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Re: Improvement for update_equiv_regs (fwd)


On Wed, 13 Sep 2000, Jeffrey A Law wrote:
> The concern I had with this patch, then and now,is that it seems to me that
> passes creating these function invariants ought to be adding REG_EQUAL notes
> for them.

As far as I understood Joern, the problem are insns of the form

 (set (reg X) (plus (frame pointer) (constant)))

which don't have a REG_EQUAL note.  I really doubt we want to carry a
redundant REG_EQUAL note through all the optimization passes for every
insn that could possibly be used to make an equivalence.

The only reason we need a REG_EQUAL note at that point is that the code
immediately below looks for one in order to turn it into a REG_EQUIV note.
So generating one on the spot if it seems worthwhile seems like a pretty
reasonable approach to me.  It's equivalent to generating the REG_EQUIV
note on the spot instead of converting an existing REG_EQUAL note.


Bernd


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