1//===- LiveDebugValues.cpp - Tracking Debug Value MIs ---------------------===//
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#include "LiveDebugValues.h"
10
11#include "llvm/CodeGen/LiveDebugValuesPass.h"
12#include "llvm/CodeGen/MachineDominators.h"
13#include "llvm/CodeGen/MachineFunction.h"
14#include "llvm/CodeGen/MachineFunctionPass.h"
15#include "llvm/CodeGen/Passes.h"
16#include "llvm/CodeGen/TargetPassConfig.h"
17#include "llvm/InitializePasses.h"
18#include "llvm/Pass.h"
19#include "llvm/Support/CommandLine.h"
20#include "llvm/Target/TargetMachine.h"
21#include "llvm/TargetParser/Triple.h"
22
23/// \file LiveDebugValues.cpp
24///
25/// The LiveDebugValues pass extends the range of variable locations
26/// (specified by DBG_VALUE instructions) from single blocks to successors
27/// and any other code locations where the variable location is valid.
28/// There are currently two implementations: the "VarLoc" implementation
29/// explicitly tracks the location of a variable, while the "InstrRef"
30/// implementation tracks the values defined by instructions through locations.
31///
32/// This file implements neither; it merely registers the pass, allows the
33/// user to pick which implementation will be used to propagate variable
34/// locations.
35
36#define DEBUG_TYPE "livedebugvalues"
37
38using namespace llvm;
39
40static cl::opt<bool>
41 ForceInstrRefLDV("force-instr-ref-livedebugvalues", cl::Hidden,
42 cl::desc("Use instruction-ref based LiveDebugValues with "
43 "normal DBG_VALUE inputs"),
44 cl::init(Val: false));
45
46static cl::opt<cl::boolOrDefault> ValueTrackingVariableLocations(
47 "experimental-debug-variable-locations",
48 cl::desc("Use experimental new value-tracking variable locations"));
49
50// Options to prevent pathological compile-time behavior. If InputBBLimit and
51// InputDbgValueLimit are both exceeded, range extension is disabled.
52static cl::opt<unsigned> InputBBLimit(
53 "livedebugvalues-input-bb-limit",
54 cl::desc("Maximum input basic blocks before DBG_VALUE limit applies"),
55 cl::init(Val: 10000), cl::Hidden);
56static cl::opt<unsigned> InputDbgValueLimit(
57 "livedebugvalues-input-dbg-value-limit",
58 cl::desc(
59 "Maximum input DBG_VALUE insts supported by debug range extension"),
60 cl::init(Val: 50000), cl::Hidden);
61
62namespace {
63/// Generic LiveDebugValues pass. Calls through to VarLocBasedLDV or
64/// InstrRefBasedLDV to perform location propagation, via the LDVImpl
65/// base class.
66class LiveDebugValuesLegacy : public MachineFunctionPass {
67public:
68 static char ID;
69
70 LiveDebugValuesLegacy();
71 ~LiveDebugValuesLegacy() override = default;
72
73 /// Calculate the liveness information for the given machine function.
74 bool runOnMachineFunction(MachineFunction &MF) override;
75
76 void getAnalysisUsage(AnalysisUsage &AU) const override {
77 AU.setPreservesCFG();
78 AU.addRequired<TargetPassConfig>();
79 MachineFunctionPass::getAnalysisUsage(AU);
80 }
81};
82
83struct LiveDebugValues {
84 LiveDebugValues();
85 ~LiveDebugValues() = default;
86 bool run(MachineFunction &MF, bool ShouldEmitDebugEntryValues);
87
88private:
89 std::unique_ptr<LDVImpl> InstrRefImpl;
90 std::unique_ptr<LDVImpl> VarLocImpl;
91 MachineDominatorTree MDT;
92};
93} // namespace
94
95char LiveDebugValuesLegacy::ID = 0;
96
97char &llvm::LiveDebugValuesID = LiveDebugValuesLegacy::ID;
98
99INITIALIZE_PASS(LiveDebugValuesLegacy, DEBUG_TYPE, "Live DEBUG_VALUE analysis",
100 false, false)
101
102/// Default construct and initialize the pass.
103LiveDebugValuesLegacy::LiveDebugValuesLegacy() : MachineFunctionPass(ID) {}
104
105LiveDebugValues::LiveDebugValues() {
106 InstrRefImpl =
107 std::unique_ptr<LDVImpl>(llvm::makeInstrRefBasedLiveDebugValues());
108 VarLocImpl = std::unique_ptr<LDVImpl>(llvm::makeVarLocBasedLiveDebugValues());
109}
110
111PreservedAnalyses
112LiveDebugValuesPass::run(MachineFunction &MF,
113 MachineFunctionAnalysisManager &MFAM) {
114 if (!LiveDebugValues().run(MF, ShouldEmitDebugEntryValues))
115 return PreservedAnalyses::all();
116 auto PA = getMachineFunctionPassPreservedAnalyses();
117 PA.preserveSet<CFGAnalyses>();
118 return PA;
119}
120
121void LiveDebugValuesPass::printPipeline(
122 raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) {
123 OS << MapClassName2PassName(name());
124 if (ShouldEmitDebugEntryValues)
125 OS << "<emit-debug-entry-values>";
126}
127
128bool LiveDebugValuesLegacy::runOnMachineFunction(MachineFunction &MF) {
129 auto *TPC = &getAnalysis<TargetPassConfig>();
130 return LiveDebugValues().run(
131 MF, ShouldEmitDebugEntryValues: TPC->getTM<TargetMachine>().Options.ShouldEmitDebugEntryValues());
132}
133
134bool LiveDebugValues::run(MachineFunction &MF,
135 bool ShouldEmitDebugEntryValues) {
136 bool InstrRefBased = MF.useDebugInstrRef();
137 // Allow the user to force selection of InstrRef LDV.
138 InstrRefBased |= ForceInstrRefLDV;
139
140 LDVImpl *TheImpl = &*VarLocImpl;
141
142 MachineDominatorTree *DomTree = nullptr;
143 if (InstrRefBased) {
144 DomTree = &MDT;
145 MDT.recalculate(Func&: MF);
146 TheImpl = &*InstrRefImpl;
147 }
148
149 return TheImpl->ExtendRanges(MF, DomTree, ShouldEmitDebugEntryValues,
150 InputBBLimit, InputDbgValLimit: InputDbgValueLimit);
151}
152
153bool llvm::debuginfoShouldUseDebugInstrRef(const Triple &T) {
154 // Enable by default on x86_64, disable if explicitly turned off on cmdline.
155 if (T.getArch() == llvm::Triple::x86_64 &&
156 ValueTrackingVariableLocations != cl::boolOrDefault::BOU_FALSE)
157 return true;
158
159 // Enable if explicitly requested on command line.
160 return ValueTrackingVariableLocations == cl::boolOrDefault::BOU_TRUE;
161}
162