Re: FWD: FLOATING-POINT CONSISTENCY, -FFLOAT-STORE, AND X86

[Edward Jason Riedy <ejr at CS dot Berkeley dot EDU>]

Oh well.  And Craig Burley writes:
 - 
 - Let me see if I understand the above, by translating it, and perhaps
 - helping continue to clarify the picture....

I'm afraid my statement reads as a slant against Sun compiler engineers.
It shouldn't.  I don't doubt that they are trying to make x86 give the 
same numeric results as the Ultra.  They picked a float-store-like 
solution on a non-primary platform to avoid a probable re-design.  It's 
a valid engineering choice.  It's also documented in their man page
(under -fstore).

My statement was more an echo of what I hear from various users.

But yes, your translation is correct.  The Sun compiler defaults to 
the equivalent of -ffloat-store on x86, and that slaughters performance.  
They also give a large number of compiler options to play with FP modes 
and precisions.  It's really nice in that aspect.  I'd love to see 
things like that added to gcc, but obviously I'm going to have to wait 
until I learn enough to do it.  ;)

Jason