On Sun, Nov 17, 2024 at 4:30 AM Lewis Hyatt <lhy...@gmail.com> wrote:
>
> The size of struct gimple increases by 8 bytes with the change in size of
> location_t from 32- to 64-bit; adjust the WORD markings in the comments
> accordingly. It seems that most of the WORD markings were off by one already,
> probably not having been updated after a previous reduction in the size of a
> gimple, so they have become retroactively correct again, and only a couple
> needed adjustment actually.
>
> Also move the 32-bit num_ops member of struct gimple to the end; since there
> is now 4 bytes of padding after it, this may enable reuse of the tail
> padding for some derived structures.
>
> gcc/ChangeLog:
>
> * gimple.h (struct gimple): Update word marking comments to reflect
> the new size of location_t. Move the 32-bit int field to the end.
> (struct gphi): Likewise.
> ---
> gcc/gimple.h | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/gcc/gimple.h b/gcc/gimple.h
> index 4a6e0e97d1e..6929c792dc5 100644
> --- a/gcc/gimple.h
> +++ b/gcc/gimple.h
> @@ -268,9 +268,6 @@ struct GTY((desc ("gimple_statement_structure (&%h)"),
> tag ("GSS_BASE"),
> Locus information for debug info. */
> location_t location;
>
> - /* Number of operands in this tuple. */
> - unsigned num_ops;
> -
Can you instead swap location and num_ops and insert
unsigned int pad : 32;
after the bits section? Or is the intent to allow the tail padding to
be re-used? I guess
all the [ WORD 1-n] : base class comments need adjustment? Since
'gimple' looks POD
to me, is tail padding even re-used?
Thanks,
Richard.
> /* [ WORD 3 ]
> Basic block holding this statement. */
> basic_block bb;
> @@ -283,8 +280,12 @@ struct GTY((desc ("gimple_statement_structure (&%h)"),
> tag ("GSS_BASE"),
> and the prev pointer being the last. */
> gimple *next;
> gimple *GTY((skip)) prev;
> -};
>
> + /* [WORD 6]
> + Number of operands in this tuple. */
> + unsigned num_ops;
> + /* (4 bytes trailing padding) */
> +};
>
> /* Base structure for tuples with operands. */
>
> @@ -479,7 +480,7 @@ struct GTY((tag("GSS_PHI")))
> /* [ WORD 8 ] */
> tree result;
>
> - /* [ WORD 9 ] */
> + /* [ WORD 9-14 ] */
> struct phi_arg_d GTY ((length ("%h.nargs"))) args[1];
> };
>
