comiss vs. ucomiss

[Tom Rodriguez]

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

tom

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 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
>
>