[LLVMbugs] [Bug 12742] New: Make RegionInfo independent of DominanceFrontier

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=12742

             Bug #: 12742
           Summary: Make RegionInfo independent of DominanceFrontier
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Global Analyses
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: benny.kra at gmail.com
                CC: chandlerc at gmail.com, grosser at fim.uni-passau.de,
                    llvmbugs at cs.uiuc.edu
    Classification: Unclassified


The last in-tree user of DominanceFrontiers is the RegionInfo analysis. With
Chandler's recent work on a new way to handle partial inlining[1] it may find
its way into the default pipeline eventually and we really don't want to have
the O(n^2) domfrontier computation in there again after all the work to remove
it from other passes. Moving RegionInfo off domfrontier would also allow to
remove it entirely.

RegionInfo uses domfrontier to check if blocks form a SESE region. It really
feels like overkill to use domfrontier for this but I don't see what exactly is
needed to avoid it and only use ordinary dominator trees.

[1]
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20120430/142236.html

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