[tree-ssa] PATCH: Feedback-based prefetching

[Zdenek Dvorak]

Hello,

> This patch adds a new optimization to the tree-ssa branch:  

why tree-ssa branch? I don't see how this is relevant.

You might also want to check hammer-3_3-branch where I have something
very similar (see vpt.c:speculative_prefetching*).

> feedback-based prefetching.  The 
> optimization works on the assumption there will be two compilation 
> passes, with a training 
> run in between.  During the first pass, we make good guesses as to 
> places that are likely to  
> benefit from the insertion of prefetches, and we insert prefetches in 
> all those places (mostly 
> based on induction variables, and the current gcc induction-variable 
> based prefetching 
> mechanism).  In addition to inserting lots of prefetch instructions, 
> the first pass also inserts 
> profile data collection code, to collect information during the 
> training run about the  
> effectiveness of the inserted prefetches.  During the training run, 
> this data is collected, and 
> written to a file, "TRACE_FILE", which goes into the current working 
> directory.

You should use infrastructure provided by value-prof.c for this.

Zdenek