[clang][bytecode] Diagnose invalid declrefs differently if we've... (#113140)

... tried their initializer already. In that case, diagnose the
non-const initializer instead of the reference to a non-constexpr
variable later. This is used in a lot of openmp tests.

Author: tbaederr

clang/lib/AST/ByteCode/Compiler.cpp

@@ -6097,7 +6097,8 @@ bool Compiler<Emitter>::visitDeclRef(const ValueDecl *D, const Expr *E) {
 
           if (VD->evaluateValue())
             return revisit(VD);
-          return this->emitInvalidDeclRef(cast<DeclRefExpr>(E), E);
+          return this->emitInvalidDeclRef(cast<DeclRefExpr>(E),
+                                          /*InitializerFailed=*/true, E);
         }
       }
     } else {
@@ -6123,7 +6124,7 @@ bool Compiler<Emitter>::visitDeclRef(const ValueDecl *D, const Expr *E) {
   }
 
   if (const auto *DRE = dyn_cast<DeclRefExpr>(E))
-    return this->emitInvalidDeclRef(DRE, E);
+    return this->emitInvalidDeclRef(DRE, /*InitializerFailed=*/false, E);
   return false;
 }
 

clang/lib/AST/ByteCode/Interp.h

@@ -2818,9 +2818,18 @@ inline bool InvalidCast(InterpState &S, CodePtr OpPC, CastKind Kind,
   return false;
 }
 
-inline bool InvalidDeclRef(InterpState &S, CodePtr OpPC,
-                           const DeclRefExpr *DR) {
+inline bool InvalidDeclRef(InterpState &S, CodePtr OpPC, const DeclRefExpr *DR,
+                           bool InitializerFailed) {
   assert(DR);
+
+  if (InitializerFailed) {
+    const SourceInfo &Loc = S.Current->getSource(OpPC);
+    const auto *VD = cast<VarDecl>(DR->getDecl());
+    S.FFDiag(Loc, diag::note_constexpr_var_init_non_constant, 1) << VD;
+    S.Note(VD->getLocation(), diag::note_declared_at);
+    return false;
+  }
+
   return CheckDeclRef(S, OpPC, DR);
 }
 

clang/lib/AST/ByteCode/Opcodes.td

@@ -769,7 +769,7 @@ def InvalidCast : Opcode {
 }
 
 def InvalidDeclRef : Opcode {
-  let Args = [ArgDeclRef];
+  let Args = [ArgDeclRef, ArgBool];
 }
 
 def SizelessVectorElementSize : Opcode;

clang/test/AST/ByteCode/openmp.cpp

@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -fexperimental-new-constant-interpreter -verify=expected,both -fopenmp %s
+// RUN: %clang_cc1 -verify=ref,both -fopenmp %s
+
+int test1() {
+  int i;
+  int &j = i; // both-note {{declared here}}
+  float *f;
+  // both-note@+2 {{initializer of 'j' is not a constant expression}}
+  // both-error@+1 {{integral constant expression}}
+  #pragma omp for simd aligned(f:j)
+  for (int i = 0; i < 10; ++i);
+}
+