🚀 go-pugleaf

In article <5969@mimsy.UUCP> mark@mimsy.UUCP (Mark Weiser) writes:
>In article <978@ames.UUCP> lamaster@pioneer.UUCP (Hugh LaMaster) writes:
>>...How likely is it that a compiler [can] detect the case when it can use 
>> an instruction like this and generate code automatically to use it?
>
>This is of course a good point, and it seems that this is going to be
>one of those hard cases for compiler writers.  But it opens the issue
>of subroutine libraries as providing an environment which also needs
>support in the instruction set.  The Unix string routines are a good
>example, because they are even now often recoded in assembly for efficiency.
>Various pieces of Unix kernel frequently suffer the same fate
>(e.g. tty buffers).  But once one is into instructions which are good
>for certain operating systems or environments, rather than certain languages,
>one has narrowed one's market.  For instance, the Am29000 special string
>compare is useless if strings are encoded as a length followed by the chars.  

Yes, you are right:  when the length is known, things are *much* easier.
But, the instruction is still a useful primitive:  it can be used to find
out, in one cycle, whether or not a 32-bit word contains a byte of
interest.  The compiler may not generate it, but it can be used in hand-
coded inner loops for this purpose.

    bcase