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Re: [PATCH 0/2] Multiarch hooks for memcpy variants
- From: Siddhesh Poyarekar <siddhesh at gotplt dot org>
- To: Wilco Dijkstra <Wilco dot Dijkstra at arm dot com>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Cc: nd <nd at arm dot com>
- Date: Fri, 11 Aug 2017 16:52:41 +0530
- Subject: Re: [PATCH 0/2] Multiarch hooks for memcpy variants
- Authentication-results: sourceware.org; auth=none
- References: <DB6PR0801MB20534ED1010DDF1B033821EE83890@DB6PR0801MB2053.eurprd08.prod.outlook.com>
On Friday 11 August 2017 04:41 PM, Wilco Dijkstra wrote:
> Siddhesh Poyarekar wrote:
>> Functions like mempcpy, __mempcpy_chk and __memcpy_chk continue to call the
>> generic memcpy implementation. These two patches fix this by adding ifunc
>> entry points for these functions for generic, thunderx and falkor.
> I don't understand what the goal of this is since on AArch64 we always transform
> mempcpy to memcpy. Also why use ifuncs on the _chk variants? Are they ever
> used in cases where the last 1% of performance matters?
I started off by writing this for __memcpy_chk because gcc transforms
memcpy to __memcpy_chk in some cases with -O3 and then extended it to
mempcpy for completeness. I'm not going to push too hard for mempcpy if
you strongly oppose it, but I am definitely interested in getting
__memcpy_chk ifuncs in.