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[ConstantFolding] Accept offset in ConstantFoldLoadFromConstPtr (NFCI) 

As this API is now internally offset-based, we can accept a starting
offset and remove the need to create a temporary bitcast+gep
sequence to perform an offset load. The API now mirrors the
ConstantFoldLoadFromConst() API.
This commit is contained in:
Nikita Popov 2021-10-23 17:58:07 +02:00
parent d8e4170b0a
commit 710596a1e1
3 changed files with 21 additions and 27 deletions
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13
llvm/include/llvm/Analysis/ConstantFolding.h
View File

@ -138,10 +138,15 @@ Constant *ConstantFoldLoadFromConst(Constant *C, Type *Ty, const APInt &Offset,
Constant *ConstantFoldLoadFromConst(Constant *C, Type *Ty,
const DataLayout &DL);
/// ConstantFoldLoadFromConstPtr - Return the value that a load from C would
/// produce if it is constant and determinable. If this is not determinable,
/// return null.
Constant *ConstantFoldLoadFromConstPtr(Constant *C, Type *Ty, const DataLayout &DL);
/// Return the value that a load from C with offset Offset would produce if it
/// is constant and determinable. If this is not determinable, return null.
Constant *ConstantFoldLoadFromConstPtr(Constant *C, Type *Ty, APInt Offset,
const DataLayout &DL);
/// Return the value that a load from C would produce if it is constant and
/// determinable. If this is not determinable, return null.
Constant *ConstantFoldLoadFromConstPtr(Constant *C, Type *Ty,
const DataLayout &DL);
/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
/// getelementptr constantexpr, return the constant value being addressed by the

8
llvm/lib/Analysis/ConstantFolding.cpp
View File

@ -690,8 +690,8 @@ Constant *llvm::ConstantFoldLoadFromConst(Constant *C, Type *Ty,
}
Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C, Type *Ty,
APInt Offset,
const DataLayout &DL) {
APInt Offset(DL.getIndexTypeSizeInBits(C->getType()), 0);
C = cast<Constant>(C->stripAndAccumulateConstantOffsets(
DL, Offset, /* AllowNonInbounds */ true));
@ -715,6 +715,12 @@ Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C, Type *Ty,
return nullptr;
}
Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C, Type *Ty,
const DataLayout &DL) {
APInt Offset(DL.getIndexTypeSizeInBits(C->getType()), 0);
return ConstantFoldLoadFromConstPtr(C, Ty, Offset, DL);
}
namespace {
/// One of Op0/Op1 is a constant expression.

27
llvm/lib/Transforms/Utils/VNCoercion.cpp
View File

@ -403,19 +403,10 @@ int analyzeLoadFromClobberingMemInst(Type *LoadTy, Value *LoadPtr,
if (Offset == -1)
return Offset;
unsigned AS = Src->getType()->getPointerAddressSpace();
// Otherwise, see if we can constant fold a load from the constant with the
// offset applied as appropriate.
if (Offset) {
Src = ConstantExpr::getBitCast(Src,
Type::getInt8PtrTy(Src->getContext(), AS));
Constant *OffsetCst =
ConstantInt::get(Type::getInt64Ty(Src->getContext()), (unsigned)Offset);
Src = ConstantExpr::getGetElementPtr(Type::getInt8Ty(Src->getContext()),
Src, OffsetCst);
}
Src = ConstantExpr::getBitCast(Src, PointerType::get(LoadTy, AS));
if (ConstantFoldLoadFromConstPtr(Src, LoadTy, DL))
unsigned IndexSize = DL.getIndexTypeSizeInBits(Src->getType());
if (ConstantFoldLoadFromConstPtr(Src, LoadTy, APInt(IndexSize, Offset), DL))
return Offset;
return -1;
}
@ -584,19 +575,11 @@ T *getMemInstValueForLoadHelper(MemIntrinsic *SrcInst, unsigned Offset,
MemTransferInst *MTI = cast<MemTransferInst>(SrcInst);
Constant *Src = cast<Constant>(MTI->getSource());
unsigned AS = Src->getType()->getPointerAddressSpace();
// Otherwise, see if we can constant fold a load from the constant with the
// offset applied as appropriate.
if (Offset) {
Src = ConstantExpr::getBitCast(Src,
Type::getInt8PtrTy(Src->getContext(), AS));
Constant *OffsetCst =
ConstantInt::get(Type::getInt64Ty(Src->getContext()), (unsigned)Offset);
Src = ConstantExpr::getGetElementPtr(Type::getInt8Ty(Src->getContext()),
Src, OffsetCst);
}
Src = ConstantExpr::getBitCast(Src, PointerType::get(LoadTy, AS));
return ConstantFoldLoadFromConstPtr(Src, LoadTy, DL);
unsigned IndexSize = DL.getIndexTypeSizeInBits(Src->getType());
return ConstantFoldLoadFromConstPtr(
Src, LoadTy, APInt(IndexSize, Offset), DL);
}
/// This function is called when we have a