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Reapply [InstCombine] Extract bitcast -> gep transform

Browse Source 
Relative to the original patch, an InstCombine test has been
added to show a previously missed pattern, and the Coroutine
test that resulted in the revert has been regenerated.

-----

Move this into a separate function, to make sure that early
returns do not accidentally skip other transforms. This previously
happened for the isSized() check, which skipped folds like
distributing a bitcast over a select.
This commit is contained in:
Nikita Popov 2021-06-21 20:22:06 +02:00
parent 4ce7d65381
commit 3520bd21c8
3 changed files with 58 additions and 54 deletions
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90
lib/Transforms/InstCombine/InstCombineCasts.cpp
View File

@ -2603,6 +2603,52 @@ 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());
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.
@ -2616,11 +2662,6 @@ 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
@ -2629,43 +2670,8 @@ Instruction *InstCombinerImpl::visitBitCast(BitCastInst &CI) {
if (Instruction *V = PromoteCastOfAllocation(CI, *AI))
return V;
// 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 (Instruction *I = convertBitCastToGEP(CI, Builder, DL))
return I;
}
if (FixedVectorType *DestVTy = dyn_cast<FixedVectorType>(DestTy)) {

19
test/Transforms/Coroutines/coro-retcon-once-value.ll
View File

@ -12,12 +12,11 @@ define {i8*, i32} @f(i8* %buffer, i32* %array) {
; CHECK-NEXT: store i32* [[ARRAY:%.*]], i32** [[ARRAY_SPILL_ADDR]], align 8
; CHECK-NEXT: [[LOAD:%.*]] = load i32, i32* [[ARRAY]], align 4
; CHECK-NEXT: [[LOAD_POS:%.*]] = icmp sgt i32 [[LOAD]], 0
; CHECK-NEXT: [[TMP0:%.*]] = select i1 [[LOAD_POS]], void (i8*, i1)* @f.resume.0, void (i8*, i1)* @f.resume.1
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[LOAD_POS]], i32 [[LOAD]], i32 0
; CHECK-NEXT: [[TMP2:%.*]] = bitcast void (i8*, i1)* [[TMP0]] to i8*
; CHECK-NEXT: [[TMP3:%.*]] = insertvalue { i8*, i32 } undef, i8* [[TMP2]], 0
; CHECK-NEXT: [[TMP4:%.*]] = insertvalue { i8*, i32 } [[TMP3]], i32 [[TMP1]], 1
; CHECK-NEXT: ret { i8*, i32 } [[TMP4]]
; CHECK-NEXT: [[TMP0:%.*]] = select i1 [[LOAD_POS]], i32 [[LOAD]], i32 0
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[LOAD_POS]], i8* bitcast (void (i8*, i1)* @f.resume.0 to i8*), i8* bitcast (void (i8*, i1)* @f.resume.1 to i8*)
; CHECK-NEXT: [[TMP2:%.*]] = insertvalue { i8*, i32 } undef, i8* [[TMP1]], 0
; CHECK-NEXT: [[TMP3:%.*]] = insertvalue { i8*, i32 } [[TMP2]], i32 [[TMP0]], 1
; CHECK-NEXT: ret { i8*, i32 } [[TMP3]]
;
entry:
%id = call token @llvm.coro.id.retcon.once(i32 8, i32 8, i8* %buffer, i8* bitcast (void (i8*, i1)* @prototype to i8*), i8* bitcast (i8* (i32)* @allocate to i8*), i8* bitcast (void (i8*)* @deallocate to i8*))
@ -58,10 +57,10 @@ define void @test(i32* %array) {
; CHECK-NEXT: store i32* [[ARRAY:%.*]], i32** [[TMP0]], align 8
; CHECK-NEXT: [[LOAD_I:%.*]] = load i32, i32* [[ARRAY]], align 4
; CHECK-NEXT: [[LOAD_POS_I:%.*]] = icmp sgt i32 [[LOAD_I]], 0
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[LOAD_POS_I]], void (i8*, i1)* @f.resume.0, void (i8*, i1)* @f.resume.1
; CHECK-NEXT: [[TMP2:%.*]] = select i1 [[LOAD_POS_I]], i32 [[LOAD_I]], i32 0
; CHECK-NEXT: call void @print(i32 [[TMP2]])
; CHECK-NEXT: call void [[TMP1]](i8* nonnull [[DOTSUB]], i1 zeroext false)
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[LOAD_POS_I]], i32 [[LOAD_I]], i32 0
; CHECK-NEXT: call void @print(i32 [[TMP1]])
; CHECK-NEXT: [[CONT_CAST:%.*]] = select i1 [[LOAD_POS_I]], void (i8*, i1)* @f.resume.0, void (i8*, i1)* @f.resume.1
; CHECK-NEXT: call void [[CONT_CAST]](i8* nonnull [[DOTSUB]], i1 zeroext false)
; CHECK-NEXT: ret void
;
entry:

3
test/Transforms/InstCombine/bitcast.ll
View File

@ -584,8 +584,7 @@ declare void @f1()
declare void @f2()
define i8* @select_bitcast_unsized_pointer(i1 %c) {
; CHECK-LABEL: @select_bitcast_unsized_pointer(
; CHECK-NEXT: [[S:%.*]] = select i1 [[C:%.*]], void ()* @f1, void ()* @f2
; CHECK-NEXT: [[B:%.*]] = bitcast void ()* [[S]] to i8*
; CHECK-NEXT: [[B:%.*]] = select i1 [[C:%.*]], i8* bitcast (void ()* @f1 to i8*), i8* bitcast (void ()* @f2 to i8*)
; CHECK-NEXT: ret i8* [[B]]
;
%s = select i1 %c, void ()* @f1, void ()* @f2