Create an explicit copy for byval parameters even
when inlining a readonly function.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46393 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/InlineFunction.cpp b/lib/Transforms/Utils/InlineFunction.cpp
index 5525830..acd2b10 100644
--- a/lib/Transforms/Utils/InlineFunction.cpp
+++ b/lib/Transforms/Utils/InlineFunction.cpp
@@ -240,12 +240,15 @@
E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) {
Value *ActualArg = *AI;
- // 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()) {
+ // 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)) {
const Type *AggTy = cast<PointerType>(I->getType())->getElementType();
const Type *VoidPtrTy = PointerType::getUnqual(Type::Int8Ty);
diff --git a/test/CFrontend/2008-01-26-ReadOnlyByVal.c b/test/CFrontend/2008-01-26-ReadOnlyByVal.c
new file mode 100644
index 0000000..cea6d1e
--- /dev/null
+++ b/test/CFrontend/2008-01-26-ReadOnlyByVal.c
@@ -0,0 +1,19 @@
+// RUN: %llvmgcc %s -S -O1 -o - | llvm-as | opt -std-compile-opts | llvm-dis | not grep add
+
+struct S { int A; int B; int C; int D; };
+
+int f(struct S x) __attribute__ ((const));
+
+static int __attribute__ ((const)) g(struct S x) {
+ x.A = x.B;
+ return f(x);
+}
+
+int h(void) {
+ struct S x;
+ int r;
+ x.A = 0;
+ x.B = 9;
+ r = g(x);
+ return r + x.A;
+}