[clang][Interp] Skip unnamed bit fields in initializers

Fixes the Codegen/CSKY/csky-hard-abi.c test

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -971,6 +971,11 @@ bool ByteCodeExprGen<Emitter>::visitInitList(ArrayRef<const Expr *> Inits,
 
   unsigned InitIndex = 0;
   for (const Expr *Init : Inits) {
+    // Skip unnamed bitfields.
+    while (InitIndex < R->getNumFields() &&
+           R->getField(InitIndex)->Decl->isUnnamedBitField())
+      ++InitIndex;
+
     if (!this->emitDupPtr(E))
       return false;
 

clang/lib/AST/Interp/Program.cpp

@@ -312,6 +312,11 @@ Record *Program::getOrCreateRecord(const RecordDecl *RD) {
   // Reserve space for fields.
   Record::FieldList Fields;
   for (const FieldDecl *FD : RD->fields()) {
+    // Note that we DO create fields and descriptors
+    // for unnamed bitfields here, even though we later ignore
+    // them everywhere. That's because so the FieldDecl's
+    // getFieldIndex() matches.
+
     // Reserve space for the field's descriptor and the offset.
     BaseSize += align(sizeof(InlineDescriptor));
 

clang/test/AST/Interp/records.cpp

@@ -1317,3 +1317,16 @@ namespace {
   F f;
   static_assert(f.Z == 12, "");
 }
+
+namespace UnnamedBitFields {
+  struct A {
+    int : 1;
+    double f;
+    int : 1;
+    char c;
+  };
+
+  constexpr A a = (A){1.0, 'a'};
+  static_assert(a.f == 1.0, "");
+  static_assert(a.c == 'a', "");
+}