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://github.com/llvm/llvm-project/issues/49705.
13 /// TODO Correctly handle DBG_VALUE_LISTs
14 ///
15 //===----------------------------------------------------------------------===//
16 
17 #include "WebAssembly.h"
18 #include "WebAssemblySubtarget.h"
19 #include "llvm/CodeGen/MachineFunctionPass.h"
20 using namespace llvm;
21 
22 #define DEBUG_TYPE "wasm-nullify-dbg-value-lists"
23 
24 namespace {
25 class WebAssemblyNullifyDebugValueLists final : public MachineFunctionPass {
26   StringRef getPassName() const override {
27     return "WebAssembly Nullify DBG_VALUE_LISTs";
28   }
29 
30   bool runOnMachineFunction(MachineFunction &MF) override;
31 
32 public:
33   static char ID; // Pass identification, replacement for typeid
34   WebAssemblyNullifyDebugValueLists() : MachineFunctionPass(ID) {}
35 };
36 } // end anonymous namespace
37 
38 char WebAssemblyNullifyDebugValueLists::ID = 0;
39 INITIALIZE_PASS(WebAssemblyNullifyDebugValueLists, DEBUG_TYPE,
40                 "WebAssembly Nullify DBG_VALUE_LISTs", false, false)
41 
42 FunctionPass *llvm::createWebAssemblyNullifyDebugValueLists() {
43   return new WebAssemblyNullifyDebugValueLists();
44 }
45 
46 bool WebAssemblyNullifyDebugValueLists::runOnMachineFunction(
47     MachineFunction &MF) {
48   LLVM_DEBUG(dbgs() << "********** Nullify DBG_VALUE_LISTs **********\n"
49                        "********** Function: "
50                     << MF.getName() << '\n');
51   bool Changed = false;
52   // Our backend, including WebAssemblyDebugValueManager, currently cannot
53   // handle DBG_VALUE_LISTs correctly. So this makes them undefined, which will
54   // appear as "optimized out".
55   for (auto &MBB : MF) {
56     for (auto &MI : MBB) {
57       if (MI.getOpcode() == TargetOpcode::DBG_VALUE_LIST) {
58         MI.setDebugValueUndef();
59         Changed = true;
60       }
61     }
62   }
63   return Changed;
64 }
65