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From: umh@vax5.cit.cornell.edu
Newsgroups: comp.arch
Subject: Optimising C compiler question
Message-ID: <1991Apr8.193155.3911@vax5.cit.cornell.edu>
Date: 8 Apr 91 23:31:55 GMT
Distribution: comp
Organization: CIT, Cornell University
Lines: 19

Something I wonder about.
C has provision for register variables, which are supposed to run faster than
standard variables. How come one never sees register variables in any code?
Are modern RISC compilers sufficiently good that they automatically make
sensible choice of register variables? Can I make my code run slower by using
them?

In like vein, C has the feature that you can create variables local to some
part of your function: something like
if( condition )$
       int i;
       .
       .

and i is invisble to the rest of your code. Can judicious use of this speed
things up- the compiler should know it doesn't have to save i when it leaves
that block etc?

Maynard Handley