[Bug middle-end/30521] "if (i == n) ++i;" or "i += i == n;"?

[bonzini at gnu dot org]

------- Comment #7 from bonzini at gnu dot org  2008-11-22 10:15 -------
Subject: Re:  "if (i == n) ++i;" or "i += i == n;"?


> The form of the code before CSE is caught in noce_try_addcc. The second form
> obviously not (because we don't know that the value of i.20 is "i + 1").
> 
> So this comes down to a pass ordering problem.

I'll just point out that the df merge allowed much better freedom in
pass ordering.  Ifconv1 could be anticipated before CSE and fwprop.

Paolo


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30521