[LLVMdev] Duplicate loading of double constants

[Eugene Toder]

On Mon, Aug 19, 2013 at 8:50 PM, Nick Lewycky <nlewycky at google.com> wrote:
>
> Thanks. Please file a bug for this on llvm.org/bugs .
>
Done (PR16938).


> The crux of the problem is that machine CSE runs before register
> allocation and is consequently extremely conservative when doing CSE to
> avoid potentially increasing register pressure. Of course, with such a
> small testcase, register pressure isn't a problem. MachineCSE might be able
> to do a better job here.
>
> Nick
>
I figured it was trying to avoid adding register pressure, but shouldn't it
be more aggressive with constants? Isn't register allocator smart enough to
spill constants when it runs out of registers?

Also, what do you think on commuting addps in the second example?

Thanks,
Eugene
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