[IRGen] Evaluate constant static variables referenced through member

expressions

C++ allows us to reference static variables through member expressions. Prior to
this commit, non-integer static variables that were referenced using a member
expression were always emitted using lvalue loads. The old behaviour introduced
an inconsistency between regular uses of static variables and member expressions
uses. For example, the following program compiled and linked successfully:

struct Foo {
   constexpr static const char *name = "foo";
};
int main() {
  return Foo::name[0] == 'f';
}

but this program failed to link because "Foo::name" wasn't found:

struct Foo {
   constexpr static const char *name = "foo";
};
int main() {
  Foo f;
  return f.name[0] == 'f';
}

This commit ensures that constant static variables referenced through member
expressions are emitted in the same way as ordinary static variable references.

rdar://33942261

Differential Revision: https://reviews.llvm.org/D36876

llvm-svn: 311772

1 files changed, 1 insertions, 18 deletions

diff --git a/clang/lib/CodeGen/CGExprAgg.cpp b/clang/lib/CodeGen/CGExprAgg.cpp
index a05a088f091..1ab8433864c 100644
--- a/clang/lib/CodeGen/CGExprAgg.cpp
+++ b/clang/lib/CodeGen/CGExprAgg.cpp
@@ -124,24 +124,7 @@ public:
   }
 
   // l-values.
-  void VisitDeclRefExpr(DeclRefExpr *E) {
-    // For aggregates, we should always be able to emit the variable
-    // as an l-value unless it's a reference.  This is due to the fact
-    // that we can't actually ever see a normal l2r conversion on an
-    // aggregate in C++, and in C there's no language standard
-    // actively preventing us from listing variables in the captures
-    // list of a block.
-    if (E->getDecl()->getType()->isReferenceType()) {
-      if (CodeGenFunction::ConstantEmission result
-            = CGF.tryEmitAsConstant(E)) {
-        EmitFinalDestCopy(E->getType(), result.getReferenceLValue(CGF, E));
-        return;
-      }
-    }
-
-    EmitAggLoadOfLValue(E);
-  }
-
+  void VisitDeclRefExpr(DeclRefExpr *E) { EmitAggLoadOfLValue(E); }
   void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
   void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
   void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }