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//=- LiveVariables.cpp - Live Variable Analysis for Source CFGs -*- C++ --*-==//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by Ted Kremenek and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for
// details.
//
//===----------------------------------------------------------------------===//
//
// This file implements Live Variables analysis for source-level CFGs.
//
//===----------------------------------------------------------------------===//
#include "clang/Analysis/LiveVariables.h"
#include "clang/Basic/SourceManager.h"
#include "clang/AST/Expr.h"
#include "clang/AST/CFG.h"
#include "clang/Analysis/Visitors/CFGRecStmtDeclVisitor.h"
#include "clang/Analysis/FlowSensitive/DataflowSolver.h"
#include "llvm/ADT/SmallPtrSet.h"
#include <string.h>
#include <stdio.h>
using namespace clang;
//===----------------------------------------------------------------------===//
// Dataflow initialization logic.
//===----------------------------------------------------------------------===//
namespace {
class RegisterDecls : public CFGRecStmtDeclVisitor<RegisterDecls> {
LiveVariables::AnalysisDataTy& AD;
public:
RegisterDecls(LiveVariables::AnalysisDataTy& ad) : AD(ad) {}
void VisitVarDecl(VarDecl* VD) { AD.Register(VD); }
CFG& getCFG() { return AD.getCFG(); }
};
} // end anonymous namespace
void LiveVariables::InitializeValues(const CFG& cfg) {
RegisterDecls R(getAnalysisData());
cfg.VisitBlockStmts(R);
}
//===----------------------------------------------------------------------===//
// Transfer functions.
//===----------------------------------------------------------------------===//
namespace {
static const bool Alive = true;
static const bool Dead = false;
class TransferFuncs : public CFGRecStmtVisitor<TransferFuncs> {
LiveVariables::AnalysisDataTy& AD;
LiveVariables::ValTy LiveState;
public:
TransferFuncs(LiveVariables::AnalysisDataTy& ad) : AD(ad) {}
LiveVariables::ValTy& getVal() { return LiveState; }
CFG& getCFG() { return AD.getCFG(); }
void VisitDeclRefExpr(DeclRefExpr* DR);
void VisitBinaryOperator(BinaryOperator* B);
void VisitAssign(BinaryOperator* B);
void VisitDeclStmt(DeclStmt* DS);
void VisitUnaryOperator(UnaryOperator* U);
void Visit(Stmt *S);
DeclRefExpr* FindDeclRef(Stmt *S);
};
void TransferFuncs::Visit(Stmt *S) {
if (AD.Observer)
AD.Observer->ObserveStmt(S,AD,LiveState);
static_cast<CFGStmtVisitor<TransferFuncs>*>(this)->Visit(S);
}
void TransferFuncs::VisitDeclRefExpr(DeclRefExpr* DR) {
if (VarDecl* V = dyn_cast<VarDecl>(DR->getDecl()))
LiveState(V,AD) = Alive;
}
void TransferFuncs::VisitBinaryOperator(BinaryOperator* B) {
if (B->isAssignmentOp()) VisitAssign(B);
else VisitStmt(B);
}
void TransferFuncs::VisitUnaryOperator(UnaryOperator* U) {
Stmt *S = U->getSubExpr();
switch (U->getOpcode()) {
case UnaryOperator::PostInc:
case UnaryOperator::PostDec:
case UnaryOperator::PreInc:
case UnaryOperator::PreDec:
case UnaryOperator::AddrOf:
// Walk through the subexpressions, blasting through ParenExprs
// until we either find a DeclRefExpr or some non-DeclRefExpr
// expression.
if (DeclRefExpr* DR = FindDeclRef(S)) {
// Treat the --/++/& operator as a kill.
LiveState(DR->getDecl(),AD) = Dead;
if (AD.Observer) { AD.Observer->ObserverKill(DR); }
return VisitDeclRefExpr(DR);
}
// Fall-through.
default:
return Visit(S);
}
}
DeclRefExpr* TransferFuncs::FindDeclRef(Stmt *S) {
for (;;)
if (ParenExpr* P = dyn_cast<ParenExpr>(S)) {
S = P->getSubExpr(); continue;
}
else if (DeclRefExpr* DR = dyn_cast<DeclRefExpr>(S))
return DR;
else
return NULL;
}
void TransferFuncs::VisitAssign(BinaryOperator* B) {
Stmt* LHS = B->getLHS();
// Assigning to a variable?
if (DeclRefExpr* DR = FindDeclRef(LHS)) {
LiveState(DR->getDecl(),AD) = Dead;
if (AD.Observer) { AD.Observer->ObserverKill(DR); }
// Handle things like +=, etc., which also generate "uses"
// of a variable. Do this just by visiting the subexpression.
if (B->getOpcode() != BinaryOperator::Assign)
VisitDeclRefExpr(DR);
}
else // Not assigning to a variable. Process LHS as usual.
Visit(LHS);
Visit(B->getRHS());
}
void TransferFuncs::VisitDeclStmt(DeclStmt* DS) {
// Declarations effectively "kill" a variable since they cannot
// possibly be live before they are declared.
for (ScopedDecl* D = DS->getDecl(); D != NULL; D = D->getNextDeclarator())
LiveState(D,AD) = Dead;
}
} // end anonymous namespace
//===----------------------------------------------------------------------===//
// Merge operator: if something is live on any successor block, it is live
// in the current block (a set union).
//===----------------------------------------------------------------------===//
namespace {
typedef DeclBitVector_Types::Union Merge;
typedef DataflowSolver<LiveVariables,TransferFuncs,Merge> Solver;
} // end anonymous namespace
//===----------------------------------------------------------------------===//
// External interface to run Liveness analysis.
//===----------------------------------------------------------------------===//
void LiveVariables::runOnCFG(const CFG& cfg) {
Solver S(*this);
S.runOnCFG(cfg);
}
void LiveVariables::runOnAllBlocks(const CFG& cfg,
LiveVariables::ObserverTy& Obs) {
Solver S(*this);
ObserverTy* OldObserver = getAnalysisData().Observer;
getAnalysisData().Observer = &Obs;
S.runOnAllBlocks(cfg);
getAnalysisData().Observer = OldObserver;
}
//===----------------------------------------------------------------------===//
// liveness queries
//
bool LiveVariables::isLive(const CFGBlock* B, const VarDecl* D) const {
return getBlockData(B)(D,getAnalysisData());
}
bool LiveVariables::isLive(const ValTy& Live, const VarDecl* D) const {
return Live(D,getAnalysisData());
}
//===----------------------------------------------------------------------===//
// printing liveness state for debugging
//
void LiveVariables::dumpLiveness(const ValTy& V, SourceManager& SM) const {
const AnalysisDataTy& AD = getAnalysisData();
for (AnalysisDataTy::decl_iterator I = AD.begin_decl(),
E = AD.end_decl(); I!=E; ++I)
if (V.getDeclBit(I->second)) {
SourceLocation PhysLoc = SM.getPhysicalLoc(I->first->getLocation());
fprintf(stderr, " %s <%s:%u:%u>\n",
I->first->getIdentifier()->getName(),
SM.getSourceName(PhysLoc),
SM.getLineNumber(PhysLoc),
SM.getColumnNumber(PhysLoc));
}
}
void LiveVariables::dumpBlockLiveness(SourceManager& M) const {
for (BlockDataMapTy::iterator I = getBlockDataMap().begin(),
E = getBlockDataMap().end(); I!=E; ++I) {
fprintf(stderr, "\n[ B%d (live variables at block exit) ]\n",
I->first->getBlockID());
dumpLiveness(I->second,M);
}
fprintf(stderr,"\n");
}