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Make WholeProgramDevirt understand ConstStruct vtables.

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Based on a patch by LemonBoy!

Differential Revision: https://reviews.llvm.org/D26581

llvm-svn: 289162
This commit is contained in:
Peter Collingbourne 2016-12-09 00:33:27 +00:00
parent ece7727a45
commit bb7c0a1390
3 changed files with 100 additions and 13 deletions
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50
lib/Transforms/IPO/WholeProgramDevirt.cpp
View File

@ -293,6 +293,7 @@ struct DevirtModule {
void buildTypeIdentifierMap(
std::vector<VTableBits> &Bits,
DenseMap<Metadata *, std::set<TypeMemberInfo>> &TypeIdMap);
Constant *getValueAtOffset(Constant *I, uint64_t Offset);
bool
tryFindVirtualCallTargets(std::vector<VirtualCallTarget> &TargetsForSlot,
const std::set<TypeMemberInfo> &TypeMemberInfos,
@ -382,6 +383,38 @@ void DevirtModule::buildTypeIdentifierMap(
}
}
Constant *DevirtModule::getValueAtOffset(Constant *I, uint64_t Offset) {
const DataLayout &DL = M.getDataLayout();
unsigned Op;
if (auto *C = dyn_cast<ConstantStruct>(I)) {
const StructLayout *SL = DL.getStructLayout(C->getType());
if (Offset >= SL->getSizeInBytes())
return nullptr;
Op = SL->getElementContainingOffset(Offset);
if (Offset != SL->getElementOffset(Op))
return nullptr;
} else if (auto *C = dyn_cast<ConstantArray>(I)) {
ArrayType *VTableTy = C->getType();
uint64_t ElemSize = DL.getTypeAllocSize(VTableTy->getElementType());
if (Offset % ElemSize != 0)
return nullptr;
Op = Offset / ElemSize;
if (Op >= C->getNumOperands())
return nullptr;
} else
return nullptr;
return cast<Constant>(I->getOperand(Op));
}
bool DevirtModule::tryFindVirtualCallTargets(
std::vector<VirtualCallTarget> &TargetsForSlot,
const std::set<TypeMemberInfo> &TypeMemberInfos, uint64_t ByteOffset) {
@ -389,22 +422,13 @@ bool DevirtModule::tryFindVirtualCallTargets(
if (!TM.Bits->GV->isConstant())
return false;
auto Init = dyn_cast<ConstantArray>(TM.Bits->GV->getInitializer());
if (!Init)
return false;
ArrayType *VTableTy = Init->getType();
Constant *I = TM.Bits->GV->getInitializer();
Value *V = getValueAtOffset(I, TM.Offset + ByteOffset);
uint64_t ElemSize =
M.getDataLayout().getTypeAllocSize(VTableTy->getElementType());
uint64_t GlobalSlotOffset = TM.Offset + ByteOffset;
if (GlobalSlotOffset % ElemSize != 0)
if (!V)
return false;
unsigned Op = GlobalSlotOffset / ElemSize;
if (Op >= Init->getNumOperands())
return false;
auto Fn = dyn_cast<Function>(Init->getOperand(Op)->stripPointerCasts());
auto Fn = dyn_cast<Function>(V->stripPointerCasts());
if (!Fn)
return false;

0
test/Transforms/WholeProgramDevirt/non-array-vtable.ll → test/Transforms/WholeProgramDevirt/non-aggregate-vtable.ll
View File

63
test/Transforms/WholeProgramDevirt/struct-vtable.ll Normal file
View File

@ -0,0 +1,63 @@
; RUN: opt -S -wholeprogramdevirt %s | FileCheck %s
target datalayout = "e-p:64:64"
target triple = "x86_64-unknown-linux-gnu"
%vtTy = type { void (i8*)* }
@vt = constant %vtTy { void (i8*)* @vf }, !type !0
define void @vf(i8* %this) {
ret void
}
; CHECK: define void @call
define void @call(i8* %obj) {
%vtableptr = bitcast i8* %obj to [1 x i8*]**
%vtable = load [1 x i8*]*, [1 x i8*]** %vtableptr
%vtablei8 = bitcast [1 x i8*]* %vtable to i8*
%p = call i1 @llvm.type.test(i8* %vtablei8, metadata !"typeid")
call void @llvm.assume(i1 %p)
%fptrptr = getelementptr [1 x i8*], [1 x i8*]* %vtable, i32 0, i32 0
%fptr = load i8*, i8** %fptrptr
%fptr_casted = bitcast i8* %fptr to void (i8*)*
; CHECK: call void @vf(
call void %fptr_casted(i8* %obj)
ret void
}
; CHECK: define void @call_oob
define void @call_oob(i8* %obj) {
%vtableptr = bitcast i8* %obj to [1 x i8*]**
%vtable = load [1 x i8*]*, [1 x i8*]** %vtableptr
%vtablei8 = bitcast [1 x i8*]* %vtable to i8*
%p = call i1 @llvm.type.test(i8* %vtablei8, metadata !"typeid")
call void @llvm.assume(i1 %p)
%fptrptr = getelementptr [1 x i8*], [1 x i8*]* %vtable, i32 0, i32 4
%fptr = load i8*, i8** %fptrptr
%fptr_casted = bitcast i8* %fptr to void (i8*)*
; CHECK: call void %
call void %fptr_casted(i8* %obj)
ret void
}
; CHECK: define void @call_unaligned
define void @call_unaligned(i8* %obj) {
%vtableptr = bitcast i8* %obj to [1 x i8*]**
%vtable = load [1 x i8*]*, [1 x i8*]** %vtableptr
%vtablei8 = bitcast [1 x i8*]* %vtable to i8*
%p = call i1 @llvm.type.test(i8* %vtablei8, metadata !"typeid")
call void @llvm.assume(i1 %p)
%fptrptr = getelementptr i8, i8* %vtablei8, i32 1
%fptrptr_casted = bitcast i8* %fptrptr to i8**
%fptr = load i8*, i8** %fptrptr_casted
%fptr_casted = bitcast i8* %fptr to void (i8*)*
; CHECK: call void %
call void %fptr_casted(i8* %obj)
ret void
}
declare i1 @llvm.type.test(i8*, metadata)
declare void @llvm.assume(i1)
!0 = !{i32 0, !"typeid"}