ir_visibility cleanup

This commit removes the strange differentiation between
ir_visibility_external and ir_visibility_default. We now only have
ir_visibility_external for all symbols visible across compilation units.
You may or may not attach graphs/initializers to them.

include/libfirm/typerep.h

@@ -91,10 +91,12 @@
  */
 typedef enum {
 	/**
-	 * The entity is visible outside the compilation unit, but it is defined
-	 * here.
+	 * The entity is visible across compilation units. It might have an
+	 * initializer/graph.
+	 * Note that variables with visibility_external but not initializer are
+	 * not "uninitialized" but considered to be in another compilation unit.
 	 */
-	ir_visibility_default,
+	ir_visibility_external,
 	/**
 	 * The entity is local to the compilation unit.
 	 * A local entity is not visible in other compilation units.
@@ -103,18 +105,13 @@ typedef enum {
 	 */
 	ir_visibility_local,
 	/**
-	 * The entity is defined outside the compilation unit but potentially used
-	 * here.
-	 */
-	ir_visibility_external,
-	/**
-	 * This has the same semantic as visibility_local. Additionally the symbol is
-	 * completely hidden from the linker (it only appears in the assembly).
+	 * This has the same semantic as visibility_local. Additionally the symbol
+	 * is completely hidden from the linker (it only appears in the assembly).
 	 * While visibility_local is probably still visible to debuggers,
 	 * visibility_private symbols aren't and probably won't appear in the object
 	 * files
 	 */
-	ir_visibility_private
+	ir_visibility_private,
 } ir_visibility;
 
 /**

ir/be/bedwarf.c

@@ -356,8 +356,7 @@ void be_dwarf_callframe_spilloffset(const arch_register_t *reg, int offset)
 static bool is_extern_entity(const ir_entity *entity)
 {
 	ir_visited_t visibility = get_entity_visibility(entity);
-	return visibility == ir_visibility_default
-	    || visibility == ir_visibility_external;
+	return visibility == ir_visibility_external;
 }
 
 static void emit_entity_label(const ir_entity *entity)

ir/be/begnuas.c

@@ -421,15 +421,8 @@ static int entity_is_string_const(const ir_entity *ent)
 
 static bool entity_is_null(const ir_entity *entity)
 {
-	if (entity->initializer != NULL) {
-		return initializer_is_null(entity->initializer);
-	} else if (entity_has_compound_ent_values(entity)) {
-		/* I'm too lazy to implement this case as compound graph paths will be
-		 * remove anyway in the future */
-		return false;
-	}
-	/* uninitialized, NULL is fine */
-	return true;
+	ir_initializer_t *initializer = get_entity_initializer(entity);
+	return initializer == NULL || initializer_is_null(initializer);
 }
 
 static bool is_comdat(const ir_entity *entity)
@@ -450,7 +443,7 @@ static be_gas_section_t determine_basic_section(const ir_entity *entity)
 	if (linkage & IR_LINKAGE_CONSTANT) {
 		/* mach-o is the only one with a cstring section */
 		if (be_gas_object_file_format == OBJECT_FILE_FORMAT_MACH_O
-				&& entity_is_string_const(entity))
+		    && entity_is_string_const(entity))
 			return GAS_SECTION_CSTRING;
 
 		return GAS_SECTION_RODATA;
@@ -514,7 +507,8 @@ static void emit_visibility(const ir_entity *entity)
 	if (get_entity_linkage(entity) & IR_LINKAGE_WEAK) {
 		emit_weak(entity);
 		/* Note: .weak seems to imply .globl so no need to output .globl */
-	} else if (get_entity_visibility(entity) == ir_visibility_default) {
+	} else if (get_entity_visibility(entity) == ir_visibility_external
+	           && entity_has_definition(entity)) {
 		be_emit_cstring("\t.globl ");
 		be_gas_emit_entity(entity);
 		be_emit_char('\n');
@@ -1612,24 +1606,19 @@ static void emit_global(be_gas_decl_env_t *env, const ir_entity *entity)
 		case ir_visibility_private:
 			emit_local_common(entity);
 			return;
-		case ir_visibility_default:
+		case ir_visibility_external:
 			if (linkage & IR_LINKAGE_MERGE) {
 				emit_common(entity);
 				return;
 			}
 			break;
-		case ir_visibility_external:
-			if (linkage & IR_LINKAGE_MERGE)
-				panic("merge link semantic not supported for extern entities");
-			break;
 		}
 	}
 
 	emit_visibility(entity);
-	if (visibility == ir_visibility_external) {
-		/* nothing to do for externally defined values */
+	/* nothing left to do without an initializer */
+	if (!entity_has_definition(entity))
 		return;
-	}
 
 	if (!is_po2(alignment))
 		panic("alignment not a power of 2");
@@ -1665,6 +1654,7 @@ static void emit_global(be_gas_decl_env_t *env, const ir_entity *entity)
 	}
 
 	if (entity_is_null(entity)) {
+		/* we should use .space for stuff in the bss segment */
 		unsigned size = get_type_size_bytes(type);
 		if (size > 0) {
 			be_emit_irprintf("\t.space %u, 0\n", get_type_size_bytes(type));

ir/be/ia32/ia32_emitter.c

@@ -223,7 +223,7 @@ static void ia32_emit_entity(ir_entity *entity, int no_pic_adjust)
 	be_gas_emit_entity(entity);
 
 	if (get_entity_owner(entity) == get_tls_type()) {
-		if (get_entity_visibility(entity) == ir_visibility_external) {
+		if (!entity_has_definition(entity)) {
 			be_emit_cstring("@INDNTPOFF");
 		} else {
 			be_emit_cstring("@NTPOFF");

ir/ir/irio.c

@@ -226,7 +226,6 @@ static void symtbl_init(void)
 
 	INSERT(tt_visibility, "local", ir_visibility_local);
 	INSERT(tt_visibility, "external", ir_visibility_external);
-	INSERT(tt_visibility, "default", ir_visibility_default);
 	INSERT(tt_visibility, "private", ir_visibility_private);
 
 	INSERT(tt_throws, "throw",   true);
@@ -324,7 +323,6 @@ static const char *get_visibility_name(ir_visibility visibility)
 	switch (visibility) {
 	case ir_visibility_local:    return "local";
 	case ir_visibility_external: return "external";
-	case ir_visibility_default:  return "default";
 	case ir_visibility_private:  return "private";
 	}
 	panic("INVALID_VISIBILITY");
@@ -1901,7 +1899,7 @@ static void read_entity(read_env_t *env, ir_entity_kind kind)
 	long           entnr      = read_long(env);
 	ident         *name       = NULL;
 	ident         *ld_name    = NULL;
-	ir_visibility  visibility = ir_visibility_default;
+	ir_visibility  visibility = ir_visibility_external;
 	ir_linkage     linkage    = IR_LINKAGE_DEFAULT;
 	ir_type       *owner      = NULL;
 	ir_entity     *entity     = NULL;

ir/opt/garbage_collect.c

@@ -122,7 +122,7 @@ static void visit_segment(ir_type *segment)
 
 	for (i = 0; i < n_entities; ++i) {
 		ir_entity *entity = get_compound_member(segment, i);
-		if (get_entity_visibility(entity) != ir_visibility_default
+		if (get_entity_visibility(entity) != ir_visibility_external
 				&& !(get_entity_linkage(entity) & IR_LINKAGE_HIDDEN_USER))
 			continue;
 

ir/tr/entity.c

@@ -72,7 +72,7 @@ static ir_entity *intern_new_entity(ir_type *owner, ir_entity_kind kind,
 	res->aligned              = align_is_aligned;
 	res->usage                = ir_usage_unknown;
 	res->compiler_gen         = 0;
-	res->visibility           = ir_visibility_default;
+	res->visibility           = ir_visibility_external;
 	res->offset               = -1;
 	res->offset_bit_remainder = 0;
 	res->alignment            = 0;