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Re: [PATCH] Implement fma correctly
On Tue, Oct 12, 2010 at 18:02, Richard Henderson <rth@twiddle.net> wrote:
> Given that you're already manipulating the status word, you
> could go ahead and force 53-bit rounding at the same time
> with minimal extra overhead. ÂOf course, feupdateenv does
> not reset the rounding size to match. ÂYou'd have to either
> open-code that function in order avoid doing extra work,
> or add new helper functions.
I actually have second thoughts even about the fmaf code. The problem
is that now libm is not signal-safe. There is no limitatino of using
FP math in signal handlers and you now get different results depending
on whether fmaf got interrupted or other code got interrupted.
We might have to do everything in software only without appropriate
fma hardware support.