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can be used by both the new pass manager and the old. This removes it from any of the virtual mess of the pass interfaces and lets it derive cleanly from the DominatorTreeBase<> template. In turn, tons of boilerplate interface can be nuked and it turns into a very straightforward extension of the base DominatorTree interface. The old analysis pass is now a simple wrapper. The names and style of this split should match the split between CallGraph and CallGraphWrapperPass. All of the users of DominatorTree have been updated to match using many of the same tricks as with CallGraph. The goal is that the common type remains the resulting DominatorTree rather than the pass. This will make subsequent work toward the new pass manager significantly easier. Also in numerous places things became cleaner because I switched from re-running the pass (!!! mid way through some other passes run!!!) to directly recomputing the domtree. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199104 91177308-0d34-0410-b5e6-96231b3b80d8
180 lines
5.9 KiB
C++
180 lines
5.9 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/CodeGen/Passes.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Module.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/Pass.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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// 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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Value *GetExceptionObject(ResumeInst *RI);
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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), RewindFunction(0) {
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initializeDominatorTreeWrapperPassPass(*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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/// GetExceptionObject - Return the exception object from the value passed into
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/// the 'resume' instruction (typically an aggregate). Clean up any dead
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/// instructions, including the 'resume' instruction.
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Value *DwarfEHPrepare::GetExceptionObject(ResumeInst *RI) {
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Value *V = RI->getOperand(0);
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Value *ExnObj = 0;
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InsertValueInst *SelIVI = dyn_cast<InsertValueInst>(V);
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LoadInst *SelLoad = 0;
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InsertValueInst *ExcIVI = 0;
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bool EraseIVIs = false;
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if (SelIVI) {
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if (SelIVI->getNumIndices() == 1 && *SelIVI->idx_begin() == 1) {
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ExcIVI = dyn_cast<InsertValueInst>(SelIVI->getOperand(0));
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if (ExcIVI && isa<UndefValue>(ExcIVI->getOperand(0)) &&
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ExcIVI->getNumIndices() == 1 && *ExcIVI->idx_begin() == 0) {
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ExnObj = ExcIVI->getOperand(1);
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SelLoad = dyn_cast<LoadInst>(SelIVI->getOperand(1));
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EraseIVIs = true;
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}
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}
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}
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if (!ExnObj)
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ExnObj = ExtractValueInst::Create(RI->getOperand(0), 0, "exn.obj", RI);
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RI->eraseFromParent();
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if (EraseIVIs) {
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if (SelIVI->getNumUses() == 0)
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SelIVI->eraseFromParent();
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if (ExcIVI->getNumUses() == 0)
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ExcIVI->eraseFromParent();
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if (SelLoad && SelLoad->getNumUses() == 0)
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SelLoad->eraseFromParent();
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}
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return ExnObj;
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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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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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}
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if (Resumes.empty())
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return false;
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// Find the rewind function if we didn't already.
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const TargetLowering *TLI = TM->getTargetLowering();
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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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unsigned ResumesSize = Resumes.size();
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if (ResumesSize == 1) {
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// Instead of creating a new BB and PHI node, just append the call to
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// _Unwind_Resume to the end of the single resume block.
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ResumeInst *RI = Resumes.front();
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BasicBlock *UnwindBB = RI->getParent();
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Value *ExnObj = GetExceptionObject(RI);
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// Call the _Unwind_Resume function.
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CallInst *CI = CallInst::Create(RewindFunction, ExnObj, "", 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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BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", &Fn);
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PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), ResumesSize,
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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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BasicBlock *Parent = RI->getParent();
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BranchInst::Create(UnwindBB, Parent);
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Value *ExnObj = GetExceptionObject(RI);
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PN->addIncoming(ExnObj, Parent);
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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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