Re: Guard use of modulo in cshift (speedup protein)

[Michael Matz <matz at suse dot de>]

Hi,

On Tue, 10 Apr 2012, Steven Bosscher wrote:

> This is OK.

r186283.

> Do you think it would be worthwhile to do this transformation in the 
> middle end too, based on profile information for values?

I'd think so, but it probably requires a new profiler that counts for how 
often 0 <= A <= B for every "A % B".  Just profiling the range of values 
might be misleading (because A <= N and B <= M and N <= M doesn't imply 
that A <= B often holds).

But it would possibly be an interesting experiment already to do such 
transformation generally (without profiling) and see what it gives on some 
benchmarks.  Just to get a feel what's on the plate.

> IIRC value-prof 
> handles constant divmod but not ranges for modulo operations.


Ciao,
Michael.