we don't have to make an explicit copy of a byval argument when
inlining a function if we know that the function does not write
to *any* memory. This implements test/Transforms/Inline/byval2.ll
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45912 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/InlineFunction.cpp b/lib/Transforms/Utils/InlineFunction.cpp
index a4978f0..f730d53 100644
--- a/lib/Transforms/Utils/InlineFunction.cpp
+++ b/lib/Transforms/Utils/InlineFunction.cpp
@@ -241,10 +241,12 @@
Value *ActualArg = *AI;
// When byval arguments actually inlined, we need to make the copy implied
- // by them actually explicit.
- // TODO: If we know that the callee never modifies the struct, we can
- // remove this copy.
- if (CalledFunc->paramHasAttr(ArgNo+1, ParamAttr::ByVal)) {
+ // by them explicit. However, we don't do this if the callee is readonly
+ // or readnone, because the copy would be unneeded: the callee doesn't
+ // modify the struct.
+ if (CalledFunc->paramHasAttr(ArgNo+1, ParamAttr::ByVal) &&
+ !CalledFunc->paramHasAttr(0, ParamAttr::ReadOnly) &&
+ !CalledFunc->paramHasAttr(0, ParamAttr::ReadNone)) {
const Type *AggTy = cast<PointerType>(I->getType())->getElementType();
const Type *VoidPtrTy = PointerType::getUnqual(Type::Int8Ty);