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Re: pr14627
On Wednesday 13 April 2005 15:13, Diego Novillo wrote:
> Disallowing constants in PHI arguments would certainly make life
> a tiny bit easier on the optimizers. I can't see any drawbacks
> from an optimization POV, because we'd have the value in
> SSA_NAME_VALUE.
>
> However, we'd probably (1) see increased memory consumption by
> all the additional 'NAME = CST' assignments in the IL, and (2)
> compile times may go up.
In exchange for (2), you get rid of the time you spend in uncprop
now. And uncprop may not catch all the cases that it should get
(it's a dominator tree pass so it can't look through PHIs, but
ccp/vrp may still propagate constants through PHIs), so you may
get better code also.
To see the effects for (1), someone will just have to try...
Gr.
Steven