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Date: Mon, 12 Jun 2017 22:28:52 +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 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
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