[LLVMbugs] [Bug 2744] New: 150x slowdown with llvm-gcc -O2 over -O1

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Mon Sep 1 14:40:11 PDT 2008


           Summary: 150x slowdown with llvm-gcc -O2 over -O1
           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

Created an attachment (id=1974)
 --> (http://llvm.org/bugs/attachment.cgi?id=1974)

Attached is part of the preprocessed source for bash 3.2:

  $ time llvm-gcc foo.c -O2 -c

  real    3m33.351s
  user    1m52.482s
  sys     0m0.592s

  $ time llvm-gcc foo.c -O1 -c

  real    0m1.377s
  user    0m0.652s
  sys     0m0.014s

I'm not sure which pass is responsible. The problem doesn't occur with opt

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