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//===-- WinEHPrepare - 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 lowers LLVM IR exception handling into something closer to what the
// backend wants. It snifs the personality function to see which kind of
// preparation is necessary. If the personality function uses the Itanium LSDA,
// this pass delegates to the DWARF EH preparation pass.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/Passes.h"
#include "llvm/Analysis/LibCallSemantics.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/Pass.h"
using namespace llvm;
#define DEBUG_TYPE "winehprepare"
namespace {
class WinEHPrepare : public FunctionPass {
FunctionPass *DwarfPrepare;
public:
static char ID; // Pass identification, replacement for typeid.
WinEHPrepare(const TargetMachine *TM = nullptr)
: FunctionPass(ID), DwarfPrepare(createDwarfEHPass(TM)) {}
bool runOnFunction(Function &Fn) override;
bool doFinalization(Module &M) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
const char *getPassName() const override {
return "Windows exception handling preparation";
}
};
} // end anonymous namespace
char WinEHPrepare::ID = 0;
INITIALIZE_TM_PASS(WinEHPrepare, "winehprepare",
"Prepare Windows exceptions", false, false)
FunctionPass *llvm::createWinEHPass(const TargetMachine *TM) {
return new WinEHPrepare(TM);
}
static bool isMSVCPersonality(EHPersonality Pers) {
return Pers == EHPersonality::MSVC_Win64SEH ||
Pers == EHPersonality::MSVC_CXX;
}
bool WinEHPrepare::runOnFunction(Function &Fn) {
SmallVector<LandingPadInst *, 4> LPads;
SmallVector<ResumeInst *, 4> Resumes;
for (BasicBlock &BB : Fn) {
if (auto *LP = BB.getLandingPadInst())
LPads.push_back(LP);
if (auto *Resume = dyn_cast<ResumeInst>(BB.getTerminator()))
Resumes.push_back(Resume);
}
// No need to prepare functions that lack landing pads.
if (LPads.empty())
return false;
// Classify the personality to see what kind of preparation we need.
EHPersonality Pers = ClassifyEHPersonality(LPads.back()->getPersonalityFn());
// Delegate through to the DWARF pass if this is unrecognized.
if (!isMSVCPersonality(Pers))
return DwarfPrepare->runOnFunction(Fn);
// FIXME: Cleanups are unimplemented. Replace them with unreachable.
if (Resumes.empty())
return false;
for (ResumeInst *Resume : Resumes) {
IRBuilder<>(Resume).CreateUnreachable();
Resume->eraseFromParent();
}
return true;
}
bool WinEHPrepare::doFinalization(Module &M) {
return DwarfPrepare->doFinalization(M);
}
void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
DwarfPrepare->getAnalysisUsage(AU);
}
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