x86-64: Optimize e_expf with FMA [BZ #21912]

FMA optimized e_expf improves performance by more than 50% on Skylake.

	[BZ #21912]
	* sysdeps/x86_64/fpu/multiarch/Makefile (libm-sysdep_routines):
	Add e_expf-fma.
	* sysdeps/x86_64/fpu/multiarch/e_expf-fma.S: New file.
	* sysdeps/x86_64/fpu/multiarch/e_expf.c: Likewise.
	* sysdeps/x86_64/fpu/multiarch/ifunc-fma.h: Likewise.

1 files changed, 34 insertions, 0 deletions

diff --git a/sysdeps/x86_64/fpu/multiarch/ifunc-fma.h b/sysdeps/x86_64/fpu/multiarch/ifunc-fma.h
new file mode 100644
index 0000000000..383c41ffb1
--- /dev/null
+++ b/sysdeps/x86_64/fpu/multiarch/ifunc-fma.h
@@ -0,0 +1,34 @@
+/* Common definition for ifunc selections optimized with AVX2/FMA.
+   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/>.  */
+
+#include <init-arch.h>
+
+extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
+extern __typeof (REDIRECT_NAME) OPTIMIZE (fma) attribute_hidden;
+
+static inline void *
+IFUNC_SELECTOR (void)
+{
+  const struct cpu_features* cpu_features = __get_cpu_features ();
+
+  if (CPU_FEATURES_ARCH_P (cpu_features, FMA_Usable)
+      && CPU_FEATURES_ARCH_P (cpu_features, AVX2_Usable))
+    return OPTIMIZE (fma);
+
+  return OPTIMIZE (sse2);
+}