powerpc: Add a POWER8-optimized version of expf()

This implementation is based on the one already used at
sysdeps/x86_64/fpu/e_expf.S.

This implementation improves the performance by ~14% on average in synthetic
benchmarks at the cost of decreasing accuracy to 1 ULP.

4 files changed, 83 insertions, 1 deletions

diff --git a/sysdeps/powerpc/powerpc64/fpu/multiarch/Makefile b/sysdeps/powerpc/powerpc64/fpu/multiarch/Makefile
index 0e3eac7190..331763e926 100644
--- a/sysdeps/powerpc/powerpc64/fpu/multiarch/Makefile
+++ b/sysdeps/powerpc/powerpc64/fpu/multiarch/Makefile
@@ -24,7 +24,8 @@ libm-sysdep_routines += s_isnan-power7 s_isnan-power6x s_isnan-power6 \
 			s_modff-power5+ s_modff-ppc64 e_hypot-ppc64 \
 			e_hypot-power7 e_hypotf-ppc64 e_hypotf-power7 \
 			s_isnan-power8 s_isinf-power8 s_finite-power8 \
-			s_llrint-power8 s_llround-power8
+			s_llrint-power8 s_llround-power8 \
+			e_expf-power8 e_expf-ppc64
 
 CFLAGS-s_logbf-power7.c = -mcpu=power7
 CFLAGS-s_logbl-power7.c = -mcpu=power7
diff --git a/sysdeps/powerpc/powerpc64/fpu/multiarch/e_expf-power8.S b/sysdeps/powerpc/powerpc64/fpu/multiarch/e_expf-power8.S
new file mode 100644
index 0000000000..02eff243e1
--- /dev/null
+++ b/sysdeps/powerpc/powerpc64/fpu/multiarch/e_expf-power8.S
@@ -0,0 +1,26 @@
+/* __ieee754_expf() POWER8 version.
+   Copyright (C) 2016 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/>.  */
+
+#include <sysdep.h>
+
+#undef strong_alias
+#define strong_alias(a, b)
+
+#define __ieee754_expf __ieee754_expf_power8
+
+#include <sysdeps/powerpc/powerpc64/power8/fpu/e_expf.S>
diff --git a/sysdeps/powerpc/powerpc64/fpu/multiarch/e_expf-ppc64.c b/sysdeps/powerpc/powerpc64/fpu/multiarch/e_expf-ppc64.c
new file mode 100644
index 0000000000..40f9e3a8fa
--- /dev/null
+++ b/sysdeps/powerpc/powerpc64/fpu/multiarch/e_expf-ppc64.c
@@ -0,0 +1,24 @@
+/* __ieee_expf() PowerPC64 version.
+   Copyright (C) 2016 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/>.  */
+
+#undef strong_alias
+#define strong_alias(a, b)
+
+#define __ieee754_expf __ieee754_expf_ppc64
+
+#include <sysdeps/ieee754/flt-32/e_expf.c>
diff --git a/sysdeps/powerpc/powerpc64/fpu/multiarch/e_expf.c b/sysdeps/powerpc/powerpc64/fpu/multiarch/e_expf.c
new file mode 100644
index 0000000000..1d9a8c69a0
--- /dev/null
+++ b/sysdeps/powerpc/powerpc64/fpu/multiarch/e_expf.c
@@ -0,0 +1,31 @@
+/* Multiple versions of ieee754_expf.
+   Copyright (C) 2016 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/>.  */
+
+#include <math.h>
+#include <math_ldbl_opt.h>
+#include "init-arch.h"
+
+extern __typeof (__ieee754_expf) __ieee754_expf_ppc64 attribute_hidden;
+extern __typeof (__ieee754_expf) __ieee754_expf_power8 attribute_hidden;
+
+libc_ifunc (__ieee754_expf,
+	    (hwcap2 & PPC_FEATURE2_ARCH_2_07)
+	    ? __ieee754_expf_power8
+	    : __ieee754_expf_ppc64);
+
+strong_alias (__ieee754_expf, __expf_finite)