[LLVMbugs] [Bug 5157] New: ScalarEvolution should canonicalize nosw/nousw

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Thu Oct 8 23:13:55 PDT 2009


           Summary: ScalarEvolution should canonicalize nosw/nousw
           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: edwintorok at gmail.com
                CC: llvmbugs at cs.uiuc.edu

ScalarEvolution only sets the nooverflow flags when creating a SCEV for a PHI
For example if a loop has both an induction variable, and a pointer being
incremented by 1 each loop, then:
induction variable will be <0,+,1> (SubClassData 2),
the pointer will be Base + <0,+,1> (SubClassData 0).
If I extract the offset from the pointer it'll be different from the induction
variable (SubClassData 2!=0), although they are in fact equal.

I think SCEV should canonicalize the subclassdata, and set it for pointers too.

For now I workaround this by recreating the addrec from its operands before
using it (that way subclassdata is always 0).

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