[LLVMbugs] [Bug 2619] New: poor optimization in presence of bitcast'ed pointer

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Thu Jul 31 09:35:19 PDT 2008


           Summary: poor optimization in presence of bitcast'ed pointer
           Product: libraries
           Version: trunk
          Platform: Macintosh
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Scalar Optimizations
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: daniel at zuster.org
                CC: llvmbugs at cs.uiuc.edu

Created an attachment (id=1874)
 --> (http://llvm.org/bugs/attachment.cgi?id=1874)
failing testcase

The attached test case (foo.ll) should optimize down to a constant return. I
believe the presence of the bitcast is inhibiting further optimization though. 

A relatively simple fix (I believe) would be to reduce the stores through a
bitcasted pointer to separate stores into the proper type when obvious. 

Alternatively, this code arises from a lowered memset, which could be changed
to lower in a type specific way. The original .ll is also attached.

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