[Bug middle-end/108623] We need to grow the precision field in tree_type_common for PowerPC

["rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108623

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|other                       |middle-end
             Target|                            |powerpc*

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
There are 15 spare bits at the end of the bits, a better solution is to
re-order things so precision remains aligned to 16 bits, for example by moving
the
6 bits adjacent to it to the "spare" and extending precision to a full 16 bits.

Like with the following which aligns all >1 bit fields to at least 8 bits

diff --git a/gcc/tree-core.h b/gcc/tree-core.h
index acd8deea34e..e5513208511 100644
--- a/gcc/tree-core.h
+++ b/gcc/tree-core.h
@@ -1686,18 +1686,8 @@ struct GTY(()) tree_type_common {
   tree attributes;
   unsigned int uid;

-  unsigned int precision : 10;
-  unsigned no_force_blk_flag : 1;
-  unsigned needs_constructing_flag : 1;
-  unsigned transparent_aggr_flag : 1;
-  unsigned restrict_flag : 1;
-  unsigned contains_placeholder_bits : 2;
-
+  unsigned int precision : 16;
   ENUM_BITFIELD(machine_mode) mode : 8;
-
-  /* TYPE_STRING_FLAG for INTEGER_TYPE and ARRAY_TYPE.
-     TYPE_CXX_ODR_P for RECORD_TYPE and UNION_TYPE.  */
-  unsigned string_flag : 1;
   unsigned lang_flag_0 : 1;
   unsigned lang_flag_1 : 1;
   unsigned lang_flag_2 : 1;
@@ -1713,12 +1703,22 @@ struct GTY(()) tree_type_common {
      so we need to store the value 32 (not 31, as we need the zero
      as well), hence six bits.  */
   unsigned align : 6;
+  /* TYPE_STRING_FLAG for INTEGER_TYPE and ARRAY_TYPE.
+     TYPE_CXX_ODR_P for RECORD_TYPE and UNION_TYPE.  */
+  unsigned string_flag : 1;
+  unsigned no_force_blk_flag : 1;
+
   unsigned warn_if_not_align : 6;
+  unsigned needs_constructing_flag : 1;
+  unsigned transparent_aggr_flag : 1;
+
+  unsigned contains_placeholder_bits : 2;
+  unsigned restrict_flag : 1;
   unsigned typeless_storage : 1;
   unsigned empty_flag : 1;
   unsigned indivisible_p : 1;
   unsigned no_named_args_stdarg_p : 1;
-  unsigned spare : 15;
+  unsigned spare : 9;

   alias_set_type alias_set;
   tree pointer_to;