[Vm-dev] bitXor: is slower than - on Spur32 (MacOSX) r3684

[Eliot Miranda]

> On Apr 23, 2016, at 2:44 PM, Eliot Miranda <eliot.miranda at gmail.com> wrote:
> 
> Hi Nicolas,
> 
>> On Apr 23, 2016, at 2:22 PM, Nicolas Cellier <nicolas.cellier.aka.nice at gmail.com> wrote:
>> 
>> Hi,
>> for large integers (> 64 bits), a bitClear: implementation using bitXor: is faster than by using - indeed we don't have to care of carry.
>> 
>> {
>> [(12398767868759866578644 bitOr: 567812564128976768553) - 567812564128976768553] bench.
>> [(12398767868759866578644 bitOr: 567812564128976768553) bitXor: 567812564128976768553] bench.
>> }
>> #('3,480,000 per second. 288 nanoseconds per run.'
>> '4,950,000 per second. 202 nanoseconds per run.')
>> 
>> For large integers < 64 bits or small integers, I would expect sort of similar speed, but bitXor: is slower:
>> 
>> {
>> [(1234 bitOr: 5678) - 5678] bench.
>> [(1234 bitOr: 5678) bitXor: 5678] bench.
>> }
>> 
>> #('170,000,000 per second. 5.88 nanoseconds per run.'
>>  '133,000,000 per second. 7.53 nanoseconds per run.')
>> 
>> {
>> [(12398767868754 bitOr: 5678125641253) - 5678125641253] bench.
>> [(12398767868754 bitOr: 5678125641253) bitXor: 5678125641253] bench.
>> }
>> #('7,100,000 per second. 141 nanoseconds per run.'
>> '5,110,000 per second. 196 nanoseconds per run.')
>> 
>> OK, (Smalltalk specialSelectors includes: #bitXor:) is false, but is it the sole explanation?
> 
> 
> I expect so.  You can test the primitive performance by invoking both via perform:with:, using e.g. #== or #= as a control.

Oh, and you can test the difference between inlined and no inlined #+ by eg copying a test method that uses bitXor: and replacing the #bitXor: literal with #+.  #+ is only inlined for special selector send 176, etc, not for ordinary sends.

_,,,^..^,,,_ (phone)

> 
> I would suggest using the VM profiler, which will show you immediately but
> a) you need the latest VM to run it in Mac OS X
> b) it is currently dog slow because it gets confused by CoreAUC which it thinks has a 2.5Mb text symbol in and spends all its time tallying it
> c) somewhere along the line Morohic changes result in its UI hiding behind an alignment morph the size of the inner window which has to be manually removed
> So I have done maintenance to do before it's usable.  I fixed the VM.  The rest will follow soon.