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[PATCH] Use fsqrt and fsqrts unconditionally on ppc64


Hi!

Any reason why fsqrt{,s} use is conditional even in 64-bit glibc?
sysdeps/powerpc/fpu/e_sqrt{,f}.c guards the insn use with:
  /* If the CPU is 64-bit we can use the optional FP instructions we.  */
  if ((GLRO (dl_hwcap) & PPC_FEATURE_64) != 0)
and otherwise falls back to __slow_ieee754_sqrt{,f}.  But in 64-bit
code, I'd say we can always assume the CPU is 64-bit and PPC_FEATURE_64
is set and get rid of an unneeded runtime memory load, masking and more
importantly quite large fallback routine.

2006-01-20  Jakub Jelinek  <jakub@redhat.com>

	* sysdeps/powerpc/powerpc64/fpu/e_sqrt.c: New file.
	* sysdeps/powerpc/powerpc64/fpu/e_sqrtf.c: New file.
	* sysdeps/powerpc/fpu/bits/mathinline.h (__CPU_HAS_FSQRT): Define.
	(__ieee754_sqrt, __ieee754_sqrtf): Use it.

--- libc/sysdeps/powerpc/powerpc64/fpu/e_sqrt.c.jj	2006-01-20 16:36:49.000000000 +0100
+++ libc/sysdeps/powerpc/powerpc64/fpu/e_sqrt.c	2006-01-20 16:39:05.000000000 +0100
@@ -0,0 +1,29 @@
+/* Double-precision floating point square root.
+   Copyright (C) 1997, 2002, 2003, 2004, 2006 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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <math.h>
+#include <math_private.h>
+
+double
+__ieee754_sqrt (double x)
+{
+  double z;
+  __asm __volatile ("fsqrt %0,%1" : "=f" (z) : "f" (x));
+  return z;
+}
--- libc/sysdeps/powerpc/powerpc64/fpu/e_sqrtf.c.jj	2006-01-20 16:36:52.000000000 +0100
+++ libc/sysdeps/powerpc/powerpc64/fpu/e_sqrtf.c	2006-01-20 16:37:55.000000000 +0100
@@ -0,0 +1,29 @@
+/* Single-precision floating point square root.
+   Copyright (C) 1997, 2003, 2004, 2006 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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <math.h>
+#include <math_private.h>
+
+float
+__ieee754_sqrtf (float x)
+{
+  double z;
+  __asm ("fsqrts %0,%1" : "=f" (z) : "f" (x));
+  return z;
+}
--- libc/sysdeps/powerpc/fpu/bits/mathinline.h.jj	2004-10-01 12:05:04.000000000 +0200
+++ libc/sysdeps/powerpc/fpu/bits/mathinline.h	2006-01-20 16:45:16.000000000 +0100
@@ -1,5 +1,5 @@
 /* Inline math functions for powerpc.
-   Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2004
+   Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2004, 2006
    Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
@@ -123,12 +123,18 @@ __NTH (fdimf (float __x, float __y))
 #endif /* !__NO_MATH_INLINES && __OPTIMIZE__ */
 
 /* This code is used internally in the GNU libc.  */
-#  ifdef __LIBC_INTERNAL_MATH_INLINES
+#ifdef __LIBC_INTERNAL_MATH_INLINES
 
 #include <sysdep.h>
 #include <ldsodefs.h>
 #include <dl-procinfo.h>
 
+# if __WORDSIZE == 64
+#  define __CPU_HAS_FSQRT 1
+# else
+#  define __CPU_HAS_FSQRT ((GLRO(dl_hwcap) & PPC_FEATURE_64) != 0)
+# endif
+
 extern double __slow_ieee754_sqrt (double);
 __MATH_INLINE double
 __NTH (__ieee754_sqrt (double __x))
@@ -136,7 +142,7 @@ __NTH (__ieee754_sqrt (double __x))
   double __z;
 
   /* If the CPU is 64-bit we can use the optional FP instructions we.  */
-  if ((GLRO(dl_hwcap) & PPC_FEATURE_64) != 0)
+  if (__CPU_HAS_FSQRT)
   {
     /* Volatile is required to prevent the compiler from moving the
        fsqrt instruction above the branch.  */
@@ -158,7 +164,7 @@ __NTH (__ieee754_sqrtf (float __x))
   float __z;
 
   /* If the CPU is 64-bit we can use the optional FP instructions we.  */
-  if ((GLRO(dl_hwcap) & PPC_FEATURE_64) != 0)
+  if (__CPU_HAS_FSQRT)
   {
     /* Volatile is required to prevent the compiler from moving the
        fsqrts instruction above the branch.  */
@@ -172,5 +178,5 @@ __NTH (__ieee754_sqrtf (float __x))
 
   return __z;
 }
-#  endif /* __LIBC_INTERNAL_MATH_INLINES */
+#endif /* __LIBC_INTERNAL_MATH_INLINES */
 #endif /* __GNUC__ && !_SOFT_FLOAT */

	Jakub


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