[LLVMbugs] [Bug 2077] New: incorrect gvn memcpy simplification

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=2077

           Summary: incorrect gvn memcpy simplification
           Product: new-bugs
           Version: unspecified
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          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=1439)
 --> (http://llvm.org/bugs/attachment.cgi?id=1439)
testcase .ll

The function @badly_optimized does:

  initialize %memtmp (by calling @initialize)
  memcpy %memtmp to %tmp
  memcpy %tmp to %z
  pass %z to @passed_uninitialized

After GVN (opt -gvn) it does:

  initialize %tmp (by calling @initialize)
  memcpy %memtmp to %z   <= This is not "memcpy %tmp to %z"!
  pass %z to @passed_uninitialized


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