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Revert "[InstCombine] Extract bitcast -> gep transform" 

This reverts commit d9f5d7b959.
This reverts commit 5780611d7e.

This causes a failure in Coroutine tests.
This commit is contained in:
Nikita Popov 2021-06-21 21:31:42 +02:00
parent 862313cf59
commit 6922ab73a5
2 changed files with 42 additions and 96 deletions
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95
llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
View File

@ -2603,57 +2603,6 @@ Instruction *InstCombinerImpl::optimizeBitCastFromPhi(CastInst &CI,
return RetVal;
}
static Instruction *convertBitCastToGEP(BitCastInst &CI, IRBuilderBase &Builder,
const DataLayout &DL) {
Value *Src = CI.getOperand(0);
PointerType *SrcPTy = cast<PointerType>(Src->getType());
PointerType *DstPTy = cast<PointerType>(CI.getType());
// Bitcasts involving opaque pointers cannot be converted into a GEP.
if (SrcPTy->isOpaque() || DstPTy->isOpaque())
return nullptr;
Type *DstElTy = DstPTy->getElementType();
Type *SrcElTy = SrcPTy->getElementType();
// When the type pointed to is not sized the cast cannot be
// turned into a gep.
if (!SrcElTy->isSized())
return nullptr;
// If the source and destination are pointers, and this cast is equivalent
// to a getelementptr X, 0, 0, 0... turn it into the appropriate gep.
// This can enhance SROA and other transforms that want type-safe pointers.
unsigned NumZeros = 0;
while (SrcElTy && SrcElTy != DstElTy) {
SrcElTy = GetElementPtrInst::getTypeAtIndex(SrcElTy, (uint64_t)0);
++NumZeros;
}
// If we found a path from the src to dest, create the getelementptr now.
if (SrcElTy == DstElTy) {
SmallVector<Value *, 8> Idxs(NumZeros + 1, Builder.getInt32(0));
GetElementPtrInst *GEP =
GetElementPtrInst::Create(SrcPTy->getElementType(), Src, Idxs);
// If the source pointer is dereferenceable, then assume it points to an
// allocated object and apply "inbounds" to the GEP.
bool CanBeNull, CanBeFreed;
if (Src->getPointerDereferenceableBytes(DL, CanBeNull, CanBeFreed)) {
// In a non-default address space (not 0), a null pointer can not be
// assumed inbounds, so ignore that case (dereferenceable_or_null).
// The reason is that 'null' is not treated differently in these address
// spaces, and we consequently ignore the 'gep inbounds' special case
// for 'null' which allows 'inbounds' on 'null' if the indices are
// zeros.
if (SrcPTy->getAddressSpace() == 0 || !CanBeNull)
GEP->setIsInBounds();
}
return GEP;
}
return nullptr;
}
Instruction *InstCombinerImpl::visitBitCast(BitCastInst &CI) {
// If the operands are integer typed then apply the integer transforms,
// otherwise just apply the common ones.
@ -2667,6 +2616,11 @@ Instruction *InstCombinerImpl::visitBitCast(BitCastInst &CI) {
return replaceInstUsesWith(CI, Src);
if (isa<PointerType>(SrcTy) && isa<PointerType>(DestTy)) {
PointerType *SrcPTy = cast<PointerType>(SrcTy);
PointerType *DstPTy = cast<PointerType>(DestTy);
Type *DstElTy = DstPTy->getElementType();
Type *SrcElTy = SrcPTy->getElementType();
// If we are casting a alloca to a pointer to a type of the same
// size, rewrite the allocation instruction to allocate the "right" type.
// There is no need to modify malloc calls because it is their bitcast that
@ -2675,8 +2629,43 @@ Instruction *InstCombinerImpl::visitBitCast(BitCastInst &CI) {
if (Instruction *V = PromoteCastOfAllocation(CI, *AI))
return V;
if (Instruction *I = convertBitCastToGEP(CI, Builder, DL))
return I;
// When the type pointed to is not sized the cast cannot be
// turned into a gep.
Type *PointeeType =
cast<PointerType>(Src->getType()->getScalarType())->getElementType();
if (!PointeeType->isSized())
return nullptr;
// If the source and destination are pointers, and this cast is equivalent
// to a getelementptr X, 0, 0, 0... turn it into the appropriate gep.
// This can enhance SROA and other transforms that want type-safe pointers.
unsigned NumZeros = 0;
while (SrcElTy && SrcElTy != DstElTy) {
SrcElTy = GetElementPtrInst::getTypeAtIndex(SrcElTy, (uint64_t)0);
++NumZeros;
}
// If we found a path from the src to dest, create the getelementptr now.
if (SrcElTy == DstElTy) {
SmallVector<Value *, 8> Idxs(NumZeros + 1, Builder.getInt32(0));
GetElementPtrInst *GEP =
GetElementPtrInst::Create(SrcPTy->getElementType(), Src, Idxs);
// If the source pointer is dereferenceable, then assume it points to an
// allocated object and apply "inbounds" to the GEP.
bool CanBeNull, CanBeFreed;
if (Src->getPointerDereferenceableBytes(DL, CanBeNull, CanBeFreed)) {
// In a non-default address space (not 0), a null pointer can not be
// assumed inbounds, so ignore that case (dereferenceable_or_null).
// The reason is that 'null' is not treated differently in these address
// spaces, and we consequently ignore the 'gep inbounds' special case
// for 'null' which allows 'inbounds' on 'null' if the indices are
// zeros.
if (SrcPTy->getAddressSpace() == 0 || !CanBeNull)
GEP->setIsInBounds();
}
return GEP;
}
}
if (FixedVectorType *DestVTy = dyn_cast<FixedVectorType>(DestTy)) {

43
llvm/test/Transforms/InstCombine/opaque-ptr.ll
View File

@ -1,43 +0,0 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S -instcombine < %s | FileCheck %s
define ptr @bitcast_opaque_to_opaque(ptr %a) {
; CHECK-LABEL: @bitcast_opaque_to_opaque(
; CHECK-NEXT: ret ptr [[A:%.*]]
;
%b = bitcast ptr %a to ptr
ret ptr %b
}
define ptr @bitcast_typed_to_opaque(i8* %a) {
; CHECK-LABEL: @bitcast_typed_to_opaque(
; CHECK-NEXT: [[B:%.*]] = bitcast i8* [[A:%.*]] to ptr
; CHECK-NEXT: ret ptr [[B]]
;
%b = bitcast i8* %a to ptr
ret ptr %b
}
define i8* @bitcast_opaque_to_typed(ptr %a) {
; CHECK-LABEL: @bitcast_opaque_to_typed(
; CHECK-NEXT: [[B:%.*]] = bitcast ptr [[A:%.*]] to i8*
; CHECK-NEXT: ret i8* [[B]]
;
%b = bitcast ptr %a to i8*
ret i8* %b
}
;define ptr @addrspacecast_opaque_to_opaque(ptr addrspace(1) %a) {
; %b = addrspacecast ptr addrspace(1) %a to ptr
; ret ptr %b
;}
;define ptr @addrspacecast_typed_to_opaque(i8 addrspace(1)* %a) {
; %b = addrspacecast i8 addrspace(1)* %a to ptr
; ret ptr %b
;}
;define i8* @addrspacecast_opaque_to_typed(ptr addrspace(1) %a) {
; %b = addrspacecast ptr addrspace(1) %a to i8*
; ret i8* %b
;}