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Re: [tree-ssa] PATCH to improve optimization at ssa rewrite time
- From: Diego Novillo <dnovillo at redhat dot com>
- To: Jason Merrill <jason at redhat dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
- Date: 13 May 2003 15:23:16 -0400
- Subject: Re: [tree-ssa] PATCH to improve optimization at ssa rewrite time
- Organization: Red Hat Canada
- References: <firstname.lastname@example.org>
On Tue, 2003-05-13 at 15:09, Jason Merrill wrote:
> This is very useful in conjunction with expression temporaries, which
> produce a lot of redundant statements.
> Oddly, this doesn't work for plain "i = 42". Something to look into.
Because 'i = 42' is not cached in the avail_exprs table. It's stored in
the const_and_copies table for constant/copy propagation. Both tables
are accessed in a different way. For available expressions, we use the
expression (RHS) as index, for constant and copies we use the variable
on the LHS as index.