348 lines
12 KiB
C++
348 lines
12 KiB
C++
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//===- LexicalScopes.cpp - Collecting lexical scope info ------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements LexicalScopes analysis.
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//
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// This pass collects lexical scope information and maps machine instructions
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// to respective lexical scopes.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/LexicalScopes.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/Config/llvm-config.h"
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#include "llvm/IR/DebugInfoMetadata.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/Metadata.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include <cassert>
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#include <string>
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#include <tuple>
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#include <utility>
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using namespace llvm;
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#define DEBUG_TYPE "lexicalscopes"
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/// reset - Reset the instance so that it's prepared for another function.
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void LexicalScopes::reset() {
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MF = nullptr;
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CurrentFnLexicalScope = nullptr;
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LexicalScopeMap.clear();
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AbstractScopeMap.clear();
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InlinedLexicalScopeMap.clear();
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AbstractScopesList.clear();
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DominatedBlocks.clear();
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}
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/// initialize - Scan machine function and constuct lexical scope nest.
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void LexicalScopes::initialize(const MachineFunction &Fn) {
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reset();
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// Don't attempt any lexical scope creation for a NoDebug compile unit.
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if (Fn.getFunction().getSubprogram()->getUnit()->getEmissionKind() ==
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DICompileUnit::NoDebug)
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return;
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MF = &Fn;
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SmallVector<InsnRange, 4> MIRanges;
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DenseMap<const MachineInstr *, LexicalScope *> MI2ScopeMap;
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extractLexicalScopes(MIRanges, MI2ScopeMap);
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if (CurrentFnLexicalScope) {
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constructScopeNest(CurrentFnLexicalScope);
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assignInstructionRanges(MIRanges, MI2ScopeMap);
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}
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}
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/// extractLexicalScopes - Extract instruction ranges for each lexical scopes
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/// for the given machine function.
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void LexicalScopes::extractLexicalScopes(
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SmallVectorImpl<InsnRange> &MIRanges,
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DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
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// Scan each instruction and create scopes. First build working set of scopes.
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for (const auto &MBB : *MF) {
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const MachineInstr *RangeBeginMI = nullptr;
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const MachineInstr *PrevMI = nullptr;
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const DILocation *PrevDL = nullptr;
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for (const auto &MInsn : MBB) {
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// Check if instruction has valid location information.
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const DILocation *MIDL = MInsn.getDebugLoc();
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if (!MIDL) {
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PrevMI = &MInsn;
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continue;
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}
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// If scope has not changed then skip this instruction.
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if (MIDL == PrevDL) {
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PrevMI = &MInsn;
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continue;
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}
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// Ignore DBG_VALUE and similar instruction that do not contribute to any
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// instruction in the output.
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if (MInsn.isMetaInstruction())
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continue;
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if (RangeBeginMI) {
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// If we have already seen a beginning of an instruction range and
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// current instruction scope does not match scope of first instruction
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// in this range then create a new instruction range.
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InsnRange R(RangeBeginMI, PrevMI);
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MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
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MIRanges.push_back(R);
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}
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// This is a beginning of a new instruction range.
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RangeBeginMI = &MInsn;
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// Reset previous markers.
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PrevMI = &MInsn;
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PrevDL = MIDL;
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}
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// Create last instruction range.
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if (RangeBeginMI && PrevMI && PrevDL) {
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InsnRange R(RangeBeginMI, PrevMI);
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MIRanges.push_back(R);
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MI2ScopeMap[RangeBeginMI] = getOrCreateLexicalScope(PrevDL);
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}
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}
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}
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/// findLexicalScope - Find lexical scope, either regular or inlined, for the
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/// given DebugLoc. Return NULL if not found.
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LexicalScope *LexicalScopes::findLexicalScope(const DILocation *DL) {
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DILocalScope *Scope = DL->getScope();
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if (!Scope)
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return nullptr;
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// The scope that we were created with could have an extra file - which
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// isn't what we care about in this case.
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Scope = Scope->getNonLexicalBlockFileScope();
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if (auto *IA = DL->getInlinedAt()) {
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auto I = InlinedLexicalScopeMap.find(std::make_pair(Scope, IA));
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return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;
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}
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return findLexicalScope(Scope);
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}
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/// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
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/// not available then create new lexical scope.
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LexicalScope *LexicalScopes::getOrCreateLexicalScope(const DILocalScope *Scope,
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const DILocation *IA) {
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if (IA) {
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// Skip scopes inlined from a NoDebug compile unit.
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if (Scope->getSubprogram()->getUnit()->getEmissionKind() ==
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DICompileUnit::NoDebug)
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return getOrCreateLexicalScope(IA);
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// Create an abstract scope for inlined function.
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getOrCreateAbstractScope(Scope);
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// Create an inlined scope for inlined function.
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return getOrCreateInlinedScope(Scope, IA);
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}
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return getOrCreateRegularScope(Scope);
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}
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/// getOrCreateRegularScope - Find or create a regular lexical scope.
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LexicalScope *
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LexicalScopes::getOrCreateRegularScope(const DILocalScope *Scope) {
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assert(Scope && "Invalid Scope encoding!");
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Scope = Scope->getNonLexicalBlockFileScope();
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auto I = LexicalScopeMap.find(Scope);
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if (I != LexicalScopeMap.end())
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return &I->second;
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// FIXME: Should the following dyn_cast be DILexicalBlock?
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LexicalScope *Parent = nullptr;
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if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
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Parent = getOrCreateLexicalScope(Block->getScope());
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I = LexicalScopeMap.emplace(std::piecewise_construct,
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std::forward_as_tuple(Scope),
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std::forward_as_tuple(Parent, Scope, nullptr,
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false)).first;
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if (!Parent) {
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assert(cast<DISubprogram>(Scope)->describes(&MF->getFunction()));
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assert(!CurrentFnLexicalScope);
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CurrentFnLexicalScope = &I->second;
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}
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return &I->second;
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}
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/// getOrCreateInlinedScope - Find or create an inlined lexical scope.
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LexicalScope *
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LexicalScopes::getOrCreateInlinedScope(const DILocalScope *Scope,
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const DILocation *InlinedAt) {
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assert(Scope && "Invalid Scope encoding!");
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Scope = Scope->getNonLexicalBlockFileScope();
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std::pair<const DILocalScope *, const DILocation *> P(Scope, InlinedAt);
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auto I = InlinedLexicalScopeMap.find(P);
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if (I != InlinedLexicalScopeMap.end())
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return &I->second;
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LexicalScope *Parent;
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if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
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Parent = getOrCreateInlinedScope(Block->getScope(), InlinedAt);
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else
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Parent = getOrCreateLexicalScope(InlinedAt);
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I = InlinedLexicalScopeMap
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.emplace(std::piecewise_construct, std::forward_as_tuple(P),
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std::forward_as_tuple(Parent, Scope, InlinedAt, false))
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.first;
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return &I->second;
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}
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/// getOrCreateAbstractScope - Find or create an abstract lexical scope.
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LexicalScope *
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LexicalScopes::getOrCreateAbstractScope(const DILocalScope *Scope) {
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assert(Scope && "Invalid Scope encoding!");
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Scope = Scope->getNonLexicalBlockFileScope();
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auto I = AbstractScopeMap.find(Scope);
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if (I != AbstractScopeMap.end())
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return &I->second;
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// FIXME: Should the following isa be DILexicalBlock?
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LexicalScope *Parent = nullptr;
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if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
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Parent = getOrCreateAbstractScope(Block->getScope());
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I = AbstractScopeMap.emplace(std::piecewise_construct,
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std::forward_as_tuple(Scope),
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std::forward_as_tuple(Parent, Scope,
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nullptr, true)).first;
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if (isa<DISubprogram>(Scope))
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AbstractScopesList.push_back(&I->second);
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return &I->second;
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}
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/// constructScopeNest - Traverse the Scope tree depth-first, storing
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/// traversal state in WorkStack and recording the depth-first
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/// numbering (setDFSIn, setDFSOut) for edge classification.
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void LexicalScopes::constructScopeNest(LexicalScope *Scope) {
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assert(Scope && "Unable to calculate scope dominance graph!");
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SmallVector<std::pair<LexicalScope *, size_t>, 4> WorkStack;
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WorkStack.push_back(std::make_pair(Scope, 0));
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unsigned Counter = 0;
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while (!WorkStack.empty()) {
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auto &ScopePosition = WorkStack.back();
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LexicalScope *WS = ScopePosition.first;
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size_t ChildNum = ScopePosition.second++;
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const SmallVectorImpl<LexicalScope *> &Children = WS->getChildren();
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if (ChildNum < Children.size()) {
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auto &ChildScope = Children[ChildNum];
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WorkStack.push_back(std::make_pair(ChildScope, 0));
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ChildScope->setDFSIn(++Counter);
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} else {
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WorkStack.pop_back();
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WS->setDFSOut(++Counter);
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}
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}
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}
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/// assignInstructionRanges - Find ranges of instructions covered by each
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/// lexical scope.
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void LexicalScopes::assignInstructionRanges(
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SmallVectorImpl<InsnRange> &MIRanges,
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DenseMap<const MachineInstr *, LexicalScope *> &MI2ScopeMap) {
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LexicalScope *PrevLexicalScope = nullptr;
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for (const auto &R : MIRanges) {
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LexicalScope *S = MI2ScopeMap.lookup(R.first);
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assert(S && "Lost LexicalScope for a machine instruction!");
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if (PrevLexicalScope && !PrevLexicalScope->dominates(S))
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PrevLexicalScope->closeInsnRange(S);
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S->openInsnRange(R.first);
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S->extendInsnRange(R.second);
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PrevLexicalScope = S;
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}
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if (PrevLexicalScope)
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PrevLexicalScope->closeInsnRange();
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}
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/// getMachineBasicBlocks - Populate given set using machine basic blocks which
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/// have machine instructions that belong to lexical scope identified by
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/// DebugLoc.
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void LexicalScopes::getMachineBasicBlocks(
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const DILocation *DL, SmallPtrSetImpl<const MachineBasicBlock *> &MBBs) {
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assert(MF && "Method called on a uninitialized LexicalScopes object!");
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MBBs.clear();
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LexicalScope *Scope = getOrCreateLexicalScope(DL);
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if (!Scope)
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return;
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if (Scope == CurrentFnLexicalScope) {
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for (const auto &MBB : *MF)
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MBBs.insert(&MBB);
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return;
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}
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// The scope ranges can cover multiple basic blocks in each span. Iterate over
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// all blocks (in the order they are in the function) until we reach the one
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// containing the end of the span.
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SmallVectorImpl<InsnRange> &InsnRanges = Scope->getRanges();
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for (auto &R : InsnRanges)
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for (auto CurMBBIt = R.first->getParent()->getIterator(),
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EndBBIt = std::next(R.second->getParent()->getIterator());
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CurMBBIt != EndBBIt; CurMBBIt++)
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MBBs.insert(&*CurMBBIt);
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}
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bool LexicalScopes::dominates(const DILocation *DL, MachineBasicBlock *MBB) {
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assert(MF && "Unexpected uninitialized LexicalScopes object!");
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LexicalScope *Scope = getOrCreateLexicalScope(DL);
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if (!Scope)
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return false;
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// Current function scope covers all basic blocks in the function.
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if (Scope == CurrentFnLexicalScope && MBB->getParent() == MF)
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return true;
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// Fetch all the blocks in DLs scope. Because the range / block list also
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// contain any subscopes, any instruction that DL dominates can be found in
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// the block set.
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//
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// Cache the set of fetched blocks to avoid repeatedly recomputing the set in
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// the LiveDebugValues pass.
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std::unique_ptr<BlockSetT> &Set = DominatedBlocks[DL];
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if (!Set) {
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Set = std::make_unique<BlockSetT>();
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getMachineBasicBlocks(DL, *Set);
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}
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return Set->contains(MBB);
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}
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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LLVM_DUMP_METHOD void LexicalScope::dump(unsigned Indent) const {
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raw_ostream &err = dbgs();
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err.indent(Indent);
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err << "DFSIn: " << DFSIn << " DFSOut: " << DFSOut << "\n";
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const MDNode *N = Desc;
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err.indent(Indent);
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N->dump();
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if (AbstractScope)
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err << std::string(Indent, ' ') << "Abstract Scope\n";
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if (!Children.empty())
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err << std::string(Indent + 2, ' ') << "Children ...\n";
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for (unsigned i = 0, e = Children.size(); i != e; ++i)
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if (Children[i] != this)
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Children[i]->dump(Indent + 2);
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}
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#endif
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