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Re: New optimized string routines for Intel and alignment of stack.
- From: Florian Weimer <fweimer at redhat dot com>
- To: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- Cc: libc-alpha at sourceware dot org
- Date: Tue, 7 Jun 2016 14:23:22 +0200
- Subject: Re: New optimized string routines for Intel and alignment of stack.
- Authentication-results: sourceware.org; auth=none
- References: <57566200 dot 2040203 at redhat dot com> <dea8c68f-cc02-9427-4e54-acd795a930cf at redhat dot com> <5756B542 dot 4060608 at linaro dot org>
On 06/07/2016 01:51 PM, Adhemerval Zanella wrote:
Besides string routines, do we have any C code that relies on stack alignment
on 32-bit x86?
Perhaps not today, but unless we change the ABI to the original
definition, GCC is free to exploit the stack alignment for optimization
purposes in the future.
Also, is there any performance issue with current unaligned version or are you
just worry that we might remove them in the future due a better optimized version
that assumes aligned stack?
I think there is a performance penalty from not using vectorized copies
for small structs. Even unaligned SSE loads/stores would be a win for
the example I posted, I assume.