Index: lib/Analysis/BasicAliasAnalysis.cpp =================================================================== --- lib/Analysis/BasicAliasAnalysis.cpp +++ lib/Analysis/BasicAliasAnalysis.cpp @@ -1160,6 +1160,10 @@ int64_t GEPBaseOffset = DecompGEP.StructOffset; if (DecompGEP.VarIndices.empty()) GEPBaseOffset += DecompGEP.OtherOffset; + // We can't get GEP offset to identify pointer alias if the GEP has variable + // indeces. + else + return false; return (GEPBaseOffset >= ObjectBaseOffset + (int64_t)ObjectAccessSize); } Index: test/Analysis/BasicAA/negoffset.ll =================================================================== --- test/Analysis/BasicAA/negoffset.ll +++ test/Analysis/BasicAA/negoffset.ll @@ -61,8 +61,8 @@ ; CHECK-DAG: MayAlias: i32* %a2.0, i32* %r2.1i ; CHECK-DAG: NoAlias: i32* %a1, i32* %r2.0 ; CHECK-DAG: NoAlias: i32* %a1, i32* %r2.1 -; CHECK-DAG: NoAlias: i32* %a1, i32* %r2.i -; CHECK-DAG: NoAlias: i32* %a1, i32* %r2.1i +; CHECK-DAG: MayAlias: i32* %a1, i32* %r2.i +; CHECK-DAG: MayAlias: i32* %a1, i32* %r2.1i %complex = type { i32, i32, [4 x i32] } define void @complex1(i32 %i) { %alloca = alloca %complex @@ -79,9 +79,9 @@ } ; CHECK-LABEL: Function: complex2: -; CHECK-DAG: NoAlias: i32* %alloca, i32* %p120 -; CHECK-DAG: NoAlias: i32* %alloca, i32* %pi20 -; CHECK-DAG: NoAlias: i32* %alloca, i32* %pij1 +; CHECK-DAG: NoAlias: i32* %alloca, i32* %p120 +; CHECK-DAG: MayAlias: i32* %alloca, i32* %pi20 +; CHECK-DAG: MayAlias: i32* %alloca, i32* %pij1 ; CHECK-DAG: MayAlias: i32* %a3, i32* %pij1 %inner = type { i32, i32 } %outer = type { i32, i32, [10 x %inner] } @@ -96,3 +96,24 @@ ret void } +; CHECK-LABEL: Function: pointer_offset: +; CHECK-DAG: MayAlias: i32** %add.ptr, i32** %p1 +; CHECK-DAG: MayAlias: i32** %add.ptr, i32** %q2 +%struct.X = type { i32*, i32* } +define i32 @pointer_offset(i32 signext %i, i32 signext %j, i32 zeroext %off) { +entry: + %i.addr = alloca i32 + %j.addr = alloca i32 + %x = alloca %struct.X + store i32 %i, i32* %i.addr + store i32 %j, i32* %j.addr + %0 = bitcast %struct.X* %x to i8* + %p1 = getelementptr inbounds %struct.X, %struct.X* %x, i32 0, i32 0 + store i32* %i.addr, i32** %p1 + %q2 = getelementptr inbounds %struct.X, %struct.X* %x, i32 0, i32 1 + store i32* %j.addr, i32** %q2 + %add.ptr = getelementptr inbounds i32*, i32** %q2, i32 %off + %1 = load i32*, i32** %add.ptr + %2 = load i32, i32* %1 + ret i32 %2 +}