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Re: [tree-ssa] Thread jumps to blocks with PHIs
- From: Jan Hubicka <hubicka at ucw dot cz>
- To: law at redhat dot com
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Fri, 19 Dec 2003 00:14:57 +0100
- Subject: Re: [tree-ssa] Thread jumps to blocks with PHIs
- References: <200312182127.hBILRIVJ022629@speedy.slc.redhat.com>
>
> This patch allows the jump threader to target a block with PHI nodes.
>
> Much like threading through a block with PHI nodes, we have to mark
> variables appearing in those PHI nodes as needing to be rewritten out
> of SSA form.
>
> The only other complication is that we record the edge that leads to
> the final target rather than the final block. This makes the code
> handle cases where out-of-ssa has to split the edge leading to
> the target block. Whee. About a 7% increase in the number of threading
> opportunities we find in the dominator jump threader and a tiny decrease
> in the number of threading opportunities in the RTL threader (which is
> precisely what we want -- to catch this stuff at the tree level rather
> than at the RTL level).
Just out of curiosity, how compares the number of threading opurtunities
discovered by each of those two beasts?
Honza