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Message-ID: <20170613155513.GB27071@port70.net>
Date: Tue, 13 Jun 2017 17:55:13 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] s390x: Add single instruction math functions
* David Edelsohn <dje.gcc@...il.com> [2017-06-12 17:02:27 -0400]:
> 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?
>
hm i didnt know about that
then the patch is probably ok.
> Thanks, David
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