Detect and select i586/i686 implementation at run-time
Commit Message
On Thu, Aug 27, 2015 at 5:35 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Thu, Aug 27, 2015 at 5:10 AM, Ondřej Bílka <neleai@seznam.cz> wrote:
>> On Wed, Aug 26, 2015 at 08:57:05AM -0700, H.J. Lu wrote:
>>> We detect i586 and i686 features at run-time by checking CX8 and CMOV
>>> CPUID features bits. We can use these information to select the best
>>> implementation in ix86 multiarch. HAS_I586/HAS_I686 is true if i586/i686
>>> instructions are available on the processor.
>>>
>>> Due to the reordering and the other nifty extensions in i686, it is not
>>> really good to use heavily i586 optimized code on an i686. It's better
>>> to use i486 or i386 code if it isn't an i586. USE_I586/USE_I686 is true
>>> if i586/i686 implementation should be used for the processor. USE_I586
>>> is true only if i686 instructions aren't available. If i686 instructions
>>> are available, we always choose i686, i486 or i386 implementation, in
>>> that order, and we never choose i586 implementation for i686-class
>>> processors.
>>>
>> Here I couldn't test if its improvement so I won't help with that.
>>
>> However as it covers historic extensions a better alternative would be
>> use corresponding mmx to sse2 variant. Question here is again how much
>> we support these.
>
> The i486, i586, i686 version of multi-arch functions won't be used
> on processors with SSE. The preferred version will be used on
> older processors. It is an improvement for processors with SSE
> as well as older processors.
>
This is the patch I am checking in.
Thanks.
From 6a2c1d2d0b16703700709c94dcfc56569e3aba7a Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Mon, 17 Aug 2015 10:19:05 -0700
Subject: [PATCH 02/24] Detect and select i586/i686 implementation at run-time
We detect i586 and i686 features at run-time by checking CX8 and CMOV
CPUID features bits. We can use these information to select the best
implementation in ix86 multiarch. HAS_I586/HAS_I686 is true if i586/i686
instructions are available on the processor.
Due to the reordering and the other nifty extensions in i686, it is not
really good to use heavily i586 optimized code on an i686. It's better
to use i486 code if it isn't an i586. USE_I586/USE_I686 is true if
i586/i686 implementation should be used for the processor. USE_I586
is true only if i686 instructions aren't available. If i686 instructions
are available, we always choose i686 or i486 implementation, in that order,
and we never choose i586 implementation for i686-class processors.
* sysdeps/i386/init-arch.h: New file.
* sysdeps/i386/i586/init-arch.h: Likewise.
* sysdeps/i386/i686/init-arch.h: Likewise.
* sysdeps/x86/cpu-features.c (init_cpu_features): Set bit_I586
bit if CX8 is available. Set bit_I686 bit if CMOV is available.
* sysdeps/x86/cpu-features.h (bit_I586): New.
(bit_I686): Likewise.
(bit_CX8): Likewise.
(bit_CMOV): Likewise.
(index_CX8): Likewise.
(index_CMOV): Likewise.
(index_I586): Likewise.
(index_I686): Likewise.
(reg_CX8): Likewise.
(reg_CMOV): Likewise.
(HAS_I586): Defined as HAS_ARCH_FEATURE (I586) if i586 isn't
available at compile-time.
(HAS_I686): Defined as HAS_ARCH_FEATURE (I686) if i686 isn't
available at compile-time.
* sysdeps/x86/init-arch.h (USE_I586): New macro.
(USE_I686): Likewise.
---
sysdeps/i386/i586/init-arch.h | 19 +++++++++++++++++++
sysdeps/i386/i686/init-arch.h | 19 +++++++++++++++++++
sysdeps/i386/init-arch.h | 19 +++++++++++++++++++
sysdeps/x86/cpu-features.c | 8 ++++++++
sysdeps/x86/cpu-features.h | 20 +++++++++++++++++---
sysdeps/x86/init-arch.h | 13 +++++++++++++
6 files changed, 95 insertions(+), 3 deletions(-)
create mode 100644 sysdeps/i386/i586/init-arch.h
create mode 100644 sysdeps/i386/i686/init-arch.h
create mode 100644 sysdeps/i386/init-arch.h
new file mode 100644
@@ -0,0 +1,19 @@
+/* Copyright (C) 2015 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/>. */
+
+#define MINIMUM_ISA 586
+#include <sysdeps/x86/init-arch.h>
new file mode 100644
@@ -0,0 +1,19 @@
+/* Copyright (C) 2015 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/>. */
+
+#define MINIMUM_ISA 686
+#include <sysdeps/x86/init-arch.h>
new file mode 100644
@@ -0,0 +1,19 @@
+/* Copyright (C) 2015 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/>. */
+
+#define MINIMUM_ISA 486
+#include <sysdeps/x86/init-arch.h>
@@ -150,6 +150,14 @@ init_cpu_features (struct cpu_features *cpu_features)
else
kind = arch_kind_other;
+ /* Support i586 if CX8 is available. */
+ if (HAS_CPU_FEATURE (CX8))
+ cpu_features->feature[index_I586] |= bit_I586;
+
+ /* Support i686 if CMOV is available. */
+ if (HAS_CPU_FEATURE (CMOV))
+ cpu_features->feature[index_I686] |= bit_I686;
+
if (cpu_features->max_cpuid >= 7)
__cpuid_count (7, 0,
cpu_features->cpuid[COMMON_CPUID_INDEX_7].eax,
@@ -31,10 +31,14 @@
#define bit_AVX_Fast_Unaligned_Load (1 << 11)
#define bit_AVX512F_Usable (1 << 12)
#define bit_AVX512DQ_Usable (1 << 13)
+#define bit_I586 (1 << 14)
+#define bit_I686 (1 << 15)
/* CPUID Feature flags. */
/* COMMON_CPUID_INDEX_1. */
+#define bit_CX8 (1 << 8)
+#define bit_CMOV (1 << 15)
#define bit_SSE2 (1 << 26)
#define bit_SSSE3 (1 << 9)
#define bit_SSE4_1 (1 << 19)
@@ -69,6 +73,8 @@
# include <ifunc-defines.h>
# include <rtld-global-offsets.h>
+# define index_CX8 COMMON_CPUID_INDEX_1*CPUID_SIZE+CPUID_EDX_OFFSET
+# define index_CMOV COMMON_CPUID_INDEX_1*CPUID_SIZE+CPUID_EDX_OFFSET
# define index_SSE2 COMMON_CPUID_INDEX_1*CPUID_SIZE+CPUID_EDX_OFFSET
# define index_SSSE3 COMMON_CPUID_INDEX_1*CPUID_SIZE+CPUID_ECX_OFFSET
# define index_SSE4_1 COMMON_CPUID_INDEX_1*CPUID_SIZE+CPUID_ECX_OFFSET
@@ -89,6 +95,8 @@
# define index_AVX_Fast_Unaligned_Load FEATURE_INDEX_1*FEATURE_SIZE
# define index_AVX512F_Usable FEATURE_INDEX_1*FEATURE_SIZE
# define index_AVX512DQ_Usable FEATURE_INDEX_1*FEATURE_SIZE
+# define index_I586 FEATURE_INDEX_1*FEATURE_SIZE
+# define index_I686 FEATURE_INDEX_1*FEATURE_SIZE
# if defined (_LIBC) && !IS_IN (nonlib)
# ifdef __x86_64__
@@ -193,6 +201,8 @@ extern const struct cpu_features *__get_cpu_features (void)
# define HAS_ARCH_FEATURE(name) \
((__get_cpu_features ()->feature[index_##name] & (bit_##name)) != 0)
+# define index_CX8 COMMON_CPUID_INDEX_1
+# define index_CMOV COMMON_CPUID_INDEX_1
# define index_SSE2 COMMON_CPUID_INDEX_1
# define index_SSSE3 COMMON_CPUID_INDEX_1
# define index_SSE4_1 COMMON_CPUID_INDEX_1
@@ -207,6 +217,8 @@ extern const struct cpu_features *__get_cpu_features (void)
# define index_POPCOUNT COMMON_CPUID_INDEX_1
# define index_OSXSAVE COMMON_CPUID_INDEX_1
+# define reg_CX8 edx
+# define reg_CMOV edx
# define reg_SSE2 edx
# define reg_SSSE3 ecx
# define reg_SSE4_1 ecx
@@ -234,6 +246,8 @@ extern const struct cpu_features *__get_cpu_features (void)
# define index_AVX_Fast_Unaligned_Load FEATURE_INDEX_1
# define index_AVX512F_Usable FEATURE_INDEX_1
# define index_AVX512DQ_Usable FEATURE_INDEX_1
+# define index_I586 FEATURE_INDEX_1
+# define index_I686 FEATURE_INDEX_1
#endif /* !__ASSEMBLER__ */
@@ -242,7 +256,7 @@ extern const struct cpu_features *__get_cpu_features (void)
#elif defined __i586__ || defined __pentium__
# define HAS_CPUID 1
# define HAS_I586 1
-# define HAS_I686 0
+# define HAS_I686 HAS_ARCH_FEATURE (I686)
#elif (defined __i686__ || defined __pentiumpro__ \
|| defined __pentium4__ || defined __nocona__ \
|| defined __atom__ || defined __core2__ \
@@ -261,8 +275,8 @@ extern const struct cpu_features *__get_cpu_features (void)
# define HAS_I686 1
#else
# define HAS_CPUID 0
-# define HAS_I586 0
-# define HAS_I686 0
+# define HAS_I586 HAS_ARCH_FEATURE (I586)
+# define HAS_I686 HAS_ARCH_FEATURE (I686)
#endif
#endif /* cpu_features_h */
@@ -20,3 +20,16 @@
#else
# include <ldsodefs.h>
#endif
+
+#ifndef __x86_64__
+/* Due to the reordering and the other nifty extensions in i686, it is
+ not really good to use heavily i586 optimized code on an i686. It's
+ better to use i486 code if it isn't an i586. */
+# if MINIMUM_ISA == 686
+# define USE_I586 0
+# define USE_I686 1
+# else
+# define USE_I586 (HAS_ARCH_FEATURE (I586) && !HAS_ARCH_FEATURE (I686))
+# define USE_I686 HAS_ARCH_FEATURE (I686)
+# endif
+#endif
--
2.4.3