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//=== WebAssemblyExceptionPrepare.cpp - WebAssembly Exception Preparation -===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// \file
/// \brief Does various transformations for exception handling.
///
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "WebAssembly.h"
#include "WebAssemblySubtarget.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
using namespace llvm;
#define DEBUG_TYPE "wasm-exception-prepare"
namespace {
class WebAssemblyExceptionPrepare final : public MachineFunctionPass {
StringRef getPassName() const override {
return "WebAssembly Prepare Exception";
}
bool runOnMachineFunction(MachineFunction &MF) override;
bool replaceFuncletReturns(MachineFunction &MF);
public:
static char ID; // Pass identification, replacement for typeid
WebAssemblyExceptionPrepare() : MachineFunctionPass(ID) {}
};
} // end anonymous namespace
char WebAssemblyExceptionPrepare::ID = 0;
INITIALIZE_PASS(WebAssemblyExceptionPrepare, DEBUG_TYPE,
"WebAssembly Exception Preparation", false, false)
FunctionPass *llvm::createWebAssemblyExceptionPrepare() {
return new WebAssemblyExceptionPrepare();
}
bool WebAssemblyExceptionPrepare::runOnMachineFunction(MachineFunction &MF) {
bool Changed = false;
if (!MF.getFunction().hasPersonalityFn())
return false;
Changed |= replaceFuncletReturns(MF);
// TODO More transformations will be added
return Changed;
}
bool WebAssemblyExceptionPrepare::replaceFuncletReturns(MachineFunction &MF) {
bool Changed = false;
const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
for (auto &MBB : MF) {
auto Pos = MBB.getFirstTerminator();
if (Pos == MBB.end())
continue;
MachineInstr *TI = &*Pos;
switch (TI->getOpcode()) {
case WebAssembly::CATCHRET: {
// Replace a catchret with a branch
MachineBasicBlock *TBB = TI->getOperand(0).getMBB();
if (!MBB.isLayoutSuccessor(TBB))
BuildMI(MBB, TI, TI->getDebugLoc(), TII.get(WebAssembly::BR))
.addMBB(TBB);
TI->eraseFromParent();
Changed = true;
break;
}
case WebAssembly::CLEANUPRET: {
// Replace a cleanupret with a rethrow
BuildMI(MBB, TI, TI->getDebugLoc(), TII.get(WebAssembly::RETHROW))
.addImm(0);
TI->eraseFromParent();
Changed = true;
break;
}
}
}
return Changed;
}
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