[LLVMbugs] [Bug 1800] New: after instcombine, loop is only executed once

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Wed Nov 14 12:31:38 PST 2007


           Summary: after instcombine, loop is only executed once
           Product: new-bugs
           Version: unspecified
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: baldrick at free.fr
                CC: llvmbugs at cs.uiuc.edu

Created an attachment (id=1221)
 --> (http://llvm.org/bugs/attachment.cgi?id=1221)
testcase .ll

$ lli ic.bc
$ opt -instcombine ic.bc | lli

After instcombine the copy loop is only executed once, rather
than five times, meaning only the first character (h) is copied.
I think this is because instcombine is turning this:

       %max13512 = select i1 %tmp13411, i32 %tmp13310, i32 0
       %tmp13713 = icmp eq i32 %max13512, 1
       br i1 %tmp13713, label %bb143.loopexit, label %bb.nph


       br i1 %tmp13411, label %bb143.loopexit, label %bb.nph

which is wrong if %tmp13310 is not equal to 1.

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