[PATCH 2/2] xtensa: Optimize ctzsi2 and ffssi2 a bit

[PATCH 2/2] xtensa: Optimize ctzsi2 and ffssi2 a bit

[Takayuki 'January June' Suwa]

This patch saves one byte when the Code Density Option is enabled,

gcc/ChangeLog:

	* config/xtensa/xtensa.md (ctzsi2, ffssi2):
	Rearrange the emitting codes.
---
 gcc/config/xtensa/xtensa.md | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index b4989832169..764da63f91c 100644
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -477,8 +477,8 @@
   emit_insn (gen_negsi2 (temp, operands[1]));
   emit_insn (gen_andsi3 (temp, temp, operands[1]));
   emit_insn (gen_clzsi2 (temp, temp));
-  emit_insn (gen_negsi2 (temp, temp));
-  emit_insn (gen_addsi3 (operands[0], temp, GEN_INT (31)));
+  emit_move_insn (operands[0], GEN_INT (31));
+  emit_insn (gen_subsi3 (operands[0], operands[0], temp));
   DONE;
 })
 
@@ -491,8 +491,8 @@
   emit_insn (gen_negsi2 (temp, operands[1]));
   emit_insn (gen_andsi3 (temp, temp, operands[1]));
   emit_insn (gen_clzsi2 (temp, temp));
-  emit_insn (gen_negsi2 (temp, temp));
-  emit_insn (gen_addsi3 (operands[0], temp, GEN_INT (32)));
+  emit_move_insn (operands[0], GEN_INT (32));
+  emit_insn (gen_subsi3 (operands[0], operands[0], temp));
   DONE;
 })
 
-- 
2.30.2

Re: [PATCH 2/2] xtensa: Optimize ctzsi2 and ffssi2 a bit

[Max Filippov]

On Wed, Jan 11, 2023 at 8:26 PM Takayuki 'January June' Suwa
<jjsuwa_sys3175@yahoo.co.jp> wrote:
>
> This patch saves one byte when the Code Density Option is enabled,
>
> gcc/ChangeLog:
>
>         * config/xtensa/xtensa.md (ctzsi2, ffssi2):
>         Rearrange the emitting codes.
> ---
>  gcc/config/xtensa/xtensa.md | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)

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

-- 
Thanks.
-- Max