9.13.5 HPPA Assembler Directives

as for the HPPA supports many additional directives for compatibility with the native assembler. This section describes them only briefly. For detailed information on HPPA-specific assembler directives, see HP9000 Series 800 Assembly Language Reference Manual (HP 92432-90001).

as does not support the following assembler directives described in the HP manual:

     .endm           .liston
     .enter          .locct
     .leave          .macro
     .listoff

Beyond those implemented for compatibility, as supports one additional assembler directive for the HPPA: .param . It conveys register argument locations for static functions. Its syntax closely follows the .export directive.

These are the additional directives in as for the HPPA:

.block n
.blockz n
Reserve n bytes of storage, and initialize them to zero.
.call
Mark the beginning of a procedure call. Only the special case with no arguments is allowed.
.callinfo [ param = value , ... ] [ flag , ... ]
Specify a number of parameters and flags that define the environment for a procedure.

param may be any of ‘ frame ’ (frame size), ‘ entry_gr ’ (end of general register range), ‘ entry_fr ’ (end of float register range), ‘ entry_sr ’ (end of space register range).

The values for flag are ‘ calls ’ or ‘ caller ’ (proc has subroutines), ‘ no_calls ’ (proc does not call subroutines), ‘ save_rp ’ (preserve return pointer), ‘ save_sp ’ (proc preserves stack pointer), ‘ no_unwind ’ (do not unwind this proc), ‘ hpux_int ’ (proc is interrupt routine).

.code
Assemble into the standard section called ‘ $TEXT$ ’, subsection ‘ $CODE$ ’.
.copyright " string "
In the SOM object format, insert string into the object code, marked as a copyright string.
.copyright " string "
In the ELF object format, insert string into the object code, marked as a version string.
.enter
Not yet supported; the assembler rejects programs containing this directive.
.entry
Mark the beginning of a procedure.
.exit
Mark the end of a procedure.
.export name [ , typ ] [ , param = r ]
Make a procedure name available to callers. typ , if present, must be one of ‘ absolute ’, ‘ code ’ (ELF only, not SOM), ‘ data ’, ‘ entry ’, ‘ data ’, ‘ entry ’, ‘ millicode ’, ‘ plabel ’, ‘ pri_prog ’, or ‘ sec_prog ’.

param , if present, provides either relocation information for the procedure arguments and result, or a privilege level. param may be ‘ argw n ’ (where n ranges from 0 to 3 , and indicates one of four one-word arguments); ‘ rtnval ’ (the procedure's result); or ‘ priv_lev ’ (privilege level). For arguments or the result, r specifies how to relocate, and must be one of ‘ no ’ (not relocatable), ‘ gr ’ (argument is in general register), ‘ fr ’ (in floating point register), or ‘ fu ’ (upper half of float register). For ‘ priv_lev ’, r is an integer.

.half n
Define a two-byte integer constant n ; synonym for the portable as directive .short .
.import name [ , typ ]
Converse of .export ; make a procedure available to call. The arguments use the same conventions as the first two arguments for .export .
.label name
Define name as a label for the current assembly location.
.leave
Not yet supported; the assembler rejects programs containing this directive.
.origin lc
Advance location counter to lc . Synonym for the as portable directive .org .
.param name [ , typ ] [ , param = r ]
Similar to .export , but used for static procedures.
.proc
Use preceding the first statement of a procedure.
.procend
Use following the last statement of a procedure.
label .reg expr
Synonym for .equ ; define label with the absolute expression expr as its value.
.space secname [ , params ]
Switch to section secname , creating a new section by that name if necessary. You may only use params when creating a new section, not when switching to an existing one. secname may identify a section by number rather than by name.

If specified, the list params declares attributes of the section, identified by keywords. The keywords recognized are ‘ spnum= exp ’ (identify this section by the number exp , an absolute expression), ‘ sort= exp ’ (order sections according to this sort key when linking; exp is an absolute expression), ‘ unloadable ’ (section contains no loadable data), ‘ notdefined ’ (this section defined elsewhere), and ‘ private ’ (data in this section not available to other programs).

.spnum secnam
Allocate four bytes of storage, and initialize them with the section number of the section named secnam . (You can define the section number with the HPPA .space directive.)


.string " str "
Copy the characters in the string str to the object file. See Strings , for information on escape sequences you can use in as strings.

Warning! The HPPA version of .string differs from the usual as definition: it does not write a zero byte after copying str .

.stringz " str "
Like .string , but appends a zero byte after copying str to object file.
.subspa name [ , params ]
.nsubspa name [ , params ]
Similar to .space , but selects a subsection name within the current section. You may only specify params when you create a subsection (in the first instance of .subspa for this name ).

If specified, the list params declares attributes of the subsection, identified by keywords. The keywords recognized are ‘ quad= expr ’ (“quadrant” for this subsection), ‘ align= expr ’ (alignment for beginning of this subsection; a power of two), ‘ access= expr ’ (value for “access rights” field), ‘ sort= expr ’ (sorting order for this subspace in link), ‘ code_only ’ (subsection contains only code), ‘ unloadable ’ (subsection cannot be loaded into memory), ‘ comdat ’ (subsection is comdat), ‘ common ’ (subsection is common block), ‘ dup_comm ’ (subsection may have duplicate names), or ‘ zero ’ (subsection is all zeros, do not write in object file).

.nsubspa always creates a new subspace with the given name, even if one with the same name already exists.

comdat ’, ‘ common ’ and ‘ dup_comm ’ can be used to implement various flavors of one-only support when using the SOM linker. The SOM linker only supports specific combinations of these flags. The details are not documented. A brief description is provided here.

comdat ’ provides a form of linkonce support. It is useful for both code and data subspaces. A ‘ comdat ’ subspace has a key symbol marked by the ‘ is_comdat ’ flag or ‘ ST_COMDAT ’. Only the first subspace for any given key is selected. The key symbol becomes universal in shared links. This is similar to the behavior of ‘ secondary_def ’ symbols.

common ’ provides Fortran named common support. It is only useful for data subspaces. Symbols with the flag ‘ is_common ’ retain this flag in shared links. Referencing a ‘ is_common ’ symbol in a shared library from outside the library doesn't work. Thus, ‘ is_common ’ symbols must be output whenever they are needed.

common ’ and ‘ dup_comm ’ together provide Cobol common support. The subspaces in this case must all be the same length. Otherwise, this support is similar to the Fortran common support.

dup_comm ’ by itself provides a type of one-only support for code. Only the first ‘ dup_comm ’ subspace is selected. There is a rather complex algorithm to compare subspaces. Code symbols marked with the ‘ dup_common ’ flag are hidden. This support was intended for "C++ duplicate inlines".

A simplified technique is used to mark the flags of symbols based on the flags of their subspace. A symbol with the scope SS_UNIVERSAL and type ST_ENTRY, ST_CODE or ST_DATA is marked with the corresponding settings of ‘ comdat ’, ‘ common ’ and ‘ dup_comm ’ from the subspace, respectively. This avoids having to introduce additional directives to mark these symbols. The HP assembler sets ‘ is_common ’ from ‘ common ’. However, it doesn't set the ‘ dup_common ’ from ‘ dup_comm ’. It doesn't have ‘ comdat ’ support.

.version " str "
Write str as version identifier in object code.