================
@@ -3086,13 +3086,51 @@ Instruction
*InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
if (GEPType->isVectorTy())
return nullptr;
+ if (!GEP.isInBounds()) {
+ unsigned IdxWidth =
+ DL.getIndexSizeInBits(PtrOp->getType()->getPointerAddressSpace());
+ APInt BasePtrOffset(IdxWidth, 0);
+ Value *UnderlyingPtrOp =
+ PtrOp->stripAndAccumulateInBoundsConstantOffsets(DL, BasePtrOffset);
+ bool CanBeNull, CanBeFreed;
+ uint64_t DerefBytes = UnderlyingPtrOp->getPointerDereferenceableBytes(
+ DL, CanBeNull, CanBeFreed);
+ if (!CanBeNull && !CanBeFreed && DerefBytes != 0) {
+ if (GEP.accumulateConstantOffset(DL, BasePtrOffset) &&
+ BasePtrOffset.isNonNegative()) {
+ APInt AllocSize(IdxWidth, DerefBytes);
+ if (BasePtrOffset.ule(AllocSize)) {
+ return GetElementPtrInst::CreateInBounds(
+ GEP.getSourceElementType(), PtrOp, Indices, GEP.getName());
+ }
+ }
+ }
+ }
+
+ // nusw + nneg -> nuw
+ if (GEP.hasNoUnsignedSignedWrap() && !GEP.hasNoUnsignedWrap() &&
+ all_of(GEP.indices(), [&](Value *Idx) {
+ return isKnownNonNegative(Idx, SQ.getWithInstruction(&GEP));
+ })) {
+ GEP.setNoWrapFlags(GEP.getNoWrapFlags() |
GEPNoWrapFlags::noUnsignedWrap());
+ return &GEP;
+ }
+
+ // These rewrites is trying to preserve inbounds/nuw attributes. So we want
to
+ // do this after having tried to derive "nuw" above.
if (GEP.getNumIndices() == 1) {
- // We can only preserve inbounds if the original gep is inbounds, the add
- // is nsw, and the add operands are non-negative.
- auto CanPreserveInBounds = [&](bool AddIsNSW, Value *Idx1, Value *Idx2) {
- SimplifyQuery Q = SQ.getWithInstruction(&GEP);
- return GEP.isInBounds() && AddIsNSW && isKnownNonNegative(Idx1, Q) &&
- isKnownNonNegative(Idx2, Q);
+ auto GetPreservedNoWrapFlags = [&](bool AddIsNUW, Value *Idx1,
+ Value *Idx2) {
+ // Preserve "inbounds nuw" if the original gep is "inbounds nuw", and the
+ // add is "nuw". Preserve "nuw" if the original gep is "nuw", and the add
+ // is "nuw".
+ GEPNoWrapFlags Flags = GEPNoWrapFlags::none();
+ if (GEP.hasNoUnsignedWrap() && AddIsNUW) {
+ Flags |= GEPNoWrapFlags::noUnsignedWrap();
+ if (GEP.isInBounds())
+ Flags |= GEPNoWrapFlags::inBounds();
----------------
nikic wrote:
Same comment here, we should just be returning the original Flags instead of
reconstructing them. Note that this works for all of `nuw`, `inbounds nuw` and
`nusw nuw`: https://alive2.llvm.org/ce/z/QSweWW
https://github.com/llvm/llvm-project/pull/135155
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