llvm-project

0b042885 - [clang][CodeGen] Compute the pointer-overflow offset from the index list (#225139)

[clang][CodeGen] Compute the pointer-overflow offset from the index list (#225139) Follow up to #223446. EmitGEPOffsetInBytes recreated the offset by walking the GEP value that EmitCheckedInBoundsGEP had just created. That required a separate path for the case where CreateGEP folded the result, because a folded GEP need not be a GEP at all: `gep(null, 1)` becomes `inttoptr(1)`, and `gep(@g, 0)` becomes `@g`. Pass ElemTy and IdxList instead and walk those directly. This removes the constant path, the cast to GEPOperator, and two asserts that restated the caller's own behaviour. This is not quite NFC. The constant path reported OffsetOverflows as false unconditionally, so a constant GEP whose byte offset wrapped to exactly zero satisfied the TotalOffset == Zero early return and emitted no check. The unified path computes the flag, so such a GEP now emits one. It is provably valid, since TotalOffset == 0 makes the computed address equal the base, so this is extra IR at -O0 rather than a change in behaviour. Add constant-base cases to ubsan-pointer-overflow-constant-fold.c, including the wraps-to-zero case: it passes before this change only because no check is emitted at all. Assisted-by: Kiro CLI / Claude Opus 5