1 ///===- DroppedVariableStats.cpp ----------------------------------------===//
2 ///
3 /// Part of the LLVM Project, under the Apache License v2.0 with LLVM
4 /// Exceptions. See https://llvm.org/LICENSE.txt for license information.
5 /// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 ///
7 ///===---------------------------------------------------------------------===//
8 /// \file
9 /// Dropped Variable Statistics for Debug Information. Reports any number
10 /// of #dbg_value that get dropped due to an optimization pass.
11 ///
12 ///===---------------------------------------------------------------------===//
13
14 #include "llvm/IR/DroppedVariableStats.h"
15 #include "llvm/IR/DebugInfoMetadata.h"
16 #include "llvm/IR/DiagnosticInfo.h"
17 #include "llvm/IR/Function.h"
18
19 using namespace llvm;
20
DroppedVariableStats(bool DroppedVarStatsEnabled)21 DroppedVariableStats::DroppedVariableStats(bool DroppedVarStatsEnabled)
22 : DroppedVariableStatsEnabled(DroppedVarStatsEnabled) {
23 if (DroppedVarStatsEnabled)
24 llvm::outs() << "Pass Level, Pass Name, Num of Dropped Variables, Func or "
25 "Module Name\n";
26 }
27
setup()28 void DroppedVariableStats::setup() {
29 DebugVariablesStack.push_back({DenseMap<const Function *, DebugVariables>()});
30 InlinedAts.push_back({DenseMap<StringRef, DenseMap<VarID, DILocation *>>()});
31 }
32
cleanup()33 void DroppedVariableStats::cleanup() {
34 assert(!DebugVariablesStack.empty() &&
35 "DebugVariablesStack shouldn't be empty!");
36 assert(!InlinedAts.empty() && "InlinedAts shouldn't be empty!");
37 DebugVariablesStack.pop_back();
38 InlinedAts.pop_back();
39 }
40
calculateDroppedStatsAndPrint(DebugVariables & DbgVariables,StringRef FuncName,StringRef PassID,StringRef FuncOrModName,StringRef PassLevel,const Function * Func)41 void DroppedVariableStats::calculateDroppedStatsAndPrint(
42 DebugVariables &DbgVariables, StringRef FuncName, StringRef PassID,
43 StringRef FuncOrModName, StringRef PassLevel, const Function *Func) {
44 unsigned DroppedCount = 0;
45 DenseSet<VarID> &DebugVariablesBeforeSet = DbgVariables.DebugVariablesBefore;
46 DenseSet<VarID> &DebugVariablesAfterSet = DbgVariables.DebugVariablesAfter;
47 auto It = InlinedAts.back().find(FuncName);
48 if (It == InlinedAts.back().end())
49 return;
50 DenseMap<VarID, DILocation *> &InlinedAtsMap = It->second;
51 // Find an Instruction that shares the same scope as the dropped #dbg_value
52 // or has a scope that is the child of the scope of the #dbg_value, and has
53 // an inlinedAt equal to the inlinedAt of the #dbg_value or it's inlinedAt
54 // chain contains the inlinedAt of the #dbg_value, if such an Instruction is
55 // found, debug information is dropped.
56 for (VarID Var : DebugVariablesBeforeSet) {
57 if (DebugVariablesAfterSet.contains(Var))
58 continue;
59 visitEveryInstruction(DroppedCount, InlinedAtsMap, Var);
60 removeVarFromAllSets(Var, Func);
61 }
62 if (DroppedCount > 0) {
63 llvm::outs() << PassLevel << ", " << PassID << ", " << DroppedCount << ", "
64 << FuncOrModName << "\n";
65 PassDroppedVariables = true;
66 } else
67 PassDroppedVariables = false;
68 }
69
updateDroppedCount(DILocation * DbgLoc,const DIScope * Scope,const DIScope * DbgValScope,DenseMap<VarID,DILocation * > & InlinedAtsMap,VarID Var,unsigned & DroppedCount)70 bool DroppedVariableStats::updateDroppedCount(
71 DILocation *DbgLoc, const DIScope *Scope, const DIScope *DbgValScope,
72 DenseMap<VarID, DILocation *> &InlinedAtsMap, VarID Var,
73 unsigned &DroppedCount) {
74 // If the Scope is a child of, or equal to the DbgValScope and is inlined at
75 // the Var's InlinedAt location, return true to signify that the Var has
76 // been dropped.
77 if (isScopeChildOfOrEqualTo(Scope, DbgValScope))
78 if (isInlinedAtChildOfOrEqualTo(DbgLoc->getInlinedAt(),
79 InlinedAtsMap[Var])) {
80 // Found another instruction in the variable's scope, so there exists a
81 // break point at which the variable could be observed. Count it as
82 // dropped.
83 DroppedCount++;
84 return true;
85 }
86 return false;
87 }
88
run(DebugVariables & DbgVariables,StringRef FuncName,bool Before)89 void DroppedVariableStats::run(DebugVariables &DbgVariables, StringRef FuncName,
90 bool Before) {
91 auto &VarIDSet = (Before ? DbgVariables.DebugVariablesBefore
92 : DbgVariables.DebugVariablesAfter);
93 auto &InlinedAtsMap = InlinedAts.back();
94 if (Before)
95 InlinedAtsMap.try_emplace(FuncName, DenseMap<VarID, DILocation *>());
96 VarIDSet = DenseSet<VarID>();
97 visitEveryDebugRecord(VarIDSet, InlinedAtsMap, FuncName, Before);
98 }
99
populateVarIDSetAndInlinedMap(const DILocalVariable * DbgVar,DebugLoc DbgLoc,DenseSet<VarID> & VarIDSet,DenseMap<StringRef,DenseMap<VarID,DILocation * >> & InlinedAtsMap,StringRef FuncName,bool Before)100 void DroppedVariableStats::populateVarIDSetAndInlinedMap(
101 const DILocalVariable *DbgVar, DebugLoc DbgLoc, DenseSet<VarID> &VarIDSet,
102 DenseMap<StringRef, DenseMap<VarID, DILocation *>> &InlinedAtsMap,
103 StringRef FuncName, bool Before) {
104 VarID Key{DbgVar->getScope(), DbgLoc->getInlinedAtScope(), DbgVar};
105 VarIDSet.insert(Key);
106 if (Before)
107 InlinedAtsMap[FuncName].try_emplace(Key, DbgLoc.getInlinedAt());
108 }
109
removeVarFromAllSets(VarID Var,const Function * F)110 void DroppedVariableStats::removeVarFromAllSets(VarID Var, const Function *F) {
111 // Do not remove Var from the last element, it will be popped from the
112 // stack.
113 for (auto &DebugVariablesMap : llvm::drop_end(DebugVariablesStack))
114 DebugVariablesMap[F].DebugVariablesBefore.erase(Var);
115 }
116
isScopeChildOfOrEqualTo(const DIScope * Scope,const DIScope * DbgValScope)117 bool DroppedVariableStats::isScopeChildOfOrEqualTo(const DIScope *Scope,
118 const DIScope *DbgValScope) {
119 while (Scope != nullptr) {
120 if (VisitedScope.insert(Scope).second) {
121 if (Scope == DbgValScope) {
122 VisitedScope.clear();
123 return true;
124 }
125 Scope = Scope->getScope();
126 } else {
127 VisitedScope.clear();
128 return false;
129 }
130 }
131 return false;
132 }
133
isInlinedAtChildOfOrEqualTo(const DILocation * InlinedAt,const DILocation * DbgValInlinedAt)134 bool DroppedVariableStats::isInlinedAtChildOfOrEqualTo(
135 const DILocation *InlinedAt, const DILocation *DbgValInlinedAt) {
136 if (DbgValInlinedAt == InlinedAt)
137 return true;
138 if (!DbgValInlinedAt)
139 return false;
140 auto *IA = InlinedAt;
141 while (IA) {
142 if (IA == DbgValInlinedAt)
143 return true;
144 IA = IA->getInlinedAt();
145 }
146 return false;
147 }
148