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Re: [PATCH] Fix PR46556 (poor address generation)


On 10/05/2011 07:22 PM, William J. Schmidt wrote:
I don't know off the top of my head -- I'll have to gather that
information.  The issue is that the profitability is really
context-sensitive, so just the isolated costs of insns aren't enough.
The forward propagation of the add into (mem (reg REG)) looks like a
slam dunk in the absence of other information, but if there are other
nearby references using nonzero offsets from REG, this just extends the
lifetimes of X and Y without eliminating the need for REG.

True, however there are other passes that do this kind of un-CSE and lifetime reduction.


Paolo


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