Author: baldrick
Date: Sat Jan 26 00:41:49 2008
New Revision: 46393
URL: http://llvm.org/viewvc/llvm-project?rev=46393&view=rev
Log:
Create an explicit copy for byval parameters even
when inlining a readonly function.
Added:
llvm/trunk/test/CFrontend/2008-01-26-ReadOnlyByVal.c
Modified:
llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp
Modified: llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp?rev=46393&r1=46392&r2=46393&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp Sat Jan 26 00:41:49 2008
@@ -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);
Added: llvm/trunk/test/CFrontend/2008-01-26-ReadOnlyByVal.c
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CFrontend/2008-01-26-ReadOnlyByVal.c?rev=46393&view=auto
==============================================================================
--- llvm/trunk/test/CFrontend/2008-01-26-ReadOnlyByVal.c (added)
+++ llvm/trunk/test/CFrontend/2008-01-26-ReadOnlyByVal.c Sat Jan 26 00:41:49
2008
@@ -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;
+}
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