RPCS3/llvm
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm.git synced 2024-11-25 12:49:50 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

when eliding a byval copy due to inlining a readonly function, we have

Browse Source 
to make sure that the reused alloca has sufficient alignment.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122236 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-12-20 08:10:40 +00:00
parent e7ae705c32
commit 0b66f63a26
2 changed files with 66 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

47
lib/Transforms/Utils/InlineFunction.cpp
View File

@ -229,17 +229,56 @@ static void UpdateCallGraphAfterInlining(CallSite CS,
CallerNode->removeCallEdgeFor(CS);
}
/// HandleByValArgument - When inlining a call site that has a byval argument,
/// we have to make the implicit memcpy explicit by adding it.
static Value *HandleByValArgument(Value *Arg, Instruction *TheCall,
const Function *CalledFunc,
InlineFunctionInfo &IFI,
unsigned ByValAlignment) {
if (CalledFunc->onlyReadsMemory())
return Arg;
const Type *AggTy = cast<PointerType>(Arg->getType())->getElementType();
// If the called function is readonly, then it could not mutate the caller's
// copy of the byval'd memory. In this case, it is safe to elide the copy and
// temporary.
if (CalledFunc->onlyReadsMemory()) {
// If the byval argument has a specified alignment that is greater than the
// passed in pointer, then we either have to round up the input pointer or
// give up on this transformation.
if (ByValAlignment <= 1) // 0 = unspecified, 1 = no particular alignment.
return Arg;
// See if the argument is a (bitcasted) pointer to an alloca. If so, we can
// round up the alloca if needed.
if (AllocaInst *AI = dyn_cast<AllocaInst>(Arg->stripPointerCasts())) {
unsigned AIAlign = AI->getAlignment();
// If the alloca is known at least aligned as much as the byval, we can do
// this optimization.
if (AIAlign >= ByValAlignment)
return Arg;
// If the alloca has a specified alignment that is less than the byval,
// then we can safely bump it up.
if (AIAlign) {
AI->setAlignment(ByValAlignment);
return Arg;
}
// If the alignment has an unspecified alignment, then we can only modify
// it if we have TD information. Doing so without TD info could end up
// with us rounding the alignment *down* accidentally, which is badness.
if (IFI.TD) {
AIAlign = std::max(ByValAlignment, IFI.TD->getPrefTypeAlignment(AggTy));
AI->setAlignment(AIAlign);
return Arg;
}
}
// Otherwise, we have to make a memcpy to get a safe alignment, pretty lame.
}
LLVMContext &Context = Arg->getContext();
const Type *AggTy = cast<PointerType>(Arg->getType())->getElementType();
const Type *VoidPtrTy = Type::getInt8PtrTy(Context);
// Create the alloca. If we have TargetData, use nice alignment.

23
test/Transforms/Inline/byval.ll
View File

@ -81,3 +81,26 @@ entry:
; CHECK: call void @g3(%struct.ss* %S1)
; CHECK: ret void
}
; Inlining a byval struct should NOT cause an explicit copy
; into an alloca if the function is readonly, but should increase an alloca's
; alignment to satisfy an explicit alignment request.
define internal i32 @f4(%struct.ss* byval align 64 %b) nounwind readonly {
call void @g3(%struct.ss* %b)
ret i32 4
}
define i32 @test4() nounwind {
entry:
%S = alloca %struct.ss, align 2 ; <%struct.ss*> [#uses=4]
%X = call i32 @f4( %struct.ss* byval align 64 %S ) nounwind
ret i32 %X
; CHECK: @test4()
; CHECK: %S = alloca %struct.ss, align 64
; CHECK-NOT: call void @llvm.memcpy
; CHECK: call void @g3
; CHECK: ret i32 4
}