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Create an explicit copy for byval parameters even

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when inlining a readonly function.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46393 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2008-01-26 06:41:49 +00:00
parent f69d5d7398
commit 418ab3729c
2 changed files with 28 additions and 6 deletions
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15
lib/Transforms/Utils/InlineFunction.cpp
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@ -240,12 +240,15 @@ bool llvm::InlineFunction(CallSite CS, CallGraph *CG, const TargetData *TD) {
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);

19
test/CFrontend/2008-01-26-ReadOnlyByVal.c Normal file
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@ -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;
}