pos->second;
1333 // Because we process the basic blocks in pre-order of the dominator tree, a
1334 // candidate that doesn't dominate the current instruction won't dominate any
1335 // future instruction either. Therefore, we pop it out of the stack. This
1336 // optimization makes the algorithm O(n).
1337 while (!Candidates.empty()) {
1338 Instruction *Candidate = Candidates.back();
1339 if (DT->dominates(Def: Candidate, User: Dominatee))
1340 return Candidate;
1341 Candidates.pop_back();
1342 }
1343 return nullptr;
1344}
1345
1346bool SeparateConstOffsetFromGEP::reuniteExts(Instruction *I) {
1347 if (!I->getType()->isIntOrIntVectorTy())
1348 return false;
1349
1350 // Dom: LHS+RHS
1351 // I: sext(LHS)+sext(RHS)
1352 // If Dom can't sign overflow and Dom dominates I, optimize I to sext(Dom).
1353 // TODO: handle zext
1354 Value *LHS = nullptr, *RHS = nullptr;
1355 if (match(V: I, P: m_Add(L: m_SExt(Op: m_Value(V&: LHS)), R: m_SExt(Op: m_Value(V&: RHS))))) {
1356 if (LHS->getType() == RHS->getType()) {
1357 ExprKey Key = createNormalizedCommutablePair(A: LHS, B: RHS);
1358 if (auto *Dom = findClosestMatchingDominator(Key, Dominatee: I, DominatingExprs&: DominatingAdds)) {
1359 Instruction *NewSExt =
1360 new SExtInst(Dom, I->getType(), "", I->getIterator());
1361 NewSExt->takeName(V: I);
1362 I->replaceAllUsesWith(V: NewSExt);
1363 NewSExt->setDebugLoc(I->getDebugLoc());
1364 RecursivelyDeleteTriviallyDeadInstructions(V: I);
1365 return true;
1366 }
1367 }
1368 } else if (match(V: I, P: m_Sub(L: m_SExt(Op: m_Value(V&: LHS)), R: m_SExt(Op: m_Value(V&: RHS))))) {
1369 if (LHS->getType() == RHS->getType()) {
1370 if (auto *Dom =
1371 findClosestMatchingDominator(Key: {LHS, RHS}, Dominatee: I, DominatingExprs&: DominatingSubs)) {
1372 Instruction *NewSExt =
1373 new SExtInst(Dom, I->getType(), "", I->getIterator());
1374 NewSExt->takeName(V: I);
1375 I->replaceAllUsesWith(V: NewSExt);
1376 NewSExt->setDebugLoc(I->getDebugLoc());
1377 RecursivelyDeleteTriviallyDeadInstructions(V: I);
1378 return true;
1379 }
1380 }
1381 }
1382
1383 // Add I to DominatingExprs if it's an add/sub that can't sign overflow.
1384 if (match(V: I, P: m_NSWAdd(L: m_Value(V&: LHS), R: m_Value(V&: RHS)))) {
1385 if (programUndefinedIfPoison(Inst: I)) {
1386 ExprKey Key = createNormalizedCommutablePair(A: LHS, B: RHS);
1387 DominatingAdds[Key].push_back(Elt: I);
1388 }
1389 } else if (match(V: I, P: m_NSWSub(L: m_Value(V&: LHS), R: m_Value(V&: RHS)))) {
1390 if (programUndefinedIfPoison(Inst: I))
1391 DominatingSubs[{LHS, RHS}].push_back(Elt: I);
1392 }
1393 return false;
1394}
1395
1396bool SeparateConstOffsetFromGEP::reuniteExts(Function &F) {
1397 bool Changed = false;
1398 DominatingAdds.clear();
1399 DominatingSubs.clear();
1400 for (const auto Node : depth_first(G: DT)) {
1401 BasicBlock *BB = Node->getBlock();
1402 for (Instruction &I : llvm::make_early_inc_range(Range&: *BB))
1403 Changed |= reuniteExts(I: &I);
1404 }
1405 return Changed;
1406}
1407
1408void SeparateConstOffsetFromGEP::verifyNoDeadCode(Function &F) {
1409 for (BasicBlock &B : F) {
1410 for (Instruction &I : B) {
1411 if (isInstructionTriviallyDead(I: &I)) {
1412 std::string ErrMessage;
1413 raw_string_ostream RSO(ErrMessage);
1414 RSO << "Dead instruction detected!\n" << I << "\n";
1415 llvm_unreachable(RSO.str().c_str());
1416 }
1417 }
1418 }
1419}
1420
1421bool SeparateConstOffsetFromGEP::isLegalToSwapOperand(
1422 GetElementPtrInst *FirstGEP, GetElementPtrInst *SecondGEP, Loop *CurLoop) {
1423 if (!FirstGEP || !FirstGEP->hasOneUse())
1424 return false;
1425
1426 if (!SecondGEP || FirstGEP->getParent() != SecondGEP->getParent())
1427 return false;
1428
1429 if (FirstGEP == SecondGEP)
1430 return false;
1431
1432 unsigned FirstNum = FirstGEP->getNumOperands();
1433 unsigned SecondNum = SecondGEP->getNumOperands();
1434 // Give up if the number of operands are not 2.
1435 if (FirstNum != SecondNum || FirstNum != 2)
1436 return false;
1437
1438 Value *FirstBase = FirstGEP->getOperand(i_nocapture: 0);
1439 Value *SecondBase = SecondGEP->getOperand(i_nocapture: 0);
1440 Value *FirstOffset = FirstGEP->getOperand(i_nocapture: 1);
1441 // Give up if the index of the first GEP is loop invariant.
1442 if (CurLoop->isLoopInvariant(V: FirstOffset))
1443 return false;
1444
1445 // Give up if base doesn't have same type.
1446 if (FirstBase->getType() != SecondBase->getType())
1447 return false;
1448
1449 Instruction *FirstOffsetDef = dyn_cast<Instruction>(Val: FirstOffset);
1450
1451 // Check if the second operand of first GEP has constant coefficient.
1452 // For an example, for the following code, we won't gain anything by
1453 // hoisting the second GEP out because the second GEP can be folded away.
1454 // %scevgep.sum.ur159 = add i64 %idxprom48.ur, 256
1455 // %67 = shl i64 %scevgep.sum.ur159, 2
1456 // %uglygep160 = getelementptr i8* %65, i64 %67
1457 // %uglygep161 = getelementptr i8* %uglygep160, i64 -1024
1458
1459 // Skip constant shift instruction which may be generated by Splitting GEPs.
1460 if (FirstOffsetDef && FirstOffsetDef->isShift() &&
1461 isa<ConstantInt>(Val: FirstOffsetDef->getOperand(i: 1)))
1462 FirstOffsetDef = dyn_cast<Instruction>(Val: FirstOffsetDef->getOperand(i: 0));
1463
1464 // Give up if FirstOffsetDef is an Add or Sub with constant.
1465 // Because it may not profitable at all due to constant folding.
1466 if (FirstOffsetDef)
1467 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Val: FirstOffsetDef)) {
1468 unsigned opc = BO->getOpcode();
1469 if ((opc == Instruction::Add || opc == Instruction::Sub) &&
1470 (isa<ConstantInt>(Val: BO->getOperand(i_nocapture: 0)) ||
1471 isa<ConstantInt>(Val: BO->getOperand(i_nocapture: 1))))
1472 return false;
1473 }
1474 return true;
1475}
1476
1477bool SeparateConstOffsetFromGEP::hasMoreThanOneUseInLoop(Value *V, Loop *L) {
1478 // TODO: Could look at uses of globals, but we need to make sure we are
1479 // looking at the correct function.
1480 if (isa<Constant>(Val: V))
1481 return false;
1482
1483 int UsesInLoop = 0;
1484 for (User *U : V->users()) {
1485 if (Instruction *User = dyn_cast<Instruction>(Val: U))
1486 if (L->contains(Inst: User))
1487 if (++UsesInLoop > 1)
1488 return true;
1489 }
1490 return false;
1491}
1492
1493void SeparateConstOffsetFromGEP::swapGEPOperand(GetElementPtrInst *First,
1494 GetElementPtrInst *Second) {
1495 Value *Offset1 = First->getOperand(i_nocapture: 1);
1496 Value *Offset2 = Second->getOperand(i_nocapture: 1);
1497 First->setOperand(i_nocapture: 1, Val_nocapture: Offset2);
1498 Second->setOperand(i_nocapture: 1, Val_nocapture: Offset1);
1499
1500 // We changed p+o+c to p+c+o, p+c may not be inbound anymore.
1501 const DataLayout &DAL = First->getDataLayout();
1502 APInt Offset(DAL.getIndexSizeInBits(
1503 AS: cast<PointerType>(Val: First->getType())->getAddressSpace()),
1504 0);
1505 Value *NewBase =
1506 First->stripAndAccumulateInBoundsConstantOffsets(DL: DAL, Offset);
1507 uint64_t ObjectSize;
1508 if (!getObjectSize(Ptr: NewBase, Size&: ObjectSize, DL: DAL, TLI) ||
1509 Offset.ugt(RHS: ObjectSize)) {
1510 // TODO(gep_nowrap): Make flag preservation more precise.
1511 First->setNoWrapFlags(GEPNoWrapFlags::none());
1512 Second->setNoWrapFlags(GEPNoWrapFlags::none());
1513 } else
1514 First->setIsInBounds(true);
1515}
1516
1517void SeparateConstOffsetFromGEPPass::printPipeline(
1518 raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) {
1519 static_cast<PassInfoMixin<SeparateConstOffsetFromGEPPass> *>(this)
1520 ->printPipeline(OS, MapClassName2PassName);
1521 OS << '<';
1522 if (LowerGEP)
1523 OS << "lower-gep";
1524 OS << '>';
1525}
1526
1527PreservedAnalyses
1528SeparateConstOffsetFromGEPPass::run(Function &F, FunctionAnalysisManager &AM) {
1529 auto *DT = &AM.getResult<DominatorTreeAnalysis>(IR&: F);
1530 auto *LI = &AM.getResult<LoopAnalysis>(IR&: F);
1531 auto *TLI = &AM.getResult<TargetLibraryAnalysis>(IR&: F);
1532 auto GetTTI = [&AM](Function &F) -> TargetTransformInfo & {
1533 return AM.getResult<TargetIRAnalysis>(IR&: F);
1534 };
1535 SeparateConstOffsetFromGEP Impl(DT, LI, TLI, GetTTI, LowerGEP);
1536 if (!Impl.run(F))
1537 return PreservedAnalyses::all();
1538 PreservedAnalyses PA;
1539 PA.preserveSet<CFGAnalyses>();
1540 return PA;
1541}
1542