[LLVMbugs] [Bug 2571] New: Shootout-C++/ackermann has gcc/llc of 0.23x on Linux

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=2571

           Summary: Shootout-C++/ackermann has gcc/llc of 0.23x on Linux
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: nicholas at mxc.ca
                CC: llvmbugs at cs.uiuc.edu


For whatever reason, ackermann runs very slowly on Linux

  GCC: 0.92s
  CBE: 2.19s
  LLC: 4.01s

making it the slowest test in the Linux results. This bug is to figure out why.
More numbers:

  Using g++ (Debian 4.3.1-6) 4.3.1
  g++ -O2: 5.9s
  g++ -O2 -fwhole-program: 3.1s
  g++ -O3: 0.93s
  g++ -O3 -fno-strict-aliasing: 0.93s

Is it just unrolling loops?


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