[llvm] db6b30b - [InstCombine] Remove GEP of bitcast folds (NFC)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Thu Apr 6 00:15:41 PDT 2023
Author: Nikita Popov
Date: 2023-04-06T09:15:33+02:00
New Revision: db6b30b1831095c216378a9df215b7c0ae6b959f
URL: https://github.com/llvm/llvm-project/commit/db6b30b1831095c216378a9df215b7c0ae6b959f
DIFF: https://github.com/llvm/llvm-project/commit/db6b30b1831095c216378a9df215b7c0ae6b959f.diff
LOG: [InstCombine] Remove GEP of bitcast folds (NFC)
These only support typed pointers, and as such are no longer
relevant.
Added:
Modified:
llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 9ca3459a3dfd..4177f64c6abe 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2327,175 +2327,6 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
if (GEPType->isVectorTy())
return nullptr;
- // Handle gep(bitcast x) and gep(gep x, 0, 0, 0).
- Value *StrippedPtr = PtrOp->stripPointerCasts();
- PointerType *StrippedPtrTy = cast<PointerType>(StrippedPtr->getType());
-
- // TODO: The basic approach of these folds is not compatible with opaque
- // pointers, because we can't use bitcasts as a hint for a desirable GEP
- // type. Instead, we should perform canonicalization directly on the GEP
- // type. For now, skip these.
- if (StrippedPtr != PtrOp && !StrippedPtrTy->isOpaque()) {
- bool HasZeroPointerIndex = false;
- Type *StrippedPtrEltTy = StrippedPtrTy->getNonOpaquePointerElementType();
-
- if (auto *C = dyn_cast<ConstantInt>(GEP.getOperand(1)))
- HasZeroPointerIndex = C->isZero();
-
- // Transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ...
- // into : GEP [10 x i8]* X, i32 0, ...
- //
- // Likewise, transform: GEP (bitcast i8* X to [0 x i8]*), i32 0, ...
- // into : GEP i8* X, ...
- //
- // This occurs when the program declares an array extern like "int X[];"
- if (HasZeroPointerIndex) {
- if (auto *CATy = dyn_cast<ArrayType>(GEPEltType)) {
- // GEP (bitcast i8* X to [0 x i8]*), i32 0, ... ?
- if (CATy->getElementType() == StrippedPtrEltTy) {
- // -> GEP i8* X, ...
- SmallVector<Value *, 8> Idx(drop_begin(GEP.indices()));
- GetElementPtrInst *Res = GetElementPtrInst::Create(
- StrippedPtrEltTy, StrippedPtr, Idx, GEP.getName());
- Res->setIsInBounds(GEP.isInBounds());
- if (StrippedPtrTy->getAddressSpace() == GEP.getAddressSpace())
- return Res;
- // Insert Res, and create an addrspacecast.
- // e.g.,
- // GEP (addrspacecast i8 addrspace(1)* X to [0 x i8]*), i32 0, ...
- // ->
- // %0 = GEP i8 addrspace(1)* X, ...
- // addrspacecast i8 addrspace(1)* %0 to i8*
- return new AddrSpaceCastInst(Builder.Insert(Res), GEPType);
- }
-
- if (auto *XATy = dyn_cast<ArrayType>(StrippedPtrEltTy)) {
- // GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... ?
- if (CATy->getElementType() == XATy->getElementType()) {
- // -> GEP [10 x i8]* X, i32 0, ...
- // At this point, we know that the cast source type is a pointer
- // to an array of the same type as the destination pointer
- // array. Because the array type is never stepped over (there
- // is a leading zero) we can fold the cast into this GEP.
- if (StrippedPtrTy->getAddressSpace() == GEP.getAddressSpace()) {
- GEP.setSourceElementType(XATy);
- return replaceOperand(GEP, 0, StrippedPtr);
- }
- // Cannot replace the base pointer directly because StrippedPtr's
- // address space is
diff erent. Instead, create a new GEP followed by
- // an addrspacecast.
- // e.g.,
- // GEP (addrspacecast [10 x i8] addrspace(1)* X to [0 x i8]*),
- // i32 0, ...
- // ->
- // %0 = GEP [10 x i8] addrspace(1)* X, ...
- // addrspacecast i8 addrspace(1)* %0 to i8*
- SmallVector<Value *, 8> Idx(GEP.indices());
- Value *NewGEP =
- Builder.CreateGEP(StrippedPtrEltTy, StrippedPtr, Idx,
- GEP.getName(), GEP.isInBounds());
- return new AddrSpaceCastInst(NewGEP, GEPType);
- }
- }
- }
- } else if (GEP.getNumOperands() == 2 && !IsGEPSrcEleScalable) {
- // Skip if GEP source element type is scalable. The type alloc size is
- // unknown at compile-time.
- // Transform things like: %t = getelementptr i32*
- // bitcast ([2 x i32]* %str to i32*), i32 %V into: %t1 = getelementptr [2
- // x i32]* %str, i32 0, i32 %V; bitcast
- if (StrippedPtrEltTy->isArrayTy() &&
- DL.getTypeAllocSize(StrippedPtrEltTy->getArrayElementType()) ==
- DL.getTypeAllocSize(GEPEltType)) {
- Type *IdxType = DL.getIndexType(GEPType);
- Value *Idx[2] = {Constant::getNullValue(IdxType), GEP.getOperand(1)};
- Value *NewGEP = Builder.CreateGEP(StrippedPtrEltTy, StrippedPtr, Idx,
- GEP.getName(), GEP.isInBounds());
-
- // V and GEP are both pointer types --> BitCast
- return CastInst::CreatePointerBitCastOrAddrSpaceCast(NewGEP, GEPType);
- }
-
- // Transform things like:
- // %V = mul i64 %N, 4
- // %t = getelementptr i8* bitcast (i32* %arr to i8*), i32 %V
- // into: %t1 = getelementptr i32* %arr, i32 %N; bitcast
- if (GEPEltType->isSized() && StrippedPtrEltTy->isSized()) {
- // Check that changing the type amounts to dividing the index by a scale
- // factor.
- uint64_t ResSize = DL.getTypeAllocSize(GEPEltType).getFixedValue();
- uint64_t SrcSize =
- DL.getTypeAllocSize(StrippedPtrEltTy).getFixedValue();
- if (ResSize && SrcSize % ResSize == 0) {
- Value *Idx = GEP.getOperand(1);
- unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits();
- uint64_t Scale = SrcSize / ResSize;
-
- // Earlier transforms ensure that the index has the right type
- // according to Data Layout, which considerably simplifies the
- // logic by eliminating implicit casts.
- assert(Idx->getType() == DL.getIndexType(GEPType) &&
- "Index type does not match the Data Layout preferences");
-
- bool NSW;
- if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) {
- // Successfully decomposed Idx as NewIdx * Scale, form a new GEP.
- // If the multiplication NewIdx * Scale may overflow then the new
- // GEP may not be "inbounds".
- Value *NewGEP =
- Builder.CreateGEP(StrippedPtrEltTy, StrippedPtr, NewIdx,
- GEP.getName(), GEP.isInBounds() && NSW);
-
- // The NewGEP must be pointer typed, so must the old one -> BitCast
- return CastInst::CreatePointerBitCastOrAddrSpaceCast(NewGEP,
- GEPType);
- }
- }
- }
-
- // Similarly, transform things like:
- // getelementptr i8* bitcast ([100 x double]* X to i8*), i32 %tmp
- // (where tmp = 8*tmp2) into:
- // getelementptr [100 x double]* %arr, i32 0, i32 %tmp2; bitcast
- if (GEPEltType->isSized() && StrippedPtrEltTy->isSized() &&
- StrippedPtrEltTy->isArrayTy()) {
- // Check that changing to the array element type amounts to dividing the
- // index by a scale factor.
- uint64_t ResSize = DL.getTypeAllocSize(GEPEltType).getFixedValue();
- uint64_t ArrayEltSize =
- DL.getTypeAllocSize(StrippedPtrEltTy->getArrayElementType())
- .getFixedValue();
- if (ResSize && ArrayEltSize % ResSize == 0) {
- Value *Idx = GEP.getOperand(1);
- unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits();
- uint64_t Scale = ArrayEltSize / ResSize;
-
- // Earlier transforms ensure that the index has the right type
- // according to the Data Layout, which considerably simplifies
- // the logic by eliminating implicit casts.
- assert(Idx->getType() == DL.getIndexType(GEPType) &&
- "Index type does not match the Data Layout preferences");
-
- bool NSW;
- if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) {
- // Successfully decomposed Idx as NewIdx * Scale, form a new GEP.
- // If the multiplication NewIdx * Scale may overflow then the new
- // GEP may not be "inbounds".
- Type *IndTy = DL.getIndexType(GEPType);
- Value *Off[2] = {Constant::getNullValue(IndTy), NewIdx};
-
- Value *NewGEP =
- Builder.CreateGEP(StrippedPtrEltTy, StrippedPtr, Off,
- GEP.getName(), GEP.isInBounds() && NSW);
- // The NewGEP must be pointer typed, so must the old one -> BitCast
- return CastInst::CreatePointerBitCastOrAddrSpaceCast(NewGEP,
- GEPType);
- }
- }
- }
- }
- }
-
if (!GEP.isInBounds()) {
unsigned IdxWidth =
DL.getIndexSizeInBits(PtrOp->getType()->getPointerAddressSpace());
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