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[Bug tree-optimization/34176] [4.3 Regression] SCCVN breaks gettext
- From: "matz at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 22 Nov 2007 14:03:35 -0000
- Subject: [Bug tree-optimization/34176] [4.3 Regression] SCCVN breaks gettext
- References: <bug-34176-10053@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- 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