x86-64: Add log2f with FMA

For workload-spec2017.wrf, on Skylake, it improves performance by:

                           Before            After     Improvement
reciprocal-throughput      16.5937          14.0789       17%
latency                    41.7755          35.3586       18%

	* sysdeps/x86_64/fpu/multiarch/Makefile (libm-sysdep_routines):
	Add e_log2f-fma.
	(CFLAGS-e_log2f-fma.c): New.
	* sysdeps/x86_64/fpu/multiarch/e_log2f-fma.c: New file.
	* sysdeps/x86_64/fpu/multiarch/e_log2f.c: Likewise.

4 files changed, 53 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index 603cdae..7e904db 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,14 @@
 2017-10-22  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* sysdeps/x86_64/fpu/multiarch/Makefile (libm-sysdep_routines):
+	Add e_log2f-fma.
+	(CFLAGS-e_log2f-fma.c): New.
+	* sysdeps/x86_64/fpu/multiarch/e_log2f-fma.c: New file.
+	* sysdeps/x86_64/fpu/multiarch/e_log2f.c: Likewise.
+
+2017-10-22  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* sysdeps/x86_64/fpu/multiarch/Makefile (libm-sysdep_routines):
 	Add e_logf-fma.
 	(CFLAGS-e_logf-fma.c): New.
 	* sysdeps/x86_64/fpu/multiarch/e_logf-fma.c: New file.
diff --git a/sysdeps/x86_64/fpu/multiarch/Makefile b/sysdeps/x86_64/fpu/multiarch/Makefile
index 97d886a..5338a6b 100644
--- a/sysdeps/x86_64/fpu/multiarch/Makefile
+++ b/sysdeps/x86_64/fpu/multiarch/Makefile
@@ -37,10 +37,11 @@ CFLAGS-slowpow-fma.c = -mfma -mavx2
 CFLAGS-s_sin-fma.c = -mfma -mavx2
 CFLAGS-s_tan-fma.c = -mfma -mavx2
 
-libm-sysdep_routines += e_exp2f-fma e_expf-fma e_logf-fma
+libm-sysdep_routines += e_exp2f-fma e_expf-fma e_log2f-fma e_logf-fma
 
 CFLAGS-e_exp2f-fma.c = -mfma -mavx2
 CFLAGS-e_expf-fma.c = -mfma -mavx2
+CFLAGS-e_log2f-fma.c = -mfma -mavx2
 CFLAGS-e_logf-fma.c = -mfma -mavx2
 
 libm-sysdep_routines += e_exp-fma4 e_log-fma4 e_pow-fma4 s_atan-fma4 \
diff --git a/sysdeps/x86_64/fpu/multiarch/e_log2f-fma.c b/sysdeps/x86_64/fpu/multiarch/e_log2f-fma.c
new file mode 100644
index 0000000..8a76b83
--- /dev/null
+++ b/sysdeps/x86_64/fpu/multiarch/e_log2f-fma.c
@@ -0,0 +1,3 @@
+#define __log2f __log2f_fma
+
+#include <sysdeps/ieee754/flt-32/e_log2f.c>
diff --git a/sysdeps/x86_64/fpu/multiarch/e_log2f.c b/sysdeps/x86_64/fpu/multiarch/e_log2f.c
new file mode 100644
index 0000000..be12c45
--- /dev/null
+++ b/sysdeps/x86_64/fpu/multiarch/e_log2f.c
@@ -0,0 +1,40 @@
+/* Multiple versions of log2f.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+extern float __redirect_log2f (float);
+
+#define SYMBOL_NAME log2f
+#include "ifunc-fma.h"
+
+libc_ifunc_redirected (__redirect_log2f, __log2f, IFUNC_SELECTOR ());
+
+#ifdef SHARED
+__hidden_ver1 (__log2f, __GI___log2f, __redirect_log2f)
+  __attribute__ ((visibility ("hidden")));
+
+# include <shlib-compat.h>
+versioned_symbol (libm, __log2f, log2f, GLIBC_2_27);
+#else
+weak_alias (__log2f, log2f)
+#endif
+
+strong_alias (__log2f, __ieee754_log2f)
+strong_alias (__log2f, __log2f_finite)
+
+#define __log2f __log2f_sse2
+#include <sysdeps/ieee754/flt-32/e_log2f.c>