WebAssemblyNullifyDebugValueLists.cpp

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//=== WebAssemblyNullifyDebugValueLists.cpp - Nullify DBG_VALUE_LISTs   ---===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// Nullify DBG_VALUE_LISTs instructions as a temporary measure before we
/// implement DBG_VALUE_LIST handling in WebAssemblyDebugValueManager.
/// See https://github.com/llvm/llvm-project/issues/49705.
/// TODO Correctly handle DBG_VALUE_LISTs
///
//===----------------------------------------------------------------------===//
 
#include "WebAssembly.h"
#include "llvm/CodeGen/MachineFunctionAnalysisManager.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachinePassManager.h"
#include "llvm/IR/Analysis.h"
using namespace llvm;
 
#define DEBUG_TYPE "wasm-nullify-dbg-value-lists"
 
namespace {
class WebAssemblyNullifyDebugValueListsLegacy final
    : public MachineFunctionPass {
  StringRef getPassName() const override {
    return "WebAssembly Nullify DBG_VALUE_LISTs";
  }
 
  bool runOnMachineFunction(MachineFunction &MF) override;
 
public:
  static char ID; // Pass identification, replacement for typeid
  WebAssemblyNullifyDebugValueListsLegacy() : MachineFunctionPass(ID) {}
};
} // end anonymous namespace
 
char WebAssemblyNullifyDebugValueListsLegacy::ID = 0;
INITIALIZE_PASS(WebAssemblyNullifyDebugValueListsLegacy, DEBUG_TYPE,
                "WebAssembly Nullify DBG_VALUE_LISTs", false, false)
 
FunctionPass *llvm::createWebAssemblyNullifyDebugValueListsLegacyPass() {
  return new WebAssemblyNullifyDebugValueListsLegacy();
}
 
static bool nullifyDebugValueLists(MachineFunction &MF) {
  LLVM_DEBUG(dbgs() << "********** Nullify DBG_VALUE_LISTs **********\n"
                       "********** Function: "
                    << MF.getName() << '\n');
  bool Changed = false;
  // Our backend, including WebAssemblyDebugValueManager, currently cannot
  // handle DBG_VALUE_LISTs correctly. So this makes them undefined, which will
  // appear as "optimized out".
  for (auto &MBB : MF) {
    for (auto &MI : MBB) {
      if (MI.getOpcode() == TargetOpcode::DBG_VALUE_LIST) {
        MI.setDebugValueUndef();
        Changed = true;
      }
    }
  }
  return Changed;
}
 
bool WebAssemblyNullifyDebugValueListsLegacy::runOnMachineFunction(
    MachineFunction &MF) {
  return nullifyDebugValueLists(MF);
}
 
PreservedAnalyses WebAssemblyNullifyDebugValueListsPass::run(
    MachineFunction &MF, MachineFunctionAnalysisManager &MFAM) {
  return nullifyDebugValueLists(MF) ? getMachineFunctionPassPreservedAnalyses()
                                          .preserveSet<CFGAnalyses>()
                                    : PreservedAnalyses::all();
}