[PATCH v2 3/9] math: Simplify hypotf implementation

[PATCH v2 3/9] math: Simplify hypotf implementation

[Wilco Dijkstra]

Hi Adhemerval,

+  if ((isinf (x) || isinf (y))
+      && !issignaling (x) && !issignaling (y))
+    return INFINITY;
+  if (isnan (x) || isnan (y))
+    return x + y;

These checks are inefficient. It's partly because GCC uses FP comparisons for
isinf/isnan when integer arithmetic is faster on almost all targets and more
correct for signaling NaNs. However GCC doesn't seem to treat these as
unlikely and so there are 3 comparisons and 3 taken branches before entering
the main code. If you change it to:

if (!isfinite (x) || !isfinite (y))
{
  if ((isinf (x) || isinf (y))
      && !issignaling (x) && !issignaling (y))
    return INFINITY;
 return x + y;
}

then it uses only 2 comparisons and we fallthrough into the common case.
This gives a speedup of 10%.

Wilco

[PATCH v2 3/9] math: Simplify hypotf implementation

[Adhemerval Zanella]

Use isnan()/isinf() instead of GET_FLOAT_WORD and integer operations.
There is also no need to check for 0.0.

The file Copyright is also changed to use  GPL, the implementation was
completely changed by 7c10fd3515f to use double precision instead of
scaling and this change removes all the GET_FLOAT_WORD usage.

Checked on x86_64-linux-gnu.
---
 sysdeps/ieee754/flt-32/e_hypotf.c | 57 +++++++++++++------------------
 1 file changed, 23 insertions(+), 34 deletions(-)

diff --git a/sysdeps/ieee754/flt-32/e_hypotf.c b/sysdeps/ieee754/flt-32/e_hypotf.c
index e770947dc1..6495a91cd4 100644
--- a/sysdeps/ieee754/flt-32/e_hypotf.c
+++ b/sysdeps/ieee754/flt-32/e_hypotf.c
@@ -1,46 +1,35 @@
-/* e_hypotf.c -- float version of e_hypot.c.
- */
+/* Euclidean distance function.  Float/Binary32 version.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
 
-/*
- * ====================================================
- * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
- *
- * Developed at SunPro, a Sun Microsystems, Inc. business.
- * Permission to use, copy, modify, and distribute this
- * software is freely granted, provided that this notice
- * is preserved.
- * ====================================================
- */
+   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 <math.h>
 #include <math_private.h>
 #include <libm-alias-finite.h>
 
 float
-__ieee754_hypotf(float x, float y)
+__ieee754_hypotf (float x, float y)
 {
-	double d_x, d_y;
-	int32_t ha, hb;
-
-	GET_FLOAT_WORD(ha,x);
-	ha &= 0x7fffffff;
-	GET_FLOAT_WORD(hb,y);
-	hb &= 0x7fffffff;
-	if (ha == 0x7f800000 && !issignaling (y))
-	  return fabsf(x);
-	else if (hb == 0x7f800000 && !issignaling (x))
-	  return fabsf(y);
-	else if (ha > 0x7f800000 || hb > 0x7f800000)
-	  return fabsf(x) * fabsf(y);
-	else if (ha == 0)
-	  return fabsf(y);
-	else if (hb == 0)
-	  return fabsf(x);
-
-	d_x = (double) x;
-	d_y = (double) y;
+  if ((isinf (x) || isinf (y))
+      && !issignaling (x) && !issignaling (y))
+    return INFINITY;
+  if (isnan (x) || isnan (y))
+    return x + y;
 
-	return (float) sqrt(d_x * d_x + d_y * d_y);
+  return sqrt ((double) x * (double) x + (double) y * (double) y);
 }
 #ifndef __ieee754_hypotf
 libm_alias_finite (__ieee754_hypotf, __hypotf)
-- 
2.32.0

[PATCH v2 3/9] math: Simplify hypotf implementation

[Adhemerval Zanella]

Use isnan()/isinf() instead of GET_FLOAT_WORD and integer operations.
There is also no need to check for 0.0.

The file Copyright is also changed to use  GPL, the implementation was
completely changed by 7c10fd3515f to use double precision instead of
scaling and this change removes all the GET_FLOAT_WORD usage.

Checked on x86_64-linux-gnu.
---
 sysdeps/ieee754/flt-32/e_hypotf.c | 57 +++++++++++++------------------
 1 file changed, 23 insertions(+), 34 deletions(-)

diff --git a/sysdeps/ieee754/flt-32/e_hypotf.c b/sysdeps/ieee754/flt-32/e_hypotf.c
index e770947dc1..6495a91cd4 100644
--- a/sysdeps/ieee754/flt-32/e_hypotf.c
+++ b/sysdeps/ieee754/flt-32/e_hypotf.c
@@ -1,46 +1,35 @@
-/* e_hypotf.c -- float version of e_hypot.c.
- */
+/* Euclidean distance function.  Float/Binary32 version.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
 
-/*
- * ====================================================
- * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
- *
- * Developed at SunPro, a Sun Microsystems, Inc. business.
- * Permission to use, copy, modify, and distribute this
- * software is freely granted, provided that this notice
- * is preserved.
- * ====================================================
- */
+   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 <math.h>
 #include <math_private.h>
 #include <libm-alias-finite.h>
 
 float
-__ieee754_hypotf(float x, float y)
+__ieee754_hypotf (float x, float y)
 {
-	double d_x, d_y;
-	int32_t ha, hb;
-
-	GET_FLOAT_WORD(ha,x);
-	ha &= 0x7fffffff;
-	GET_FLOAT_WORD(hb,y);
-	hb &= 0x7fffffff;
-	if (ha == 0x7f800000 && !issignaling (y))
-	  return fabsf(x);
-	else if (hb == 0x7f800000 && !issignaling (x))
-	  return fabsf(y);
-	else if (ha > 0x7f800000 || hb > 0x7f800000)
-	  return fabsf(x) * fabsf(y);
-	else if (ha == 0)
-	  return fabsf(y);
-	else if (hb == 0)
-	  return fabsf(x);
-
-	d_x = (double) x;
-	d_y = (double) y;
+  if ((isinf (x) || isinf (y))
+      && !issignaling (x) && !issignaling (y))
+    return INFINITY;
+  if (isnan (x) || isnan (y))
+    return x + y;
 
-	return (float) sqrt(d_x * d_x + d_y * d_y);
+  return sqrt ((double) x * (double) x + (double) y * (double) y);
 }
 #ifndef __ieee754_hypotf
 libm_alias_finite (__ieee754_hypotf, __hypotf)
-- 
2.32.0