comiss vs. ucomiss

Tom Rodriguez Thomas.Rodriguez at Sun.COM
Tue Oct 14 12:27:07 PDT 2008

I wouldn't expect it to be any different execution-wise.  It's just odd.


On Oct 14, 2008, at 11:08 AM, Jiva, Azeem wrote:

> 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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