From 6bbe7ef049bc1b9d150a21ccd082c2f65f344682 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Thu, 20 Feb 2025 13:12:27 -0500
Subject: kernel/amd64: i8237: Optimize set channel select

There is no need for an intermediary register before setting %AL. This
commit removes redundant instructions to reduce the amount of cycles
used for this operation.

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/arch/amd64/isa/i8237.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

(limited to 'sys/arch/amd64/isa')

diff --git a/sys/arch/amd64/isa/i8237.S b/sys/arch/amd64/isa/i8237.S
index 00b5bd9..ef6090a 100644
--- a/sys/arch/amd64/isa/i8237.S
+++ b/sys/arch/amd64/isa/i8237.S
@@ -95,9 +95,8 @@ i8237_set_mode:
     jg 1f
 
     /* Set channel select bits */
-    mov %dil, %bl
-    andb $3, %bl
-    mov %bl, %al
+    mov %dil, %al
+    andb $3, %al
 
     /* Set channel mode bits */
     mov %sil, %dl
-- 
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