comiss vs. ucomiss

Jiva, Azeem Azeem.Jiva at
Tue Oct 14 11:08:59 PDT 2008

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 [mailto:hotspot-
> compiler-dev-bounces at] 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 and and
> noticed that uses comiss/comisd for floating point compares
> with SSE but 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

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