* [PATCH] x86_64: Add log2 with FMA
@ 2023-08-10 18:24 H.J. Lu
2023-08-10 21:39 ` Noah Goldstein
2023-08-11 9:25 ` Paul Zimmermann
0 siblings, 2 replies; 3+ messages in thread
From: H.J. Lu @ 2023-08-10 18:24 UTC (permalink / raw)
To: libc-alpha
On Skylake, it improves log2 bench performance by:
Before After Improvement
max 208.779 63.827 69%
min 9.977 6.55 34%
mean 10.366 6.8191 34%
---
sysdeps/x86_64/fpu/multiarch/Makefile | 2 ++
sysdeps/x86_64/fpu/multiarch/e_log2-fma.c | 3 ++
sysdeps/x86_64/fpu/multiarch/e_log2.c | 43 +++++++++++++++++++++++
3 files changed, 48 insertions(+)
create mode 100644 sysdeps/x86_64/fpu/multiarch/e_log2-fma.c
create mode 100644 sysdeps/x86_64/fpu/multiarch/e_log2.c
diff --git a/sysdeps/x86_64/fpu/multiarch/Makefile b/sysdeps/x86_64/fpu/multiarch/Makefile
index e37e488c37..f773255721 100644
--- a/sysdeps/x86_64/fpu/multiarch/Makefile
+++ b/sysdeps/x86_64/fpu/multiarch/Makefile
@@ -34,6 +34,7 @@ libm-sysdep_routines += \
e_atan2-fma \
e_exp-fma \
e_log-fma \
+ e_log2-fma \
e_pow-fma \
s_atan-fma \
s_sin-fma \
@@ -45,6 +46,7 @@ CFLAGS-e_asin-fma.c = -mfma -mavx2
CFLAGS-e_atan2-fma.c = -mfma -mavx2
CFLAGS-e_exp-fma.c = -mfma -mavx2
CFLAGS-e_log-fma.c = -mfma -mavx2
+CFLAGS-e_log2-fma.c = -mfma -mavx2
CFLAGS-e_pow-fma.c = -mfma -mavx2
CFLAGS-s_atan-fma.c = -mfma -mavx2
CFLAGS-s_sin-fma.c = -mfma -mavx2
diff --git a/sysdeps/x86_64/fpu/multiarch/e_log2-fma.c b/sysdeps/x86_64/fpu/multiarch/e_log2-fma.c
new file mode 100644
index 0000000000..9fbebc1b47
--- /dev/null
+++ b/sysdeps/x86_64/fpu/multiarch/e_log2-fma.c
@@ -0,0 +1,3 @@
+#define __log2 __log2_fma
+
+#include <sysdeps/ieee754/dbl-64/e_log2.c>
diff --git a/sysdeps/x86_64/fpu/multiarch/e_log2.c b/sysdeps/x86_64/fpu/multiarch/e_log2.c
new file mode 100644
index 0000000000..c0320caf36
--- /dev/null
+++ b/sysdeps/x86_64/fpu/multiarch/e_log2.c
@@ -0,0 +1,43 @@
+/* Multiple versions of log2.
+ Copyright (C) 2023 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
+ <https://www.gnu.org/licenses/>. */
+
+#include <libm-alias-double.h>
+#include <libm-alias-finite.h>
+
+extern double __redirect_log2 (double);
+
+#define SYMBOL_NAME log2
+#include "ifunc-fma.h"
+
+libc_ifunc_redirected (__redirect_log2, __log2, IFUNC_SELECTOR ());
+
+#ifdef SHARED
+__hidden_ver1 (__log2, __GI___log2, __redirect_log2)
+ __attribute__ ((visibility ("hidden")));
+
+versioned_symbol (libm, __ieee754_log2, log2, GLIBC_2_29);
+libm_alias_double_other (__log2, log2)
+#else
+libm_alias_double (__log2, log2)
+#endif
+
+strong_alias (__log2, __ieee754_log2)
+libm_alias_finite (__log2, __log2)
+
+#define __log2 __log2_sse2
+#include <sysdeps/ieee754/dbl-64/e_log2.c>
--
2.41.0
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] x86_64: Add log2 with FMA
2023-08-10 18:24 [PATCH] x86_64: Add log2 with FMA H.J. Lu
@ 2023-08-10 21:39 ` Noah Goldstein
2023-08-11 9:25 ` Paul Zimmermann
1 sibling, 0 replies; 3+ messages in thread
From: Noah Goldstein @ 2023-08-10 21:39 UTC (permalink / raw)
To: H.J. Lu; +Cc: libc-alpha
On Thu, Aug 10, 2023 at 1:24 PM H.J. Lu via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> On Skylake, it improves log2 bench performance by:
>
> Before After Improvement
> max 208.779 63.827 69%
> min 9.977 6.55 34%
> mean 10.366 6.8191 34%
> ---
> sysdeps/x86_64/fpu/multiarch/Makefile | 2 ++
> sysdeps/x86_64/fpu/multiarch/e_log2-fma.c | 3 ++
> sysdeps/x86_64/fpu/multiarch/e_log2.c | 43 +++++++++++++++++++++++
> 3 files changed, 48 insertions(+)
> create mode 100644 sysdeps/x86_64/fpu/multiarch/e_log2-fma.c
> create mode 100644 sysdeps/x86_64/fpu/multiarch/e_log2.c
>
> diff --git a/sysdeps/x86_64/fpu/multiarch/Makefile b/sysdeps/x86_64/fpu/multiarch/Makefile
> index e37e488c37..f773255721 100644
> --- a/sysdeps/x86_64/fpu/multiarch/Makefile
> +++ b/sysdeps/x86_64/fpu/multiarch/Makefile
> @@ -34,6 +34,7 @@ libm-sysdep_routines += \
> e_atan2-fma \
> e_exp-fma \
> e_log-fma \
> + e_log2-fma \
> e_pow-fma \
> s_atan-fma \
> s_sin-fma \
> @@ -45,6 +46,7 @@ CFLAGS-e_asin-fma.c = -mfma -mavx2
> CFLAGS-e_atan2-fma.c = -mfma -mavx2
> CFLAGS-e_exp-fma.c = -mfma -mavx2
> CFLAGS-e_log-fma.c = -mfma -mavx2
> +CFLAGS-e_log2-fma.c = -mfma -mavx2
> CFLAGS-e_pow-fma.c = -mfma -mavx2
> CFLAGS-s_atan-fma.c = -mfma -mavx2
> CFLAGS-s_sin-fma.c = -mfma -mavx2
> diff --git a/sysdeps/x86_64/fpu/multiarch/e_log2-fma.c b/sysdeps/x86_64/fpu/multiarch/e_log2-fma.c
> new file mode 100644
> index 0000000000..9fbebc1b47
> --- /dev/null
> +++ b/sysdeps/x86_64/fpu/multiarch/e_log2-fma.c
> @@ -0,0 +1,3 @@
> +#define __log2 __log2_fma
> +
> +#include <sysdeps/ieee754/dbl-64/e_log2.c>
> diff --git a/sysdeps/x86_64/fpu/multiarch/e_log2.c b/sysdeps/x86_64/fpu/multiarch/e_log2.c
> new file mode 100644
> index 0000000000..c0320caf36
> --- /dev/null
> +++ b/sysdeps/x86_64/fpu/multiarch/e_log2.c
> @@ -0,0 +1,43 @@
> +/* Multiple versions of log2.
> + Copyright (C) 2023 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
> + <https://www.gnu.org/licenses/>. */
> +
> +#include <libm-alias-double.h>
> +#include <libm-alias-finite.h>
> +
> +extern double __redirect_log2 (double);
> +
> +#define SYMBOL_NAME log2
> +#include "ifunc-fma.h"
> +
> +libc_ifunc_redirected (__redirect_log2, __log2, IFUNC_SELECTOR ());
> +
> +#ifdef SHARED
> +__hidden_ver1 (__log2, __GI___log2, __redirect_log2)
> + __attribute__ ((visibility ("hidden")));
> +
> +versioned_symbol (libm, __ieee754_log2, log2, GLIBC_2_29);
> +libm_alias_double_other (__log2, log2)
> +#else
> +libm_alias_double (__log2, log2)
> +#endif
> +
> +strong_alias (__log2, __ieee754_log2)
> +libm_alias_finite (__log2, __log2)
> +
> +#define __log2 __log2_sse2
> +#include <sysdeps/ieee754/dbl-64/e_log2.c>
> --
> 2.41.0
>
LGTM
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] x86_64: Add log2 with FMA
2023-08-10 18:24 [PATCH] x86_64: Add log2 with FMA H.J. Lu
2023-08-10 21:39 ` Noah Goldstein
@ 2023-08-11 9:25 ` Paul Zimmermann
1 sibling, 0 replies; 3+ messages in thread
From: Paul Zimmermann @ 2023-08-11 9:25 UTC (permalink / raw)
To: H.J. Lu; +Cc: libc-alpha
Hi H.J.,
> On Skylake, it improves log2 bench performance by:
>
> Before After Improvement
> max 208.779 63.827 69%
> min 9.977 6.55 34%
> mean 10.366 6.8191 34%
for what concerns accuracy, after a limited search, I get a small improvement
for the largest known error. It was 0.554114 ulp before (obtained for
x=0x1.0b53197bd66c8p+0), and I find 0.547517 ulp now (obtained for
x=0x1.140c8ac38f327p+0).
Paul
^ permalink raw reply [flat|nested] 3+ messages in thread
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