[Chicken-users] type-and-range-check optimizations in unsafe mode

[Will M Farr]

Hello all,

I've noticed with a bit more poking around the chicken runtime that  
there are at least two places where chicken performs "safety" checks  
even if you specify -unsafe (felix or others please correct me if I'm  
reading the code incorrectly):

- structure getters and setters
- vector-refs

There may be more places.  I don't really know how much time these  
type checks take up---Serrano and Feeley claim in _Storage Use  
Analysis and its Applications_ (http://www-sop.inria.fr/mimosa/fp/ 
Bigloo/bigloo-5.html#Papers-&-Reports ), Section 4, that they don't  
take up much time *if* a compiler uses copy propogation and inlining  
effectively, but cite benchmarks that say 25% if the compiler  
doesn't.  Would people be interested me going through the runtime and  
breaking the type-and-range checks out of procedures like vector-ref  
and vector-set! such that they are only performed in safe mode?  The  
general principles I propose are:

1. C_xxx in runtime.c check as few argument types and ranges as  
possible consistent with genericity of operation.
2. Type and range checks are inserted in library.scm before calling  
C_xxxx procedures so that they are absent in the unsafe library code  
and in any unsafe code which inlines the library procedures (using  
(declare (unsafe) (usual-integrations) (inline)), would inline these  
I assume).

This shouldn't be too much work, and it's pretty straightforward work  
at that.  I would be happy to implement it and submit patches if  
felix and others think it's OK to include.  We could then check for  
improvement on, say, the shootout benchmarks.

Will