Re: [PATCH] PowerPC: modf optimization

[Adhemerval Zanella <azanella at linux dot vnet dot ibm dot com>]

On 03/27/2013 11:11 AM, Andreas Jaeger wrote:
>
> I'm fine with the benchtests addition (see one comment below).
>
> I'm not sure about the __ceil, __floor issue and would like feedback from others on how to handle this,
I have added the copyright header and I changed to patch to use the new modf
implementation for POWER5 or higher only, making the s_floor and s_ceil addition
not required anymore.

I also increased the iterations to 5e8 and I got the following results in a POWER7
machine with 64 bits:

MASTER: modf: ITERS:5e+08: TOTAL:5.96664s, MAX:42.302ns, MIN:9.104ns, 8.37993e+07 iter/s
PATCH:  modf: ITERS:5e+08: TOTAL:3.00147s, MAX:40.334ns, MIN:5.63ns,  1.66585e+08 iter/s

And clock_gettime is an vDSO for PowerPC, however afaik CLOCK_PROCESS_CPUTIME_ID
fall-back to a syscall even for x86_64. Maybe we should increase the default
iterations for all benchtests.

Any tips, comments, advices?

---

2013-03-31  Adhemerval Zanella  <azanella@linux.vnet.ibm.com>

    * sysdeps/powerpc/fpu/s_modf.c: New file: modf optimization for POWER.
    * sysdeps/powerpc/fpu/s_modff.c: New file: modff optimization for POWER.
    * sysdeps/powerpc/powerpc64/power5/Implies: Add powerpc/power5 and
    powerpc/power5/fpu folders.
    * sysdeps/powerpc/powerpc32/power5/Implies: Likewise.
    * benchtests/Makefile: Add modf testcase.
    * benchtests/bench-modf.c: New file: Benchmark test for modf.

--

diff --git a/benchtests/Makefile b/benchtests/Makefile
index 74938b9..dbbc44c 100644
--- a/benchtests/Makefile
+++ b/benchtests/Makefile
@@ -43,7 +43,7 @@
 #   See pow-inputs for an example.
 
 subdir := benchtests
-bench := exp pow
+bench := exp pow modf
 
 exp-ITER = 100000
 exp-ARGLIST = double
diff --git a/benchtests/bench-modf.c b/benchtests/bench-modf.c
new file mode 100644
index 0000000..1f91556
--- /dev/null
+++ b/benchtests/bench-modf.c
@@ -0,0 +1,27 @@
+/* Copyright (C) 2013 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+extern double modf ( double, double*);
+#define CALL_BENCH_FUNC(j, i) modf ( in[j].arg0, &i);
+struct args { double arg0; } in[] = {{42.42}, {-42.42}
+};
+#define NUM_SAMPLES (sizeof (in) / sizeof (struct args))
+static volatile double ret = 0.0;
+#define BENCH_FUNC(j) ({double iptr; ret =  CALL_BENCH_FUNC (j, iptr);})
+#define ITER 250000000
+#define FUNCNAME "modf"
+#include "bench-skeleton.c"
diff --git a/sysdeps/powerpc/power5/fpu/s_modf.c b/sysdeps/powerpc/power5/fpu/s_modf.c
new file mode 100644
index 0000000..b45bf66
--- /dev/null
+++ b/sysdeps/powerpc/power5/fpu/s_modf.c
@@ -0,0 +1,58 @@
+/* Copyright (C) 2013 Free Software Foundation, Inc.
+   This file is part of the GNU C Library
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#include <math.h>
+#include <math_private.h>
+#include <math_ldbl_opt.h>
+
+double
+__modf (double x, double *iptr)
+{
+  if (__builtin_isinf (x))
+    {
+      *iptr = x;
+      return __copysign (0.0, x);
+    }
+  else if (__builtin_isnan (x))
+    {
+      *iptr = NAN;
+      return NAN;
+    }
+
+  if (x >= 0.0)
+    {
+      *iptr = __floor (x);
+      return (x - *iptr);
+    }
+  else
+    {
+      *iptr = __ceil (x);
+      return (x - *iptr);
+    }
+}
+weak_alias (__modf, modf)
+#ifdef NO_LONG_DOUBLE
+strong_alias (__modf, __modfl)
+weak_alias (__modf, modfl)
+#endif
+#ifdef IS_IN_libm
+# if LONG_DOUBLE_COMPAT(libm, GLIBC_2_0)
+compat_symbol (libm, __modf, modfl, GLIBC_2_0);
+# endif
+#elif LONG_DOUBLE_COMPAT(libc, GLIBC_2_0)
+compat_symbol (libc, __modf, modfl, GLIBC_2_0);
+#endif
diff --git a/sysdeps/powerpc/power5/fpu/s_modff.c b/sysdeps/powerpc/power5/fpu/s_modff.c
new file mode 100644
index 0000000..55759cd
--- /dev/null
+++ b/sysdeps/powerpc/power5/fpu/s_modff.c
@@ -0,0 +1,46 @@
+/* Copyright (C) 2013 Free Software Foundation, Inc.
+   This file is part of the GNU C Library
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#include <math.h>
+#include <math_private.h>
+
+float
+__modff (float x, float *iptr)
+{
+  if (__builtin_isinff (x))
+    {
+      *iptr = x;
+      return __copysignf (0.0, x);
+    }
+  else if (__builtin_isnanf (x))
+    {
+      *iptr = NAN;
+      return NAN;
+    }
+
+  if (x >= 0.0)
+    {
+      *iptr = __floorf (x);
+      return (x - *iptr);
+    }
+  else
+    {
+      *iptr = __ceilf (x);
+      return (x - *iptr);
+    }
+}
+weak_alias (__modff, modff)
diff --git a/sysdeps/powerpc/powerpc32/power5/Implies b/sysdeps/powerpc/powerpc32/power5/Implies
index 17139bf..17949d4 100644
--- a/sysdeps/powerpc/powerpc32/power5/Implies
+++ b/sysdeps/powerpc/powerpc32/power5/Implies
@@ -1,2 +1,4 @@
+powerpc/power5/fpu
+powerpc/power5
 powerpc/powerpc32/power4/fpu
 powerpc/powerpc32/power4
diff --git a/sysdeps/powerpc/powerpc64/power5/Implies b/sysdeps/powerpc/powerpc64/power5/Implies
index bedb20b..b36831e 100644
--- a/sysdeps/powerpc/powerpc64/power5/Implies
+++ b/sysdeps/powerpc/powerpc64/power5/Implies
@@ -1,2 +1,4 @@
+powerpc/power5/fpu
+powerpc/power5
 powerpc/powerpc64/power4/fpu
 powerpc/powerpc64/power4