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Date: Mon, 12 Jun 2017 17:02:27 -0400
From: David Edelsohn <dje.gcc@...il.com>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] s390x: Add single instruction math functions
On Mon, Jun 12, 2017 at 4:28 PM, Szabolcs Nagy <nsz@...t70.net> wrote:
> * David Edelsohn <dje.gcc@...il.com> [2017-06-12 09:54:54 -0400]:
>> On Mon, Jun 12, 2017 at 9:28 AM, David Edelsohn <dje.gcc@...il.com> wrote:
>> > On Mon, Jun 12, 2017 at 5:03 AM, Szabolcs Nagy <nsz@...t70.net> wrote:
>> >> * David Edelsohn <dje.gcc@...il.com> [2017-06-11 22:46:09 -0400]:
>> >>> The following IBM table of supported and tested systems
>> >>>
>> >>> https://www-03.ibm.com/systems/z/os/linux/resources/testedplatforms.html
>> >>>
>> >>> shows that RHEL 7 and SLES 12 require at least z196, and Ubuntu 16.04
>> >>> requires at least zEC12.
>> >>>
>> >>> I can't find any official hardware requirements description for Alpine
>> >>> Linux. I tend to doubt that user would run it on older hardware,
>> >>> especially hardware no longer supported by other, modern Linux
>> >>> distributions.
>> >>>
>> >>> Building musl libc on older hardware is a nice accomplishment, but
>> >>> investing effort and complexity to maintain support probably isn't
>> >>> useful to any musl libc user and probably isn't a productive use of
>> >>> developer resources.
>> >>>
>> >>> I will continue to inquire if there is a simple technique to accomplish this.
>> >
>> > Apparently GCC 7.1 added architecture macros.
>> >
>> > As Tuan referenced, Alpine Linux also requires z196 as the minimum
>> > architecture level. I believe that it would be better for s390-musl
>> > to default to z196 ISA than musl to require GCC 7.1.
>>
>> Would a patch such as the following be acceptable?
>>
>> Thanks, David
>>
>> diff --git a/configure b/configure
>> index c2db298..a9e0256 100755
>> --- a/configure
>> +++ b/configure
>> @@ -494,6 +494,15 @@ fnmatch '-mtune=*|*\ -mtune=*' "$CC $CFLAGS" || tryldflag C
>> fi
>>
>> #
>> +# On s390x, default to z196 architecture and zEC12 tuning to support newer math
>> +# instructions.
>> +#
>> +if test "$ARCH" = "s390x" ; then
>> +fnmatch '-march=*|*\ -march=*' "$CC $CFLAGS" || tryldflag CFLAGS_AUTO
>> -march=z196
>> +fnmatch '-mtune=*|*\ -mtune=*' "$CC $CFLAGS" || tryldflag CFLAGS_AUTO
>> -mtune=zEC12
>> +fi
>> +
>> +#
>> # Even with -std=c99, gcc accepts some constructs which are constraint
>> # violations. We want to treat these as errors regardless of whether
>> # other purely stylistic warnings are enabled -- especially implicit
>
> well the toolchain may be configured for a different/newer cpu
> and then we may not want to override that.. what about
>
> diff --git a/configure b/configure
> index c2db298c..bcaf3a7d 100755
> --- a/configure
> +++ b/configure
> @@ -656,6 +656,12 @@ trycppif __LITTLE_ENDIAN__ "$t" && SUBARCH=${SUBARCH}le
> trycppif _SOFT_FLOAT "$t" && fail "$0: error: soft-float not supported on powerpc64"
> fi
>
> +if test "$ARCH" = "s390x" ; then
> +echo 'float x; void f(){__asm__("fiebra %0,6,%1,4":"=f"(x):"f"(x));}' > "$tmpc"
> +$CC $CFLAGS_C99FSE $CPPFLAGS $CFLAGS -c -o /dev/null "$tmpc" >/dev/null 2>&1 ||
> + fail "$0: error: s390x isa level is too low, use at least -march=z196"
> +fi
> +
> if test "$ARCH" = "sh" ; then
> tryflag CFLAGS_AUTO -Wa,--isa=any
> trycppif __BIG_ENDIAN__ "$t" && SUBARCH=${SUBARCH}eb
Why is the x86 configure logic that I used as a template correct?
Thanks, David
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