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Re: Is SSE FP ABI breaking on i386?

To: Tim Prince <tprince at computer dot org>
Subject: Re: Is SSE FP ABI breaking on i386?
From: Jan Hubicka <jh at suse dot cz>
Date: Fri, 16 Feb 2001 19:15:17 +0100
Cc: Jan Hubicka <jh at suse dot cz>, Geert Bosch <bosch at gnat dot com>, discuss at x86-64 dot org, drepper at cygnus dot com, gcc at gcc dot gnu dot org, rth at cygnus dot com
References: <20010215152609.9659C34D89@nile.gnat.com> <20010216124052.C31478@atrey.karlin.mff.cuni.cz> <008f01c09829$8a068ca0$8fbc9a40@amr.corp.intel.com>

> If you spill in XF mode, without observing the additional alignment
> requirements, you will be introducing large performance problems, as certain
> commercial compilers have done.  I'm not sure it is possible to get more
Sure - even aligned XFmode access is much slower on Athlon, than DFmode.
Thats why I want to ensure that this is really required.
> than 8-byte alignment on Windows (e.g. cygwin).  People used to say the ABI
> forbade use of more than 4-byte alignment on Windows, and the c++ support in
> gcc-2.95 continues to be incompatible with 8-byte alignment binutils
We can enforce the alignment of stack frame in the prologue - Cygnus is having
code for this not yet merged to mainline and I will probably try to cleanup
the patches and submit next week because I need them for the SSE anyway.

Honza

References:
- Re: Is SSE FP ABI breaking on i386?
  - From: Geert Bosch
- Re: Is SSE FP ABI breaking on i386?
  - From: Jan Hubicka
- Re: Is SSE FP ABI breaking on i386?
  - From: Tim Prince

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