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Re: Language-independent functions-as-trees representation
- From: Mark Mitchell <mark at codesourcery dot com>
- To: Jason Merrill <jason at redhat dot com>
- Cc: Richard Henderson <rth at redhat dot com>, Per Bothner <per at bothner dot com>, Diego Novillo <dnovillo at redhat dot com>, "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
- Date: Sun, 21 Jul 2002 15:58:57 -0700
- Subject: Re: Language-independent functions-as-trees representation
Why? We don't currently share expressions in RTL; why would we want to do
so in SIMPLE?
Maybe this will make more sense after my other comment below.
Besides that, it makes things like rtx_equal_p simple/faster to implement,
and could save tons of memory.
Sorry, I don't follow. Most computations care very much about where they
are in the control flow; if I move computations about arbitrarily, their
values will tend to change. The value of "x + y" is different before and
after I increment x. It's the job of CSE to recognize when we can share
values between multiple instances of an expression.
I was implicitly (sorry!) in SSA form.
--
Mark Mitchell mark@codesourcery.com
CodeSourcery, LLC http://www.codesourcery.com