Index: lib/Analysis/BasicAliasAnalysis.cpp =================================================================== --- lib/Analysis/BasicAliasAnalysis.cpp +++ lib/Analysis/BasicAliasAnalysis.cpp @@ -1008,10 +1008,22 @@ // equal each other so we can exit early. if (C1 && C2) return NoAlias; - if (isKnownNonEqual(GEP1->getOperand(GEP1->getNumOperands() - 1), - GEP2->getOperand(GEP2->getNumOperands() - 1), - DL)) - return NoAlias; + { + Value *GEP1LastIdx = GEP1->getOperand(GEP1->getNumOperands() - 1); + Value *GEP2LastIdx = GEP2->getOperand(GEP2->getNumOperands() - 1); + if (isa(GEP1LastIdx) || isa(GEP2LastIdx)) { + // If one of the indices is a PHI node, be safe and only use + // computeKnownBits so we don't make any assumptions about the + // relationships between the two indices. This is important if we're + // asking about values from different loop iterations. See PR32314. + KnownBits Known1 = computeKnownBits(GEP1LastIdx, DL); + KnownBits Known2 = computeKnownBits(GEP2LastIdx, DL); + if (Known1.Zero.intersects(Known2.One) || + Known1.One.intersects(Known2.Zero)) + return NoAlias; + } else if (isKnownNonEqual(GEP1LastIdx, GEP2LastIdx, DL)) + return NoAlias; + } return MayAlias; } else if (!LastIndexedStruct || !C1 || !C2) { return MayAlias; Index: test/Transforms/GVN/pr32314.ll =================================================================== --- /dev/null +++ test/Transforms/GVN/pr32314.ll @@ -0,0 +1,53 @@ +; NOTE: Assertions have been autogenerated by utils/update_test_checks.py +; RUN: opt -S -gvn < %s | FileCheck %s + +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-unknown-linux-gnu" + +; The load in the loop can not bypass the data from the previous loop. The store above it in the loop aliases. +define void @foo() { +; CHECK-LABEL: @foo( +; CHECK-NEXT: entry: +; CHECK-NEXT: [[A:%.*]] = alloca [3 x i32], align 4 +; CHECK-NEXT: br label [[FOR_BODY:%.*]] +; CHECK: for.cond.cleanup: +; CHECK-NEXT: ret void +; CHECK: for.body: +; CHECK-NEXT: [[INDVARS_IV:%.*]] = phi i64 [ 1, [[ENTRY:%.*]] ], [ [[INDVARS_IV_NEXT:%.*]], [[FOR_BODY]] ] +; CHECK-NEXT: [[P_017:%.*]] = phi i32* [ undef, [[ENTRY]] ], [ [[ARRAYIDX3:%.*]], [[FOR_BODY]] ] +; CHECK-NEXT: [[TMP0:%.*]] = add nsw i64 [[INDVARS_IV]], -1 +; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr inbounds [3 x i32], [3 x i32]* [[A]], i64 0, i64 [[TMP0]] +; CHECK-NEXT: store i32 50, i32* [[ARRAYIDX]], align 4 +; CHECK-NEXT: [[TMP1:%.*]] = shl i64 [[INDVARS_IV]], 1 +; CHECK-NEXT: [[TMP2:%.*]] = load i32, i32* [[P_017]], align 4 +; CHECK-NEXT: [[TMP3:%.*]] = trunc i64 [[TMP1]] to i32 +; CHECK-NEXT: [[ADD1:%.*]] = add nsw i32 [[TMP2]], [[TMP3]] +; CHECK-NEXT: [[ARRAYIDX3]] = getelementptr inbounds [3 x i32], [3 x i32]* [[A]], i64 0, i64 [[INDVARS_IV]] +; CHECK-NEXT: store i32 60, i32* [[ARRAYIDX3]], align 4 +; CHECK-NEXT: [[INDVARS_IV_NEXT]] = add nuw nsw i64 [[INDVARS_IV]], 1 +; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i64 [[INDVARS_IV_NEXT]], 3 +; CHECK-NEXT: br i1 [[EXITCOND]], label [[FOR_BODY]], label [[FOR_COND_CLEANUP:%.*]] +; +entry: + %a = alloca [3 x i32], align 4 + br label %for.body + +for.cond.cleanup: ; preds = %for.body + ret void + +for.body: ; preds = %for.body, %entry + %indvars.iv = phi i64 [ 1, %entry ], [ %indvars.iv.next, %for.body ] + %p.017 = phi i32* [ undef, %entry ], [ %arrayidx3, %for.body ] + %0 = add nsw i64 %indvars.iv, -1 + %arrayidx = getelementptr inbounds [3 x i32], [3 x i32]* %a, i64 0, i64 %0 + store i32 50, i32* %arrayidx, align 4 + %1 = shl i64 %indvars.iv, 1 + %2 = load i32, i32* %p.017, align 4 + %3 = trunc i64 %1 to i32 + %add1 = add nsw i32 %2, %3 + %arrayidx3 = getelementptr inbounds [3 x i32], [3 x i32]* %a, i64 0, i64 %indvars.iv + store i32 60, i32* %arrayidx3, align 4 + %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1 + %exitcond = icmp ne i64 %indvars.iv.next, 3 + br i1 %exitcond, label %for.body, label %for.cond.cleanup +}