Revert r46393: readonly/readnone functions are no
longer allowed to write through byval arguments.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46416 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/InlineFunction.cpp b/lib/Transforms/Utils/InlineFunction.cpp
index acd2b10..5525830 100644
--- a/lib/Transforms/Utils/InlineFunction.cpp
+++ b/lib/Transforms/Utils/InlineFunction.cpp
@@ -240,15 +240,12 @@
E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) {
Value *ActualArg = *AI;
- // When byval arguments are inlined, we need to make the copy implied
- // by them explicit. It is tempting to think that this is not needed if
- // the callee is readonly, because the callee doesn't modify the struct.
- // However this would be wrong: readonly means that any writes the callee
- // performs are not visible to the caller. But writes by the callee to
- // an argument passed byval are by definition not visible to the caller!
- // Since we allow this kind of readonly function, there needs to be an
- // explicit copy in order to keep the writes invisible after inlining.
- if (CalledFunc->paramHasAttr(ArgNo+1, ParamAttr::ByVal)) {
+ // When byval arguments actually inlined, we need to make the copy implied
+ // 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->onlyReadsMemory()) {
const Type *AggTy = cast<PointerType>(I->getType())->getElementType();
const Type *VoidPtrTy = PointerType::getUnqual(Type::Int8Ty);