[llvm] b7179d9 - [InstCombine] Extract GEP of bitcast folds into separate function (NFC)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Thu Jan 27 01:48:07 PST 2022
Author: Nikita Popov
Date: 2022-01-27T10:48:00+01:00
New Revision: b7179d92799c7a375b7f8fa1a2a91c5fda713423
URL: https://github.com/llvm/llvm-project/commit/b7179d92799c7a375b7f8fa1a2a91c5fda713423
DIFF: https://github.com/llvm/llvm-project/commit/b7179d92799c7a375b7f8fa1a2a91c5fda713423.diff
LOG: [InstCombine] Extract GEP of bitcast folds into separate function (NFC)
Added:
Modified:
llvm/lib/Transforms/InstCombine/InstCombineInternal.h
llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
index a7d1ff202e5e..e8c82786a3c3 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -149,6 +149,7 @@ class LLVM_LIBRARY_VISIBILITY InstCombinerImpl final
Instruction *visitPHINode(PHINode &PN);
Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
Instruction *visitGEPOfGEP(GetElementPtrInst &GEP, GEPOperator *Src);
+ Instruction *visitGEPOfBitcast(BitCastInst *BCI, GetElementPtrInst &GEP);
Instruction *visitAllocaInst(AllocaInst &AI);
Instruction *visitAllocSite(Instruction &FI);
Instruction *visitFree(CallInst &FI);
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 5de1d6fa4567..5c1192537b96 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2079,6 +2079,109 @@ Instruction *InstCombinerImpl::visitGEPOfGEP(GetElementPtrInst &GEP,
return nullptr;
}
+// Note that we may have also stripped an address space cast in between.
+Instruction *InstCombinerImpl::visitGEPOfBitcast(BitCastInst *BCI,
+ GetElementPtrInst &GEP) {
+ Type *GEPEltType = GEP.getSourceElementType();
+ Value *SrcOp = BCI->getOperand(0);
+ PointerType *SrcType = cast<PointerType>(BCI->getSrcTy());
+ Type *SrcEltType = SrcType->getPointerElementType();
+
+ // GEP directly using the source operand if this GEP is accessing an element
+ // of a bitcasted pointer to vector or array of the same dimensions:
+ // gep (bitcast <c x ty>* X to [c x ty]*), Y, Z --> gep X, Y, Z
+ // gep (bitcast [c x ty]* X to <c x ty>*), Y, Z --> gep X, Y, Z
+ auto areMatchingArrayAndVecTypes = [](Type *ArrTy, Type *VecTy,
+ const DataLayout &DL) {
+ auto *VecVTy = cast<FixedVectorType>(VecTy);
+ return ArrTy->getArrayElementType() == VecVTy->getElementType() &&
+ ArrTy->getArrayNumElements() == VecVTy->getNumElements() &&
+ DL.getTypeAllocSize(ArrTy) == DL.getTypeAllocSize(VecTy);
+ };
+ if (GEP.getNumOperands() == 3 &&
+ ((GEPEltType->isArrayTy() && isa<FixedVectorType>(SrcEltType) &&
+ areMatchingArrayAndVecTypes(GEPEltType, SrcEltType, DL)) ||
+ (isa<FixedVectorType>(GEPEltType) && SrcEltType->isArrayTy() &&
+ areMatchingArrayAndVecTypes(SrcEltType, GEPEltType, DL)))) {
+
+ // Create a new GEP here, as using `setOperand()` followed by
+ // `setSourceElementType()` won't actually update the type of the
+ // existing GEP Value. Causing issues if this Value is accessed when
+ // constructing an AddrSpaceCastInst
+ SmallVector<Value *, 8> Indices(GEP.indices());
+ Value *NGEP = GEP.isInBounds()
+ ? Builder.CreateInBoundsGEP(SrcEltType, SrcOp, Indices)
+ : Builder.CreateGEP(SrcEltType, SrcOp, Indices);
+ NGEP->takeName(&GEP);
+
+ // Preserve GEP address space to satisfy users
+ if (NGEP->getType()->getPointerAddressSpace() != GEP.getAddressSpace())
+ return new AddrSpaceCastInst(NGEP, GEP.getType());
+
+ return replaceInstUsesWith(GEP, NGEP);
+ }
+
+ // See if we can simplify:
+ // X = bitcast A* to B*
+ // Y = gep X, <...constant indices...>
+ // into a gep of the original struct. This is important for SROA and alias
+ // analysis of unions. If "A" is also a bitcast, wait for A/X to be merged.
+ unsigned OffsetBits = DL.getIndexTypeSizeInBits(GEP.getType());
+ APInt Offset(OffsetBits, 0);
+
+ // If the bitcast argument is an allocation, The bitcast is for convertion
+ // to actual type of allocation. Removing such bitcasts, results in having
+ // GEPs with i8* base and pure byte offsets. That means GEP is not aware of
+ // struct or array hierarchy.
+ // By avoiding such GEPs, phi translation and MemoryDependencyAnalysis have
+ // a better chance to succeed.
+ if (!isa<BitCastInst>(SrcOp) && GEP.accumulateConstantOffset(DL, Offset) &&
+ !isAllocationFn(SrcOp, &TLI)) {
+ // If this GEP instruction doesn't move the pointer, just replace the GEP
+ // with a bitcast of the real input to the dest type.
+ if (!Offset) {
+ // If the bitcast is of an allocation, and the allocation will be
+ // converted to match the type of the cast, don't touch this.
+ if (isa<AllocaInst>(SrcOp)) {
+ // See if the bitcast simplifies, if so, don't nuke this GEP yet.
+ if (Instruction *I = visitBitCast(*BCI)) {
+ if (I != BCI) {
+ I->takeName(BCI);
+ BCI->getParent()->getInstList().insert(BCI->getIterator(), I);
+ replaceInstUsesWith(*BCI, I);
+ }
+ return &GEP;
+ }
+ }
+
+ if (SrcType->getPointerAddressSpace() != GEP.getAddressSpace())
+ return new AddrSpaceCastInst(SrcOp, GEP.getType());
+ return new BitCastInst(SrcOp, GEP.getType());
+ }
+
+ // Otherwise, if the offset is non-zero, we need to find out if there is a
+ // field at Offset in 'A's type. If so, we can pull the cast through the
+ // GEP.
+ SmallVector<Value*, 8> NewIndices;
+ if (FindElementAtOffset(SrcType, Offset.getSExtValue(), NewIndices)) {
+ Value *NGEP =
+ GEP.isInBounds()
+ ? Builder.CreateInBoundsGEP(SrcEltType, SrcOp, NewIndices)
+ : Builder.CreateGEP(SrcEltType, SrcOp, NewIndices);
+
+ if (NGEP->getType() == GEP.getType())
+ return replaceInstUsesWith(GEP, NGEP);
+ NGEP->takeName(&GEP);
+
+ if (NGEP->getType()->getPointerAddressSpace() != GEP.getAddressSpace())
+ return new AddrSpaceCastInst(NGEP, GEP.getType());
+ return new BitCastInst(NGEP, GEP.getType());
+ }
+ }
+
+ return nullptr;
+}
+
Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
Value *PtrOp = GEP.getOperand(0);
SmallVector<Value *, 8> Indices(GEP.indices());
@@ -2495,102 +2598,9 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
ASCStrippedPtrOp = BC;
}
- if (auto *BCI = dyn_cast<BitCastInst>(ASCStrippedPtrOp)) {
- Value *SrcOp = BCI->getOperand(0);
- PointerType *SrcType = cast<PointerType>(BCI->getSrcTy());
- Type *SrcEltType = SrcType->getPointerElementType();
-
- // GEP directly using the source operand if this GEP is accessing an element
- // of a bitcasted pointer to vector or array of the same dimensions:
- // gep (bitcast <c x ty>* X to [c x ty]*), Y, Z --> gep X, Y, Z
- // gep (bitcast [c x ty]* X to <c x ty>*), Y, Z --> gep X, Y, Z
- auto areMatchingArrayAndVecTypes = [](Type *ArrTy, Type *VecTy,
- const DataLayout &DL) {
- auto *VecVTy = cast<FixedVectorType>(VecTy);
- return ArrTy->getArrayElementType() == VecVTy->getElementType() &&
- ArrTy->getArrayNumElements() == VecVTy->getNumElements() &&
- DL.getTypeAllocSize(ArrTy) == DL.getTypeAllocSize(VecTy);
- };
- if (GEP.getNumOperands() == 3 &&
- ((GEPEltType->isArrayTy() && isa<FixedVectorType>(SrcEltType) &&
- areMatchingArrayAndVecTypes(GEPEltType, SrcEltType, DL)) ||
- (isa<FixedVectorType>(GEPEltType) && SrcEltType->isArrayTy() &&
- areMatchingArrayAndVecTypes(SrcEltType, GEPEltType, DL)))) {
-
- // Create a new GEP here, as using `setOperand()` followed by
- // `setSourceElementType()` won't actually update the type of the
- // existing GEP Value. Causing issues if this Value is accessed when
- // constructing an AddrSpaceCastInst
- Value *NGEP = GEP.isInBounds()
- ? Builder.CreateInBoundsGEP(SrcEltType, SrcOp, Indices)
- : Builder.CreateGEP(SrcEltType, SrcOp, Indices);
- NGEP->takeName(&GEP);
-
- // Preserve GEP address space to satisfy users
- if (NGEP->getType()->getPointerAddressSpace() != GEP.getAddressSpace())
- return new AddrSpaceCastInst(NGEP, GEPType);
-
- return replaceInstUsesWith(GEP, NGEP);
- }
-
- // See if we can simplify:
- // X = bitcast A* to B*
- // Y = gep X, <...constant indices...>
- // into a gep of the original struct. This is important for SROA and alias
- // analysis of unions. If "A" is also a bitcast, wait for A/X to be merged.
- unsigned OffsetBits = DL.getIndexTypeSizeInBits(GEPType);
- APInt Offset(OffsetBits, 0);
-
- // If the bitcast argument is an allocation, The bitcast is for convertion
- // to actual type of allocation. Removing such bitcasts, results in having
- // GEPs with i8* base and pure byte offsets. That means GEP is not aware of
- // struct or array hierarchy.
- // By avoiding such GEPs, phi translation and MemoryDependencyAnalysis have
- // a better chance to succeed.
- if (!isa<BitCastInst>(SrcOp) && GEP.accumulateConstantOffset(DL, Offset) &&
- !isAllocationFn(SrcOp, &TLI)) {
- // If this GEP instruction doesn't move the pointer, just replace the GEP
- // with a bitcast of the real input to the dest type.
- if (!Offset) {
- // If the bitcast is of an allocation, and the allocation will be
- // converted to match the type of the cast, don't touch this.
- if (isa<AllocaInst>(SrcOp)) {
- // See if the bitcast simplifies, if so, don't nuke this GEP yet.
- if (Instruction *I = visitBitCast(*BCI)) {
- if (I != BCI) {
- I->takeName(BCI);
- BCI->getParent()->getInstList().insert(BCI->getIterator(), I);
- replaceInstUsesWith(*BCI, I);
- }
- return &GEP;
- }
- }
-
- if (SrcType->getPointerAddressSpace() != GEP.getAddressSpace())
- return new AddrSpaceCastInst(SrcOp, GEPType);
- return new BitCastInst(SrcOp, GEPType);
- }
-
- // Otherwise, if the offset is non-zero, we need to find out if there is a
- // field at Offset in 'A's type. If so, we can pull the cast through the
- // GEP.
- SmallVector<Value*, 8> NewIndices;
- if (FindElementAtOffset(SrcType, Offset.getSExtValue(), NewIndices)) {
- Value *NGEP =
- GEP.isInBounds()
- ? Builder.CreateInBoundsGEP(SrcEltType, SrcOp, NewIndices)
- : Builder.CreateGEP(SrcEltType, SrcOp, NewIndices);
-
- if (NGEP->getType() == GEPType)
- return replaceInstUsesWith(GEP, NGEP);
- NGEP->takeName(&GEP);
-
- if (NGEP->getType()->getPointerAddressSpace() != GEP.getAddressSpace())
- return new AddrSpaceCastInst(NGEP, GEPType);
- return new BitCastInst(NGEP, GEPType);
- }
- }
- }
+ if (auto *BCI = dyn_cast<BitCastInst>(ASCStrippedPtrOp))
+ if (Instruction *I = visitGEPOfBitcast(BCI, GEP))
+ return I;
if (!GEP.isInBounds()) {
unsigned IdxWidth =
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