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Re: PATCH: Check GLIBC_IFUNC to enable/disable ifunc features
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Siddhesh Poyarekar <siddhesh at sourceware dot org>
- Cc: "Carlos O'Donell" <carlos at redhat dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Thu, 30 Jun 2016 06:42:30 -0700
- Subject: Re: PATCH: Check GLIBC_IFUNC to enable/disable ifunc features
- Authentication-results: sourceware.org; auth=none
- References: <CAMe9rOq1+_rMbs1mt3=Md=Wx=7ZxUbD+BhOx-qrO5TBRBrRLww at mail dot gmail dot com> <20160630030947 dot GD3824 at devel dot intra dot reserved-bit dot com> <CAMe9rOrd+DEP1POnXaUaOrCaGqMmrftJbR_6ydFCXQeWueWmag at mail dot gmail dot com> <20160630034351 dot GE3824 at devel dot intra dot reserved-bit dot com> <CAMe9rOpNGtU=mVWEC5fvAABD_bkdM=8kx49KOc_yYkEXiPfx=w at mail dot gmail dot com> <20160630114416 dot GA7564 at devel dot intra dot reserved-bit dot com> <CAMe9rOp0z6coVK51_wp=s1zJaYA0wyVt2+ZJE1qHTqCQjexgKw at mail dot gmail dot com> <20160630125142 dot GB7564 at devel dot intra dot reserved-bit dot com>
On Thu, Jun 30, 2016 at 5:51 AM, Siddhesh Poyarekar
<siddhesh@sourceware.org> wrote:
> On Thu, Jun 30, 2016 at 05:01:28AM -0700, H.J. Lu wrote:
>> My scheme is
>>
>> do
>> {
>> if (*env == GLIBC_IFUNC=.*)
>> {
>> process
>> break
>> }
>> env++
>> }
>>
>> We only need to check GLIBC_IFUNC only if it hasn't been found. With
>> GLIBC_IFUNC_X86_XXX, we have to do
>>
>> do
>> {
>> if (*env == GLIBC_IFUNC_X86_*)
>> process
>> env++
>> }
>>
>> We need to check GLIBC_IFUNC_X86 in each iteration.
>
> OK, then how about GLIBC_IFUNC_X86=avx,sse2,sse3..., i.e. a
> comma-separated value for the GLIBC_IFUNC_<ARCH> environment variable.
comma-separator is fine. But we need to both turn it on and off.
Also do we need _X86? GLIBC_IFUNC is processor specific. Why
pollute environment with
GLIBC_IFUNC_ARM
GLIBC_IFUNC_X86
...
--
H.J.