[LLVMbugs] [Bug 1265] NEW: pointless masking being generated for zext values

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Wed Mar 21 13:17:48 PDT 2007


           Summary: pointless masking being generated for zext values
           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

Running opt -std-compile-opts on the attached bytecode results in:

        tail call void @report__test( i64 or (i64 and (i64 zext (i32 ptrtoint 
([7 x i8]* @str1 to i32) to i64), i64 4294967295), i64 shl (i64 zext (i32 
ptrtoint (%struct.string___XUB* @C.1.384 to i32) to i64), i64 32)) )

Note how an i32 is being zero extended to an i64, then the upper 32 bits of
the result, which are necessarily zero, are being pointlessly masked off.

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