forked from OSchip/llvm-project
124 lines
4.2 KiB
C++
124 lines
4.2 KiB
C++
//===-- DwarfEHPrepare - Prepare exception handling for code generation ---===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass mulches exception handling code into a form adapted to code
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// generation. Required if using dwarf exception handling.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "dwarfehprepare"
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#include "llvm/Function.h"
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#include "llvm/Instructions.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/Support/CallSite.h"
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#include "llvm/Target/TargetLowering.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/SSAUpdater.h"
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using namespace llvm;
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STATISTIC(NumResumesLowered, "Number of resume calls lowered");
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namespace {
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class DwarfEHPrepare : public FunctionPass {
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const TargetMachine *TM;
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const TargetLowering *TLI;
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// RewindFunction - _Unwind_Resume or the target equivalent.
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Constant *RewindFunction;
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bool InsertUnwindResumeCalls(Function &Fn);
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public:
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static char ID; // Pass identification, replacement for typeid.
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DwarfEHPrepare(const TargetMachine *tm) :
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FunctionPass(ID), TM(tm), TLI(TM->getTargetLowering()),
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RewindFunction(0) {
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initializeDominatorTreePass(*PassRegistry::getPassRegistry());
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}
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virtual bool runOnFunction(Function &Fn);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const { }
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const char *getPassName() const {
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return "Exception handling preparation";
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}
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};
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} // end anonymous namespace
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char DwarfEHPrepare::ID = 0;
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FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm) {
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return new DwarfEHPrepare(tm);
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}
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/// InsertUnwindResumeCalls - Convert the ResumeInsts that are still present
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/// into calls to the appropriate _Unwind_Resume function.
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bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) {
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bool UsesNewEH = false;
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SmallVector<ResumeInst*, 16> Resumes;
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for (Function::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
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TerminatorInst *TI = I->getTerminator();
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if (ResumeInst *RI = dyn_cast<ResumeInst>(TI))
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Resumes.push_back(RI);
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else if (InvokeInst *II = dyn_cast<InvokeInst>(TI))
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UsesNewEH = II->getUnwindDest()->isLandingPad();
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}
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if (Resumes.empty())
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return UsesNewEH;
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// Find the rewind function if we didn't already.
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if (!RewindFunction) {
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LLVMContext &Ctx = Resumes[0]->getContext();
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FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
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Type::getInt8PtrTy(Ctx), false);
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const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
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RewindFunction = Fn.getParent()->getOrInsertFunction(RewindName, FTy);
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}
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// Create the basic block where the _Unwind_Resume call will live.
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LLVMContext &Ctx = Fn.getContext();
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BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", &Fn);
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PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), Resumes.size(),
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"exn.obj", UnwindBB);
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// Extract the exception object from the ResumeInst and add it to the PHI node
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// that feeds the _Unwind_Resume call.
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for (SmallVectorImpl<ResumeInst*>::iterator
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I = Resumes.begin(), E = Resumes.end(); I != E; ++I) {
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ResumeInst *RI = *I;
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BranchInst::Create(UnwindBB, RI->getParent());
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ExtractValueInst *ExnObj = ExtractValueInst::Create(RI->getOperand(0),
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0, "exn.obj", RI);
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PN->addIncoming(ExnObj, RI->getParent());
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RI->eraseFromParent();
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++NumResumesLowered;
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}
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// Call the function.
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CallInst *CI = CallInst::Create(RewindFunction, PN, "", UnwindBB);
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CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
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// We never expect _Unwind_Resume to return.
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new UnreachableInst(Ctx, UnwindBB);
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return true;
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}
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bool DwarfEHPrepare::runOnFunction(Function &Fn) {
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bool Changed = InsertUnwindResumeCalls(Fn);
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return Changed;
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}
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