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(as.info)Alpha Directives

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Alpha Assembler Directives
--------------------------

   `as' for the Alpha supports many additional directives for
compatibility with the native assembler.  This section describes them
only briefly.

   These are the additional directives in `as' for the Alpha:

`.arch CPU'
     Specifies the target processor.  This is equivalent to the `-mCPU'
     command-line option.  Note: Options, for a list of
     values for CPU.

`.ent FUNCTION[, N]'
     Mark the beginning of FUNCTION.  An optional number may follow for
     compatibility with the OSF/1 assembler, but is ignored.  When
     generating `.mdebug' information, this will create a procedure
     descriptor for the function.  In ELF, it will mark the symbol as a
     function a-la the generic `.type' directive.

`.end FUNCTION'
     Mark the end of FUNCTION.  In ELF, it will set the size of the
     symbol a-la the generic `.size' directive.

`.mask MASK, OFFSET'
     Indicate which of the integer registers are saved in the current
     function's stack frame.  MASK is interpreted a bit mask in which
     bit N set indicates that register N is saved.  The registers are
     saved in a block located OFFSET bytes from the "canonical frame
     address" (CFA) which is the value of the stack pointer on entry to
     the function.  The registers are saved sequentially, except that
     the return address register (normally `$26') is saved first.

     This and the other directives that describe the stack frame are
     currently only used when generating `.mdebug' information.  They
     may in the future be used to generate DWARF2 `.debug_frame' unwind
     information for hand written assembly.

`.fmask MASK, OFFSET'
     Indicate which of the floating-point registers are saved in the
     current stack frame.  The MASK and OFFSET parameters are
     interpreted as with `.mask'.

`.frame FRAMEREG, FRAMEOFFSET, RETREG[, ARGOFFSET]'
     Describes the shape of the stack frame.  The frame pointer in use
     is FRAMEREG; normally this is either `$fp' or `$sp'.  The frame
     pointer is FRAMEOFFSET bytes below the CFA.  The return address is
     initially located in RETREG until it is saved as indicated in
     `.mask'.  For compatibility with OSF/1 an optional ARGOFFSET
     parameter is accepted and ignored.  It is believed to indicate the
     offset from the CFA to the saved argument registers.

`.prologue N'
     Indicate that the stack frame is set up and all registers have been
     spilled.  The argument N indicates whether and how the function
     uses the incoming "procedure vector" (the address of the called
     function) in `$27'.  0 indicates that `$27' is not used; 1
     indicates that the first two instructions of the function use `$27'
     to perform a load of the GP register; 2 indicates that `$27' is
     used in some non-standard way and so the linker cannot elide the
     load of the procedure vector during relaxation.

`.gprel32 EXPRESSION'
     Computes the difference between the address in EXPRESSION and the
     GP for the current object file, and stores it in 4 bytes.  In
     addition to being smaller than a full 8 byte address, this also
     does not require a dynamic relocation when used in a shared
     library.

`.t_floating EXPRESSION'
     Stores EXPRESSION as an IEEE double precision value.

`.s_floating EXPRESSION'
     Stores EXPRESSION as an IEEE single precision value.

`.f_floating EXPRESSION'
     Stores EXPRESSION as a VAX F format value.

`.g_floating EXPRESSION'
     Stores EXPRESSION as a VAX G format value.

`.d_floating EXPRESSION'
     Stores EXPRESSION as a VAX D format value.

`.set FEATURE'
     Enables or disables various assembler features.  Using the positive
     name of the feature enables while using `noFEATURE' disables.

    `at'
          Indicates that macro expansions may clobber the "assembler
          temporary" (`$at' or `$28') register.  Some macros may not be
          expanded without this and will generate an error message if
          `noat' is in effect.  When `at' is in effect, a warning will
          be generated if `$at' is used by the programmer.

    `macro'
          Enables the expasion of macro instructions.  Note that
          variants of real instructions, such as `br label' vs `br
          $31,label' are considered alternate forms and not macros.

    `move'
    `reorder'
    `volatile'
          These control whether and how the assembler may re-order
          instructions.  Accepted for compatibility with the OSF/1
          assembler, but `as' does not do instruction scheduling, so
          these features are ignored.

   The following directives are recognized for compatibility with the
OSF/1 assembler but are ignored.

     .proc           .aproc
     .reguse         .livereg
     .option         .aent
     .ugen           .eflag
     .alias          .noalias