5ef4d5f9c1
Summary: This lowers exception catching-related instructions: 1. Lowers `wasm.catch` intrinsic to `catch` instruction 2. Removes `catchpad` and `cleanuppad` instructions; they are not necessary after isel phase. (`MachineBasicBlock::isEHFuncletEntry()` or `MachineBasicBlock::isEHPad()` can be used instead.) 3. Lowers `catchret` and `cleanupret` instructions to pseudo `catchret` and `cleanupret` instructions in isel, which will be replaced with other instructions in `WebAssemblyExceptionPrepare` pass. 4. Adds 'WebAssemblyExceptionPrepare` pass, which is for running various transformation for EH. Currently this pass only replaces `catchret` and `cleanupret` instructions into appropriate wasm instructions to make this patch successfully run until the end. Currently this does not handle lowering of intrinsics related to LSDA info generation (`wasm.landingpad.index` and `wasm.lsda`), because they cannot be tested without implementing `EHStreamer`'s wasm-specific handlers. They are marked as TODO, which is needed to make isel pass. Also this does not generate `try` and `end_try` markers yet, which will be handled in later patches. This patch is based on the first wasm EH proposal. (https://github.com/WebAssembly/exception-handling/blob/master/proposals/Exceptions.md) Reviewers: dschuff, majnemer Subscribers: jfb, sbc100, jgravelle-google, sunfish, llvm-commits Differential Revision: https://reviews.llvm.org/D44090 llvm-svn: 333705
89 lines
2.6 KiB
C++
89 lines
2.6 KiB
C++
//=== WebAssemblyExceptionPrepare.cpp - WebAssembly Exception Preparation -===//
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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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/// \file
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/// \brief Does various transformations for exception handling.
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///
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//===----------------------------------------------------------------------===//
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#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
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#include "WebAssembly.h"
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#include "WebAssemblySubtarget.h"
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#include "llvm/CodeGen/MachineInstrBuilder.h"
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using namespace llvm;
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#define DEBUG_TYPE "wasm-exception-prepare"
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namespace {
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class WebAssemblyExceptionPrepare final : public MachineFunctionPass {
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StringRef getPassName() const override {
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return "WebAssembly Prepare Exception";
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}
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bool runOnMachineFunction(MachineFunction &MF) override;
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bool replaceFuncletReturns(MachineFunction &MF);
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public:
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static char ID; // Pass identification, replacement for typeid
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WebAssemblyExceptionPrepare() : MachineFunctionPass(ID) {}
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};
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} // end anonymous namespace
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char WebAssemblyExceptionPrepare::ID = 0;
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INITIALIZE_PASS(WebAssemblyExceptionPrepare, DEBUG_TYPE,
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"WebAssembly Exception Preparation", false, false)
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FunctionPass *llvm::createWebAssemblyExceptionPrepare() {
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return new WebAssemblyExceptionPrepare();
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}
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bool WebAssemblyExceptionPrepare::runOnMachineFunction(MachineFunction &MF) {
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bool Changed = false;
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if (!MF.getFunction().hasPersonalityFn())
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return false;
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Changed |= replaceFuncletReturns(MF);
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// TODO More transformations will be added
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return Changed;
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}
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bool WebAssemblyExceptionPrepare::replaceFuncletReturns(MachineFunction &MF) {
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bool Changed = false;
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const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
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for (auto &MBB : MF) {
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auto Pos = MBB.getFirstTerminator();
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if (Pos == MBB.end())
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continue;
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MachineInstr *TI = &*Pos;
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switch (TI->getOpcode()) {
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case WebAssembly::CATCHRET: {
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// Replace a catchret with a branch
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MachineBasicBlock *TBB = TI->getOperand(0).getMBB();
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if (!MBB.isLayoutSuccessor(TBB))
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BuildMI(MBB, TI, TI->getDebugLoc(), TII.get(WebAssembly::BR))
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.addMBB(TBB);
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TI->eraseFromParent();
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Changed = true;
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break;
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}
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case WebAssembly::CLEANUPRET: {
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// Replace a cleanupret with a rethrow
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BuildMI(MBB, TI, TI->getDebugLoc(), TII.get(WebAssembly::RETHROW))
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.addImm(0);
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TI->eraseFromParent();
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Changed = true;
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break;
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}
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}
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}
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return Changed;
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}
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