Dead stores checker: Fix <rdar://problem/6506065> by being more selective when say that a store is dead even though the computed value is used in the enclosing expression.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@62552 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/CheckDeadStores.cpp b/lib/Analysis/CheckDeadStores.cpp
index cad19f4..4f51cd8 100644
--- a/lib/Analysis/CheckDeadStores.cpp
+++ b/lib/Analysis/CheckDeadStores.cpp
@@ -39,6 +39,9 @@
virtual ~DeadStoreObs() {}
+ bool isConsumedExpr(Expr* E) const;
+
+
void Report(VarDecl* V, DeadStoreKind dsk, SourceLocation L, SourceRange R) {
std::string name = V->getNameAsString();
@@ -145,10 +148,9 @@
return;
// Otherwise, issue a warning.
- DeadStoreKind dsk =
- Parents.isSubExpr(B)
- ? Enclosing
- : (isIncrement(VD,B) ? DeadIncrement : Standard);
+ DeadStoreKind dsk = isConsumedExpr(B)
+ ? Enclosing
+ : (isIncrement(VD,B) ? DeadIncrement : Standard);
CheckVarDecl(VD, DR, B->getRHS(), dsk, AD, Live);
}
@@ -161,7 +163,7 @@
// about preincrements to dead variables when the preincrement occurs
// as a subexpression. This can lead to false negatives, e.g. "(++x);"
// A generalized dead code checker should find such issues.
- if (U->isPrefix() && Parents.isSubExpr(U))
+ if (U->isPrefix() && isConsumedExpr(U))
return;
Expr *Ex = U->getSubExpr()->IgnoreParenCasts();
@@ -203,6 +205,43 @@
} // end anonymous namespace
+bool DeadStoreObs::isConsumedExpr(Expr* E) const {
+ Stmt *P = Parents.getParent(E);
+ Stmt *DirectChild = E;
+
+ // Ignore parents that are parentheses or casts.
+ while (P && (isa<ParenExpr>(E) || isa<CastExpr>(E))) {
+ DirectChild = P;
+ P = Parents.getParent(P);
+ }
+
+ if (!P)
+ return false;
+
+ switch (P->getStmtClass()) {
+ default:
+ return isa<Expr>(P);
+ case Stmt::BinaryOperatorClass: {
+ BinaryOperator *BE = cast<BinaryOperator>(P);
+ return BE->getOpcode()==BinaryOperator::Comma && DirectChild==BE->getLHS();
+ }
+ case Stmt::ForStmtClass:
+ return DirectChild == cast<ForStmt>(P)->getCond();
+ case Stmt::WhileStmtClass:
+ return DirectChild == cast<WhileStmt>(P)->getCond();
+ case Stmt::DoStmtClass:
+ return DirectChild == cast<DoStmt>(P)->getCond();
+ case Stmt::IfStmtClass:
+ return DirectChild == cast<IfStmt>(P)->getCond();
+ case Stmt::IndirectGotoStmtClass:
+ return DirectChild == cast<IndirectGotoStmt>(P)->getTarget();
+ case Stmt::SwitchStmtClass:
+ return DirectChild == cast<SwitchStmt>(P)->getCond();
+ case Stmt::ReturnStmtClass:
+ return true;
+ }
+}
+
//===----------------------------------------------------------------------===//
// Driver function to invoke the Dead-Stores checker on a CFG.
//===----------------------------------------------------------------------===//