[PATCH] xtensa: Turn on -fsplit-wide-types-early by default

[PATCH] xtensa: Turn on -fsplit-wide-types-early by default

[Takayuki 'January June' Suwa]

Since GCC10, the "subreg2" optimization pass was no longer tied to enabling
"subreg1" unless -fsplit-wide-types-early was turned on (PR88233).  However
on the Xtensa port, the lack of "subreg2" can degrade the quality of the
output code, especially for those that produce many D[FC]mode pseudos.

This patch turns on -fsplit-wide-types-early by default in order to restore
the previous behavior.

gcc/ChangeLog:

	* common/config/xtensa/xtensa-common.cc
	(xtensa_option_optimization_table): Add OPT_fsplit_wide_types_early
	for OPT_LEVELS_ALL in order to restore pre-GCC10 behavior.
---
 gcc/common/config/xtensa/xtensa-common.cc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/gcc/common/config/xtensa/xtensa-common.cc b/gcc/common/config/xtensa/xtensa-common.cc
index fbbe9b0aad7..0f27763aa71 100644
--- a/gcc/common/config/xtensa/xtensa-common.cc
+++ b/gcc/common/config/xtensa/xtensa-common.cc
@@ -34,6 +34,8 @@ static const struct default_options xtensa_option_optimization_table[] =
        assembler, so GCC cannot do a good job of reordering blocks.
        Do not enable reordering unless it is explicitly requested.  */
     { OPT_LEVELS_ALL, OPT_freorder_blocks, NULL, 0 },
+    /* Split multi-word types early (pre-GCC10 behavior).  */
+    { OPT_LEVELS_ALL, OPT_fsplit_wide_types_early, NULL, 1 },
     { OPT_LEVELS_NONE, 0, NULL, 0 }
   };
 
-- 
2.20.1

Re: [PATCH] xtensa: Turn on -fsplit-wide-types-early by default

[Max Filippov]

On Sun, Aug 14, 2022 at 2:31 AM Takayuki 'January June' Suwa
<jjsuwa_sys3175@yahoo.co.jp> wrote:
>
> Since GCC10, the "subreg2" optimization pass was no longer tied to enabling
> "subreg1" unless -fsplit-wide-types-early was turned on (PR88233).  However
> on the Xtensa port, the lack of "subreg2" can degrade the quality of the
> output code, especially for those that produce many D[FC]mode pseudos.
>
> This patch turns on -fsplit-wide-types-early by default in order to restore
> the previous behavior.
>
> gcc/ChangeLog:
>
>         * common/config/xtensa/xtensa-common.cc
>         (xtensa_option_optimization_table): Add OPT_fsplit_wide_types_early
>         for OPT_LEVELS_ALL in order to restore pre-GCC10 behavior.
> ---
>  gcc/common/config/xtensa/xtensa-common.cc | 2 ++
>  1 file changed, 2 insertions(+)

Regtested for target=xtensa-linux-uclibc, no new regressions.
Committed to master.

-- 
Thanks.
-- Max