Re: fix opt/8634

[Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>]

Hello,

> > I believe purge_addressof costs us almost nothing (I cannot be sure,
> > as it has no timevar, but the fact that nobody bothered to add one
> > tells something); is this really the right place where to attempt to
> > save?
> 
> It's got to be about the same cost as purge_builtin_constant_p,
> as both involve one linear scan of the insn stream.  Which was
> identified as a definite regression in gcse times, which led to
> a sequence of patches that avoided running it whenever possible.
> 
> If you added a timevar, you'd notice that you've just about
> exactly doubled the amount of time spent here.

OK; then it seems that there is something rotten in the very heart of
gcc.  How can it not be slow when just a simple pass over insns takes
a non-trivial time?

Zdenek