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Re: [tree-ssa] PATCH: Feedback-based prefetching
- From: Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>
- To: Caroline Tice <ctice at apple dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Fri, 12 Dec 2003 01:13:29 +0100
- Subject: Re: [tree-ssa] PATCH: Feedback-based prefetching
- References: <4007BC69-2C35-11D8-B37F-000393BB90B6@apple.com>
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