comiss vs. ucomiss
Azeem.Jiva at amd.com
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.
AMD Java Labs
> -----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?
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