memmove() in 2.4.0-test12, alpha platform

memmove() in 2.4.0-test12, alpha platform

[Alexander Zarochentcev]

Hello !

New (since test12) optimized memmove function seems to be broken
on alpha platform. 

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


example:
	 
       static char p[] = "abcdefghijklmnopkrstuvwxyz01234567890";
       memmove(p + 2, p + 13, 17);
       printk ("DEBUG: memmove test: %s\n", p);

produces:

       DEBUG: memmove test: abyz0123tuvwxyz0123tuvwxyz01234567890


Old memmove variant didn't have this problem.

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

[Ivan Kokshaysky]

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

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

[Alexander Zarochentcev]

On Thu, Dec 21, 2000 at 06:40:46PM +0300, Ivan Kokshaysky wrote:
> 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

Ok. It works.

Thanks.

-- 
Alex.
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