[clang][Interp] Only lazily visit constant globals

Differential Revision: https://reviews.llvm.org/D158516

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -2536,7 +2536,8 @@ bool ByteCodeExprGen<Emitter>::VisitDeclRefExpr(const DeclRefExpr *E) {
   // This happens in C.
   if (!Ctx.getLangOpts().CPlusPlus) {
     if (const auto *VD = dyn_cast<VarDecl>(D);
-        VD && VD->hasGlobalStorage() && VD->getAnyInitializer()) {
+        VD && VD->hasGlobalStorage() && VD->getAnyInitializer() &&
+        VD->getType().isConstQualified()) {
       if (!this->visitVarDecl(VD))
         return false;
       // Retry.

clang/test/AST/Interp/c.c

@@ -14,11 +14,15 @@ _Static_assert(!!1.0, ""); // pedantic-ref-warning {{not an integer constant exp
                            // pedantic-expected-warning {{not an integer constant expression}}
 _Static_assert(!!1, "");
 
-/// FIXME: Should also be rejected in the new interpreter
-int a = (1 == 1 ? 5 : 3);
+int a = (1 == 1 ? 5 : 3); // expected-note {{declared here}} \
+                          // pedantic-expected-note {{declared here}}
 _Static_assert(a == 5, ""); // ref-error {{not an integral constant expression}} \
                             // pedantic-ref-error {{not an integral constant expression}} \
-                            // pedantic-expected-warning {{not an integer constant expression}}
+                            // expected-error {{not an integral constant expression}} \
+                            // expected-note {{read of non-const variable}} \
+                            // pedantic-expected-error {{not an integral constant expression}} \
+                            // pedantic-expected-note {{read of non-const variable}}
+
 
 const int b = 3;
 _Static_assert(b == 3, ""); // pedantic-ref-warning {{not an integer constant expression}} \