[PATCH 12/17] math: Use log10f from CORE-MATH

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=UTF-8, Size: 12012 bytes --]

The CORE-MATH implementation is correctly rounded (for any rounding mode)
and shows better performance compared to the generic log10f.

The code was adapted to glibc style and to use the definition of
math_config.h (to handle errno, overflow, and underflow).

Benchtest on x64_64 (Ryzen 9 5900X, gcc 14.2.1), aarch64 (Neoverse-N1,
gcc 13.3.1), and powerpc (POWER10, gcc 13.2.1):

Latency                      master        patched   improvement
x86_64                      49.9017        33.5143        32.84%
x86_64v2                    50.4878        33.5623        33.52%
x86_64v3                    50.0991        27.6078        44.89%
i686                        140.874        106.086        24.69%
aarch64                     19.2846        11.3573        41.11%
power10                     14.0994        7.7739        44.86%
powerpc                     14.2898        7.92497        44.54%

reciprocal-throughput        master        patched   improvement
x86_64                      17.8336        12.9074        27.62%
x86_64v2                    16.4418        11.3220        31.14%
x86_64v3                    15.6002        10.5158        32.59%
i686                        66.0678        80.2287        -21.43%
aarch64                      9.4906        6.8393        27.94%
power10                      7.5255        5.5084        26.80%
powerpc                      9.5204        6.98055        26.68%

The performance decrease for i686 is mostly due the use of x87 fpu,
when building with '-msse2 -mfpmath=sse':

                             master        patched   improvement
latency                     140.874        77.1137        45.26%
reciprocal-throughput        64.481        56.4397        12.47%

Signed-off-by: Alexei Sibidanov <sibid@uvic.ca>
Signed-off-by: Paul Zimmermann <Paul.Zimmermann@inria.fr>
Signed-off-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
---
 sysdeps/i386/fpu/e_log10f.S       |  66 ----------
 sysdeps/ieee754/flt-32/e_log10f.c | 196 +++++++++++++++++++++++-------
 2 files changed, 152 insertions(+), 110 deletions(-)
 delete mode 100644 sysdeps/i386/fpu/e_log10f.S

diff --git a/sysdeps/i386/fpu/e_log10f.S b/sysdeps/i386/fpu/e_log10f.S
deleted file mode 100644
index 47f82e1993..0000000000
--- a/sysdeps/i386/fpu/e_log10f.S
+++ /dev/null
@@ -1,66 +0,0 @@
-/*
- * Public domain.
- */
-
-#include <machine/asm.h>
-#include <libm-alias-finite.h>
-
-	.section .rodata.cst8,"aM",@progbits,8
-
-	.p2align 3
-	.type one,@object
-one:	.double 1.0
-	ASM_SIZE_DIRECTIVE(one)
-	/* It is not important that this constant is precise.  It is only
-	   a value which is known to be on the safe side for using the
-	   fyl2xp1 instruction.  */
-	.type limit,@object
-limit:	.double 0.29
-	ASM_SIZE_DIRECTIVE(limit)
-
-
-#ifdef PIC
-# define MO(op) op##@GOTOFF(%edx)
-#else
-# define MO(op) op
-#endif
-
-	.text
-ENTRY(__ieee754_log10f)
-	fldlg2			// log10(2)
-	flds	4(%esp)		// x : log10(2)
-#ifdef PIC
-	LOAD_PIC_REG (dx)
-#endif
-	fxam
-	fnstsw
-	fld	%st		// x : x : log10(2)
-	sahf
-	jc	3f		// in case x is NaN or ±Inf
-4:	fsubl	MO(one)		// x-1 : x : log10(2)
-	fld	%st		// x-1 : x-1 : x : log10(2)
-	fabs			// |x-1| : x-1 : x : log10(2)
-	fcompl	MO(limit)	// x-1 : x : log10(2)
-	fnstsw			// x-1 : x : log10(2)
-	andb	$0x45, %ah
-	jz	2f
-	fxam
-	fnstsw
-	andb	$0x45, %ah
-	cmpb	$0x40, %ah
-	jne	5f
-	fabs			// log10(1) is +0 in all rounding modes.
-5:	fstp	%st(1)		// x-1 : log10(2)
-	fyl2xp1			// log10(x)
-	ret
-
-2:	fstp	%st(0)		// x : log10(2)
-	fyl2x			// log10(x)
-	ret
-
-3:	jp	4b		// in case x is ±Inf
-	fstp	%st(1)
-	fstp	%st(1)
-	ret
-END (__ieee754_log10f)
-libm_alias_finite (__ieee754_log10f, __log10f)
diff --git a/sysdeps/ieee754/flt-32/e_log10f.c b/sysdeps/ieee754/flt-32/e_log10f.c
index 791895e042..8620805634 100644
--- a/sysdeps/ieee754/flt-32/e_log10f.c
+++ b/sysdeps/ieee754/flt-32/e_log10f.c
@@ -1,54 +1,162 @@
-/* e_log10f.c -- float version of e_log10.c.
- */
-
-/*
- * ====================================================
- * 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.
- * ====================================================
- */
+/* Correctly-rounded radix-10 logarithm function for binary32 value.
+
+Copyright (c) 2022-2023 Alexei Sibidanov.
+
+This file is part of the CORE-MATH project
+project (file src/binary32/expm1/expm1f.c, revision bc385c2).
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
 
 #include <math.h>
-#include <math_private.h>
-#include <fix-int-fp-convert-zero.h>
+#include <stdint.h>
 #include <libm-alias-finite.h>
+#include "math_config.h"
 
-static const float
-two25      =  3.3554432000e+07, /* 0x4c000000 */
-ivln10     =  4.3429449201e-01, /* 0x3ede5bd9 */
-log10_2hi  =  3.0102920532e-01, /* 0x3e9a2080 */
-log10_2lo  =  7.9034151668e-07; /* 0x355427db */
+static __attribute__ ((noinline)) float
+as_special (float x)
+{
+  uint32_t ux = asuint (x);
+  if (ux == 0x7f800000u)
+    return x; /* +inf */
+  uint32_t ax = ux << 1;
+  if (ax == 0u)
+    { /* -0.0 */
+      __math_divzerof (1);
+    }
+  if (ax > 0xff000000u)
+    return x + x; /* nan */
+  return __math_invalidf (x);
+}
 
 float
-__ieee754_log10f(float x)
+__ieee754_log10f (float x)
 {
-	float y,z;
-	int32_t i,k,hx;
-
-	GET_FLOAT_WORD(hx,x);
-
-	k=0;
-	if (hx < 0x00800000) {			/* x < 2**-126  */
-	    if (__builtin_expect((hx&0x7fffffff)==0, 0))
-	      return -two25/fabsf (x);	/* log(+-0)=-inf  */
-	    if (__builtin_expect(hx<0, 0))
-		return (x-x)/(x-x);	/* log(-#) = NaN */
-	    k -= 25; x *= two25; /* subnormal number, scale up x */
-	    GET_FLOAT_WORD(hx,x);
+  static const double tr[] =
+    {
+      0x1p+0,         0x1.f81f82p-1,  0x1.f07c1fp-1,  0x1.e9131acp-1,
+      0x1.e1e1e1ep-1, 0x1.dae6077p-1, 0x1.d41d41dp-1, 0x1.cd85689p-1,
+      0x1.c71c71cp-1, 0x1.c0e0704p-1, 0x1.bacf915p-1, 0x1.b4e81b5p-1,
+      0x1.af286bdp-1, 0x1.a98ef6p-1,  0x1.a41a41ap-1, 0x1.9ec8e95p-1,
+      0x1.999999ap-1, 0x1.948b0fdp-1, 0x1.8f9c19p-1,  0x1.8acb90fp-1,
+      0x1.8618618p-1, 0x1.8181818p-1, 0x1.7d05f41p-1, 0x1.78a4c81p-1,
+      0x1.745d174p-1, 0x1.702e05cp-1, 0x1.6c16c17p-1, 0x1.6816817p-1,
+      0x1.642c859p-1, 0x1.605816p-1,  0x1.5c9882cp-1, 0x1.58ed231p-1,
+      0x1.5555555p-1, 0x1.51d07ebp-1, 0x1.4e5e0a7p-1, 0x1.4afd6ap-1,
+      0x1.47ae148p-1, 0x1.446f865p-1, 0x1.4141414p-1, 0x1.3e22cbdp-1,
+      0x1.3b13b14p-1, 0x1.3813814p-1, 0x1.3521cfbp-1, 0x1.323e34ap-1,
+      0x1.2f684bep-1, 0x1.2c9fb4ep-1, 0x1.29e412ap-1, 0x1.27350b9p-1,
+      0x1.2492492p-1, 0x1.21fb781p-1, 0x1.1f7047ep-1, 0x1.1cf06aep-1,
+      0x1.1a7b961p-1, 0x1.1811812p-1, 0x1.15b1e5fp-1, 0x1.135c811p-1,
+      0x1.1111111p-1, 0x1.0ecf56cp-1, 0x1.0c9715p-1,  0x1.0a6810ap-1,
+      0x1.0842108p-1, 0x1.0624dd3p-1, 0x1.041041p-1,  0x1.0204081p-1,
+      0.5
+    };
+  static const double tl[] =
+    {
+      -0x1.d45fd6237ebe3p-47, 0x1.b947689311b6ep-8, 0x1.b5e909c96d7d5p-7,
+      0x1.45f4f59ed2165p-6,   0x1.af5f92cbd8f1ep-6, 0x1.0ba01a606de8cp-5,
+      0x1.3ed119b9a2b7bp-5,   0x1.714834298eec2p-5, 0x1.a30a9d98357fbp-5,
+      0x1.d41d512670813p-5,   0x1.02428c0f65519p-4, 0x1.1a23444eecc3ep-4,
+      0x1.31b30543f4cb4p-4,   0x1.48f3ed39bfd04p-4, 0x1.5fe8049a0e423p-4,
+      0x1.769140a6aa008p-4,   0x1.8cf1836c98cb3p-4, 0x1.a30a9d55541a1p-4,
+      0x1.b8de4d1ee823ep-4,   0x1.ce6e4202ca2e6p-4, 0x1.e3bc1accace07p-4,
+      0x1.f8c9683b5abd4p-4,   0x1.06cbd68ca9a6ep-3, 0x1.11142f19df73p-3,
+      0x1.1b3e71fa7a97fp-3,   0x1.254b4d37a46e3p-3, 0x1.2f3b6912cbf07p-3,
+      0x1.390f683115886p-3,   0x1.42c7e7fffc5a8p-3, 0x1.4c65808c78d3cp-3,
+      0x1.55e8c50751c55p-3,   0x1.5f52445dec3d8p-3, 0x1.68a288c3f12p-3,
+      0x1.71da17bdf0d19p-3,   0x1.7af973608afd9p-3, 0x1.84011952a2579p-3,
+      0x1.8cf1837a7ea6p-3,    0x1.95cb2891e43d6p-3, 0x1.9e8e7b0f869ep-3,
+      0x1.a73beaa5db18dp-3,   0x1.afd3e394558d3p-3, 0x1.b856cf060d9f1p-3,
+      0x1.c0c5134de1ffcp-3,   0x1.c91f1371bc99fp-3, 0x1.d1652ffcd3f53p-3,
+      0x1.d997c6f635e75p-3,   0x1.e1b733ab90f3bp-3, 0x1.e9c3ceadac856p-3,
+      0x1.f1bdeec43a305p-3,   0x1.f9a5e7a5fa3fep-3, 0x1.00be05ac02f2bp-2,
+      0x1.04a054d81a2d4p-2,   0x1.087a0835957fbp-2, 0x1.0c4b457099517p-2,
+      0x1.101431aa1fe51p-2,   0x1.13d4f08b98dd8p-2, 0x1.178da53edb892p-2,
+      0x1.1b3e71e9f9d58p-2,   0x1.1ee777defdeedp-2, 0x1.2288d7b48e23bp-2,
+      0x1.2622b0f52e49fp-2,   0x1.29b522a4c6314p-2, 0x1.2d404b0e30f8p-2,
+      0x1.30c4478f3fbe5p-2,   0x1.34413509f7915p-2
+    };
+  static const union
+  {
+    float f;
+    uint32_t u;
+  } st[] =
+  {
+    { 0x1p+0 },        { 0x1.4p+3 },      { 0x1.9p+6 },       { 0x1.f4p+9 },
+    { 0x1.388p+13 },   { 0x1.86ap+16 },   { 0x1.e848p+19 },   { 0x1.312dp+23 },
+    { 0x1.7d784p+26 }, { 0x1.dcd65p+29 }, { 0x1.2a05f2p+33 }, { 0 },
+    { 0 },             { 0 },             { 0 },              { 0 }
+  };
+  static const double b[] =
+    { 
+      0x1.bcb7b15c5a2f8p-2, -0x1.bcbb1dbb88ebap-3, 0x1.2871c39d521c6p-3
+    };
+  static const double c[] =
+    {
+      0x1.bcb7b1526e50ep-2,  -0x1.bcb7b1526e53dp-3, 0x1.287a7636f3fa2p-3,
+      -0x1.bcb7b146a14b3p-4, 0x1.63c627d5219cbp-4,  -0x1.2880736c8762dp-4,
+      0x1.fc1ecf913961ap-5
+    };
+  uint32_t ux = asuint (x);
+  if (__glibc_unlikely (ux < (1 << 23) || ux >= 0x7f800000u))
+    {
+      if (ux == 0 || ux >= 0x7f800000u)
+	return as_special (x);
+      /* subnormal */
+      int n = __builtin_clz (ux) - 8;
+      ux <<= n;
+      ux -= n << 23;
+    }
+  unsigned m = ux & ((1 << 23) - 1), j = (m + (1 << (23 - 7))) >> (23 - 6);
+  double ix = tr[j], l = tl[j];
+  int e = ((int) ux >> 23) - 127;
+  unsigned je = e + 1;
+  je = (je * 0x4d104d4) >> 28;
+  if (__glibc_unlikely (ux == st[je].u))
+    return je;
+
+  double tz = asdouble (((int64_t) m | ((int64_t) 1023 << 23)) << (52 - 23));
+  double z = tz * ix - 1, z2 = z * z;
+  double r
+      = ((e * 0x1.34413509f79ffp-2 + l) + z * b[0]) + z2 * (b[1] + z * b[2]);
+  float ub = r, lb = r + 0x1.b008p-34;
+  if (__glibc_unlikely (ub != lb))
+    {
+      double f = z
+		 * ((c[0] + z * c[1])
+		    + z2
+			  * ((c[2] + z * c[3])
+			     + z2 * (c[4] + z * c[5] + z2 * c[6])));
+      f -= 0x1.0cee0ed4ca7e9p-54 * e;
+      f += l - tl[0];
+      double el = e * 0x1.34413509f7ap-2;
+      r = el + f;
+      ub = r;
+      tz = r;
+      if (__glibc_unlikely (!((asuint64 (tz) & ((1 << 28) - 1)))))
+	{
+	  double dr = (el - r) + f;
+	  r += dr * 32;
+	  ub = r;
 	}
-	if (__builtin_expect(hx >= 0x7f800000, 0)) return x+x;
-	k += (hx>>23)-127;
-	i  = ((uint32_t)k&0x80000000)>>31;
-	hx = (hx&0x007fffff)|((0x7f-i)<<23);
-	y  = (float)(k+i);
-	if (FIX_INT_FP_CONVERT_ZERO && y == 0.0f)
-	  y = 0.0f;
-	SET_FLOAT_WORD(x,hx);
-	z  = y*log10_2lo + ivln10*__ieee754_logf(x);
-	return  z+y*log10_2hi;
+    }
+  return ub;
 }
 libm_alias_finite (__ieee754_log10f, __log10f)
-- 
2.43.0