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Revert r46393: readonly/readnone functions are no 

longer allowed to write through byval arguments.

llvm-svn: 46416
This commit is contained in:
Duncan Sands 2008-01-27 18:12:58 +00:00
parent 888560d62c
commit 053c9871cd
2 changed files with 9 additions and 12 deletions
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15
llvm/lib/Transforms/Utils/InlineFunction.cpp
View File

@ -240,15 +240,12 @@ 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 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);

6
llvm/test/Transforms/Inline/byval2.ll
View File

@ -1,7 +1,7 @@
; RUN: llvm-as < %s | opt -inline | llvm-dis | grep {llvm.memcpy}
; RUN: llvm-as < %s | opt -inline | llvm-dis | not grep {llvm.memcpy}
; Inlining a byval struct should cause an explicit copy
; into an alloca even if the function is readonly
; Inlining a byval struct should NOT cause an explicit copy
; into an alloca if the function is readonly
%struct.ss = type { i32, i64 }
@.str = internal constant [10 x i8] c"%d, %lld\0A\00" ; <[10 x i8]*> [#uses=1]