From 9d4c13124adfe9a9c6cdc22a220eff1eeff63b77 Mon Sep 17 00:00:00 2001 From: James Molloy Date: Fri, 23 Oct 2015 14:17:03 +0000 Subject: [PATCH] [BasicAA] Bugfix for r251016 If the loaded type sizes don't match the element type of the sequential type, all bets are off and the addresses may, indeed, overlap. Surprisingly, this just got caught in one test, on one builder, out of the 30+ builders testing this change. Congratulations go to http://lab.llvm.org:8011/builders/clang-aarch64-lnt/builds/5205. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251112 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/BasicAliasAnalysis.cpp | 10 ++++++++-- test/Analysis/BasicAA/sequential-gep.ll | 11 +++++++++++ 2 files changed, 19 insertions(+), 2 deletions(-) diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp index 7c1255578a2..59b2953c3b9 100644 --- a/lib/Analysis/BasicAliasAnalysis.cpp +++ b/lib/Analysis/BasicAliasAnalysis.cpp @@ -815,11 +815,17 @@ static AliasResult aliasSameBasePointerGEPs(const GEPOperator *GEP1, // Because array indices greater than the number of elements are valid in // GEPs, unless we know the intermediate indices are identical between // GEP1 and GEP2 we cannot guarantee that the last indexed arrays don't - // partially overlap. + // partially overlap. We also need to check that the loaded size matches + // the element size, otherwise we could still have overlap. + const uint64_t ElementSize = + DL.getTypeStoreSize(cast(Ty)->getElementType()); + if (V1Size != ElementSize || V2Size != ElementSize) + return MayAlias; + for (unsigned i = 0, e = GEP1->getNumIndices() - 1; i != e; ++i) if (GEP1->getOperand(i + 1) != GEP2->getOperand(i + 1)) return MayAlias; - + // Now we know that the array/pointer that GEP1 indexes into and that // that GEP2 indexes into must either precisely overlap or be disjoint. // Because they cannot partially overlap and because fields in an array diff --git a/test/Analysis/BasicAA/sequential-gep.ll b/test/Analysis/BasicAA/sequential-gep.ll index f59843742f4..c17a782aa04 100644 --- a/test/Analysis/BasicAA/sequential-gep.ll +++ b/test/Analysis/BasicAA/sequential-gep.ll @@ -40,4 +40,15 @@ define void @t4([8 x i32]* %p, i32 %addend, i32* %q) { ret void } +; CHECK: Function: t5 +; CHECK: PartialAlias: i32* %gep2, i64* %bc +define void @t5([8 x i32]* %p, i32 %addend, i32* %q) { + %knownnonzero = load i32, i32* %q, !range !0 + %add = add nsw nuw i32 %addend, %knownnonzero + %gep1 = getelementptr [8 x i32], [8 x i32]* %p, i32 2, i32 %addend + %gep2 = getelementptr [8 x i32], [8 x i32]* %p, i32 2, i32 %add + %bc = bitcast i32* %gep1 to i64* + ret void +} + !0 = !{ i32 1, i32 5 } -- 2.34.1