[PATCH] S390: Optimize __memcpy_z196.

[Stefan Liebler]

Just as information, if nobody opposes, I'll commit this patch tomorrow.

On 6/19/20 3:49 PM, Stefan Liebler wrote:
> This patch introduces an extra loop without pfd instructions
> as it turned out that the pfd instructions are usefull
> for copies >=64KB but are counterproductive for smaller copies.
> ---
>  sysdeps/s390/memcpy-z900.S | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/sysdeps/s390/memcpy-z900.S b/sysdeps/s390/memcpy-z900.S
> index f2e9aaeb2d..dc2f491ec3 100644
> --- a/sysdeps/s390/memcpy-z900.S
> +++ b/sysdeps/s390/memcpy-z900.S
> @@ -184,25 +184,34 @@ ENTRY(MEMCPY_Z196)
>  	je      .L_Z196_4
>  .L_Z196_start2:
>  	aghi    %r4,-1
> -	srlg    %r5,%r4,8
> -	ltgr    %r5,%r5
> +	risbg	%r5,%r4,8,128+63,56 # r0 = r5 / 256
>  	jne     .L_Z196_5
>  .L_Z196_3:
>  	exrl    %r4,.L_Z196_14
>  .L_Z196_4:
>  	br      %r14
>  .L_Z196_5:
> -	cgfi    %r5,262144      # Switch to mvcle for copies >64MB
> -	jh      __memcpy_mvcle
> +	cgfi	%r5,255		# Switch to loop with pfd for copies >=64kB
> +	jh	.L_Z196_6
>  .L_Z196_2:
> -	pfd     1,768(%r3)
> -	pfd     2,768(%r1)
>  	mvc     0(256,%r1),0(%r3)
>  	aghi    %r5,-1
>  	la      %r1,256(%r1)
>  	la      %r3,256(%r3)
>  	jne     .L_Z196_2
>  	j       .L_Z196_3
> +.L_Z196_6:
> +	cgfi    %r5,262144      # Switch to mvcle for copies >64MB
> +	jh      __memcpy_mvcle
> +.L_Z196_7:
> +	pfd     1,1024(%r3)
> +	pfd     2,1024(%r1)
> +	mvc     0(256,%r1),0(%r3)
> +	aghi    %r5,-1
> +	la      %r1,256(%r1)
> +	la      %r3,256(%r3)
> +	jne     .L_Z196_7
> +	j       .L_Z196_3
>  .L_Z196_14:
>  	mvc     0(1,%r1),0(%r3)
>  END(MEMCPY_Z196)
>