llvm/lib/Target/WebAssembly/WebAssemblyNullifyDebugValueLists.cpp

   1 //=== WebAssemblyNullifyDebugValueLists.cpp - Nullify DBG_VALUE_LISTs   ---===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 ///
   9 /// \file
  10 /// Nullify DBG_VALUE_LISTs instructions as a temporary measure before we
  11 /// implement DBG_VALUE_LIST handling in WebAssemblyDebugValueManager.
  12 /// See https://bugs.llvm.org/show_bug.cgi?id=50361.
  13 /// TODO Correctly handle DBG_VALUE_LISTs
  14 ///
  15 //===----------------------------------------------------------------------===//
  16
  17 #include "WebAssembly.h"
  18 #include "WebAssemblySubtarget.h"
  19 using namespace llvm;
  20
  21 #define DEBUG_TYPE "wasm-nullify-dbg-value-lists"
  22
  23 namespace {
  24 class WebAssemblyNullifyDebugValueLists final : public MachineFunctionPass {
  25   StringRef getPassName() const override {
  26     return "WebAssembly Nullify DBG_VALUE_LISTs";
  27   }
  28
  29   bool runOnMachineFunction(MachineFunction &MF) override;
  30
  31 public:
  32   static char ID; // Pass identification, replacement for typeid
  33   WebAssemblyNullifyDebugValueLists() : MachineFunctionPass(ID) {}
  34 };
  35 } // end anonymous namespace
  36
  37 char WebAssemblyNullifyDebugValueLists::ID = 0;
  38 INITIALIZE_PASS(WebAssemblyNullifyDebugValueLists, DEBUG_TYPE,
  39                 "WebAssembly Nullify DBG_VALUE_LISTs", false, false)
  40
  41 FunctionPass *llvm::createWebAssemblyNullifyDebugValueLists() {
  42   return new WebAssemblyNullifyDebugValueLists();
  43 }
  44
  45 bool WebAssemblyNullifyDebugValueLists::runOnMachineFunction(
  46     MachineFunction &MF) {
  47   LLVM_DEBUG(dbgs() << "********** Nullify DBG_VALUE_LISTs **********\n"
  48                        "********** Function: "
  49                     << MF.getName() << '\n');
  50   const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
  51   SmallVector<MachineInstr *, 2> DbgValueLists;
  52   for (auto &MBB : MF)
  53     for (auto &MI : MBB)
  54       if (MI.getOpcode() == TargetOpcode::DBG_VALUE_LIST)
  55         DbgValueLists.push_back(&MI);
  56
  57   // Our backend, including WebAssemblyDebugValueManager, currently cannot
  58   // handle DBG_VALUE_LISTs correctly. So this converts DBG_VALUE_LISTs to
  59   // "DBG_VALUE $noreg", which will appear as "optimized out".
  60   for (auto *DVL : DbgValueLists) {
  61     BuildMI(*DVL->getParent(), DVL, DVL->getDebugLoc(),
  62             TII.get(TargetOpcode::DBG_VALUE), false, Register(),
  63             DVL->getOperand(0).getMetadata(), DVL->getOperand(1).getMetadata());
  64     DVL->eraseFromParent();
  65   }
  66
  67   return !DbgValueLists.empty();
  68 }