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Re: FWD: FLOATING-POINT CONSISTENCY, -FFLOAT-STORE, AND X86
- To: Edward Jason Riedy <ejr at CS dot Berkeley dot EDU>, Joe Buck <jbuck at synopsys dot com>
- Subject: Re: FWD: FLOATING-POINT CONSISTENCY, -FFLOAT-STORE, AND X86
- From: Jamie Lokier <egcs at tantalophile dot demon dot co dot uk>
- Date: Wed, 16 Dec 1998 01:05:46 +0000
- Cc: hjstein at bfr dot co dot il, egcs at cygnus dot com
- References: <199812150119.RAA03420@yamato.synopsys.com> <199812150251.SAA11628@lotus.CS.Berkeley.EDU>
On Mon, Dec 14, 1998 at 06:51:28PM -0800, Edward Jason Riedy wrote:
> Using 80-bit spills is a quick approximation to extending the FP stack
> into memory, and it should give some of the benefit with very little
> (hopefully) hassle. Of course, 80 bits is wider than the normal spill,
> so it eats more memory bandwidth, cache space, etc. Anyone who's that
> concerned will bend over backwards to avoid spills anyways.
I like this 80-bit spills idea.
But given that you can just put the FPU into 64-bit precision mode
anyway to get predictable arithmetic, I would like to see the option to
use just 64-bit spills for those programs that do run the FPU in 64-bit
precision mode.
Maybe that option could be implied by -ffast-math.
-- Jamie