[LLVMbugs] [Bug 2206] New: The bitwise-instruction optimizer doesn' t know about alignment of globals.

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Mon Apr 7 17:40:24 PDT 2008


           Summary: The bitwise-instruction optimizer doesn't know about
                    alignment of globals.
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: fvbommel at wxs.nl
                CC: llvmbugs at cs.uiuc.edu

Consider "i64 and (i64 ptrtoint (i64 (i64)* @cons to i64), i64 -8)"[1].
(Where @cons is a global function with an alignment >= 8 specified)
Such expressions aren't simplified by "opt -std-compile-opts", even though the
relevant bits of the ptrtoint result are guaranteed to be zero because of
above-mentioned alignment and similar optimizations are performed if the
pointer is replaced by an integer.

[1]: That expression was shortened for readability, and not actually tested in
this form. The actual expression was "i64 inttoptr (i64 and (i64 or (i64
ptrtoint (i64 (i64)* @cons to i64), i64 1), i64 -8) to i64 (i64)*)".

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