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Re: [PATCH] Save fp registers on x64 function resolution.
- From: Alexander Monakov <amonakov at ispras dot ru>
- To: GNU C Library <libc-alpha at sourceware dot org>
- Date: Tue, 30 Jul 2013 13:53:07 +0400 (MSK)
- Subject: Re: [PATCH] Save fp registers on x64 function resolution.
- References: <20130726091501 dot GA7231 at domone dot kolej dot mff dot cuni dot cz>
To reiterate the point that other people have made previously:
GCC 4.8 has gained an ability to spill to SSE registers rather than to stack.
Assuming that some/all distributions will not pass -mno-sse on x86-64, you
already have a problem even without external modules such as malloc hooks or
audit libraries.
I don't understand why there is concern about the additional cost to
save/restore SSE registers. That code is only executed once per symbol at the
time of resolution, where it is negligible compared to the cost of symbol
lookup. In case PLT profiling is active, you have the additional cost on each
call, but there it is again negligible compared to the profiling routines.
Alexander