From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Mon, 16 Jun 2025 13:17:35 +0000 (-0300)
Subject: powerpc: Remove modff optimization
X-Git-Tag: glibc-2.42~85
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=5c2b21c478068f4f3140b020416dccdead1401e6;p=thirdparty%2Fglibc.git

powerpc: Remove modff optimization

The generic implementation is slight more optimized than the powerpc
one, where it has a more optimized inf/nan check (by not using FP
unit checks, along with branch prediction hints), and removed one
branch by issuing trunc instead of a combination of floor/ceil (which
also generated less code).

On power10 with gcc 14.2.1:

reciprocal-throughput        master        patch        difference
workload-0_1                 1.5210       1.3942             8.34%
workload-1_maxint            2.0926       1.3940            33.38%
workload-maxint_maxfloat     1.7851       1.3940            21.91%
workload-integral            1.5216       1.3941             8.37%

latency                      master        patch        difference
workload-0_1                 1.5928       2.6337           -65.35%
workload-1_maxint            3.2929       2.6337            20.02%
workload-maxint_maxfloat     1.9697       2.6341           -33.73%
workload-integral            2.0597       2.6337           -27.87%

Checked on powerpc64le-linux-gnu.
Reviewed-by: Sachin Monga <smonga@linux.ibm.com>
---

diff --git a/sysdeps/ieee754/flt-32/s_modff.c b/sysdeps/ieee754/flt-32/s_modff.c
index e6d2e4ab49..965136bac9 100644
--- a/sysdeps/ieee754/flt-32/s_modff.c
+++ b/sysdeps/ieee754/flt-32/s_modff.c
@@ -64,4 +64,6 @@ __modff (float x, float *iptr)
   return asfloat (t & SIGN_MASK);
 #endif
 }
+#ifndef __modff
 libm_alias_float (__modf, modf)
+#endif
diff --git a/sysdeps/powerpc/fpu/math-use-builtins-trunc.h b/sysdeps/powerpc/fpu/math-use-builtins-trunc.h
new file mode 100644
index 0000000000..fd186d3510
--- /dev/null
+++ b/sysdeps/powerpc/fpu/math-use-builtins-trunc.h
@@ -0,0 +1,8 @@
+#define USE_TRUNC_BUILTIN 0
+#ifdef _ARCH_PWR5X
+# define USE_TRUNCF_BUILTIN 1
+#else
+# define USE_TRUNCF_BUILTIN 0
+#endif
+#define USE_TRUNCL_BUILTIN 0
+#define USE_TRUNCF128_BUILTIN 0
diff --git a/sysdeps/powerpc/fpu/s_modff.c b/sysdeps/powerpc/fpu/s_modff.c
deleted file mode 100644
index 79eeb7b810..0000000000
--- a/sysdeps/powerpc/fpu/s_modff.c
+++ /dev/null
@@ -1,55 +0,0 @@
-/* Copyright (C) 2013-2025 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 <https://www.gnu.org/licenses/>.  */
-
-/* ISA 2.07 provides fast GPR to FP instruction (mfvsr{d,wz}) which make
-   generic implementation faster.  Also disables for old ISAs that do not
-   have ceil/floor instructions.  */
-#if defined(_ARCH_PWR8) || !defined(_ARCH_PWR5X)
-# include <sysdeps/ieee754/flt-32/s_modff.c>
-#else
-# include <math.h>
-# include <libm-alias-float.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 copysignf (x - *iptr, x);
-    }
-  else
-    {
-      *iptr = ceilf (x);
-      return copysignf (x - *iptr, x);
-    }
-}
-# ifndef __modff
-libm_alias_float (__modf, modf)
-# endif
-#endif
diff --git a/sysdeps/powerpc/powerpc32/power4/fpu/multiarch/s_modff-power5+.c b/sysdeps/powerpc/powerpc32/power4/fpu/multiarch/s_modff-power5+.c
index 69591da43f..15bfa0bba9 100644
--- a/sysdeps/powerpc/powerpc32/power4/fpu/multiarch/s_modff-power5+.c
+++ b/sysdeps/powerpc/powerpc32/power4/fpu/multiarch/s_modff-power5+.c
@@ -17,4 +17,4 @@
    <https://www.gnu.org/licenses/>.  */
 
 #define __modff __modff_power5plus
-#include <sysdeps/powerpc/fpu/s_modff.c>
+#include <sysdeps/ieee754/flt-32/s_modff.c>
diff --git a/sysdeps/powerpc/powerpc64/be/fpu/multiarch/s_modff-power5+.c b/sysdeps/powerpc/powerpc64/be/fpu/multiarch/s_modff-power5+.c
index 69591da43f..15bfa0bba9 100644
--- a/sysdeps/powerpc/powerpc64/be/fpu/multiarch/s_modff-power5+.c
+++ b/sysdeps/powerpc/powerpc64/be/fpu/multiarch/s_modff-power5+.c
@@ -17,4 +17,4 @@
    <https://www.gnu.org/licenses/>.  */
 
 #define __modff __modff_power5plus
-#include <sysdeps/powerpc/fpu/s_modff.c>
+#include <sysdeps/ieee754/flt-32/s_modff.c>