* [PATCH] s390: Use long branches across object boundaries (jgh instead of jh)
@ 2021-11-09 17:50 Florian Weimer
2021-11-09 19:06 ` Carlos O'Donell
0 siblings, 1 reply; 3+ messages in thread
From: Florian Weimer @ 2021-11-09 17:50 UTC (permalink / raw)
To: libc-alpha
Cc: Stefan Liebler, Nick Clifton, Arjun Shankar, Carlos O'Donell
Depending on the layout chosen by the linker, the 16-bit displacement
of the jh instruction is insufficient to reach the target label.
Analysis of the linker failure was carried out by Nick Clifton.
Tested on a z13 and z15, s390x-linux-gnu only.
---
sysdeps/s390/memmem-arch13.S | 2 +-
sysdeps/s390/strstr-arch13.S | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/sysdeps/s390/memmem-arch13.S b/sysdeps/s390/memmem-arch13.S
index c5c8d8c97e..58df8cdb14 100644
--- a/sysdeps/s390/memmem-arch13.S
+++ b/sysdeps/s390/memmem-arch13.S
@@ -41,7 +41,7 @@ ENTRY(MEMMEM_ARCH13)
# error The arch13 variant of memmem needs the z13 variant of memmem!
# endif
clgfi %r5,9
- jh MEMMEM_Z13
+ jgh MEMMEM_Z13
aghik %r0,%r5,-1 /* vll needs highest index. */
bc 4,0(%r14) /* cc==1: return if needle-len == 0. */
diff --git a/sysdeps/s390/strstr-arch13.S b/sysdeps/s390/strstr-arch13.S
index c7183e627c..222a6de91a 100644
--- a/sysdeps/s390/strstr-arch13.S
+++ b/sysdeps/s390/strstr-arch13.S
@@ -49,7 +49,7 @@ ENTRY(STRSTR_ARCH13)
# error The arch13 variant of strstr needs the z13 variant of strstr!
# endif
clgfi %r4,9
- jh STRSTR_Z13
+ jgh STRSTR_Z13
/* In case of a partial match, the vstrs instruction returns the index
of the partial match in a vector-register. Then we have to
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] s390: Use long branches across object boundaries (jgh instead of jh)
2021-11-09 17:50 [PATCH] s390: Use long branches across object boundaries (jgh instead of jh) Florian Weimer
@ 2021-11-09 19:06 ` Carlos O'Donell
2021-11-10 13:57 ` Stefan Liebler
0 siblings, 1 reply; 3+ messages in thread
From: Carlos O'Donell @ 2021-11-09 19:06 UTC (permalink / raw)
To: Florian Weimer, libc-alpha; +Cc: Stefan Liebler, Nick Clifton, Arjun Shankar
On 11/9/21 12:50, Florian Weimer wrote:
> Depending on the layout chosen by the linker, the 16-bit displacement
> of the jh instruction is insufficient to reach the target label.
>
> Analysis of the linker failure was carried out by Nick Clifton.
>
> Tested on a z13 and z15, s390x-linux-gnu only.
Looks correct to me. Converting from BRC to BRCL doubles the available offset bits.
I tested assembling a few variants and they look good to me.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
> ---
> sysdeps/s390/memmem-arch13.S | 2 +-
> sysdeps/s390/strstr-arch13.S | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/sysdeps/s390/memmem-arch13.S b/sysdeps/s390/memmem-arch13.S
> index c5c8d8c97e..58df8cdb14 100644
> --- a/sysdeps/s390/memmem-arch13.S
> +++ b/sysdeps/s390/memmem-arch13.S
> @@ -41,7 +41,7 @@ ENTRY(MEMMEM_ARCH13)
> # error The arch13 variant of memmem needs the z13 variant of memmem!
> # endif
> clgfi %r5,9
> - jh MEMMEM_Z13
OK. jh is BRC (branch relative on condition, A7-M-4-RI) with a 16-bit offset.
> + jgh MEMMEM_Z13
OK. jgh is BRCL (branch relative on condition long, C0-M-4-RI) with a 32-bit offset.
>
> aghik %r0,%r5,-1 /* vll needs highest index. */
> bc 4,0(%r14) /* cc==1: return if needle-len == 0. */
> diff --git a/sysdeps/s390/strstr-arch13.S b/sysdeps/s390/strstr-arch13.S
> index c7183e627c..222a6de91a 100644
> --- a/sysdeps/s390/strstr-arch13.S
> +++ b/sysdeps/s390/strstr-arch13.S
> @@ -49,7 +49,7 @@ ENTRY(STRSTR_ARCH13)
> # error The arch13 variant of strstr needs the z13 variant of strstr!
> # endif
> clgfi %r4,9
> - jh STRSTR_Z13
> + jgh STRSTR_Z13
Likewise.
>
> /* In case of a partial match, the vstrs instruction returns the index
> of the partial match in a vector-register. Then we have to
>
--
Cheers,
Carlos.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] s390: Use long branches across object boundaries (jgh instead of jh)
2021-11-09 19:06 ` Carlos O'Donell
@ 2021-11-10 13:57 ` Stefan Liebler
0 siblings, 0 replies; 3+ messages in thread
From: Stefan Liebler @ 2021-11-10 13:57 UTC (permalink / raw)
To: Carlos O'Donell, Florian Weimer, libc-alpha
Cc: Nick Clifton, Arjun Shankar
On 09/11/2021 20:06, Carlos O'Donell wrote:
> On 11/9/21 12:50, Florian Weimer wrote:
>> Depending on the layout chosen by the linker, the 16-bit displacement
>> of the jh instruction is insufficient to reach the target label.
>>
>> Analysis of the linker failure was carried out by Nick Clifton.
>>
>> Tested on a z13 and z15, s390x-linux-gnu only.
>
> Looks correct to me. Converting from BRC to BRCL doubles the available offset bits.
> I tested assembling a few variants and they look good to me.
>
> Reviewed-by: Carlos O'Donell <carlos@redhat.com>
>
>> ---
>> sysdeps/s390/memmem-arch13.S | 2 +-
>> sysdeps/s390/strstr-arch13.S | 2 +-
>> 2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/sysdeps/s390/memmem-arch13.S b/sysdeps/s390/memmem-arch13.S
>> index c5c8d8c97e..58df8cdb14 100644
>> --- a/sysdeps/s390/memmem-arch13.S
>> +++ b/sysdeps/s390/memmem-arch13.S
>> @@ -41,7 +41,7 @@ ENTRY(MEMMEM_ARCH13)
>> # error The arch13 variant of memmem needs the z13 variant of memmem!
>> # endif
>> clgfi %r5,9
>> - jh MEMMEM_Z13
>
> OK. jh is BRC (branch relative on condition, A7-M-4-RI) with a 16-bit offset.
>
>> + jgh MEMMEM_Z13
>
> OK. jgh is BRCL (branch relative on condition long, C0-M-4-RI) with a 32-bit offset.
>
>>
>> aghik %r0,%r5,-1 /* vll needs highest index. */
>> bc 4,0(%r14) /* cc==1: return if needle-len == 0. */
>> diff --git a/sysdeps/s390/strstr-arch13.S b/sysdeps/s390/strstr-arch13.S
>> index c7183e627c..222a6de91a 100644
>> --- a/sysdeps/s390/strstr-arch13.S
>> +++ b/sysdeps/s390/strstr-arch13.S
>> @@ -49,7 +49,7 @@ ENTRY(STRSTR_ARCH13)
>> # error The arch13 variant of strstr needs the z13 variant of strstr!
>> # endif
>> clgfi %r4,9
>> - jh STRSTR_Z13
>> + jgh STRSTR_Z13
>
> Likewise.
>
>>
>> /* In case of a partial match, the vstrs instruction returns the index
>> of the partial match in a vector-register. Then we have to
>>
>
>
This patch is okay. Thanks for catching this.
I've also had a look into the wcsmbs implementations like
sysdeps/s390/wcscpy-vx.S where we jump to c-implementation as fallback.
There we also use jg which is brcl with all bits set in the condition mask.
Thanks,
Stefan
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-11-09 17:50 [PATCH] s390: Use long branches across object boundaries (jgh instead of jh) Florian Weimer
2021-11-09 19:06 ` Carlos O'Donell
2021-11-10 13:57 ` Stefan Liebler
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