[LLVMbugs] [Bug 2698] New: InstCombine caused 20% slowdown in bzip2

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Wed Aug 20 22:58:05 PDT 2008


           Summary: InstCombine caused 20% slowdown in bzip2
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Scalar Optimizations
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: nicholas at mxc.ca
                CC: llvmbugs at cs.uiuc.edu

Created an attachment (id=1941)
 --> (http://llvm.org/bugs/attachment.cgi?id=1941)
trouble inducing patch

Evan tracked down a 20% slowdown in bzip2 to r54876. I've attached the
appropriate patch. The change was to fold xor's into icmp by messing with the
icmp predicate.

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