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