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Re: [tree-ssa] Fix profile updating code
- From: law at redhat dot com
- To: Richard Henderson <rth at redhat dot com>
- Cc: Jan Hubicka <jh at suse dot cz>, gcc-patches at gcc dot gnu dot org, dnovillo at redhat dot com
- Date: Fri, 30 Apr 2004 14:59:55 -0600
- Subject: Re: [tree-ssa] Fix profile updating code
- Reply-to: law at redhat dot com
In message <20040430194241.GA5140@redhat.com>, Richard Henderson writes:
>On Fri, Apr 30, 2004 at 09:43:31AM +0200, Jan Hubicka wrote:
>> Is there any chance that RTL jump threading will simply go? It is
>> memory/CPU hog and Jeff advertises counts that are so little on GCC
>> bootstrap so I don't think it can pay back.
>
>Probably. Just need some numbers on how many times it triggers,
>and possibly for what.
Be aware that the RTL version runs multiple times. What we need to
initially target is removing the first iteration of the RTL version.
The RTL version can find things which are exposed by lowering
(for example 64->32bit conditionals).
The RTL version can also find things which are missed by the tree version
because we do not iterate between dom/jump threading and DCE until nothing
changes. To fix this the tree version needs to be better at threading
through real statements which are only used to set a value used by
the conditional we want to thread through.
jeff