[Libre-soc-bugs] [Bug 671] New: convert spec pseudocode to use XLEN width

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=671

            Bug ID: 671
           Summary: convert spec pseudocode to use XLEN width
           Product: Libre-SOC's first SoC
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: CONFIRMED
          Severity: enhancement
          Priority: ---
         Component: Source Code
          Assignee: lkcl at lkcl.net
          Reporter: lkcl at lkcl.net
                CC: libre-soc-bugs at lists.libre-soc.org
   NLnet milestone: ---

all pseudocode needs to use XLEN width instead of
hard-coded values 64 as width.

due to MSB0 numbering GREAT CARE NEEDS TO BE TAKEN

    RS[56:63]

becomes

    RS[XLEN-8:XLEN-1]

things that operate on the entire number such as Logical XOR
or "add" instructions DO NOT need conversion.

    Pseudo-code:

    RT <- (RA|0) + EXTS(SI)

does NOT need conversion.

    prod[0:127] <- MULS((RA), EXTS(SI))
    RT <- prod[64:127]

needs conversion to:

    prod[0:XLEN*2] <- MULS(.....)
    RT <- prod[XLEN:XLEN*2-1]

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