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//==- DeadStores.cpp - Check for stores to dead variables --------*- C++ -*-==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines a DeadStores, a flow-sensitive checker that looks for
// stores to variables that are no longer live.
//
//===----------------------------------------------------------------------===//
#include "clang/Analysis/LocalCheckers.h"
#include "clang/Analysis/Analyses/LiveVariables.h"
#include "clang/Analysis/Visitors/CFGRecStmtVisitor.h"
#include "clang/Basic/Diagnostic.h"
#include "clang/AST/ASTContext.h"
#include "llvm/Support/Compiler.h"
using namespace clang;
namespace {
class VISIBILITY_HIDDEN DeadStoreObs : public LiveVariables::ObserverTy {
ASTContext &Ctx;
Diagnostic &Diags;
public:
DeadStoreObs(ASTContext &ctx,Diagnostic &diags) : Ctx(ctx), Diags(diags){}
virtual ~DeadStoreObs() {}
virtual void ObserveStmt(Stmt* S,
const LiveVariables::AnalysisDataTy& AD,
const LiveVariables::ValTy& Live) {
if (BinaryOperator* B = dyn_cast<BinaryOperator>(S)) {
if (!B->isAssignmentOp()) return; // Skip non-assignments.
if (DeclRefExpr* DR = dyn_cast<DeclRefExpr>(B->getLHS()))
if (VarDecl* VD = dyn_cast<VarDecl>(DR->getDecl()))
if (VD->hasLocalStorage() && !Live(VD,AD)) {
SourceRange R = B->getRHS()->getSourceRange();
Diags.Report(Ctx.getFullLoc(DR->getSourceRange().getBegin()),
diag::warn_dead_store, 0, 0, &R, 1);
}
}
else if(DeclStmt* DS = dyn_cast<DeclStmt>(S))
// Iterate through the decls. Warn if any initializers are complex
// expressions that are not live (never used).
for (VarDecl* V = cast<VarDecl>(DS->getDecl()); V != NULL ;
V = cast_or_null<VarDecl>(V->getNextDeclarator())) {
if (V->hasLocalStorage())
if (Expr* E = V->getInit()) {
if (!Live(DS->getDecl(),AD)) {
// Special case: check for initializations with constants.
//
// e.g. : int x = 0;
//
// If x is EVER assigned a new value later, don't issue
// a warning. This is because such initialization can be
// due to defensive programming.
if (!E->isConstantExpr(Ctx,NULL)) {
// Flag a warning.
SourceRange R = E->getSourceRange();
Diags.Report(Ctx.getFullLoc(V->getLocation()),
diag::warn_dead_store, 0, 0, &R, 1);
}
}
}
}
}
};
} // end anonymous namespace
namespace clang {
void CheckDeadStores(CFG& cfg, ASTContext &Ctx, Diagnostic &Diags) {
LiveVariables L(cfg);
L.runOnCFG(cfg);
DeadStoreObs A(Ctx, Diags);
L.runOnAllBlocks(cfg, &A);
}
} // end namespace clang
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