1//===- LexicalScopes.cpp - Collecting lexical scope 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// This file implements LexicalScopes analysis.
10//
11// This pass collects lexical scope information and maps machine instructions
12// to respective lexical scopes.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/CodeGen/LexicalScopes.h"
17#include "llvm/ADT/DenseMap.h"
18#include "llvm/ADT/SmallVector.h"
19#include "llvm/CodeGen/MachineBasicBlock.h"
20#include "llvm/CodeGen/MachineFunction.h"
21#include "llvm/CodeGen/MachineInstr.h"
22#include "llvm/Config/llvm-config.h"
23#include "llvm/IR/DebugInfoMetadata.h"
24#include "llvm/IR/Function.h"
25#include "llvm/IR/Metadata.h"
26#include "llvm/Support/Casting.h"
27#include "llvm/Support/Compiler.h"
28#include "llvm/Support/Debug.h"
29#include "llvm/Support/raw_ostream.h"
30#include <cassert>
31#include <string>
32#include <tuple>
33#include <utility>
34
35using namespace llvm;
36
37#define DEBUG_TYPE "lexicalscopes"
38
39/// reset - Reset the instance so that it's prepared for another function.
40void LexicalScopes::reset() {
41 MF = nullptr;
42 CurrentFnLexicalScope = nullptr;
43 LexicalScopeMap.clear();
44 AbstractScopeMap.clear();
45 InlinedLexicalScopeMap.clear();
46 AbstractScopesList.clear();
47 DominatedBlocks.clear();
48}
49
50/// initialize - Scan machine function and constuct lexical scope nest.
51void LexicalScopes::initialize(const MachineFunction &Fn) {
52 reset();
53 // Don't attempt any lexical scope creation for a NoDebug compile unit.
54 if (Fn.getFunction().getSubprogram()->getUnit()->getEmissionKind() ==
55 DICompileUnit::NoDebug)
56 return;
57 MF = &Fn;
58 SmallVector<InsnRange, 4> MIRanges;
59 DenseMap<const MachineInstr *, LexicalScope *> MI2ScopeMap;
60 extractLexicalScopes(MIRanges, M&: MI2ScopeMap);
61 if (CurrentFnLexicalScope) {
62 constructScopeNest(Scope: CurrentFnLexicalScope);
63 assignInstructionRanges(MIRanges, M&: MI2ScopeMap);
64 }
65}
66
67/// extractLexicalScopes - Extract instruction ranges for each lexical scopes
68/// for the given machine function.
69void LexicalScopes::extractLexicalScopes(
70 SmallVectorImpl<InsnRange> &MIRanges,
71 DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
72 // Scan each instruction and create scopes. First build working set of scopes.
73 for (const auto &MBB : *MF) {
74 const MachineInstr *RangeBeginMI = nullptr;
75 const MachineInstr *PrevMI = nullptr;
76 const DILocation *PrevDL = nullptr;
77 for (const auto &MInsn : MBB) {
78 // Ignore DBG_VALUE and similar instruction that do not contribute to any
79 // instruction in the output.
80 if (MInsn.isMetaInstruction())
81 continue;
82
83 // Check if instruction has valid location information.
84 const DILocation *MIDL = MInsn.getDebugLoc();
85 if (!MIDL) {
86 PrevMI = &MInsn;
87 continue;
88 }
89
90 // If scope has not changed then skip this instruction.
91 if (MIDL == PrevDL) {
92 PrevMI = &MInsn;
93 continue;
94 }
95
96 if (RangeBeginMI) {
97 // If we have already seen a beginning of an instruction range and
98 // current instruction scope does not match scope of first instruction
99 // in this range then create a new instruction range.
100 InsnRange R(RangeBeginMI, PrevMI);
101 MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(DL: PrevDL);
102 MIRanges.push_back(Elt: R);
103 }
104
105 // This is a beginning of a new instruction range.
106 RangeBeginMI = &MInsn;
107
108 // Reset previous markers.
109 PrevMI = &MInsn;
110 PrevDL = MIDL;
111 }
112
113 // Create last instruction range.
114 if (RangeBeginMI && PrevMI && PrevDL) {
115 InsnRange R(RangeBeginMI, PrevMI);
116 MIRanges.push_back(Elt: R);
117 MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(DL: PrevDL);
118 }
119 }
120}
121
122/// findLexicalScope - Find lexical scope, either regular or inlined, for the
123/// given DebugLoc. Return NULL if not found.
124LexicalScope *LexicalScopes::findLexicalScope(const DILocation *DL) {
125 DILocalScope *Scope = DL->getScope();
126 if (!Scope)
127 return nullptr;
128
129 // The scope that we were created with could have an extra file - which
130 // isn't what we care about in this case.
131 Scope = Scope->getNonLexicalBlockFileScope();
132
133 if (auto *IA = DL->getInlinedAt()) {
134 auto I = InlinedLexicalScopeMap.find(x: std::make_pair(x&: Scope, y&: IA));
135 return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;
136 }
137 return findLexicalScope(N: Scope);
138}
139
140/// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
141/// not available then create new lexical scope.
142LexicalScope *LexicalScopes::getOrCreateLexicalScope(const DILocalScope *Scope,
143 const DILocation *IA) {
144 if (IA) {
145 // Skip scopes inlined from a NoDebug compile unit.
146 if (Scope->getSubprogram()->getUnit()->getEmissionKind() ==
147 DICompileUnit::NoDebug)
148 return getOrCreateLexicalScope(DL: IA);
149 // Create an abstract scope for inlined function.
150 getOrCreateAbstractScope(Scope);
151 // Create an inlined scope for inlined function.
152 return getOrCreateInlinedScope(Scope, InlinedAt: IA);
153 }
154
155 return getOrCreateRegularScope(Scope);
156}
157
158/// getOrCreateRegularScope - Find or create a regular lexical scope.
159LexicalScope *
160LexicalScopes::getOrCreateRegularScope(const DILocalScope *Scope) {
161 assert(Scope && "Invalid Scope encoding!");
162 Scope = Scope->getNonLexicalBlockFileScope();
163
164 auto I = LexicalScopeMap.find(x: Scope);
165 if (I != LexicalScopeMap.end())
166 return &I->second;
167
168 // FIXME: Should the following dyn_cast be DILexicalBlock?
169 LexicalScope *Parent = nullptr;
170 if (auto *Block = dyn_cast<DILexicalBlockBase>(Val: Scope))
171 Parent = getOrCreateLexicalScope(Scope: Block->getScope());
172 I = LexicalScopeMap.emplace(args: std::piecewise_construct,
173 args: std::forward_as_tuple(args&: Scope),
174 args: std::forward_as_tuple(args&: Parent, args&: Scope, args: nullptr,
175 args: false)).first;
176
177 if (!Parent) {
178 assert(cast<DISubprogram>(Scope)->describes(&MF->getFunction()));
179 assert(!CurrentFnLexicalScope);
180 CurrentFnLexicalScope = &I->second;
181 }
182
183 return &I->second;
184}
185
186/// getOrCreateInlinedScope - Find or create an inlined lexical scope.
187LexicalScope *
188LexicalScopes::getOrCreateInlinedScope(const DILocalScope *Scope,
189 const DILocation *InlinedAt) {
190 assert(Scope && "Invalid Scope encoding!");
191 Scope = Scope->getNonLexicalBlockFileScope();
192 std::pair<const DILocalScope *, const DILocation *> P(Scope, InlinedAt);
193 auto I = InlinedLexicalScopeMap.find(x: P);
194 if (I != InlinedLexicalScopeMap.end())
195 return &I->second;
196
197 LexicalScope *Parent;
198 if (auto *Block = dyn_cast<DILexicalBlockBase>(Val: Scope))
199 Parent = getOrCreateInlinedScope(Scope: Block->getScope(), InlinedAt);
200 else
201 Parent = getOrCreateLexicalScope(DL: InlinedAt);
202
203 I = InlinedLexicalScopeMap
204 .emplace(args: std::piecewise_construct, args: std::forward_as_tuple(args&: P),
205 args: std::forward_as_tuple(args&: Parent, args&: Scope, args&: InlinedAt, args: false))
206 .first;
207 return &I->second;
208}
209
210/// getOrCreateAbstractScope - Find or create an abstract lexical scope.
211LexicalScope *
212LexicalScopes::getOrCreateAbstractScope(const DILocalScope *Scope) {
213 assert(Scope && "Invalid Scope encoding!");
214 Scope = Scope->getNonLexicalBlockFileScope();
215 auto I = AbstractScopeMap.find(x: Scope);
216 if (I != AbstractScopeMap.end())
217 return &I->second;
218
219 // FIXME: Should the following isa be DILexicalBlock?
220 LexicalScope *Parent = nullptr;
221 if (auto *Block = dyn_cast<DILexicalBlockBase>(Val: Scope))
222 Parent = getOrCreateAbstractScope(Scope: Block->getScope());
223
224 I = AbstractScopeMap.emplace(args: std::piecewise_construct,
225 args: std::forward_as_tuple(args&: Scope),
226 args: std::forward_as_tuple(args&: Parent, args&: Scope,
227 args: nullptr, args: true)).first;
228 if (isa<DISubprogram>(Val: Scope))
229 AbstractScopesList.push_back(Elt: &I->second);
230 return &I->second;
231}
232
233/// constructScopeNest - Traverse the Scope tree depth-first, storing
234/// traversal state in WorkStack and recording the depth-first
235/// numbering (setDFSIn, setDFSOut) for edge classification.
236void LexicalScopes::constructScopeNest(LexicalScope *Scope) {
237 assert(Scope && "Unable to calculate scope dominance graph!");
238 SmallVector<std::pair<LexicalScope *, size_t>, 4> WorkStack;
239 WorkStack.push_back(Elt: std::make_pair(x&: Scope, y: 0));
240 unsigned Counter = 0;
241 while (!WorkStack.empty()) {
242 auto &ScopePosition = WorkStack.back();
243 LexicalScope *WS = ScopePosition.first;
244 size_t ChildNum = ScopePosition.second++;
245 const SmallVectorImpl<LexicalScope *> &Children = WS->getChildren();
246 if (ChildNum < Children.size()) {
247 auto &ChildScope = Children[ChildNum];
248 WorkStack.push_back(Elt: std::make_pair(x: ChildScope, y: 0));
249 ChildScope->setDFSIn(++Counter);
250 } else {
251 WorkStack.pop_back();
252 WS->setDFSOut(++Counter);
253 }
254 }
255}
256
257/// assignInstructionRanges - Find ranges of instructions covered by each
258/// lexical scope.
259void LexicalScopes::assignInstructionRanges(
260 SmallVectorImpl<InsnRange> &MIRanges,
261 DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
262 LexicalScope *PrevLexicalScope = nullptr;
263 for (const auto &R : MIRanges) {
264 LexicalScope *S = MI2ScopeMap.lookup(Val: R.first);
265 assert(S && "Lost LexicalScope for a machine instruction!");
266 if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
267 PrevLexicalScope->closeInsnRange(NewScope: S);
268 S->openInsnRange(MI: R.first);
269 S->extendInsnRange(MI: R.second);
270 PrevLexicalScope = S;
271 }
272
273 if (PrevLexicalScope)
274 PrevLexicalScope->closeInsnRange();
275}
276
277/// getMachineBasicBlocks - Populate given set using machine basic blocks which
278/// have machine instructions that belong to lexical scope identified by
279/// DebugLoc.
280void LexicalScopes::getMachineBasicBlocks(
281 const DILocation *DL, SmallPtrSetImpl<const MachineBasicBlock *> &MBBs) {
282 assert(MF && "Method called on a uninitialized LexicalScopes object!");
283 MBBs.clear();
284
285 LexicalScope *Scope = getOrCreateLexicalScope(DL);
286 if (!Scope)
287 return;
288
289 if (Scope == CurrentFnLexicalScope) {
290 for (const auto &MBB : *MF)
291 MBBs.insert(Ptr: &MBB);
292 return;
293 }
294
295 // The scope ranges can cover multiple basic blocks in each span. Iterate over
296 // all blocks (in the order they are in the function) until we reach the one
297 // containing the end of the span.
298 SmallVectorImpl<InsnRange> &InsnRanges = Scope->getRanges();
299 for (auto &R : InsnRanges)
300 for (auto CurMBBIt = R.first->getParent()->getIterator(),
301 EndBBIt = std::next(x: R.second->getParent()->getIterator());
302 CurMBBIt != EndBBIt; CurMBBIt++)
303 MBBs.insert(Ptr: &*CurMBBIt);
304}
305
306bool LexicalScopes::dominates(const DILocation *DL, MachineBasicBlock *MBB) {
307 assert(MF && "Unexpected uninitialized LexicalScopes object!");
308 LexicalScope *Scope = getOrCreateLexicalScope(DL);
309 if (!Scope)
310 return false;
311
312 // Current function scope covers all basic blocks in the function.
313 if (Scope == CurrentFnLexicalScope && MBB->getParent() == MF)
314 return true;
315
316 // Fetch all the blocks in DLs scope. Because the range / block list also
317 // contain any subscopes, any instruction that DL dominates can be found in
318 // the block set.
319 //
320 // Cache the set of fetched blocks to avoid repeatedly recomputing the set in
321 // the LiveDebugValues pass.
322 std::unique_ptr<BlockSetT> &Set = DominatedBlocks[DL];
323 if (!Set) {
324 Set = std::make_unique<BlockSetT>();
325 getMachineBasicBlocks(DL, MBBs&: *Set);
326 }
327 return Set->contains(Ptr: MBB);
328}
329
330#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
331LLVM_DUMP_METHOD void LexicalScope::dump(unsigned Indent) const {
332 raw_ostream &err = dbgs();
333 err.indent(Indent);
334 err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
335 const MDNode *N = Desc;
336 err.indent(Indent);
337 N->dump();
338 if (AbstractScope)
339 err << std::string(Indent, ' ') << "Abstract Scope\n";
340
341 if (!Children.empty())
342 err << std::string(Indent + 2, ' ') << "Children ...\n";
343 for (const LexicalScope *Child : Children)
344 if (Child != this)
345 Child->dump(Indent + 2);
346}
347#endif
348