[AArch64] Fix build for non-default languages

The SVE PCS support broke go, D and Ada because those languages don't
call TARGET_INIT_BUILTINS.  We therefore ended up trying to get the
TYPE_MAIN_VARIANT of a null __SVBool_t.

We shouldn't really need to apply TYPE_MAIN_VARIANT there anyway,
since the ABI-defined types are (and need to be) their own main
variants.  This patch asserts for that instead.

2019-10-31  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/aarch64-sve-builtins.cc (register_builtin_types):
	Assert that the type we store in abi_vector_types is its own
	main variant.
	(svbool_type_p): Don't apply TYPE_MAIN_VARIANT here.

From-SVN: r277680

gcc/ChangeLog

+2019-10-31  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* config/aarch64/aarch64-sve-builtins.cc (register_builtin_types):
+	Assert that the type we store in abi_vector_types is its own
+	main variant.
+	(svbool_type_p): Don't apply TYPE_MAIN_VARIANT here.
+
 2019-10-31  Richard Earnshaw  <rearnsha@arm.com>
 
 	* config/arm/arm.c (arm_legitimize_address): Don't form negative offsets

gcc/config/aarch64/aarch64-sve-builtins.cc

@@ -2993,6 +2993,7 @@ register_builtin_types ()
 				   BITS_PER_SVE_VECTOR));
 	}
       vectype = build_distinct_type_copy (vectype);
+      gcc_assert (vectype == TYPE_MAIN_VARIANT (vectype));
       SET_TYPE_STRUCTURAL_EQUALITY (vectype);
       TYPE_ARTIFICIAL (vectype) = 1;
       abi_vector_types[i] = vectype;
@@ -3235,8 +3236,7 @@ bool
 svbool_type_p (const_tree type)
 {
   tree abi_type = abi_vector_types[VECTOR_TYPE_svbool_t];
-  return (type != error_mark_node
-	  && TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (abi_type));
+  return type != error_mark_node && TYPE_MAIN_VARIANT (type) == abi_type;
 }
 
 /* If TYPE is a built-in type defined by the SVE ABI, return the mangled name,