1 files changed, 607 insertions, 0 deletions
diff --git a/clang/lib/Analysis/LiveVariables.cpp b/clang/lib/Analysis/LiveVariables.cpp
new file mode 100644
index 0000000..ff6607d
--- /dev/null
+++ b/clang/lib/Analysis/LiveVariables.cpp
@@ -0,0 +1,607 @@
+#include "clang/Analysis/Analyses/LiveVariables.h"
+#include "clang/Analysis/Analyses/PostOrderCFGView.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 {
+
+class DataflowWorklist {
+  SmallVector<const CFGBlock *, 20> worklist;
+  llvm::BitVector enqueuedBlocks;
+  PostOrderCFGView *POV;
+public:
+  DataflowWorklist(const CFG &cfg, AnalysisDeclContext &Ctx)
+    : enqueuedBlocks(cfg.getNumBlockIDs()),
+      POV(Ctx.getAnalysis<PostOrderCFGView>()) {}
+  
+  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(), POV->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:  
+  AnalysisDeclContext &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(AnalysisDeclContext &ac, bool KillAtAssign)
+    : analysisContext(ac),
+      SSetFact(false), // Do not canonicalize ImmutableSets by default.
+      DSetFact(false), // This is a *major* performance win.
+      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;
+  }
+}
+
+void LiveVariables::Observer::anchor() { }
+
+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);
+  
+  // asImmutableSet() canonicalizes the tree, allowing us to do an easy
+  // comparison afterwards.
+  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;
+}
+
+static const Stmt *LookThroughStmt(const Stmt *S) {
+  while (S) {
+    if (const Expr *Ex = dyn_cast<Expr>(S))
+      S = Ex->IgnoreParens();    
+    if (const ExprWithCleanups *EWC = dyn_cast<ExprWithCleanups>(S)) {
+      S = EWC->getSubExpr();
+      continue;
+    }
+    if (const OpaqueValueExpr *OVE = dyn_cast<OpaqueValueExpr>(S)) {
+      S = OVE->getSourceExpr();
+      continue;
+    }
+    break;
+  }
+  return S;
+}
+
+static void AddLiveStmt(llvm::ImmutableSet<const Stmt *> &Set,
+                        llvm::ImmutableSet<const Stmt *>::Factory &F,
+                        const Stmt *S) {
+  Set = F.add(Set, LookThroughStmt(S));
+}
+
+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);
+      if (Expr *ImplicitObj = CE->getImplicitObjectArgument()) {
+        AddLiveStmt(val.liveStmts, LV.SSetFact, ImplicitObj);
+      }
+      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())) {
+          AddLiveStmt(val.liveStmts, LV.SSetFact, VA->getSizeExpr());
+        }
+      }
+      break;
+    }
+    case Stmt::PseudoObjectExprClass: {
+      // A pseudo-object operation only directly consumes its result
+      // expression.
+      Expr *child = cast<PseudoObjectExpr>(S)->getResultExpr();
+      if (!child) return;
+      if (OpaqueValueExpr *OV = dyn_cast<OpaqueValueExpr>(child))
+        child = OV->getSourceExpr();
+      child = child->IgnoreParens();
+      val.liveStmts = LV.SSetFact.add(val.liveStmts, child);
+      return;
+    }
+
+    // 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::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)
+      AddLiveStmt(val.liveStmts, LV.SSetFact, 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) {
+  AnalysisDeclContext::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(AnalysisDeclContext &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, AC);
+  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";  
+}
+
+const void *LiveVariables::getTag() { static int x; return &x; }
+const void *RelaxedLiveVariables::getTag() { static int x; return &x; }