PR40642: Fix determination of whether the final statement of a statement
expression is a discarded-value expression.
Summary:
We used to get this wrong in three ways:
1) During parsing, an expression-statement followed by the }) ending a
statement expression was always treated as producing the value of the
statement expression. That's wrong for ({ if (1) expr; })
2) During template instantiation, various kinds of statement (most
statements not appearing directly in a compound-statement) were not
treated as discarded-value expressions, resulting in missing volatile
loads (etc).
3) In all contexts, an expression-statement with attributes was not
treated as producing the value of the statement expression, eg
({ [[attr]] expr; }).
Also fix incorrect enforcement of OpenMP rule that directives can "only
be placed in the program at a position where ignoring or deleting the
directive would result in a program with correct syntax". In particular,
a label (be it goto, case, or default) should not affect whether
directives are permitted.
Reviewers: aaron.ballman, rjmccall
Subscribers: cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D57984
llvm-svn: 354090
diff --git a/clang/lib/CodeGen/CGStmt.cpp b/clang/lib/CodeGen/CGStmt.cpp
index db3f4f1..5b5113b 100644
--- a/clang/lib/CodeGen/CGStmt.cpp
+++ b/clang/lib/CodeGen/CGStmt.cpp
@@ -391,26 +391,35 @@
// at the end of a statement expression, they yield the value of their
// subexpression. Handle this by walking through all labels we encounter,
// emitting them before we evaluate the subexpr.
+ // Similar issues arise for attributed statements.
const Stmt *LastStmt = S.body_back();
- while (const LabelStmt *LS = dyn_cast<LabelStmt>(LastStmt)) {
- EmitLabel(LS->getDecl());
- LastStmt = LS->getSubStmt();
+ while (!isa<Expr>(LastStmt)) {
+ if (const auto *LS = dyn_cast<LabelStmt>(LastStmt)) {
+ EmitLabel(LS->getDecl());
+ LastStmt = LS->getSubStmt();
+ } else if (const auto *AS = dyn_cast<AttributedStmt>(LastStmt)) {
+ // FIXME: Update this if we ever have attributes that affect the
+ // semantics of an expression.
+ LastStmt = AS->getSubStmt();
+ } else {
+ llvm_unreachable("unknown value statement");
+ }
}
EnsureInsertPoint();
- QualType ExprTy = cast<Expr>(LastStmt)->getType();
+ const Expr *E = cast<Expr>(LastStmt);
+ QualType ExprTy = E->getType();
if (hasAggregateEvaluationKind(ExprTy)) {
- EmitAggExpr(cast<Expr>(LastStmt), AggSlot);
+ EmitAggExpr(E, AggSlot);
} else {
// We can't return an RValue here because there might be cleanups at
// the end of the StmtExpr. Because of that, we have to emit the result
// here into a temporary alloca.
RetAlloca = CreateMemTemp(ExprTy);
- EmitAnyExprToMem(cast<Expr>(LastStmt), RetAlloca, Qualifiers(),
- /*IsInit*/false);
+ EmitAnyExprToMem(E, RetAlloca, Qualifiers(),
+ /*IsInit*/ false);
}
-
}
return RetAlloca;