1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
|
//===-- DwarfEHPrepare - Prepare exception handling for code generation ---===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass mulches exception handling code into a form adapted to code
// generation. Required if using dwarf exception handling.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "dwarfehprepare"
#include "llvm/CodeGen/Passes.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/Pass.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
using namespace llvm;
STATISTIC(NumResumesLowered, "Number of resume calls lowered");
namespace {
class DwarfEHPrepare : public FunctionPass {
const TargetMachine *TM;
const TargetLoweringBase *TLI;
// RewindFunction - _Unwind_Resume or the target equivalent.
Constant *RewindFunction;
bool InsertUnwindResumeCalls(Function &Fn);
Value *GetExceptionObject(ResumeInst *RI);
public:
static char ID; // Pass identification, replacement for typeid.
DwarfEHPrepare(const TargetMachine *tm) :
FunctionPass(ID), TM(tm), TLI(TM->getTargetLowering()),
RewindFunction(0) {
initializeDominatorTreePass(*PassRegistry::getPassRegistry());
}
virtual bool runOnFunction(Function &Fn);
virtual void getAnalysisUsage(AnalysisUsage &AU) const { }
const char *getPassName() const {
return "Exception handling preparation";
}
};
} // end anonymous namespace
char DwarfEHPrepare::ID = 0;
FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm) {
return new DwarfEHPrepare(tm);
}
/// GetExceptionObject - Return the exception object from the value passed into
/// the 'resume' instruction (typically an aggregate). Clean up any dead
/// instructions, including the 'resume' instruction.
Value *DwarfEHPrepare::GetExceptionObject(ResumeInst *RI) {
Value *V = RI->getOperand(0);
Value *ExnObj = 0;
InsertValueInst *SelIVI = dyn_cast<InsertValueInst>(V);
LoadInst *SelLoad = 0;
InsertValueInst *ExcIVI = 0;
bool EraseIVIs = false;
if (SelIVI) {
if (SelIVI->getNumIndices() == 1 && *SelIVI->idx_begin() == 1) {
ExcIVI = dyn_cast<InsertValueInst>(SelIVI->getOperand(0));
if (ExcIVI && isa<UndefValue>(ExcIVI->getOperand(0)) &&
ExcIVI->getNumIndices() == 1 && *ExcIVI->idx_begin() == 0) {
ExnObj = ExcIVI->getOperand(1);
SelLoad = dyn_cast<LoadInst>(SelIVI->getOperand(1));
EraseIVIs = true;
}
}
}
if (!ExnObj)
ExnObj = ExtractValueInst::Create(RI->getOperand(0), 0, "exn.obj", RI);
RI->eraseFromParent();
if (EraseIVIs) {
if (SelIVI->getNumUses() == 0)
SelIVI->eraseFromParent();
if (ExcIVI->getNumUses() == 0)
ExcIVI->eraseFromParent();
if (SelLoad && SelLoad->getNumUses() == 0)
SelLoad->eraseFromParent();
}
return ExnObj;
}
/// InsertUnwindResumeCalls - Convert the ResumeInsts that are still present
/// into calls to the appropriate _Unwind_Resume function.
bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) {
bool UsesNewEH = false;
SmallVector<ResumeInst*, 16> Resumes;
for (Function::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
TerminatorInst *TI = I->getTerminator();
if (ResumeInst *RI = dyn_cast<ResumeInst>(TI))
Resumes.push_back(RI);
else if (InvokeInst *II = dyn_cast<InvokeInst>(TI))
UsesNewEH = II->getUnwindDest()->isLandingPad();
}
if (Resumes.empty())
return UsesNewEH;
// Find the rewind function if we didn't already.
if (!RewindFunction) {
LLVMContext &Ctx = Resumes[0]->getContext();
FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
Type::getInt8PtrTy(Ctx), false);
const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
RewindFunction = Fn.getParent()->getOrInsertFunction(RewindName, FTy);
}
// Create the basic block where the _Unwind_Resume call will live.
LLVMContext &Ctx = Fn.getContext();
unsigned ResumesSize = Resumes.size();
if (ResumesSize == 1) {
// Instead of creating a new BB and PHI node, just append the call to
// _Unwind_Resume to the end of the single resume block.
ResumeInst *RI = Resumes.front();
BasicBlock *UnwindBB = RI->getParent();
Value *ExnObj = GetExceptionObject(RI);
// Call the _Unwind_Resume function.
CallInst *CI = CallInst::Create(RewindFunction, ExnObj, "", UnwindBB);
CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
// We never expect _Unwind_Resume to return.
new UnreachableInst(Ctx, UnwindBB);
return true;
}
BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", &Fn);
PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), ResumesSize,
"exn.obj", UnwindBB);
// Extract the exception object from the ResumeInst and add it to the PHI node
// that feeds the _Unwind_Resume call.
for (SmallVectorImpl<ResumeInst*>::iterator
I = Resumes.begin(), E = Resumes.end(); I != E; ++I) {
ResumeInst *RI = *I;
BasicBlock *Parent = RI->getParent();
BranchInst::Create(UnwindBB, Parent);
Value *ExnObj = GetExceptionObject(RI);
PN->addIncoming(ExnObj, Parent);
++NumResumesLowered;
}
// Call the function.
CallInst *CI = CallInst::Create(RewindFunction, PN, "", UnwindBB);
CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
// We never expect _Unwind_Resume to return.
new UnreachableInst(Ctx, UnwindBB);
return true;
}
bool DwarfEHPrepare::runOnFunction(Function &Fn) {
bool Changed = InsertUnwindResumeCalls(Fn);
return Changed;
}
|
