[LLVMbugs] [Bug 907] NEW: llc compiles many small loops from 464.h264ref into poor code

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=907

           Summary: llc compiles many small loops from 464.h264ref into poor
                    code
           Product: libraries
           Version: 1.5
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: minor
          Priority: P2
         Component: Backend: PowerPC
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: sabre at nondot.org


The CBE compiles many small loops from 464.h264ref into single dispatch group units that native PPC 
backend doesn't.  It looks like it may be a combination of LSR and coallescing failures as well as lack of 
counted loops.

Attaching a small .bc file to demonstrate the issue.  Compare codegen for the function between LLC and 
the CBE.

-Chris



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