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Re: [tree-ssa] Disastrous simplification of large switch stmt
- From: Diego Novillo <dnovillo at redhat dot com>
- To: Steven Bosscher <s dot bosscher at student dot tudelft dot nl>
- Cc: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
- Date: 23 Sep 2002 11:14:20 -0400
- Subject: Re: [tree-ssa] Disastrous simplification of large switch stmt
- References: <1032772222.737.11.camel@steven>
On Mon, 2002-09-23 at 05:10, Steven Bosscher wrote:
> Look at the incredibly large number of temporaries we need to simpify
> this function. If you compare his with the original make_node(), you can
> see something needs to be fixed here.
>
Why? Is the simplified form wrong? Remember that the SIMPLE form is
not supposed to be more compact, but more explicit than the original
form. All the redundancies created while simplifying must be optimized
by the different transformations.
It is not the job of the simplifier to do dataflow analysis to figure
out if something is obviously dead or redundant. It can only deal with
things that need no dataflow analysis to figure out.
The only thing that the simplifier must do right is output the program
in SIMPLE form. Let the other passes deal with the lint produced by the
simplifier.
> (Perhaps we should put each case in the switch statement in a separate
> binding level before simplifying...)
>
Why?
Diego.