Conference turris::macro

254.0. "Alpha V7.0/later %SYSTEM-F-HPARITH w EDIV #32,R0,R2,R1" by CSC32::D_SANFORD () Thu Mar 06 1997 18:35

    OpenVMS Alpha V7.1, AMAC V3.0-23-311D -> %SYSTEM-F-HPARITH
    OpenVMS Alpha V7.0, AMAC V2.2-19-2671 -> %SYSTEM-F-HPARITH

    OpenVMS Alpha V6.2, AMAC V2.1-17-2671 -> OK

    This simple example fails after upgrading to OpenVMS Alpha V7.0 or
    later.  If fails on the line:

      EDIV    #32,R0,R2,R1    (SUBL/V instruction? from machine listing)

    With:

      %SYSTEM-F-HPARITH, high performance arithmetic trap, Imask=02000000,
       Fmask=00000000, summary=40, PC=000000000003006C, PS=0000001B
      -SYSTEM-F-INTOVF, arithmetic trap, integer overflow at 
       PC=000000000003006C, PS=0000001B

    If you don't clear R1 first, it doesn't get the overflow.  If you put
    a 1 in R0, it doesn't get the overflow.  

    Regards, Drew Sanford
    Customer Support Center
    C970306-5609

$ ! command procedure to duplicate problem
$ create a.for
        PROGRAM A
        CALL SETUP
        END
$ create b.mar
        .TITLE  B
SETUP::
        .CALL_ENTRY PRESERVE=<R2>
        CLRL    R1
        CLRL    R0
        EDIV    #32,R0,R2,R1
        RET
        .END
$ fortran a
$ MACRO/MIGRATION/NOTIE/ENABLE=OVERFLOW/NOLIST/NOOPT B
$ link a,b
$ run a

    This problem has already been fixed for the next release. Integer
    overflow could be erroneously signalled when the EDIV dividend was zero.
    
    One workaround is to disable overflow checking for that single
    instruction.
    
    Tom