[glibc] Remove architecture specific sched_cpucount optimizations

[glibc] Remove architecture specific sched_cpucount optimizations

[Adhemerval Zanella]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=db373e4c57159ac82df4b07b596dd29c4cfe9d86

commit db373e4c57159ac82df4b07b596dd29c4cfe9d86
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Wed Mar 24 18:56:34 2021 -0300

    Remove architecture specific sched_cpucount optimizations
    
    And replace the generic algorithm with the Brian Kernighan's one.
    GCC optimize it with popcnt if the architecture supports, so there
    is no need to add the extra POPCNT define to enable it.
    
    This is really a micro-optimization that only adds complexity:
    recent ABIs already support it (x86-64-v2 or power64le) and it
    simplifies the code for internal usage, since i686 does not allow an
    internal iFUNC call.
    
    Checked on x86_64-linux-gnu, aarch64-linux-gnu, and
    powerpc64le-linux-gnu.

Diff:
---
 posix/sched_cpucount.c                       | 40 ++++++++++------------------
 sysdeps/i386/i686/multiarch/sched_cpucount.c |  1 -
 sysdeps/ia64/sched_cpucount.c                | 20 --------------
 sysdeps/powerpc/sched_cpucount.c             | 22 ---------------
 sysdeps/x86_64/multiarch/sched_cpucount.c    | 36 -------------------------
 sysdeps/x86_64/sched_cpucount.c              | 25 -----------------
 6 files changed, 14 insertions(+), 130 deletions(-)

diff --git a/posix/sched_cpucount.c b/posix/sched_cpucount.c
index b0ca4ea7bc..63d0e99590 100644
--- a/posix/sched_cpucount.c
+++ b/posix/sched_cpucount.c
@@ -17,36 +17,24 @@
 
 #include <sched.h>
 
+/* Counting bits set, Brian Kernighan's way.
+   Using a open-coded routine is slight better for architectures that
+   do not have a popcount instruction (compiler might emit a library
+   call).  */
+static inline int
+countbits (__cpu_mask v)
+{
+  int s = 0;
+  for (; v != 0; s++)
+    v &= v - 1;
+  return s;
+}
 
 int
 __sched_cpucount (size_t setsize, const cpu_set_t *setp)
 {
   int s = 0;
-  const __cpu_mask *p = setp->__bits;
-  const __cpu_mask *end = &setp->__bits[setsize / sizeof (__cpu_mask)];
-
-  while (p < end)
-    {
-      __cpu_mask l = *p++;
-
-#ifdef POPCNT
-      s += POPCNT (l);
-#else
-      if (l == 0)
-	continue;
-
-      _Static_assert (sizeof (l) == sizeof (unsigned int)
-		      || sizeof (l) == sizeof (unsigned long)
-		      || sizeof (l) == sizeof (unsigned long long),
-		      "sizeof (__cpu_mask");
-      if (sizeof (__cpu_mask) == sizeof (unsigned int))
-	s += __builtin_popcount (l);
-      else if (sizeof (__cpu_mask) == sizeof (unsigned long))
-	s += __builtin_popcountl (l);
-      else
-	s += __builtin_popcountll (l);
-#endif
-    }
-
+  for (int i = 0; i < setsize / sizeof (__cpu_mask); i++)
+    s += countbits (setp->__bits[i]);
   return s;
 }
diff --git a/sysdeps/i386/i686/multiarch/sched_cpucount.c b/sysdeps/i386/i686/multiarch/sched_cpucount.c
deleted file mode 100644
index 7db31b02f8..0000000000
--- a/sysdeps/i386/i686/multiarch/sched_cpucount.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <sysdeps/x86_64/multiarch/sched_cpucount.c>
diff --git a/sysdeps/ia64/sched_cpucount.c b/sysdeps/ia64/sched_cpucount.c
deleted file mode 100644
index 8440864b02..0000000000
--- a/sysdeps/ia64/sched_cpucount.c
+++ /dev/null
@@ -1,20 +0,0 @@
-/* Copyright (C) 2007-2021 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
-   <https://www.gnu.org/licenses/>.  */
-
-#define POPCNT(l) __builtin_popcountl (l)
-
-#include <posix/sched_cpucount.c>
diff --git a/sysdeps/powerpc/sched_cpucount.c b/sysdeps/powerpc/sched_cpucount.c
deleted file mode 100644
index 8f00e3dbc8..0000000000
--- a/sysdeps/powerpc/sched_cpucount.c
+++ /dev/null
@@ -1,22 +0,0 @@
-/* Copyright (C) 2007-2021 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
-   <https://www.gnu.org/licenses/>.  */
-
-#ifdef _ARCH_PWR5
-# define POPCNT(l) __builtin_popcountl (l)
-#endif
-
-#include <posix/sched_cpucount.c>
diff --git a/sysdeps/x86_64/multiarch/sched_cpucount.c b/sysdeps/x86_64/multiarch/sched_cpucount.c
deleted file mode 100644
index 5180a11434..0000000000
--- a/sysdeps/x86_64/multiarch/sched_cpucount.c
+++ /dev/null
@@ -1,36 +0,0 @@
-/* Count bits in CPU set.  x86-64 multi-arch version.
-   This file is part of the GNU C Library.
-   Copyright (C) 2008-2021 Free Software Foundation, Inc.
-   Contributed by Ulrich Drepper <drepper@redhat.com>.
-
-   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
-   <https://www.gnu.org/licenses/>.  */
-
-#include <sched.h>
-#include "init-arch.h"
-
-#define __sched_cpucount static generic_cpucount
-#include <posix/sched_cpucount.c>
-#undef __sched_cpucount
-
-#define POPCNT(l) \
-  ({ __cpu_mask r; \
-     asm ("popcnt %1, %0" : "=r" (r) : "0" (l));\
-     r; })
-#define __sched_cpucount static popcount_cpucount
-#include <posix/sched_cpucount.c>
-#undef __sched_cpucount
-
-libc_ifunc (__sched_cpucount,
-	    CPU_FEATURE_USABLE (POPCNT) ? popcount_cpucount : generic_cpucount);
diff --git a/sysdeps/x86_64/sched_cpucount.c b/sysdeps/x86_64/sched_cpucount.c
deleted file mode 100644
index 5a27336d6d..0000000000
--- a/sysdeps/x86_64/sched_cpucount.c
+++ /dev/null
@@ -1,25 +0,0 @@
-/* Copyright (C) 2007-2021 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
-   <https://www.gnu.org/licenses/>.  */
-
-#ifdef __amdfam10
-# define POPCNT(l) \
-  ({ __cpu_mask r;							      \
-     asm ("popcntq %1, %0" : "=r" (r) : "0" (l));			      \
-     r; })
-#endif
-
-#include <posix/sched_cpucount.c>