[RISCV] Fix mgather -> riscv.masked.strided.load combine not extending indices (...
[llvm-project.git] / llvm / lib / CodeGen / RemoveRedundantDebugValues.cpp
blobba8dd49ba9291f33b9cbbdc45b59c0d66eb39da7
1 //===- RemoveRedundantDebugValues.cpp - Remove Redundant 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 //===----------------------------------------------------------------------===//
9 #include "llvm/ADT/DenseMap.h"
10 #include "llvm/ADT/DenseSet.h"
11 #include "llvm/ADT/SmallVector.h"
12 #include "llvm/ADT/Statistic.h"
13 #include "llvm/CodeGen/MachineBasicBlock.h"
14 #include "llvm/CodeGen/MachineFunctionPass.h"
15 #include "llvm/CodeGen/TargetSubtargetInfo.h"
16 #include "llvm/IR/DebugInfoMetadata.h"
17 #include "llvm/IR/Function.h"
18 #include "llvm/InitializePasses.h"
19 #include "llvm/Pass.h"
20 #include "llvm/PassRegistry.h"
22 /// \file RemoveRedundantDebugValues.cpp
23 ///
24 /// The RemoveRedundantDebugValues pass removes redundant DBG_VALUEs that
25 /// appear in MIR after the register allocator.
27 #define DEBUG_TYPE "removeredundantdebugvalues"
29 using namespace llvm;
31 STATISTIC(NumRemovedBackward, "Number of DBG_VALUEs removed (backward scan)");
32 STATISTIC(NumRemovedForward, "Number of DBG_VALUEs removed (forward scan)");
34 namespace {
36 class RemoveRedundantDebugValues : public MachineFunctionPass {
37 public:
38 static char ID;
40 RemoveRedundantDebugValues();
42 bool reduceDbgValues(MachineFunction &MF);
44 /// Remove redundant debug value MIs for the given machine function.
45 bool runOnMachineFunction(MachineFunction &MF) override;
47 void getAnalysisUsage(AnalysisUsage &AU) const override {
48 AU.setPreservesCFG();
49 MachineFunctionPass::getAnalysisUsage(AU);
53 } // namespace
55 //===----------------------------------------------------------------------===//
56 // Implementation
57 //===----------------------------------------------------------------------===//
59 char RemoveRedundantDebugValues::ID = 0;
61 char &llvm::RemoveRedundantDebugValuesID = RemoveRedundantDebugValues::ID;
63 INITIALIZE_PASS(RemoveRedundantDebugValues, DEBUG_TYPE,
64 "Remove Redundant DEBUG_VALUE analysis", false, false)
66 /// Default construct and initialize the pass.
67 RemoveRedundantDebugValues::RemoveRedundantDebugValues()
68 : MachineFunctionPass(ID) {
69 initializeRemoveRedundantDebugValuesPass(*PassRegistry::getPassRegistry());
72 // This analysis aims to remove redundant DBG_VALUEs by going forward
73 // in the basic block by considering the first DBG_VALUE as a valid
74 // until its first (location) operand is not clobbered/modified.
75 // For example:
76 // (1) DBG_VALUE $edi, !"var1", ...
77 // (2) <block of code that does affect $edi>
78 // (3) DBG_VALUE $edi, !"var1", ...
79 // ...
80 // in this case, we can remove (3).
81 // TODO: Support DBG_VALUE_LIST and other debug instructions.
82 static bool reduceDbgValsForwardScan(MachineBasicBlock &MBB) {
83 LLVM_DEBUG(dbgs() << "\n == Forward Scan == \n");
85 SmallVector<MachineInstr *, 8> DbgValsToBeRemoved;
86 DenseMap<DebugVariable, std::pair<MachineOperand *, const DIExpression *>>
87 VariableMap;
88 const auto *TRI = MBB.getParent()->getSubtarget().getRegisterInfo();
90 for (auto &MI : MBB) {
91 if (MI.isDebugValue()) {
92 DebugVariable Var(MI.getDebugVariable(), std::nullopt,
93 MI.getDebugLoc()->getInlinedAt());
94 auto VMI = VariableMap.find(Var);
95 // Just stop tracking this variable, until we cover DBG_VALUE_LIST.
96 // 1 DBG_VALUE $rax, "x", DIExpression()
97 // ...
98 // 2 DBG_VALUE_LIST "x", DIExpression(...), $rax, $rbx
99 // ...
100 // 3 DBG_VALUE $rax, "x", DIExpression()
101 if (MI.isDebugValueList() && VMI != VariableMap.end()) {
102 VariableMap.erase(VMI);
103 continue;
106 MachineOperand &Loc = MI.getDebugOperand(0);
107 if (!Loc.isReg()) {
108 // If it's not a register, just stop tracking such variable.
109 if (VMI != VariableMap.end())
110 VariableMap.erase(VMI);
111 continue;
114 // We have found a new value for a variable.
115 if (VMI == VariableMap.end() ||
116 VMI->second.first->getReg() != Loc.getReg() ||
117 VMI->second.second != MI.getDebugExpression()) {
118 VariableMap[Var] = {&Loc, MI.getDebugExpression()};
119 continue;
122 // Found an identical DBG_VALUE, so it can be considered
123 // for later removal.
124 DbgValsToBeRemoved.push_back(&MI);
127 if (MI.isMetaInstruction())
128 continue;
130 // Stop tracking any location that is clobbered by this instruction.
131 for (auto &Var : VariableMap) {
132 auto &LocOp = Var.second.first;
133 if (MI.modifiesRegister(LocOp->getReg(), TRI))
134 VariableMap.erase(Var.first);
138 for (auto &Instr : DbgValsToBeRemoved) {
139 LLVM_DEBUG(dbgs() << "removing "; Instr->dump());
140 Instr->eraseFromParent();
141 ++NumRemovedForward;
144 return !DbgValsToBeRemoved.empty();
147 // This analysis aims to remove redundant DBG_VALUEs by going backward
148 // in the basic block and removing all but the last DBG_VALUE for any
149 // given variable in a set of consecutive DBG_VALUE instructions.
150 // For example:
151 // (1) DBG_VALUE $edi, !"var1", ...
152 // (2) DBG_VALUE $esi, !"var2", ...
153 // (3) DBG_VALUE $edi, !"var1", ...
154 // ...
155 // in this case, we can remove (1).
156 static bool reduceDbgValsBackwardScan(MachineBasicBlock &MBB) {
157 LLVM_DEBUG(dbgs() << "\n == Backward Scan == \n");
158 SmallVector<MachineInstr *, 8> DbgValsToBeRemoved;
159 SmallDenseSet<DebugVariable> VariableSet;
161 for (MachineInstr &MI : llvm::reverse(MBB)) {
162 if (MI.isDebugValue()) {
163 DebugVariable Var(MI.getDebugVariable(), MI.getDebugExpression(),
164 MI.getDebugLoc()->getInlinedAt());
165 auto R = VariableSet.insert(Var);
166 // If it is a DBG_VALUE describing a constant as:
167 // DBG_VALUE 0, ...
168 // we just don't consider such instructions as candidates
169 // for redundant removal.
170 if (MI.isNonListDebugValue()) {
171 MachineOperand &Loc = MI.getDebugOperand(0);
172 if (!Loc.isReg()) {
173 // If we have already encountered this variable, just stop
174 // tracking it.
175 if (!R.second)
176 VariableSet.erase(Var);
177 continue;
181 // We have already encountered the value for this variable,
182 // so this one can be deleted.
183 if (!R.second)
184 DbgValsToBeRemoved.push_back(&MI);
185 continue;
188 // If we encountered a non-DBG_VALUE, try to find the next
189 // sequence with consecutive DBG_VALUE instructions.
190 VariableSet.clear();
193 for (auto &Instr : DbgValsToBeRemoved) {
194 LLVM_DEBUG(dbgs() << "removing "; Instr->dump());
195 Instr->eraseFromParent();
196 ++NumRemovedBackward;
199 return !DbgValsToBeRemoved.empty();
202 bool RemoveRedundantDebugValues::reduceDbgValues(MachineFunction &MF) {
203 LLVM_DEBUG(dbgs() << "\nDebug Value Reduction\n");
205 bool Changed = false;
207 for (auto &MBB : MF) {
208 Changed |= reduceDbgValsBackwardScan(MBB);
209 Changed |= reduceDbgValsForwardScan(MBB);
212 return Changed;
215 bool RemoveRedundantDebugValues::runOnMachineFunction(MachineFunction &MF) {
216 // Skip functions without debugging information.
217 if (!MF.getFunction().getSubprogram())
218 return false;
220 // Skip functions from NoDebug compilation units.
221 if (MF.getFunction().getSubprogram()->getUnit()->getEmissionKind() ==
222 DICompileUnit::NoDebug)
223 return false;
225 bool Changed = reduceDbgValues(MF);
226 return Changed;