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`WebAssemblyDebugValueManager` does not currently handle `DBG_VALUE_LIST`, which is a recent addition to LLVM. We tried to nullify them within the constructor of `WebAssemblyDebugValueManager` in D102589, but it made the class error-prone to use because it deletes instructions within the constructor and thus invalidates existing iterators within the BB, so the user of the class should take special care not to use invalidated iterators. This actually caused a bug in ExplicitLocals pass. Instead of trying to fix ExplicitLocals pass to make the iterator usage correct, which is possible but error-prone, this adds NullifyDebugValueLists pass that nullifies all `DBG_VALUE_LIST` instructions before we run WebAssembly specific passes in the backend. We can remove this pass after we implement handlers for `DBG_VALUE_LIST`s in `WebAssemblyDebugValueManager` and elsewhere. Fixes https://github.com/emscripten-core/emscripten/issues/14255. Reviewed By: dschuff Differential Revision: https://reviews.llvm.org/D102999
69 lines
2.5 KiB
C++
69 lines
2.5 KiB
C++
//=== WebAssemblyNullifyDebugValueLists.cpp - Nullify DBG_VALUE_LISTs ---===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// Nullify DBG_VALUE_LISTs instructions as a temporary measure before we
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/// implement DBG_VALUE_LIST handling in WebAssemblyDebugValueManager.
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/// See https://bugs.llvm.org/show_bug.cgi?id=50361.
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/// TODO Correctly handle DBG_VALUE_LISTs
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///
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//===----------------------------------------------------------------------===//
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#include "WebAssembly.h"
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#include "WebAssemblySubtarget.h"
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using namespace llvm;
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#define DEBUG_TYPE "wasm-nullify-dbg-value-lists"
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namespace {
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class WebAssemblyNullifyDebugValueLists final : public MachineFunctionPass {
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StringRef getPassName() const override {
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return "WebAssembly Nullify DBG_VALUE_LISTs";
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}
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bool runOnMachineFunction(MachineFunction &MF) override;
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public:
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static char ID; // Pass identification, replacement for typeid
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WebAssemblyNullifyDebugValueLists() : MachineFunctionPass(ID) {}
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};
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} // end anonymous namespace
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char WebAssemblyNullifyDebugValueLists::ID = 0;
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INITIALIZE_PASS(WebAssemblyNullifyDebugValueLists, DEBUG_TYPE,
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"WebAssembly Nullify DBG_VALUE_LISTs", false, false)
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FunctionPass *llvm::createWebAssemblyNullifyDebugValueLists() {
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return new WebAssemblyNullifyDebugValueLists();
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}
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bool WebAssemblyNullifyDebugValueLists::runOnMachineFunction(
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MachineFunction &MF) {
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LLVM_DEBUG(dbgs() << "********** Nullify DBG_VALUE_LISTs **********\n"
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"********** Function: "
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<< MF.getName() << '\n');
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const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
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SmallVector<MachineInstr *, 2> DbgValueLists;
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for (auto &MBB : MF)
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for (auto &MI : MBB)
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if (MI.getOpcode() == TargetOpcode::DBG_VALUE_LIST)
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DbgValueLists.push_back(&MI);
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// Our backend, including WebAssemblyDebugValueManager, currently cannot
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// handle DBG_VALUE_LISTs correctly. So this converts DBG_VALUE_LISTs to
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// "DBG_VALUE $noreg", which will appear as "optimized out".
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for (auto *DVL : DbgValueLists) {
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BuildMI(*DVL->getParent(), DVL, DVL->getDebugLoc(),
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TII.get(TargetOpcode::DBG_VALUE), false, Register(),
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DVL->getOperand(0).getMetadata(), DVL->getOperand(1).getMetadata());
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DVL->eraseFromParent();
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}
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return !DbgValueLists.empty();
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}
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