comiss vs. ucomiss

[Jiva, Azeem]

At least on AMD hardware latency costs are identical for comiss/comisd
and ucomiss/ucomisd and they both use the same decode paths.

--
Azeem Jiva
AMD Java Labs
T 512.602.0907


> -----Original Message-----
> From: hotspot-compiler-dev-bounces at openjdk.java.net [mailto:hotspot-
> compiler-dev-bounces at openjdk.java.net] On Behalf Of Tom Rodriguez
> Sent: Tuesday, October 14, 2008 1:04 PM
> To: hotspot compiler
> Subject: comiss vs. ucomiss
> 
> I was just making some comparisons between x86_32.ad and x86_64.ad and
> noticed that x86_32.ad uses comiss/comisd for floating point compares
> with SSE but x86_64.ad uses ucomiss/ucomisd.  The only difference
> between them is that the ucom versions don't signal for quiet NaNs.
> We have fp exception suppressed so functionally it doesn't make any
> difference.  It does seem like they should be doing the same thing
> though.  Anyone know why they emit different things?
> 
> tom