Alpha PALcode built-ins, primarily for privileged code, are used
    in the same way that Alpha instruction built-ins are used with
    two exceptions:

    o  For the queue PAL functions, the compiler does not move the
       input arguments to the Alpha registers before issuing the PAL
       call as it does for all other functions. Therefore, you must
       supply the code to do that.

    o  When using a built-in for a PAL call that returns a value, the
       source code must explicitly read R0 for the return value.

    Certain Alpha PALcode built-ins, EVAX_INSQHIQR, EVAX_INSQTIQR,
    EVAX_REMQHIQR, and EVAX_REMQHITR, support the manipulation of
    quadword queues, a function that VAX MACRO does not support. If
    you use these built-ins, you must supply the code to move the
    input arguments to R16 (and R17, for EVAX_INSQxxxx), as shown in
    the following example:

    MOVAB  Q_header, R16  ; Set up address of queue header for PAL call
    EVAX_REMQHIQR         ; Remove quadword queue entry
    EVAX_STQ  R0, entry   ; Save entry address returned in R0

    The Alpha PALcode built-ins are listed in the following table.

                                   NOTE

       You can use the .DEFINE_PAL compiler directive to custom-
       define a built-in for an Alpha PALcode operation that is not
       listed in this table.

    Built-in         Operands  Description

    EVAX_CFLUSH      <RQ>      Cache flush
    EVAX_DRAINA      <>        Drain aborts
    EVAX_LDQP        <AQ>      Load quadword physical
    EVAX_STQP        <AQ,RQ>   Store quadword physical
    EVAX_SWPCTX      <AQ>      Swap privileged context
    EVAX_BUGCHK      <RQ>      Bugcheck
    EVAX_CHMS        <>        Change mode supervisor
    EVAX_CHMU        <>        Change mode user
    EVAX_IMB         <>        Instruction memory barrier
    EVAX_SWASTEN     <RQ>      Swap AST enable
    EVAX_WR_PS_SW    <RQ>      Write processor status software field

    EVAX_MTPR_ASTEN  <RQ>      Move to processor register ASTEN
    EVAX_MTPR_ASTSR  <RQ>      Move to processor register ASTSR
    EVAX_MTPR_AT     <RQ>      Move to processor register AT
    EVAX_MTPR_FEN    <RQ>      Move to processor register FEN
    EVAX_MTPR_IPIR   <RQ>      Move to processor register IPIR
    EVAX_MTPR_IPL    <RQ>      Move to processor register IPL
    EVAX_MTPR_PRBR   <RQ>      Move to processor register PRBR
    EVAX_MTPR_SCBB   <RQ>      Move to processor register SCBB
    EVAX_MTPR_SIRR   <RQ>      Move to processor register SIRR
    EVAX_MTPR_TBIA   <>        Move to processor register TBIA
    EVAX_MTPR_TBIAP  <>        Move to processor register TBIAP
    EVAX_MTPR_TBIS   <AQ>      Move to processor register TBIS
    EVAX_MTPR_TBISD  <AQ>      Move to processor register, TB
                               invalidate single DATA
    EVAX_MTPR_TBISI  <AQ>      Move to processor register, TB
                               invalidate single ISTREAM
    EVAX_MTPR_ESP    <AQ>      Move to processor register ESP
    EVAX_MTPR_SSP    <AQ>      Move to processor register SSP
    EVAX_MTPR_USP    <AQ>      Move to processor register USP

    EVAX_MFPR_ASN    <>        Move from processor register ASN
    EVAX_MFPR_AT     <>        Move from processor register AT
    EVAX_MFPR_FEN    <>        Move from processor register FEN
    EVAX_MFPR_IPL    <>        Move from processor register IPL
    EVAX_MFPR_MCES   <>        Move from processor register MCES
    EVAX_MFPR_PCBB   <>        Move from processor register PCBB
    EVAX_MFPR_PRBR   <>        Move from processor register PRBR
    EVAX_MFPR_PTBR   <>        Move from processor register PTBR
    EVAX_MFPR_SCBB   <>        Move from processor register SCBB
    EVAX_MFPR_SISR   <>        Move from processor register SISR
    EVAX_MFPR_TBCHK  <AQ>      Move from processor register TBCHK
    EVAX_MFPR_ESP    <>        Move from processor register ESP
    EVAX_MFPR_SSP    <>        Move from processor register SSP
    EVAX_MFPR_USP    <>        Move from processor register USP
    EVAX_MFPR_WHAMI  <>        Move from processor register WHAMI

    EVAX_INSQHILR    <>        Insert entry into longword queue at
                               head interlocked-resident
    EVAX_INSQTILR    <>        Insert entry into longword queue at
                               tail interlocked-resident
    EVAX_INSQHIQR    <>        Insert entry into quadword queue at
                               head interlocked-resident
    EVAX_INSQTIQR    <>        Insert entry into quadword queue at
                               tail interlocked-resident
    EVAX_REMQHILR    <>        Remove entry from longword queue at
                               head interlocked-resident
    EVAX_REMQTILR    <>        Remove entry from longword queue at
                               tail interlocked-resident
    EVAX_REMQHIQR    <>        Remove entry from quadword queue at
                               head interlocked-resident
    EVAX_REMQTIQR    <>        Remove entry from quadword queue at
                               tail interlocked-resident

    EVAX_GENTRAP     <>        Generate trap exception

    EVAX_READ_UNQ    <>        Read unique context
    EVAX_WRITE_UNQ   <RQ>      Write unique context