[LLVMbugs] [Bug 3539] New: TargetInstrInfo:: AnalyzeBranch can modify the MBB being analyzed

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=3539

           Summary: TargetInstrInfo::AnalyzeBranch can modify the MBB being
                    analyzed
           Product: libraries
           Version: trunk
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Common Code Generator Code
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: evan.cheng at apple.com
                CC: llvmbugs at cs.uiuc.edu


AnalyzeBranch may delete instructions in the MBB if they are after the last
unconditional branch.

This may invalidate iterators or client's data structure (e.g. liveintervals
maps). The current workaround is to only allow this when the caller explicitly
permits so. The only such client is branch folding. 

The current fix is to not allow AnalyzeBranch to delete instructions. Instead,
branch folding should perform this optimization.


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