[Clang][CodeGen] Do not use the GEP result to infer offset and result type by dtcxzyw · Pull Request #134221 · llvm/llvm-project (original) (raw)

@llvm/pr-subscribers-clang-codegen

@llvm/pr-subscribers-clang

Author: Yingwei Zheng (dtcxzyw)

Changes

If CreateConstInBoundsGEP2_32 returns a constant null/gep, the cast to GetElementPtrInst will fail.
This patch uses two static helpers GEPOperator::accumulateConstantOffset/GetElementPtrInst::getIndexedType to infer offset and result type instead of depending on the GEP result.

This patch is extracted from #130734. It may be useful to fix #132449.

Full diff: https://github.com/llvm/llvm-project/pull/134221.diff

1 Files Affected:

(modified) clang/lib/CodeGen/CGBuilder.h (+14-10)

diff --git a/clang/lib/CodeGen/CGBuilder.h b/clang/lib/CodeGen/CGBuilder.h index b8036cf6e6a30..090f75d3b5d3c 100644 --- a/clang/lib/CodeGen/CGBuilder.h +++ b/clang/lib/CodeGen/CGBuilder.h @@ -64,21 +64,25 @@ class CGBuilderTy : public CGBuilderBaseTy { Address createConstGEP2_32(Address Addr, unsigned Idx0, unsigned Idx1, const llvm::Twine &Name) { const llvm::DataLayout &DL = BB->getDataLayout();

llvm::GetElementPtrInst *GEP;

llvm::Value *V; if (IsInBounds)

 GEP = cast<llvm::GetElementPtrInst>(CreateConstInBoundsGEP2_32(

     Addr.getElementType(), emitRawPointerFromAddress(Addr), Idx0, Idx1,

```
     Name));
```

 V = CreateConstInBoundsGEP2_32(Addr.getElementType(),

                                emitRawPointerFromAddress(Addr), Idx0,

                                Idx1, Name);

else

 GEP = cast<llvm::GetElementPtrInst>(CreateConstGEP2_32(

     Addr.getElementType(), emitRawPointerFromAddress(Addr), Idx0, Idx1,

```
     Name));
```

 V = CreateConstGEP2_32(Addr.getElementType(),

```
                        emitRawPointerFromAddress(Addr), Idx0, Idx1, Name);
```
llvm::APInt Offset( DL.getIndexSizeInBits(Addr.getType()->getPointerAddressSpace()), 0, /isSigned=/true);

if (!GEP->accumulateConstantOffset(DL, Offset))

 llvm_unreachable("offset of GEP with constants is always computable");

return Address(GEP, GEP->getResultElementType(),

if (!llvm::GEPOperator::accumulateConstantOffset(

       Addr.getElementType(), {getInt32(Idx0), getInt32(Idx1)}, DL,

```
       Offset))
```
```
 llvm_unreachable(
```

     "accumulateConstantOffset with constant indices should not fail.");

llvm::Type *ElementTy = llvm::GetElementPtrInst::getIndexedType(

   Addr.getElementType(), {Idx0, Idx1});

return Address(V, ElementTy, Addr.getAlignment().alignmentAtOffset( CharUnits::fromQuantity(Offset.getSExtValue())), IsInBounds ? Addr.isKnownNonNull() : NotKnownNonNull);