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From: BGB <cr88192@gmail.com>
Newsgroups: comp.arch
Subject: Re: Computer architects leaving Intel...
Date: Tue, 3 Sep 2024 03:47:21 -0500
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On 9/2/2024 8:47 PM, MitchAlsup1 wrote:
> On Mon, 2 Sep 2024 19:32:23 +0000, BGB wrote:
> 
>> On 9/1/2024 6:32 PM, MitchAlsup1 wrote:
>>>
>>> More modern machines have RND nobody will ever have REM.
>>
>> Which is probably not a lot, as off-hand I am not aware of many ISA's
>> that have floor/ceil/round in the ISA itself, rather than doing it via
>> conversion to an integer type.
> 
> VAX has round float* to float* 1978.....

So, there is this, and FRNDINT in x87.


Looks like there is ROUNDPS and ROUNDPD in SSE4.1, ...

I missed these as apparently my copies of the Intel docs were too old 
(only covering SSE2).

Looks like VRINT in ARMv8.


So, it seems I can find more examples than I thought...



I guess it is a question how often these are needed. As described in 
ARM's VRINT, it could allow doing floor() or ceil() in a single 
instruction. Not sure how much it would save as I don't expect 
floor/ceil to be common enough to justify this.


Could almost add this if needed, possibly as a hack to the usual 
Float->Int conversion process.