1 //===--- SIDebuggerInsertNops.cpp - Inserts nops for debugger usage -------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 /// \file
11 /// \brief Inserts one nop instruction for each high level source statement for
12 /// debugger usage.
13 ///
14 /// Tools, such as a debugger, need to pause execution based on user input (i.e.
15 /// breakpoint). In order to do this, one nop instruction is inserted before the
16 /// first isa instruction of each high level source statement. Further, the
17 /// debugger may replace nop instructions with trap instructions based on user
18 /// input.
19 //
20 //===----------------------------------------------------------------------===//
21
22 #include "SIInstrInfo.h"
23 #include "AMDGPUSubtarget.h"
24 #include "llvm/ADT/DenseSet.h"
25 #include "llvm/CodeGen/MachineFunction.h"
26 #include "llvm/CodeGen/MachineFunctionPass.h"
27 #include "llvm/CodeGen/MachineInstrBuilder.h"
28 #include "llvm/CodeGen/MachineModuleInfo.h"
29 using namespace llvm;
30
31 #define DEBUG_TYPE "si-debugger-insert-nops"
32 #define PASS_NAME "SI Debugger Insert Nops"
33
34 namespace {
35
36 class SIDebuggerInsertNops : public MachineFunctionPass {
37 public:
38 static char ID;
39
SIDebuggerInsertNops()40 SIDebuggerInsertNops() : MachineFunctionPass(ID) { }
getPassName() const41 const char *getPassName() const override { return PASS_NAME; }
42
getAnalysisUsage(AnalysisUsage & AU) const43 void getAnalysisUsage(AnalysisUsage &AU) const override {
44 AU.setPreservesCFG();
45 MachineFunctionPass::getAnalysisUsage(AU);
46 }
47
48 bool runOnMachineFunction(MachineFunction &MF) override;
49 };
50
51 } // anonymous namespace
52
53 INITIALIZE_PASS(SIDebuggerInsertNops, DEBUG_TYPE, PASS_NAME, false, false)
54
55 char SIDebuggerInsertNops::ID = 0;
56 char &llvm::SIDebuggerInsertNopsID = SIDebuggerInsertNops::ID;
57
createSIDebuggerInsertNopsPass()58 FunctionPass *llvm::createSIDebuggerInsertNopsPass() {
59 return new SIDebuggerInsertNops();
60 }
61
runOnMachineFunction(MachineFunction & MF)62 bool SIDebuggerInsertNops::runOnMachineFunction(MachineFunction &MF) {
63 // Skip this pass if "amdgpu-debugger-insert-nops" attribute was not
64 // specified.
65 const SISubtarget &ST = MF.getSubtarget<SISubtarget>();
66 if (!ST.debuggerInsertNops())
67 return false;
68
69 // Skip machine functions without debug info.
70 if (!MF.getMMI().hasDebugInfo())
71 return false;
72
73 // Target instruction info.
74 const SIInstrInfo *TII = ST.getInstrInfo();
75
76 // Set containing line numbers that have nop inserted.
77 DenseSet<unsigned> NopInserted;
78
79 for (auto &MBB : MF) {
80 for (auto MI = MBB.begin(); MI != MBB.end(); ++MI) {
81 // Skip DBG_VALUE instructions and instructions without location.
82 if (MI->isDebugValue() || !MI->getDebugLoc())
83 continue;
84
85 // Insert nop instruction if line number does not have nop inserted.
86 auto DL = MI->getDebugLoc();
87 if (NopInserted.find(DL.getLine()) == NopInserted.end()) {
88 BuildMI(MBB, *MI, DL, TII->get(AMDGPU::S_NOP))
89 .addImm(0);
90 NopInserted.insert(DL.getLine());
91 }
92 }
93 }
94
95 return true;
96 }
97