diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp --- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp +++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp @@ -2150,7 +2150,9 @@ // Skip if GEP source element type is scalable. The type alloc size is unknown // at compile-time. - if (GEP.getNumIndices() == 1 && !IsGEPSrcEleScalable) { + // Also skip for non-inbounds GEPs, because the optimization inside is not + // correct for regular GEPs. + if (GEP.getNumIndices() == 1 && !IsGEPSrcEleScalable && GEP.isInBounds()) { unsigned AS = GEP.getPointerAddressSpace(); if (GEP.getOperand(1)->getType()->getScalarSizeInBits() == DL.getIndexSizeInBits(AS)) { @@ -2173,7 +2175,7 @@ } if (Matched) { - // Canonicalize (gep i8* X, -(ptrtoint Y)) + // Canonicalize (gepi i8* X, -(ptrtoint Y)) // to (inttoptr (sub (ptrtoint X), (ptrtoint Y))) // The GEP pattern is emitted by the SCEV expander for certain kinds of // pointer arithmetic. @@ -2183,7 +2185,7 @@ Value *NewSub = Builder.CreateSub(PtrToInt, Index->getOperand(1)); return CastInst::Create(Instruction::IntToPtr, NewSub, GEPType); } - // Canonicalize (gep i8* X, (ptrtoint Y)-(ptrtoint X)) + // Canonicalize (gepi i8* X, (ptrtoint Y)-(ptrtoint X)) // to (bitcast Y) Value *Y; if (match(V, m_Sub(m_PtrToInt(m_Value(Y)), diff --git a/llvm/test/Other/regr-gep-provenance.ll b/llvm/test/Other/regr-gep-provenance.ll new file mode 100644 --- /dev/null +++ b/llvm/test/Other/regr-gep-provenance.ll @@ -0,0 +1,32 @@ +; NOTE: Assertions have been autogenerated by utils/update_test_checks.py +; RUN: opt < %s -S -O3 -o - | FileCheck %s + +; This test verifies that we do not optimize GEPs in a way that would lose pointer provenance (e.g. +; by optimizing a series of operations that result in `null` into a `null` (which does not have +; any provenance in particular) + +define i8 @apple(i8* %x) unnamed_addr #0 { +; CHECK-LABEL: @apple( +; CHECK-NEXT: [[E:%.*]] = load i8, i8* [[X:%.*]], align 1 +; CHECK-NEXT: ret i8 [[E]] +; + %a = ptrtoint i8* %x to i64 + %b = sub i64 0, %a + %c = getelementptr i8, i8* %x, i64 %b + %d = getelementptr i8, i8* %c, i64 %a + %e = load i8, i8* %d, align 1 + ret i8 %e +} + +define i8* @banana(i8* %b) { +; CHECK-LABEL: @banana( +; CHECK-NEXT: [[B_PTR:%.*]] = ptrtoint i8* [[B:%.*]] to i64 +; CHECK-NEXT: [[SUB:%.*]] = sub i64 0, [[B_PTR]] +; CHECK-NEXT: [[GEP:%.*]] = getelementptr i8, i8* [[B]], i64 [[SUB]] +; CHECK-NEXT: ret i8* [[GEP]] +; + %b_ptr = ptrtoint i8* %b to i64 + %sub = sub i64 0, %b_ptr + %gep = getelementptr i8, i8* %b, i64 %sub + ret i8* %gep +}