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WholeProgramDevirt: Teach the pass to handle structs of arrays. 

This will become necessary in some cases once D22296 lands.

llvm-svn: 289165
This commit is contained in:
Peter Collingbourne 2016-12-09 01:10:11 +00:00
parent 14f6b2c035
commit 8786754cc3
4 changed files with 96 additions and 27 deletions
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45
llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
View File

@ -293,7 +293,7 @@ struct DevirtModule {
void buildTypeIdentifierMap(
std::vector<VTableBits> &Bits,
DenseMap<Metadata *, std::set<TypeMemberInfo>> &TypeIdMap);
Constant *getValueAtOffset(Constant *I, uint64_t Offset);
Constant *getPointerAtOffset(Constant *I, uint64_t Offset);
bool
tryFindVirtualCallTargets(std::vector<VirtualCallTarget> &TargetsForSlot,
const std::set<TypeMemberInfo> &TypeMemberInfos,
@ -383,36 +383,36 @@ void DevirtModule::buildTypeIdentifierMap(
}
}
Constant *DevirtModule::getValueAtOffset(Constant *I, uint64_t Offset) {
Constant *DevirtModule::getPointerAtOffset(Constant *I, uint64_t Offset) {
if (I->getType()->isPointerTy()) {
if (Offset == 0)
return I;
return nullptr;
}
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)) {
unsigned Op = SL->getElementContainingOffset(Offset);
return getPointerAtOffset(cast<Constant>(I->getOperand(Op)),
Offset - SL->getElementOffset(Op));
}
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;
unsigned Op = Offset / ElemSize;
if (Op >= C->getNumOperands())
return nullptr;
} else
return nullptr;
return cast<Constant>(I->getOperand(Op));
return getPointerAtOffset(cast<Constant>(I->getOperand(Op)),
Offset % ElemSize);
}
return nullptr;
}
bool DevirtModule::tryFindVirtualCallTargets(
@ -422,13 +422,12 @@ bool DevirtModule::tryFindVirtualCallTargets(
if (!TM.Bits->GV->isConstant())
return false;
Constant *I = TM.Bits->GV->getInitializer();
Value *V = getValueAtOffset(I, TM.Offset + ByteOffset);
if (!V)
Constant *Ptr = getPointerAtOffset(TM.Bits->GV->getInitializer(),
TM.Offset + ByteOffset);
if (!Ptr)
return false;
auto Fn = dyn_cast<Function>(V->stripPointerCasts());
auto Fn = dyn_cast<Function>(Ptr->stripPointerCasts());
if (!Fn)
return false;

24
llvm/test/Transforms/WholeProgramDevirt/bad-read-from-vtable.ll
View File

@ -3,14 +3,15 @@
target datalayout = "e-p:64:64"
target triple = "x86_64-unknown-linux-gnu"
@vt = global [2 x i8*] [i8* zeroinitializer, i8* bitcast (void (i8*)* @vf to i8*)], !type !0
@vt1 = global [2 x i8*] [i8* zeroinitializer, i8* bitcast (void (i8*)* @vf to i8*)], !type !0
@vt2 = global i8* bitcast (void (i8*)* @vf to i8*), !type !1
define void @vf(i8* %this) {
ret void
}
; CHECK: define void @unaligned
define void @unaligned(i8* %obj) {
; CHECK: define void @unaligned1
define void @unaligned1(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*
@ -25,6 +26,22 @@ define void @unaligned(i8* %obj) {
ret void
}
; CHECK: define void @unaligned2
define void @unaligned2(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 !"typeid2")
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
}
; CHECK: define void @outofbounds
define void @outofbounds(i8* %obj) {
%vtableptr = bitcast i8* %obj to [1 x i8*]**
@ -61,3 +78,4 @@ declare i1 @llvm.type.test(i8*, metadata)
declare void @llvm.assume(i1)
!0 = !{i32 0, !"typeid"}
!1 = !{i32 0, !"typeid2"}

2
llvm/test/Transforms/WholeProgramDevirt/non-aggregate-vtable.ll → llvm/test/Transforms/WholeProgramDevirt/pointer-vtable.ll
View File

@ -19,7 +19,7 @@ define void @call(i8* %obj) {
%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 %
; CHECK: call void @vf(
call void %fptr_casted(i8* %obj)
ret void
}

52
llvm/test/Transforms/WholeProgramDevirt/soa-vtable.ll Normal file
View File

@ -0,0 +1,52 @@
; RUN: opt -S -wholeprogramdevirt %s | FileCheck %s
target datalayout = "e-p:64:64"
target triple = "x86_64-unknown-linux-gnu"
%vtTy = type { [2 x void (i8*)*], [2 x void (i8*)*] }
@vt = constant %vtTy { [2 x void (i8*)*] [void (i8*)* null, void (i8*)* @vf1], [2 x void (i8*)*] [void (i8*)* null, void (i8*)* @vf2] }, !type !0, !type !1
define void @vf1(i8* %this) {
ret void
}
define void @vf2(i8* %this) {
ret void
}
; CHECK: define void @call1
define void @call1(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 !"typeid1")
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 @vf1(
call void %fptr_casted(i8* %obj)
ret void
}
; CHECK: define void @call2
define void @call2(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 !"typeid2")
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 @vf2(
call void %fptr_casted(i8* %obj)
ret void
}
declare i1 @llvm.type.test(i8*, metadata)
declare void @llvm.assume(i1)
!0 = !{i32 8, !"typeid1"}
!1 = !{i32 24, !"typeid2"}