Author: Nikita Popov Date: 2020-11-28T10:17:12+01:00 New Revision: 1dea8ed8b7dd2ff5ea89dd6dcaf0b682a81e9815
URL: https://github.com/llvm/llvm-project/commit/1dea8ed8b7dd2ff5ea89dd6dcaf0b682a81e9815 DIFF: https://github.com/llvm/llvm-project/commit/1dea8ed8b7dd2ff5ea89dd6dcaf0b682a81e9815.diff LOG: [BasicAA] Remove unnecessary known size requirement The size requirement on V2 was present because it was not clear whether an unknown size would allow an access before the start of V2, which could then overlap. This is clarified since D91649: In this part of BasicAA, all accesses can occur only after the base pointer, even if they have unknown size. This makes the positive and negative offset cases symmetric. Differential Revision: https://reviews.llvm.org/D91482 Added: Modified: llvm/lib/Analysis/BasicAliasAnalysis.cpp llvm/test/Analysis/BasicAA/negoffset.ll Removed: ################################################################################ diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp index 5e6afd908ba3..2e4ee1c429dd 100644 --- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp +++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp @@ -1336,9 +1336,7 @@ AliasResult BasicAAResult::aliasGEP( // ---------------->| // |-->V1Size |-------> V2Size // GEP1 V2 - // We need to know that V2Size is not unknown, otherwise we might have - // stripped a gep with negative index ('gep <ptr>, -1, ...). - if (V1Size.hasValue() && V2Size.hasValue()) { + if (V1Size.hasValue()) { if ((-DecompGEP1.Offset).ult(V1Size.getValue())) return PartialAlias; return NoAlias; diff --git a/llvm/test/Analysis/BasicAA/negoffset.ll b/llvm/test/Analysis/BasicAA/negoffset.ll index ac1ddfdf5ac5..cc0d68a48a12 100644 --- a/llvm/test/Analysis/BasicAA/negoffset.ll +++ b/llvm/test/Analysis/BasicAA/negoffset.ll @@ -117,3 +117,13 @@ entry: %2 = load i32, i32* %1 ret i32 %2 } + +; CHECK-LABEL: Function: one_size_unknown: +; CHECK: NoModRef: Ptr: i8* %p.minus1 <-> call void @llvm.memset.p0i8.i32(i8* %p, i8 0, i32 %size, i1 false) +define void @one_size_unknown(i8* %p, i32 %size) { + %p.minus1 = getelementptr inbounds i8, i8* %p, i32 -1 + call void @llvm.memset.p0i8.i32(i8* %p, i8 0, i32 %size, i1 false) + ret void +} + +declare void @llvm.memset.p0i8.i32(i8*, i8, i32, i1) _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
