[Bug tree-optimization/34176] [4.3 Regression] SCCVN breaks gettext

[matz at suse dot de]

------- Comment #9 from matz at suse dot de  2007-11-22 14:03 -------
Subject: Re:  [4.3 Regression] SCCVN breaks
 gettext

[sorry for the breakage in last response]

It does not.  The RPO algorithm (the one proven) uses hash table deletes 
per iteration.  About the SCC algorithm they have to say this:

"Since we cannot remove the entries from the hash table after each pass as 
the RPO algorithm does, we will use two hash tables.  The iterative phase 
uses an optimistic hash table.  Once the value numbers in the SCC 
stabilize, entries are added to the valid table."

Without proof that this actually has the same properties as the RPO 
algorithm.  Had they gone through the hassle of trying to prove this they 
would have notived that it doesn't work.


> > Maybe we aren't traversing uses in function arguments during DFS walk?

No, that's not the problem.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34176