0005-Search-all-dominated-blocks-for-expressions-to-hoist.patch

[Steven Bosscher]

On Wed, Jun 23, 2010 at 9:52 PM, Maxim Kuvyrkov <maxim@codesourcery.com> wrote:
>>> The attached patch adds max-hoist-depth parameter to control depth of
>>> descend in dominator tree. The default value of 30 should be enough for
>>> most practical purposes.
>>
>> 30 seems like "infinite" for most practical cases.
>
> Exactly.  The purpose of the parameter is to avoid quadratic behavior on
> weird CFGs.  For normal graphs code hoisting should traverse the whole
> structure.
>
> The problem of excessive code hoisting that arises when looking for
> expressions in the whole dominator subtree [instead of just immediately
> dominated blocks] will be addressed in another patch I'm about to post.  The
> the GCSE-complex-constants thread.

Actually the parameter also makes a difference for code size. When I
experimented with this all this time ago, I had the best CSiBE size
scores with a depth of 5 or 6.

Ciao!
Steven