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Inliner: Handle readonly attribute per argument when adding memcpy

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Patch by: Vincent Lejeune

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193356 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tom Stellard 2013-10-24 16:38:33 +00:00
parent e662fb6083
commit 4a6b6eea2d
2 changed files with 42 additions and 14 deletions
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23
lib/Transforms/Utils/InlineFunction.cpp
View File

@ -337,33 +337,35 @@ static void UpdateCallGraphAfterInlining(CallSite 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,
static Value *HandleByValArgument(Value *PassedValue,
const Argument *ArgumentSignature,
Instruction *TheCall,
const Function *CalledFunc,
InlineFunctionInfo &IFI,
unsigned ByValAlignment) {
Type *AggTy = cast<PointerType>(Arg->getType())->getElementType();
Type *AggTy = cast<PointerType>(PassedValue->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 (CalledFunc->onlyReadsMemory() || ArgumentSignature->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;
return PassedValue;
// If the pointer is already known to be sufficiently aligned, or if we can
// round it up to a larger alignment, then we don't need a temporary.
if (getOrEnforceKnownAlignment(Arg, ByValAlignment,
if (getOrEnforceKnownAlignment(PassedValue, ByValAlignment,
IFI.TD) >= ByValAlignment)
return Arg;
return PassedValue;
// Otherwise, we have to make a memcpy to get a safe alignment. This is bad
// for code quality, but rarely happens and is required for correctness.
}
LLVMContext &Context = Arg->getContext();
LLVMContext &Context = PassedValue->getContext();
Type *VoidPtrTy = Type::getInt8PtrTy(Context);
@ -379,7 +381,7 @@ static Value *HandleByValArgument(Value *Arg, Instruction *TheCall,
Function *Caller = TheCall->getParent()->getParent();
Value *NewAlloca = new AllocaInst(AggTy, 0, Align, Arg->getName(),
Value *NewAlloca = new AllocaInst(AggTy, 0, Align, PassedValue->getName(),
&*Caller->begin()->begin());
// Emit a memcpy.
Type *Tys[3] = {VoidPtrTy, VoidPtrTy, Type::getInt64Ty(Context)};
@ -387,7 +389,7 @@ static Value *HandleByValArgument(Value *Arg, Instruction *TheCall,
Intrinsic::memcpy,
Tys);
Value *DestCast = new BitCastInst(NewAlloca, VoidPtrTy, "tmp", TheCall);
Value *SrcCast = new BitCastInst(Arg, VoidPtrTy, "tmp", TheCall);
Value *SrcCast = new BitCastInst(PassedValue, VoidPtrTy, "tmp", TheCall);
Value *Size;
if (IFI.TD == 0)
@ -588,13 +590,14 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
for (Function::const_arg_iterator I = CalledFunc->arg_begin(),
E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) {
Value *ActualArg = *AI;
const Argument *Arg = I;
// 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 (CS.isByValArgument(ArgNo)) {
ActualArg = HandleByValArgument(ActualArg, TheCall, CalledFunc, IFI,
ActualArg = HandleByValArgument(ActualArg, Arg, TheCall, CalledFunc, IFI,
CalledFunc->getParamAlignment(ArgNo+1));
// Calls that we inline may use the new alloca, so we need to clear

33
test/Transforms/Inline/byval.ll
View File

@ -25,7 +25,7 @@ entry:
store i64 2, i64* %tmp4, align 4
call void @f( %struct.ss* byval %S ) nounwind
ret i32 0
; CHECK: @test1()
; CHECK-LABEL: @test1()
; CHECK: %S1 = alloca %struct.ss
; CHECK: %S = alloca %struct.ss
; CHECK: call void @llvm.memcpy
@ -52,7 +52,7 @@ entry:
store i64 2, i64* %tmp4, align 4
%X = call i32 @f2( %struct.ss* byval %S ) nounwind
ret i32 %X
; CHECK: @test2()
; CHECK-LABEL: @test2()
; CHECK: %S = alloca %struct.ss
; CHECK-NOT: call void @llvm.memcpy
; CHECK: ret i32
@ -74,7 +74,7 @@ entry:
%S = alloca %struct.ss, align 1 ;; May not be aligned.
call void @f3( %struct.ss* byval align 64 %S) nounwind
ret void
; CHECK: @test3()
; CHECK-LABEL: @test3()
; CHECK: %S1 = alloca %struct.ss, align 64
; CHECK: %S = alloca %struct.ss
; CHECK: call void @llvm.memcpy
@ -97,10 +97,35 @@ 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-LABEL: @test4()
; CHECK: %S = alloca %struct.ss, align 64
; CHECK-NOT: call void @llvm.memcpy
; CHECK: call void @g3
; CHECK: ret i32 4
}
; Inlining a byval struct should NOT cause an explicit copy
; into an alloca if the parameter is readonly
define internal i32 @f5(%struct.ss* byval readonly %b) nounwind {
entry:
%tmp = getelementptr %struct.ss* %b, i32 0, i32 0 ; <i32*> [#uses=2]
%tmp1 = load i32* %tmp, align 4 ; <i32> [#uses=1]
%tmp2 = add i32 %tmp1, 1 ; <i32> [#uses=1]
ret i32 %tmp2
}
define i32 @test5() nounwind {
entry:
%S = alloca %struct.ss ; <%struct.ss*> [#uses=4]
%tmp1 = getelementptr %struct.ss* %S, i32 0, i32 0 ; <i32*> [#uses=1]
store i32 1, i32* %tmp1, align 8
%tmp4 = getelementptr %struct.ss* %S, i32 0, i32 1 ; <i64*> [#uses=1]
store i64 2, i64* %tmp4, align 4
%X = call i32 @f5( %struct.ss* byval %S ) nounwind
ret i32 %X
; CHECK-LABEL: @test5()
; CHECK: %S = alloca %struct.ss
; CHECK-NOT: call void @llvm.memcpy
; CHECK: ret i32
}