1 //===- MachineStripDebug.cpp - Strip debug info ---------------------------===//
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 This removes debug info from everything. It can be used to ensure
10 /// tests can be debugified without affecting the output MIR.
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/CodeGen/MachineFunctionPass.h"
14 #include "llvm/CodeGen/MachineModuleInfo.h"
15 #include "llvm/CodeGen/Passes.h"
16 #include "llvm/IR/DebugInfo.h"
17 #include "llvm/InitializePasses.h"
18 #include "llvm/Support/CommandLine.h"
19 #include "llvm/Transforms/Utils/Debugify.h"
20 
21 #define DEBUG_TYPE "mir-strip-debug"
22 
23 using namespace llvm;
24 
25 namespace {
26 cl::opt<bool>
27     OnlyDebugifiedDefault("mir-strip-debugify-only",
28                           cl::desc("Should mir-strip-debug only strip debug "
29                                    "info from debugified modules by default"),
30                           cl::init(true));
31 
32 struct StripDebugMachineModule : public ModulePass {
33   bool runOnModule(Module &M) override {
34     if (OnlyDebugified) {
35       NamedMDNode *DebugifyMD = M.getNamedMetadata("llvm.debugify");
36       if (!DebugifyMD) {
37         LLVM_DEBUG(dbgs() << "Not stripping debug info"
38                              " (debugify metadata not found)?\n");
39         return false;
40       }
41     }
42 
43     MachineModuleInfo &MMI =
44         getAnalysis<MachineModuleInfoWrapperPass>().getMMI();
45 
46     bool Changed = false;
47     for (Function &F : M.functions()) {
48       MachineFunction &MF = MMI.getOrCreateMachineFunction(F);
49       for (MachineBasicBlock &MBB : MF) {
50         for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
51              I != E;) {
52           if (I->isDebugInstr()) {
53             // FIXME: We should remove all of them. However, AArch64 emits an
54             //        invalid `DBG_VALUE $lr` with only one operand instead of
55             //        the usual three and has a test that depends on it's
56             //        preservation. Preserve it for now.
57             if (I->getNumOperands() > 1) {
58               LLVM_DEBUG(dbgs() << "Removing debug instruction " << *I);
59               I = MBB.erase(I);
60               Changed |= true;
61               continue;
62             }
63           }
64           if (I->getDebugLoc()) {
65             LLVM_DEBUG(dbgs() << "Removing location " << *I);
66             I->setDebugLoc(DebugLoc());
67             Changed |= true;
68             ++I;
69             continue;
70           }
71           LLVM_DEBUG(dbgs() << "Keeping " << *I);
72           ++I;
73         }
74       }
75     }
76 
77     Changed |= stripDebugifyMetadata(M);
78 
79     return Changed;
80   }
81 
82   StripDebugMachineModule() : StripDebugMachineModule(OnlyDebugifiedDefault) {}
83   StripDebugMachineModule(bool OnlyDebugified)
84       : ModulePass(ID), OnlyDebugified(OnlyDebugified) {}
85 
86   void getAnalysisUsage(AnalysisUsage &AU) const override {
87     AU.addRequired<MachineModuleInfoWrapperPass>();
88     AU.addPreserved<MachineModuleInfoWrapperPass>();
89     AU.setPreservesCFG();
90   }
91 
92   static char ID; // Pass identification.
93 
94 protected:
95   bool OnlyDebugified;
96 };
97 char StripDebugMachineModule::ID = 0;
98 
99 } // end anonymous namespace
100 
101 INITIALIZE_PASS_BEGIN(StripDebugMachineModule, DEBUG_TYPE,
102                       "Machine Strip Debug Module", false, false)
103 INITIALIZE_PASS_END(StripDebugMachineModule, DEBUG_TYPE,
104                     "Machine Strip Debug Module", false, false)
105 
106 ModulePass *llvm::createStripDebugMachineModulePass(bool OnlyDebugified) {
107   return new StripDebugMachineModule(OnlyDebugified);
108 }
109