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Re: [PATCH] x86-64: Implement strcmp family IFUNC selectors in C
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: GNU C Library <libc-alpha at sourceware dot org>, "Rodriguez Bahena, Victor" <victor dot rodriguez dot bahena at intel dot com>
- Date: Wed, 21 Jun 2017 10:22:52 -0700
- Subject: Re: [PATCH] x86-64: Implement strcmp family IFUNC selectors in C
- Authentication-results: sourceware.org; auth=none
- References: <20170613164151.GA12238@gmail.com> <CAMe9rOr+q75e4wQoD6=9BOFcOfvuNWDchwj4BMOEHVZuxdV6uw@mail.gmail.com>
On Mon, Jun 19, 2017 at 9:01 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Tue, Jun 13, 2017 at 9:41 AM, H.J. Lu <hongjiu.lu@intel.com> wrote:
>> Implement strcmp family IFUNC selectors in C and enable SSE4.2/AVX
>> strcmp/strncmp.
>>
>> All internal calls within libc.so can use IFUNC on x86-64 since unlike
>> x86, x86-64 supports PC-relative addressing to access the GOT entry so
>> that it can call via PLT without using an extra register. For libc.a,
>> we can't use IFUNC for functions which are called before IFUNC has been
>> initialized. Use IFUNC internally reduces the icache footprint since
>> libc.so and other codes in the process use the same implementations.
>> This patch uses IFUNC for strcmp family functions within libc.
>>
>> Any comments?
>>
>> H.J.
>> ---
>> [BZ #21572]
>> * sysdeps/x86_64/multiarch/Makefile (sysdep_routines): Add
>> strcmp-sse2, strcmp-sse4_2, strcmp-avx, strncmp-sse2,
>> strncmp-sse4_2, strncmp-avx, strcasecmp_l-sse2,
>> strcasecmp_l-sse4_2, strcasecmp_l-avx, strncase_l-sse2,
>> strncase_l-sse4_2 and strncase_l-avx.
>> * sysdeps/x86_64/multiarch/ifunc-impl-list.c
>> (__libc_ifunc_impl_list): Add tests for __strcmp_avx and
>> __strncmp_avx.
>> * sysdeps/x86_64/multiarch/ifunc-strcmp.h: New file.
>> * sysdeps/x86_64/multiarch/strcasecmp.c: Likewise.
>> * sysdeps/x86_64/multiarch/strcasecmp_l-avx.S: Likewise.
>> * sysdeps/x86_64/multiarch/strcasecmp_l-sse2.S: Likewise.
>> * sysdeps/x86_64/multiarch/strcasecmp_l-sse4_2.S: Likewise.
>> * sysdeps/x86_64/multiarch/strcasecmp_l.c: Likewise.
>> * sysdeps/x86_64/multiarch/strcmp-avx.S: Likewise.
>> * sysdeps/x86_64/multiarch/strcmp-sse2.S: Likewise.
>> * sysdeps/x86_64/multiarch/strcmp-sse4_2.S: Likewise.
>> * sysdeps/x86_64/multiarch/strcmp.c: Likewise.
>> * sysdeps/x86_64/multiarch/strncase.c: Likewise.
>> * sysdeps/x86_64/multiarch/strncase_l-avx.S : Likewise.
>> * sysdeps/x86_64/multiarch/strncase_l-sse2.S: Likewise.
>> * sysdeps/x86_64/multiarch/strncase_l-sse4_2.S: Likewise.
>> * sysdeps/x86_64/multiarch/strncase_l.c: Likewise.
>> * sysdeps/x86_64/multiarch/strncmp-avx.S: Likewise.
>> * sysdeps/x86_64/multiarch/strncmp-sse2.S: Likewise.
>> * sysdeps/x86_64/multiarch/strncmp-sse4_2.S: Likewise.
>> * sysdeps/x86_64/multiarch/strncmp.c: Likewise.
>> * sysdeps/x86_64/multiarch/strcasecmp_l.S: Removed.
>> * sysdeps/x86_64/multiarch/strcmp.S: Likewise.
>> * sysdeps/x86_64/multiarch/strncase_l.S: Likewise.
>> * sysdeps/x86_64/multiarch/strncmp.S: Likewise.
>> * sysdeps/x86_64/multiarch/strcmp-sse42.S: Include <sysdep.h>.
>> (STRCMP_SSE42): New. Defined to __strcmp_sse42 if not defined.
>> [USE_AS_STRCASECMP_L || USE_AS_STRNCASECMP_L]: Include
>> "locale-defines.h".
>> (UPDATE_STRNCMP_COUNTER): New.
>> (SECTION): Likewise.
>> (GLABEL): Likewise.
>> (LABEL): Likewise.
>> * sysdeps/x86_64/multiarch/strncmp-ssse3.S: Rewrite and enable
>> for libc.a
>
> I collected data with bench-strcmp. There are rooms for improvement
> with AVX2. Here is the updated patch without the fix for [BZ #21572].
> We will look into improving strcmp family functions with AVX2 after 2.26
> is released.
>
> Any comments?
>
I will check it in today.
--
H.J.