[LLVMdev] [RFC] Add a simple soft-float class

Bruce Hoult bruce at hoult.org
Tue Jun 17 22:29:18 PDT 2014


On Wed, Jun 18, 2014 at 4:59 PM, Owen Anderson <resistor at mac.com> wrote:

>      - Digits represented simply as a 32-bit or 64-bit integer.
>
>
> Isn’t this the same as the significand of an IEEE float?  If you go with
> 64-bit, it sounds like you’re defining something very close to Intel’s FP80.
>

Yes, that would be very similar in practical terms to x86/68k FP80, but
just without the necessity of spending time guaranteeing precisely the same
NaN or norm/denorm or LSB results as x87 hardware.

You'd have 9 or 11 more bits of mantissa than in standard IEEE too, which
is probably more useful than worrying about slight fuzziness in the LSB —
 especially as the results would be precisely the same everywhere.
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