Re: memmove() in 2.4.0-test12, alpha platform

Ivan Kokshaysky
2000-12-21T16:12:12Z

On Wed, Dec 20, 2000 at 10:03:42PM +0300, Alexander Zarochentcev wrote:
> New (since test12) optimized memmove function seems to be broken
> on alpha platform.

Indeed it is.

> If dest and src arguments are misaligned, new memmove does wrong things.

Actually it broke when dest < src. Incrementing pointers should be used in
this case.

This patch seems to work (tested in userspace).

Ivan.

--- linux/arch/alpha/lib/memmove.S.orig Tue Dec 12 00:46:26 2000
+++ linux/arch/alpha/lib/memmove.S Thu Dec 21 18:32:59 2000
@@ -26,12 +26,16 @@ memmove:
bne $1,memcpy

and $2,7,$2 /* Test for src/dest co-alignment. */
- bne $2,$misaligned
+ and $16,7,$1
+ cmpule $16,$17,$3
+ bne $3,$memmove_up /* dest < src */

and $4,7,$1
- beq $1,$skip_aligned_byte_loop_head
+ bne $2,$misaligned_dn
+ unop
+ beq $1,$skip_aligned_byte_loop_head_dn

-$aligned_byte_loop_head:
+$aligned_byte_loop_head_dn:
lda $4,-1($4)
lda $5,-1($5)
unop
@@ -48,13 +52,13 @@ $aligned_byte_loop_head:
and $4,7,$6

stq_u $1,0($4)
- bne $6,$aligned_byte_loop_head
+ bne $6,$aligned_byte_loop_head_dn

-$skip_aligned_byte_loop_head:
+$skip_aligned_byte_loop_head_dn:
lda $18,-8($18)
- blt $18,$skip_aligned_word_loop
+ blt $18,$skip_aligned_word_loop_dn

-$aligned_word_loop:
+$aligned_word_loop_dn:
ldq $1,-8($5)
nop
lda $5,-8($5)
@@ -63,22 +67,22 @@ $aligned_word_loop:
stq $1,-8($4)
nop
lda $4,-8($4)
- bge $18,$aligned_word_loop
+ bge $18,$aligned_word_loop_dn

-$skip_aligned_word_loop:
+$skip_aligned_word_loop_dn:
lda $18,8($18)
- bgt $18,$byte_loop_tail
+ bgt $18,$byte_loop_tail_dn
unop
ret $31,($26),1

.align 4
-$misaligned:
+$misaligned_dn:
nop
fnop
unop
beq $18,$egress

-$byte_loop_tail:
+$byte_loop_tail_dn:
ldq_u $3,-1($5)
ldq_u $2,-1($4)
lda $5,-1($5)
@@ -91,8 +95,77 @@ $byte_loop_tail:

bis $1,$2,$1
stq_u $1,0($4)
+ bgt $18,$byte_loop_tail_dn
+ br $egress
+
+$memmove_up:
+ mov $16,$4
+ mov $17,$5
+ bne $2,$misaligned_up
+ beq $1,$skip_aligned_byte_loop_head_up
+
+$aligned_byte_loop_head_up:
+ unop
+ ble $18,$egress
+ ldq_u $3,0($5)
+ ldq_u $2,0($4)
+
+ lda $18,-1($18)
+ extbl $3,$5,$1
+ insbl $1,$4,$1
+ mskbl $2,$4,$2
+
+ bis $1,$2,$1
+ lda $5,1($5)
+ stq_u $1,0($4)
+ lda $4,1($4)
+
+ and $4,7,$6
+ bne $6,$aligned_byte_loop_head_up
+
+$skip_aligned_byte_loop_head_up:
+ lda $18,-8($18)
+ blt $18,$skip_aligned_word_loop_up
+
+$aligned_word_loop_up:
+ ldq $1,0($5)
+ nop
+ lda $5,8($5)
+ lda $18,-8($18)
+
+ stq $1,0($4)
+ nop
+ lda $4,8($4)
+ bge $18,$aligned_word_loop_up
+
+$skip_aligned_word_loop_up:
+ lda $18,8($18)
+ bgt $18,$byte_loop_tail_up
+ unop
+ ret $31,($26),1
+
+ .align 4
+$misaligned_up:
+ nop
+ fnop
+ unop
+ beq $18,$egress
+
+$byte_loop_tail_up:
+ ldq_u $3,0($5)
+ ldq_u $2,0($4)
+ lda $18,-1($18)
+ extbl $3,$5,$1
+
+ insbl $1,$4,$1
+ mskbl $2,$4,$2
+ bis $1,$2,$1
+ stq_u $1,0($4)
+
+ lda $5,1($5)
+ lda $4,1($4)
nop
- bgt $18,$byte_loop_tail
+ bgt $18,$byte_loop_tail_up

$egress:
ret $31,($26),1