(j3.2006) BEQ, BNE?

Keith Bierman khbkhb
Fri Feb 1 16:38:43 EST 2013

Because the optimizer was long since coded and tested 

khbkhb at gmail.com 
kbiermank (AIM)

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On Feb 1, 2013, at 1:07 PM, Van Snyder <Van.Snyder at jpl.nasa.gov> wrote:

> On Fri, 2013-02-01 at 10:10 -0700, Keith Bierman wrote:
>> The no so obvious thing is what cost(s) that may impose on the
>> implementors. Folks who were certain there were fixed numbers of
>> intrinsics may have "hard" limits, the interactions with optimization
>> and debuggers, etc. Different implementors could face very different
>> costs (from what very little I recall of the NAG compiler, once upon a
>> time I think it would have been small for Malcolm). For some other
>> compilers, not so small (not huge, but the combination of scarce
>> development, integration and test resources for most compiler groups
>> should never be underestimated. The more highly optimizing the
>> environment, the more likely it is that even trivial changes will have
>> more considerable impact).
> Bob Corbett argued that if one has written
>  if ( popcnt(ieor(i,j)) == 0 )
> or
>  if ( BLE(i,j) .and. BLE(j,i) )
> or
>  if ( BGE(i,j) .and. BGE(j,i) )
> or
>  any of the dozen or so other ways to say the same thing,
> a competent optimizing compiler will have optimized "the idioms" to an
> unsigned test for equality.
> How is that "easier" than implementing BEQ and BNE?
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