diff --git a/llvm/lib/Analysis/Lint.cpp b/llvm/lib/Analysis/Lint.cpp --- a/llvm/lib/Analysis/Lint.cpp +++ b/llvm/lib/Analysis/Lint.cpp @@ -267,10 +267,14 @@ if (Formal->hasNoAliasAttr() && Actual->getType()->isPointerTy()) { AttributeList PAL = CS.getAttributes(); unsigned ArgNo = 0; - for (CallSite::arg_iterator BI = CS.arg_begin(); BI != AE; ++BI) { + for (CallSite::arg_iterator BI = CS.arg_begin(); BI != AE; + ++BI, ++ArgNo) { // Skip ByVal arguments since they will be memcpy'd to the callee's // stack so we're not really passing the pointer anyway. - if (PAL.hasParamAttribute(ArgNo++, Attribute::ByVal)) + if (PAL.hasParamAttribute(ArgNo, Attribute::ByVal)) + continue; + // If both arguments are readonly, they have no dependence. + if (Formal->onlyReadsMemory() && CS.onlyReadsMemory(ArgNo)) continue; if (AI != BI && (*BI)->getType()->isPointerTy()) { AliasResult Result = AA->alias(*AI, *BI); diff --git a/llvm/test/Analysis/Lint/noalias-readonly.ll b/llvm/test/Analysis/Lint/noalias-readonly.ll new file mode 100644 --- /dev/null +++ b/llvm/test/Analysis/Lint/noalias-readonly.ll @@ -0,0 +1,40 @@ +; RUN: opt < %s -lint -disable-output 2>&1 | FileCheck %s + +declare void @f1(i8* noalias readonly, i8*) + +define void @f2(i8* %a) { +entry: + call void @f1(i8* %a, i8* %a) + ret void +} + +; Lint should complain about us passing %a to both arguments, since the noalias +; argument may depend on writes to the other. +; CHECK: Unusual: noalias argument aliases another argument +; CHECK-NEXT: call void @f1(i8* %a, i8* %a) + +declare void @f3(i8* noalias, i8* readonly) + +define void @f4(i8* %a) { +entry: + call void @f3(i8* %a, i8* %a) + ret void +} + +; Lint should complain about us passing %a to both arguments, since writes to +; the noalias argument may cause a dependency for the other. +; CHECK: Unusual: noalias argument aliases another argument +; CHECK-NEXT: call void @f3(i8* %a, i8* %a) + +declare void @f5(i8* noalias readonly, i8* readonly) + +define void @f6(i8* %a) { +entry: + call void @f5(i8* %a, i8* %a) + ret void +} + +; Lint should not complain about passing %a to both arguments even if one is +; noalias, since they are both readonly and thus have no dependence. +; CHECK-NOT: Unusual: noalias argument aliases another argument +; CHECK-NOT: call void @f5(i8* %a, i8* %a)