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- @c Copyright (C) 1991-2022 Free Software Foundation, Inc.
- @c This is part of the GAS manual.
- @c For copying conditions, see the file as.texinfo.
- @page
- @node HPPA-Dependent
- @chapter HPPA Dependent Features
- @cindex support
- @menu
- * HPPA Notes:: Notes
- * HPPA Options:: Options
- * HPPA Syntax:: Syntax
- * HPPA Floating Point:: Floating Point
- * HPPA Directives:: HPPA Machine Directives
- * HPPA Opcodes:: Opcodes
- @end menu
- @node HPPA Notes
- @section Notes
- As a back end for @sc{gnu} @sc{cc} @code{@value{AS}} has been thoroughly tested and should
- work extremely well. We have tested it only minimally on hand written assembly
- code and no one has tested it much on the assembly output from the HP
- compilers.
- The format of the debugging sections has changed since the original
- @code{@value{AS}} port (version 1.3X) was released; therefore,
- you must rebuild all HPPA objects and libraries with the new
- assembler so that you can debug the final executable.
- The HPPA @code{@value{AS}} port generates a small subset of the relocations
- available in the SOM and ELF object file formats. Additional relocation
- support will be added as it becomes necessary.
- @node HPPA Options
- @section Options
- @code{@value{AS}} has no machine-dependent command-line options for the HPPA.
- @cindex HPPA Syntax
- @node HPPA Syntax
- @section Syntax
- The assembler syntax closely follows the HPPA instruction set
- reference manual; assembler directives and general syntax closely follow the
- HPPA assembly language reference manual, with a few noteworthy differences.
- First, a colon may immediately follow a label definition. This is
- simply for compatibility with how most assembly language programmers
- write code.
- Some obscure expression parsing problems may affect hand written code which
- uses the @code{spop} instructions, or code which makes significant
- use of the @code{!} line separator.
- @code{@value{AS}} is much less forgiving about missing arguments and other
- similar oversights than the HP assembler. @code{@value{AS}} notifies you
- of missing arguments as syntax errors; this is regarded as a feature, not a
- bug.
- Finally, @code{@value{AS}} allows you to use an external symbol without
- explicitly importing the symbol. @emph{Warning:} in the future this will be
- an error for HPPA targets.
- Special characters for HPPA targets include:
- @samp{;} is the line comment character.
- @samp{!} can be used instead of a newline to separate statements.
- Since @samp{$} has no special meaning, you may use it in symbol names.
- @node HPPA Floating Point
- @section Floating Point
- @cindex floating point, HPPA (@sc{ieee})
- @cindex HPPA floating point (@sc{ieee})
- The HPPA family uses @sc{ieee} floating-point numbers.
- @node HPPA Directives
- @section HPPA Assembler Directives
- @code{@value{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
- @cite{HP9000 Series 800 Assembly Language Reference Manual} (HP 92432-90001).
- @cindex HPPA directives not supported
- @code{@value{AS}} does @emph{not} support the following assembler directives
- described in the HP manual:
- @example
- .endm .liston
- .enter .locct
- .leave .macro
- .listoff
- @end example
- @cindex @code{.param} on HPPA
- Beyond those implemented for compatibility, @code{@value{AS}} supports one
- additional assembler directive for the HPPA: @code{.param}. It conveys
- register argument locations for static functions. Its syntax closely follows
- the @code{.export} directive.
- @cindex HPPA-only directives
- These are the additional directives in @code{@value{AS}} for the HPPA:
- @table @code
- @item .block @var{n}
- @itemx .blockz @var{n}
- Reserve @var{n} bytes of storage, and initialize them to zero.
- @item .call
- Mark the beginning of a procedure call. Only the special case with @emph{no
- arguments} is allowed.
- @item .callinfo [ @var{param}=@var{value}, @dots{} ] [ @var{flag}, @dots{} ]
- Specify a number of parameters and flags that define the environment for a
- procedure.
- @var{param} may be any of @samp{frame} (frame size), @samp{entry_gr} (end of
- general register range), @samp{entry_fr} (end of float register range),
- @samp{entry_sr} (end of space register range).
- The values for @var{flag} are @samp{calls} or @samp{caller} (proc has
- subroutines), @samp{no_calls} (proc does not call subroutines), @samp{save_rp}
- (preserve return pointer), @samp{save_sp} (proc preserves stack pointer),
- @samp{no_unwind} (do not unwind this proc), @samp{hpux_int} (proc is interrupt
- routine).
- @item .code
- Assemble into the standard section called @samp{$TEXT$}, subsection
- @samp{$CODE$}.
- @ifset SOM
- @item .copyright "@var{string}"
- In the SOM object format, insert @var{string} into the object code, marked as a
- copyright string.
- @end ifset
- @ifset ELF
- @item .copyright "@var{string}"
- In the ELF object format, insert @var{string} into the object code, marked as a
- version string.
- @end ifset
- @item .enter
- Not yet supported; the assembler rejects programs containing this directive.
- @item .entry
- Mark the beginning of a procedure.
- @item .exit
- Mark the end of a procedure.
- @item .export @var{name} [ ,@var{typ} ] [ ,@var{param}=@var{r} ]
- Make a procedure @var{name} available to callers. @var{typ}, if present, must
- be one of @samp{absolute}, @samp{code} (ELF only, not SOM), @samp{data},
- @samp{entry}, @samp{data}, @samp{entry}, @samp{millicode}, @samp{plabel},
- @samp{pri_prog}, or @samp{sec_prog}.
- @var{param}, if present, provides either relocation information for the
- procedure arguments and result, or a privilege level. @var{param} may be
- @samp{argw@var{n}} (where @var{n} ranges from @code{0} to @code{3}, and
- indicates one of four one-word arguments); @samp{rtnval} (the procedure's
- result); or @samp{priv_lev} (privilege level). For arguments or the result,
- @var{r} specifies how to relocate, and must be one of @samp{no} (not
- relocatable), @samp{gr} (argument is in general register), @samp{fr} (in
- floating point register), or @samp{fu} (upper half of float register).
- For @samp{priv_lev}, @var{r} is an integer.
- @item .half @var{n}
- Define a two-byte integer constant @var{n}; synonym for the portable
- @code{@value{AS}} directive @code{.short}.
- @item .import @var{name} [ ,@var{typ} ]
- Converse of @code{.export}; make a procedure available to call. The arguments
- use the same conventions as the first two arguments for @code{.export}.
- @item .label @var{name}
- Define @var{name} as a label for the current assembly location.
- @item .leave
- Not yet supported; the assembler rejects programs containing this directive.
- @item .origin @var{lc}
- Advance location counter to @var{lc}. Synonym for the @code{@value{AS}}
- portable directive @code{.org}.
- @item .param @var{name} [ ,@var{typ} ] [ ,@var{param}=@var{r} ]
- @c Not in HP manual; @sc{gnu} HPPA extension
- Similar to @code{.export}, but used for static procedures.
- @item .proc
- Use preceding the first statement of a procedure.
- @item .procend
- Use following the last statement of a procedure.
- @item @var{label} .reg @var{expr}
- @c ?? Not in HP manual (Jan 1988 vn)
- Synonym for @code{.equ}; define @var{label} with the absolute expression
- @var{expr} as its value.
- @item .space @var{secname} [ ,@var{params} ]
- Switch to section @var{secname}, creating a new section by that name if
- necessary. You may only use @var{params} when creating a new section, not
- when switching to an existing one. @var{secname} may identify a section by
- number rather than by name.
- If specified, the list @var{params} declares attributes of the section,
- identified by keywords. The keywords recognized are @samp{spnum=@var{exp}}
- (identify this section by the number @var{exp}, an absolute expression),
- @samp{sort=@var{exp}} (order sections according to this sort key when linking;
- @var{exp} is an absolute expression), @samp{unloadable} (section contains no
- loadable data), @samp{notdefined} (this section defined elsewhere), and
- @samp{private} (data in this section not available to other programs).
- @item .spnum @var{secnam}
- @c ?? Not in HP manual (Jan 1988)
- Allocate four bytes of storage, and initialize them with the section number of
- the section named @var{secnam}. (You can define the section number with the
- HPPA @code{.space} directive.)
- @cindex @code{string} directive on HPPA
- @item .string "@var{str}"
- Copy the characters in the string @var{str} to the object file.
- @xref{Strings,,Strings}, for information on escape sequences you can use in
- @code{@value{AS}} strings.
- @emph{Warning!} The HPPA version of @code{.string} differs from the
- usual @code{@value{AS}} definition: it does @emph{not} write a zero byte
- after copying @var{str}.
- @item .stringz "@var{str}"
- Like @code{.string}, but appends a zero byte after copying @var{str} to object
- file.
- @item .subspa @var{name} [ ,@var{params} ]
- @itemx .nsubspa @var{name} [ ,@var{params} ]
- Similar to @code{.space}, but selects a subsection @var{name} within the
- current section. You may only specify @var{params} when you create a
- subsection (in the first instance of @code{.subspa} for this @var{name}).
- If specified, the list @var{params} declares attributes of the subsection,
- identified by keywords. The keywords recognized are @samp{quad=@var{expr}}
- (``quadrant'' for this subsection), @samp{align=@var{expr}} (alignment for
- beginning of this subsection; a power of two), @samp{access=@var{expr}} (value
- for ``access rights'' field), @samp{sort=@var{expr}} (sorting order for this
- subspace in link), @samp{code_only} (subsection contains only code),
- @samp{unloadable} (subsection cannot be loaded into memory), @samp{comdat}
- (subsection is comdat), @samp{common} (subsection is common block),
- @samp{dup_comm} (subsection may have duplicate names), or @samp{zero}
- (subsection is all zeros, do not write in object file).
- @code{.nsubspa} always creates a new subspace with the given name, even
- if one with the same name already exists.
- @samp{comdat}, @samp{common} and @samp{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.
- @samp{comdat} provides a form of linkonce support. It is useful for
- both code and data subspaces. A @samp{comdat} subspace has a key symbol
- marked by the @samp{is_comdat} flag or @samp{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 @samp{secondary_def}
- symbols.
- @samp{common} provides Fortran named common support. It is only useful
- for data subspaces. Symbols with the flag @samp{is_common} retain this
- flag in shared links. Referencing a @samp{is_common} symbol in a shared
- library from outside the library doesn't work. Thus, @samp{is_common}
- symbols must be output whenever they are needed.
- @samp{common} and @samp{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.
- @samp{dup_comm} by itself provides a type of one-only support for code.
- Only the first @samp{dup_comm} subspace is selected. There is a rather
- complex algorithm to compare subspaces. Code symbols marked with the
- @samp{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 @samp{comdat}, @samp{common} and @samp{dup_comm} from the
- subspace, respectively. This avoids having to introduce additional
- directives to mark these symbols. The HP assembler sets @samp{is_common}
- from @samp{common}. However, it doesn't set the @samp{dup_common} from
- @samp{dup_comm}. It doesn't have @samp{comdat} support.
- @item .version "@var{str}"
- Write @var{str} as version identifier in object code.
- @end table
- @node HPPA Opcodes
- @section Opcodes
- For detailed information on the HPPA machine instruction set, see
- @cite{PA-RISC Architecture and Instruction Set Reference Manual}
- (HP 09740-90039).
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