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Re: C++ compile-time regressions




--On Friday, August 03, 2001 9:58 AM -0400 Richard Kenner 
<kenner@vlsi1.ultra.nyu.edu> wrote:

>     I'm just completing some benchmark runs to see if our performance
>     actually changes if i tell CSE to stop caring about memory (and run
>     store motion after reload).
>
> As far as I know, CSE is the only pass which knows the precise
> semantics of when memory locations conflict.  Remember that they aren't
> equivalence classes.
'fraid not.
Both PRE and store motion know precisely when they conflict (I.E. they use 
true_dependence), and when they aren't available/antic (I.E. Their register 
operands changed).
It's faster because it doesn't require removing from a hash table, just 
setting or resetting a bit in a bitvector.

--Dan


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