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Message-ID: <20170610182950.GV9350@port70.net>
Date: Sat, 10 Jun 2017 20:29:50 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Cc: David Edelsohn <dje.gcc@...il.com>
Subject: Re: [PATCH] s390x: Add single instruction math functions
* David Edelsohn <dje.gcc@...il.com> [2017-06-10 13:25:00 -0400]:
> On Sat, Jun 10, 2017 at 11:36 AM, Szabolcs Nagy <nsz@...t70.net> wrote:
> > * David Edelsohn <dje.gcc@...il.com> [2017-06-09 10:51:25 -0400]:
> >> The following patch is a start at single instruction math functions
> >> for s390x architecture to increase performance.
> >
> > looks good, i wonder why gcc does not have builtins support for
> > ceil, floor, nearbyint, round and trunc
> >
> > (on aarch64 the builtins expand to single instruction with
> > -fno-math-errno, but on s390x they remain libc calls
>
> Both the functions and builtins are converted to single instructions
> for me. What architecture level is your GCC assuming?
>
i think it's the default s390x config
$ s390x-linux-musl-gcc -v
Using built-in specs.
COLLECT_GCC=s390x-linux-musl-gcc
COLLECT_LTO_WRAPPER=/home/nsz/w/mcm/output/bin/../libexec/gcc/s390x-linux-musl/6.3.0/lto-wrapper
Target: s390x-linux-musl
Configured with: ../src_toolchain/configure --enable-languages=c,c++ CFLAGS='-g0 -Os' CXXFLAGS='-g0 -Os' LDFLAGS=-s --disable-nls --with-debug-prefix-map=/home/nsz/w/mcm/build-s390x-linux-musl= --enable-languages=c,c++ --disable-libquadmath --disable-libquadmath-support --disable-decimal-float --disable-multilib --disable-libcilkrts --disable-libvtv --disable-libgomp --disable-libitm --disable-werror --target=s390x-linux-musl --prefix= --libdir=/lib --disable-multilib --with-sysroot=/s390x-linux-musl --enable-tls --disable-libmudflap --disable-libsanitizer --disable-gnu-indirect-function --disable-libmpx --enable-libstdcxx-time --with-build-sysroot=/home/nsz/w/mcm/build-s390x-linux-musl/obj_sysroot
Thread model: posix
gcc version 6.3.0 (GCC)
$ cat a.c
double f(double x)
{
return __builtin_ceil(x);
}
$ s390x-linux-musl-gcc -O3 -fno-math-errno -S a.c -o -
.machinemode zarch
.machine "z900"
.text
.align 8
.globl f
.type f, @function
f:
.LFB0:
.cfi_startproc
jg ceil
.cfi_endproc
.LFE0:
.size f, .-f
.ident "GCC: (GNU) 6.3.0"
.section .note.GNU-stack,"",@progbits
> > at some point we plan to have some internal header to turn
> > math/string calls into builtins when compiling musl with gcc)
>
> I have a patch set ready for powerpc64 teed up after this patch.
>
> Thanks, David
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