Re: [Bug tree-optimization/21417] Missed jump threading opportunity on trees

[Jeffrey A Law <law at redhat dot com>]

On Mon, 2006-02-06 at 16:17 +0000, pinskia at gcc dot gnu dot org wrote:
> 
> ------- Comment #3 from pinskia at gcc dot gnu dot org  2006-02-06 16:17 -------
> the load PRE issue has been fixed but DOM does not thread the jump for some
> reason.
This patch allows DOM to thread the jump in question (which in
effect pulls the conditional out of the loop, definitely a good
thing to do when we can).

As I mentioned in a previous comment, we were being very conservative
when threading across backedges in the CFG.  We can be a little more
aggressive, specifically we can allow statements in the target block
which do not affect the control statement at the end of the target
block.

This triggered a few more times in my testbucket, so I'm confident
it's allowing us to avoid conditionals in at least a few real world
hunks of code.

Bootstrapped and regression tested on i686-pc-linux-gnu.

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