[LLVMbugs] [Bug 942] NEW: analyze missing-optimization-opportunity

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Wed Oct 11 15:47:04 PDT 2006


           Summary: analyze missing-optimization-opportunity
           Product: tools
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: bugpoint
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: nicholas at mxc.ca

I'd like to use bugpoint to isolate the parts of code where we aren't optimizing
as well as gcc (or other reference compiler). The technique is similar to the
miscompilation analysis.

Set a threshold for bugpoint, say, a 5% performance difference. Bugpoint
compiles the program with both LLVM and GCC and times the runs. It then cuts the
program in two, and compiles one half with LLVM, the other with GCC and links
them. If the program runs faster than (5% slower than GCC) then the
missing-optimization-opportunity must be in the GCC compiled half of the code,
else it's in the LLVM compiled half. Continue and isolate.

All the same tricks (loop extraction) can be applied to this too.

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