🚀 go-pugleaf

In article <15315@well.UUCP> farren@well.UUCP (Mike Farren) writes:
>Mike (With friends like these, who needs hallucinations) Meyer writes:
>>The [Lattice] compiler thinks it can do a better job of keeping stuff in
>>the registers by using them as cache than you can by tagging specific
>>variables as registers.

>O.K., but is it correct?  Has anyone done an analysis of Lattice code
>to be able to tell if this is Good or Bad?

I don't think the Lattice compiler completely ignores "register"
declarations.  It may take them as advisory information only, but
I have certainly seen code change with 5.0 when I changed what
variables were declared register.

Does it do a good job?  Yes, in most cases.  I have found that I
usually get the best code by not declaring any register variables
and letting the optimizer do its work.  In some special cases, it
helps to give the optimizer some hints by declaring register
variables, but generally it does a pretty good job.

As a side note on "register" and program semantics, remember that you
can't take the address of a register variable.  Some compilers that
don't otherwise respect register declarations use this information
to modify the assumptions made by the optimizer (I believe the MIPS
C compiler does this).

-Dan Riley (riley@tcgould.tn.cornell.edu, cornell!batcomputer!riley)
-Wilson Lab, Cornell University