maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/clang/lib/Analysis/LiveVariables.cpp

671 lines
20 KiB
C++
Raw Blame History

#include "clang/Analysis/Analyses/LiveVariables.h"
#include "clang/AST/Stmt.h"
#include "clang/Analysis/CFG.h"
#include "clang/Analysis/AnalysisContext.h"
#include "clang/AST/StmtVisitor.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/DenseMap.h"
#include <deque>
#include <algorithm>
#include <vector>
using namespace clang;
namespace {
// FIXME: This is copy-pasted from ThreadSafety.c. I wanted a patch that
// contained working code before refactoring the implementation of both
// files.
class CFGBlockSet {
llvm::BitVector VisitedBlockIDs;
public:
// po_iterator requires this iterator, but the only interface needed is the
// value_type typedef.
struct iterator {
typedef const CFGBlock *value_type;
};
CFGBlockSet() {}
CFGBlockSet(const CFG *G) : VisitedBlockIDs(G->getNumBlockIDs(), false) {}
/// \brief Set the bit associated with a particular CFGBlock.
/// This is the important method for the SetType template parameter.
bool insert(const CFGBlock *Block) {
// Note that insert() is called by po_iterator, which doesn't check to make
// sure that Block is non-null. Moreover, the CFGBlock iterator will
// occasionally hand out null pointers for pruned edges, so we catch those
// here.
if (Block == 0)
return false; // if an edge is trivially false.
if (VisitedBlockIDs.test(Block->getBlockID()))
return false;
VisitedBlockIDs.set(Block->getBlockID());
return true;
}
/// \brief Check if the bit for a CFGBlock has been already set.
/// This method is for tracking visited blocks in the main threadsafety loop.
/// Block must not be null.
bool alreadySet(const CFGBlock *Block) {
return VisitedBlockIDs.test(Block->getBlockID());
}
};
/// \brief We create a helper class which we use to iterate through CFGBlocks in
/// the topological order.
class TopologicallySortedCFG {
typedef llvm::po_iterator<const CFG*, CFGBlockSet, true> po_iterator;
std::vector<const CFGBlock*> Blocks;
typedef llvm::DenseMap<const CFGBlock *, unsigned> BlockOrderTy;
BlockOrderTy BlockOrder;
public:
typedef std::vector<const CFGBlock*>::reverse_iterator iterator;
TopologicallySortedCFG(const CFG *CFGraph) {
Blocks.reserve(CFGraph->getNumBlockIDs());
CFGBlockSet BSet(CFGraph);
for (po_iterator I = po_iterator::begin(CFGraph, BSet),
E = po_iterator::end(CFGraph, BSet); I != E; ++I) {
BlockOrder[*I] = Blocks.size() + 1;
Blocks.push_back(*I);
}
}
iterator begin() {
return Blocks.rbegin();
}
iterator end() {
return Blocks.rend();
}
bool empty() {
return begin() == end();
}
struct BlockOrderCompare;
friend struct BlockOrderCompare;
struct BlockOrderCompare {
const TopologicallySortedCFG &TSC;
public:
BlockOrderCompare(const TopologicallySortedCFG &tsc) : TSC(tsc) {}
bool operator()(const CFGBlock *b1, const CFGBlock *b2) const {
TopologicallySortedCFG::BlockOrderTy::const_iterator b1It = TSC.BlockOrder.find(b1);
TopologicallySortedCFG::BlockOrderTy::const_iterator b2It = TSC.BlockOrder.find(b2);
unsigned b1V = (b1It == TSC.BlockOrder.end()) ? 0 : b1It->second;
unsigned b2V = (b2It == TSC.BlockOrder.end()) ? 0 : b2It->second;
return b1V > b2V;
}
};
BlockOrderCompare getComparator() const {
return BlockOrderCompare(*this);
}
};
class DataflowWorklist {
SmallVector<const CFGBlock *, 20> worklist;
llvm::BitVector enqueuedBlocks;
TopologicallySortedCFG TSC;
public:
DataflowWorklist(const CFG &cfg)
: enqueuedBlocks(cfg.getNumBlockIDs()),
TSC(&cfg) {}
void enqueueBlock(const CFGBlock *block);
void enqueueSuccessors(const CFGBlock *block);
void enqueuePredecessors(const CFGBlock *block);
const CFGBlock *dequeue();
void sortWorklist();
};
}
void DataflowWorklist::enqueueBlock(const clang::CFGBlock *block) {
if (block && !enqueuedBlocks[block->getBlockID()]) {
enqueuedBlocks[block->getBlockID()] = true;
worklist.push_back(block);
}
}
void DataflowWorklist::enqueueSuccessors(const clang::CFGBlock *block) {
const unsigned OldWorklistSize = worklist.size();
for (CFGBlock::const_succ_iterator I = block->succ_begin(),
E = block->succ_end(); I != E; ++I) {
enqueueBlock(*I);
}
if (OldWorklistSize == 0 || OldWorklistSize == worklist.size())
return;
sortWorklist();
}
void DataflowWorklist::enqueuePredecessors(const clang::CFGBlock *block) {
const unsigned OldWorklistSize = worklist.size();
for (CFGBlock::const_pred_iterator I = block->pred_begin(),
E = block->pred_end(); I != E; ++I) {
enqueueBlock(*I);
}
if (OldWorklistSize == 0 || OldWorklistSize == worklist.size())
return;
sortWorklist();
}
void DataflowWorklist::sortWorklist() {
std::sort(worklist.begin(), worklist.end(), TSC.getComparator());
}
const CFGBlock *DataflowWorklist::dequeue() {
if (worklist.empty())
return 0;
const CFGBlock *b = worklist.back();
worklist.pop_back();
enqueuedBlocks[b->getBlockID()] = false;
return b;
}
namespace {
class LiveVariablesImpl {
public:
AnalysisContext &analysisContext;
std::vector<LiveVariables::LivenessValues> cfgBlockValues;
llvm::ImmutableSet<const Stmt *>::Factory SSetFact;
llvm::ImmutableSet<const VarDecl *>::Factory DSetFact;
llvm::DenseMap<const CFGBlock *, LiveVariables::LivenessValues> blocksEndToLiveness;
llvm::DenseMap<const CFGBlock *, LiveVariables::LivenessValues> blocksBeginToLiveness;
llvm::DenseMap<const Stmt *, LiveVariables::LivenessValues> stmtsToLiveness;
llvm::DenseMap<const DeclRefExpr *, unsigned> inAssignment;
const bool killAtAssign;
LiveVariables::LivenessValues
merge(LiveVariables::LivenessValues valsA,
LiveVariables::LivenessValues valsB);
LiveVariables::LivenessValues runOnBlock(const CFGBlock *block,
LiveVariables::LivenessValues val,
LiveVariables::Observer *obs = 0);
void dumpBlockLiveness(const SourceManager& M);
LiveVariablesImpl(AnalysisContext &ac, bool KillAtAssign)
: analysisContext(ac), killAtAssign(KillAtAssign) {}
};
}
static LiveVariablesImpl &getImpl(void *x) {
return *((LiveVariablesImpl *) x);
}
//===----------------------------------------------------------------------===//
// Operations and queries on LivenessValues.
//===----------------------------------------------------------------------===//
bool LiveVariables::LivenessValues::isLive(const Stmt *S) const {
return liveStmts.contains(S);
}
bool LiveVariables::LivenessValues::isLive(const VarDecl *D) const {
return liveDecls.contains(D);
}
namespace {
template <typename SET>
SET mergeSets(SET A, SET B) {
if (A.isEmpty())
return B;
for (typename SET::iterator it = B.begin(), ei = B.end(); it != ei; ++it) {
A = A.add(*it);
}
return A;
}
}
LiveVariables::LivenessValues
LiveVariablesImpl::merge(LiveVariables::LivenessValues valsA,
LiveVariables::LivenessValues valsB) {
llvm::ImmutableSetRef<const Stmt *>
SSetRefA(valsA.liveStmts.getRootWithoutRetain(), SSetFact.getTreeFactory()),
SSetRefB(valsB.liveStmts.getRootWithoutRetain(), SSetFact.getTreeFactory());
llvm::ImmutableSetRef<const VarDecl *>
DSetRefA(valsA.liveDecls.getRootWithoutRetain(), DSetFact.getTreeFactory()),
DSetRefB(valsB.liveDecls.getRootWithoutRetain(), DSetFact.getTreeFactory());
SSetRefA = mergeSets(SSetRefA, SSetRefB);
DSetRefA = mergeSets(DSetRefA, DSetRefB);
return LiveVariables::LivenessValues(SSetRefA.asImmutableSet(),
DSetRefA.asImmutableSet());
}
bool LiveVariables::LivenessValues::equals(const LivenessValues &V) const {
return liveStmts == V.liveStmts && liveDecls == V.liveDecls;
}
//===----------------------------------------------------------------------===//
// Query methods.
//===----------------------------------------------------------------------===//
static bool isAlwaysAlive(const VarDecl *D) {
return D->hasGlobalStorage();
}
bool LiveVariables::isLive(const CFGBlock *B, const VarDecl *D) {
return isAlwaysAlive(D) || getImpl(impl).blocksEndToLiveness[B].isLive(D);
}
bool LiveVariables::isLive(const Stmt *S, const VarDecl *D) {
return isAlwaysAlive(D) || getImpl(impl).stmtsToLiveness[S].isLive(D);
}
bool LiveVariables::isLive(const Stmt *Loc, const Stmt *S) {
return getImpl(impl).stmtsToLiveness[Loc].isLive(S);
}
//===----------------------------------------------------------------------===//
// Dataflow computation.
//===----------------------------------------------------------------------===//
namespace {
class TransferFunctions : public StmtVisitor<TransferFunctions> {
LiveVariablesImpl &LV;
LiveVariables::LivenessValues &val;
LiveVariables::Observer *observer;
const CFGBlock *currentBlock;
public:
TransferFunctions(LiveVariablesImpl &im,
LiveVariables::LivenessValues &Val,
LiveVariables::Observer *Observer,
const CFGBlock *CurrentBlock)
: LV(im), val(Val), observer(Observer), currentBlock(CurrentBlock) {}
void VisitBinaryOperator(BinaryOperator *BO);
void VisitBlockExpr(BlockExpr *BE);
void VisitDeclRefExpr(DeclRefExpr *DR);
void VisitDeclStmt(DeclStmt *DS);
void VisitObjCForCollectionStmt(ObjCForCollectionStmt *OS);
void VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *UE);
void VisitUnaryOperator(UnaryOperator *UO);
void Visit(Stmt *S);
};
}
static const VariableArrayType *FindVA(QualType Ty) {
const Type *ty = Ty.getTypePtr();
while (const ArrayType *VT = dyn_cast<ArrayType>(ty)) {
if (const VariableArrayType *VAT = dyn_cast<VariableArrayType>(VT))
if (VAT->getSizeExpr())
return VAT;
ty = VT->getElementType().getTypePtr();
}
return 0;
}
void TransferFunctions::Visit(Stmt *S) {
if (observer)
observer->observeStmt(S, currentBlock, val);
StmtVisitor<TransferFunctions>::Visit(S);
if (isa<Expr>(S)) {
val.liveStmts = LV.SSetFact.remove(val.liveStmts, S);
}
// Mark all children expressions live.
switch (S->getStmtClass()) {
default:
break;
case Stmt::StmtExprClass: {
// For statement expressions, look through the compound statement.
S = cast<StmtExpr>(S)->getSubStmt();
break;
}
case Stmt::CXXMemberCallExprClass: {
// Include the implicit "this" pointer as being live.
CXXMemberCallExpr *CE = cast<CXXMemberCallExpr>(S);
val.liveStmts =
LV.SSetFact.add(val.liveStmts,
CE->getImplicitObjectArgument()->IgnoreParens());
break;
}
case Stmt::DeclStmtClass: {
const DeclStmt *DS = cast<DeclStmt>(S);
if (const VarDecl *VD = dyn_cast<VarDecl>(DS->getSingleDecl())) {
for (const VariableArrayType* VA = FindVA(VD->getType());
VA != 0; VA = FindVA(VA->getElementType())) {
val.liveStmts = LV.SSetFact.add(val.liveStmts,
VA->getSizeExpr()->IgnoreParens());
}
}
break;
}
// FIXME: These cases eventually shouldn't be needed.
case Stmt::ExprWithCleanupsClass: {
S = cast<ExprWithCleanups>(S)->getSubExpr();
break;
}
case Stmt::CXXBindTemporaryExprClass: {
S = cast<CXXBindTemporaryExpr>(S)->getSubExpr();
break;
}
case Stmt::MaterializeTemporaryExprClass: {
S = cast<MaterializeTemporaryExpr>(S)->GetTemporaryExpr();
break;
}
case Stmt::UnaryExprOrTypeTraitExprClass: {
// No need to unconditionally visit subexpressions.
return;
}
}
for (Stmt::child_iterator it = S->child_begin(), ei = S->child_end();
it != ei; ++it) {
if (Stmt *child = *it) {
if (Expr *Ex = dyn_cast<Expr>(child))
child = Ex->IgnoreParens();
val.liveStmts = LV.SSetFact.add(val.liveStmts, child);
}
}
}
void TransferFunctions::VisitBinaryOperator(BinaryOperator *B) {
if (B->isAssignmentOp()) {
if (!LV.killAtAssign)
return;
// Assigning to a variable?
Expr *LHS = B->getLHS()->IgnoreParens();
if (DeclRefExpr *DR = dyn_cast<DeclRefExpr>(LHS))
if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
// Assignments to references don't kill the ref's address
if (VD->getType()->isReferenceType())
return;
if (!isAlwaysAlive(VD)) {
// The variable is now dead.
val.liveDecls = LV.DSetFact.remove(val.liveDecls, VD);
}
if (observer)
observer->observerKill(DR);
}
}
}
void TransferFunctions::VisitBlockExpr(BlockExpr *BE) {
AnalysisContext::referenced_decls_iterator I, E;
llvm::tie(I, E) =
LV.analysisContext.getReferencedBlockVars(BE->getBlockDecl());
for ( ; I != E ; ++I) {
const VarDecl *VD = *I;
if (isAlwaysAlive(VD))
continue;
val.liveDecls = LV.DSetFact.add(val.liveDecls, VD);
}
}
void TransferFunctions::VisitDeclRefExpr(DeclRefExpr *DR) {
if (const VarDecl *D = dyn_cast<VarDecl>(DR->getDecl()))
if (!isAlwaysAlive(D) && LV.inAssignment.find(DR) == LV.inAssignment.end())
val.liveDecls = LV.DSetFact.add(val.liveDecls, D);
}
void TransferFunctions::VisitDeclStmt(DeclStmt *DS) {
for (DeclStmt::decl_iterator DI=DS->decl_begin(), DE = DS->decl_end();
DI != DE; ++DI)
if (VarDecl *VD = dyn_cast<VarDecl>(*DI)) {
if (!isAlwaysAlive(VD))
val.liveDecls = LV.DSetFact.remove(val.liveDecls, VD);
}
}
void TransferFunctions::VisitObjCForCollectionStmt(ObjCForCollectionStmt *OS) {
// Kill the iteration variable.
DeclRefExpr *DR = 0;
const VarDecl *VD = 0;
Stmt *element = OS->getElement();
if (DeclStmt *DS = dyn_cast<DeclStmt>(element)) {
VD = cast<VarDecl>(DS->getSingleDecl());
}
else if ((DR = dyn_cast<DeclRefExpr>(cast<Expr>(element)->IgnoreParens()))) {
VD = cast<VarDecl>(DR->getDecl());
}
if (VD) {
val.liveDecls = LV.DSetFact.remove(val.liveDecls, VD);
if (observer && DR)
observer->observerKill(DR);
}
}
void TransferFunctions::
VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *UE)
{
// While sizeof(var) doesn't technically extend the liveness of 'var', it
// does extent the liveness of metadata if 'var' is a VariableArrayType.
// We handle that special case here.
if (UE->getKind() != UETT_SizeOf || UE->isArgumentType())
return;
const Expr *subEx = UE->getArgumentExpr();
if (subEx->getType()->isVariableArrayType()) {
assert(subEx->isLValue());
val.liveStmts = LV.SSetFact.add(val.liveStmts, subEx->IgnoreParens());
}
}
void TransferFunctions::VisitUnaryOperator(UnaryOperator *UO) {
// Treat ++/-- as a kill.
// Note we don't actually have to do anything if we don't have an observer,
// since a ++/-- acts as both a kill and a "use".
if (!observer)
return;
switch (UO->getOpcode()) {
default:
return;
case UO_PostInc:
case UO_PostDec:
case UO_PreInc:
case UO_PreDec:
break;
}
if (DeclRefExpr *DR = dyn_cast<DeclRefExpr>(UO->getSubExpr()->IgnoreParens()))
if (isa<VarDecl>(DR->getDecl())) {
// Treat ++/-- as a kill.
observer->observerKill(DR);
}
}
LiveVariables::LivenessValues
LiveVariablesImpl::runOnBlock(const CFGBlock *block,
LiveVariables::LivenessValues val,
LiveVariables::Observer *obs) {
TransferFunctions TF(*this, val, obs, block);
// Visit the terminator (if any).
if (const Stmt *term = block->getTerminator())
TF.Visit(const_cast<Stmt*>(term));
// Apply the transfer function for all Stmts in the block.
for (CFGBlock::const_reverse_iterator it = block->rbegin(),
ei = block->rend(); it != ei; ++it) {
const CFGElement &elem = *it;
if (!isa<CFGStmt>(elem))
continue;
const Stmt *S = cast<CFGStmt>(elem).getStmt();
TF.Visit(const_cast<Stmt*>(S));
stmtsToLiveness[S] = val;
}
return val;
}
void LiveVariables::runOnAllBlocks(LiveVariables::Observer &obs) {
const CFG *cfg = getImpl(impl).analysisContext.getCFG();
for (CFG::const_iterator it = cfg->begin(), ei = cfg->end(); it != ei; ++it)
getImpl(impl).runOnBlock(*it, getImpl(impl).blocksEndToLiveness[*it], &obs);
}
LiveVariables::LiveVariables(void *im) : impl(im) {}
LiveVariables::~LiveVariables() {
delete (LiveVariablesImpl*) impl;
}
LiveVariables *
LiveVariables::computeLiveness(AnalysisContext &AC,
bool killAtAssign) {
// No CFG? Bail out.
CFG *cfg = AC.getCFG();
if (!cfg)
return 0;
LiveVariablesImpl *LV = new LiveVariablesImpl(AC, killAtAssign);
// Construct the dataflow worklist. Enqueue the exit block as the
// start of the analysis.
DataflowWorklist worklist(*cfg);
llvm::BitVector everAnalyzedBlock(cfg->getNumBlockIDs());
// FIXME: we should enqueue using post order.
for (CFG::const_iterator it = cfg->begin(), ei = cfg->end(); it != ei; ++it) {
const CFGBlock *block = *it;
worklist.enqueueBlock(block);
// FIXME: Scan for DeclRefExprs using in the LHS of an assignment.
// We need to do this because we lack context in the reverse analysis
// to determine if a DeclRefExpr appears in such a context, and thus
// doesn't constitute a "use".
if (killAtAssign)
for (CFGBlock::const_iterator bi = block->begin(), be = block->end();
bi != be; ++bi) {
if (const CFGStmt *cs = bi->getAs<CFGStmt>()) {
if (const BinaryOperator *BO = dyn_cast<BinaryOperator>(cs->getStmt())) {
if (BO->getOpcode() == BO_Assign) {
if (const DeclRefExpr *DR =
dyn_cast<DeclRefExpr>(BO->getLHS()->IgnoreParens())) {
LV->inAssignment[DR] = 1;
}
}
}
}
}
}
worklist.sortWorklist();
while (const CFGBlock *block = worklist.dequeue()) {
// Determine if the block's end value has changed. If not, we
// have nothing left to do for this block.
LivenessValues &prevVal = LV->blocksEndToLiveness[block];
// Merge the values of all successor blocks.
LivenessValues val;
for (CFGBlock::const_succ_iterator it = block->succ_begin(),
ei = block->succ_end(); it != ei; ++it) {
if (const CFGBlock *succ = *it) {
val = LV->merge(val, LV->blocksBeginToLiveness[succ]);
}
}
if (!everAnalyzedBlock[block->getBlockID()])
everAnalyzedBlock[block->getBlockID()] = true;
else if (prevVal.equals(val))
continue;
prevVal = val;
// Update the dataflow value for the start of this block.
LV->blocksBeginToLiveness[block] = LV->runOnBlock(block, val);
// Enqueue the value to the predecessors.
worklist.enqueuePredecessors(block);
}
return new LiveVariables(LV);
}
static bool compare_entries(const CFGBlock *A, const CFGBlock *B) {
return A->getBlockID() < B->getBlockID();
}
static bool compare_vd_entries(const Decl *A, const Decl *B) {
SourceLocation ALoc = A->getLocStart();
SourceLocation BLoc = B->getLocStart();
return ALoc.getRawEncoding() < BLoc.getRawEncoding();
}
void LiveVariables::dumpBlockLiveness(const SourceManager &M) {
getImpl(impl).dumpBlockLiveness(M);
}
void LiveVariablesImpl::dumpBlockLiveness(const SourceManager &M) {
std::vector<const CFGBlock *> vec;
for (llvm::DenseMap<const CFGBlock *, LiveVariables::LivenessValues>::iterator
it = blocksEndToLiveness.begin(), ei = blocksEndToLiveness.end();
it != ei; ++it) {
vec.push_back(it->first);
}
std::sort(vec.begin(), vec.end(), compare_entries);
std::vector<const VarDecl*> declVec;
for (std::vector<const CFGBlock *>::iterator
it = vec.begin(), ei = vec.end(); it != ei; ++it) {
llvm::errs() << "\n[ B" << (*it)->getBlockID()
<< " (live variables at block exit) ]\n";
LiveVariables::LivenessValues vals = blocksEndToLiveness[*it];
declVec.clear();
for (llvm::ImmutableSet<const VarDecl *>::iterator si =
vals.liveDecls.begin(),
se = vals.liveDecls.end(); si != se; ++si) {
declVec.push_back(*si);
}
std::sort(declVec.begin(), declVec.end(), compare_vd_entries);
for (std::vector<const VarDecl*>::iterator di = declVec.begin(),
de = declVec.end(); di != de; ++di) {
llvm::errs() << " " << (*di)->getDeclName().getAsString()
<< " <";
(*di)->getLocation().dump(M);
llvm::errs() << ">\n";
}
}
llvm::errs() << "\n";
}
Reference in New Issue View Git Blame Copy Permalink