This is the mail archive of the mailing list for the binutils project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]

MMIX port, part 2/10: gas documentation.

Ok to commit?

Part 2/10, gas documentation:

	* doc/ (CPU_DOCS): Add c-mmix.texi
	* doc/ Regenerate.
	* doc/all.texi: @set MMIX.
	* doc/as.texinfo: Ditto.  Add MMIX gas manpage option overview.
	Include c-mmix.texi.
	* doc/c-mmix.texi: New file.

Index: doc/
RCS file: /cvs/src/src/gas/doc/,v
retrieving revision 1.12
diff -p -c -r1.12
***	2001/07/05 00:22:29	1.12
---	2001/09/30 16:52:10
*************** CPU_DOCS = \
*** 39,44 ****
--- 39,45 ----
  	c-m68k.texi \
  	c-m88k.texi \
  	c-mips.texi \
+ 	c-mmix.texi \
  	c-ns32k.texi \
  	c-pdp11.texi \
  	c-pj.texi \
Index: doc/all.texi
RCS file: /cvs/src/src/gas/doc/all.texi,v
retrieving revision 1.9
diff -p -c -r1.9 all.texi
*** all.texi	2001/07/05 00:22:29	1.9
--- all.texi	2001/09/30 16:52:10
*** 44,49 ****
--- 44,50 ----
  @set M880X0
  @set MCORE
  @set MIPS
+ @set MMIX
  @set PDP11
  @set PJ
  @set SH
Index: doc/as.texinfo
RCS file: /cvs/src/src/gas/doc/as.texinfo,v
retrieving revision 1.44
diff -p -c -r1.44 as.texinfo
*** as.texinfo	2001/09/19 07:55:23	1.44
--- as.texinfo	2001/09/30 17:00:40
*** 43,48 ****
--- 43,49 ----
  @set M880X0
  @set MCORE
  @set MIPS
+ @set MMIX
  @set PDP11
  @set PJ
  @set SH
*************** gcc(1), ld(1), and the Info entries for
*** 336,341 ****
--- 337,347 ----
   [ --trap ] [ --break ] [ -n ]
   [ --emulation=@var{name} ]
  @end ifset
+ @ifset MMIX
+  [ --fixed-special-register-names ] [ --globalize-symbols ]
+  [ --gnu-syntax ] [ --relax ] [ --no-predefined-symbols ]
+  [ --no-expand ] [ --no-merge-gregs ] [ -x ]
+ @end ifset
   [ -- | @var{files} @dots{} ]
  @c man end
  @end smallexample
*************** Assemble for a little endian target.
*** 868,873 ****
--- 874,883 ----
  @end table
  @end ifset

+ @ifset MMIX
+ See the info pages for documentation of the MMIX-specific options.
+ @end ifset
  @c man end

*************** subject, see the hardware manufacturer's
*** 5540,5545 ****
--- 5550,5558 ----
  @ifset MIPS
  * MIPS-Dependent::              MIPS Dependent Features
  @end ifset
+ @ifset MMIX
+ * MMIX-Dependent::              MMIX Dependent Features
+ @end ifset
  @ifset SH
  * SH-Dependent::                Hitachi SH Dependent Features
  @end ifset
*************** family.
*** 5662,5667 ****
--- 5675,5684 ----

  @ifset MIPS
  @include c-mips.texi
+ @end ifset
+ @ifset MMIX
+ @include c-mmix.texi
  @end ifset

  @ifset NS32K
*** /dev/null	Tue Jan  1 05:00:00 1980
--- doc/c-mmix.texi	Sun Sep 30 12:31:22 2001
*** 0 ****
--- 1,559 ----
+ @c Copyright 2001 Free Software Foundation, Inc.
+ @c This is part of the GAS manual.
+ @c For copying conditions, see the file as.texinfo.
+ @c MMIX description by Hans-Peter Nilsson,
+ @ifset GENERIC
+ @page
+ @node MMIX-Dependent
+ @chapter MMIX Dependent Features
+ @end ifset
+ @ifclear GENERIC
+ @node Machine Dependencies
+ @chapter MMIX Dependent Features
+ @end ifclear
+ @cindex MMIX support
+ @menu
+ * MMIX-Opts::              Command-line Options
+ * MMIX-Expand::            Instruction expansion
+ * MMIX-Syntax::            Syntax
+ * MMIX-mmixal::		   Differences to @code{mmixal} syntax and semantics
+ @end menu
+ @node MMIX-Opts
+ @section Command-line Options
+ @cindex options, MMIX
+ @cindex MMIX options
+ The MMIX version of @code{@value{AS}} has some machine-dependent options.
+ @cindex @samp{--fixed-special-register-names} command line option, MMIX
+ When @samp{--fixed-special-register-names} is specified, only the register
+ names specified in @ref{MMIX-Regs} are recognized in the instructions
+ @code{PUT} and @code{GET}.
+ @cindex @samp{--globalize-symbols} command line option, MMIX
+ You can use the @samp{--globalize-symbols} to make all symbols global.
+ This option is useful when splitting up a @code{mmixal} program into
+ several files.
+ @cindex @samp{--gnu-syntax} command line option, MMIX
+ The @samp{--gnu-syntax} turns off most syntax compatibility with
+ @code{mmixal}.  Its usability is currently doubtful.
+ @cindex @samp{--relax} command line option, MMIX
+ The @samp{--relax} option is not fully supported, but will eventually make
+ the object file prepared for linker relaxation.
+ @cindex @samp{--no-predefined-syms} command line option, MMIX
+ If you want to avoid inadvertently calling a predefined symbol and would
+ rather get an error, for example when using @code{@value{AS}} with a
+ compiler or other machine-generated code, specify
+ @samp{--no-predefined-syms}.  This turns off built-in predefined
+ definitions of all such symbols, including rounding-mode symbols, segment
+ symbols, @samp{BIT} symbols, and @code{TRAP} symbols used in @code{mmix}
+ ``system calls''.  It also turns off predefined special-register names,
+ except when used in @code{PUT} and @code{GET} instructions.
+ @cindex @samp{--no-expand} command line option, MMIX
+ By default, some instructions are expanded to fit the size of the operand
+ or an external symbol (@pxref{MMIX-Expand}).  By passing
+ @samp{--no-expand}, no such expansion will be done, instead causing errors
+ at link time if the operand does not fit.
+ @cindex @samp{--no-merge-gregs} command line option, MMIX
+ The @code{mmixal} documentation (@pxref{mmixsite}) specifies that global
+ registers allocated with the @samp{GREG} directive (@pxref{MMIX-greg}) and
+ initialized to the same non-zero value, will refer to the same global
+ register.  This isn't strictly enforcable in @code{@value{AS}} since the
+ final addresses aren't known until link-time, but it will do an effort
+ unless the @samp{--no-merge-gregs} option is specified.  (Register merging
+ isn't yet implemented in @code{@value{LD}}.)
+ @cindex @samp{-x} command line option, MMIX
+ @code{@value{AS}} will warn every time it expands an instruction to fit an
+ operand unless the option @samp{-x} is specified.  It is believed that
+ this behaviour is more useful than just mimicking @code{mmixal}'s
+ behaviour, in which instructions are only expanded if the @samp{-x} option
+ is specified, and assembly fails otherwise, when an instruction needs to
+ be expanded.  It needs to be kept in mind that @code{mmixal} is both an
+ assembler and linker, while @code{@value{AS}} will expand instructions
+ that at link stage can be contracted.  (Though linker relaxation isn't yet
+ implemented in @code{@value{LD}}.)
+ @node MMIX-Expand
+ @section Instruction expansion
+ @cindex instruction expansion, MMIX
+ When @code{@value{AS}} encounters an instruction with an operand that is
+ either not known or does not fit the operand size of the instruction,
+ @code{@value{AS}} (and @code{@value{LD}}) will expand the instruction into
+ a sequence of instructions semantically equivalent to the operand fitting
+ the instruction.  Expansion will take place for the following
+ instructions:
+ @table @asis
+ @item @samp{GETA}
+ Expands to a sequence of four instructions: @code{SETL}, @code{INCML},
+ @code{INCMH} and @code{INCH}.  The operand must be a multiple of four.
+ @item Conditional branches
+ A branch instruction is turned into a branch with the complemented
+ condition and prediction bit over five instructions; four instructions
+ setting @code{$255} to the operand value, which like with @code{GETA} must
+ be a multiple of four, and a final @code{GO $255,$255,0}.
+ @item @samp{PUSHJ}
+ Similar to expansion for conditional branches; four instructions set
+ @code{$255} to the operand value, followed by a @code{PUSHGO $255,$255,0}.
+ @item @samp{JMP}
+ Similar to conditional branches and @code{PUSHJ}.  The final instruction
+ is @code{GO $255,$255,0}.
+ @end table
+ The linker @code{@value{LD}} is expected to shrink these expansions for
+ code assembled with @samp{--relax} (though not currently implemented).
+ @node MMIX-Syntax
+ @section Syntax
+ The assembly syntax is supposed to be upward compatible with that
+ described in Sections 1.3 and 1.4 of @samp{The Art of Computer
+ Programming, Volume 1}.  Draft versions of those chapters as well as other
+ MMIX information is located at
+ @anchor{mmixsite}@url{}.
+ Most code examples from the mmixal package located there should work
+ unmodified when assembled and linked as single files, with a few
+ noteworthy exceptions (@pxref{MMIX-mmixal}).
+ Before an instruction is emitted, the current location is aligned to the
+ next four-byte boundary.  If a label is defined at the beginning of the
+ line, its value will be the aligned value.
+ In addition to the traditional hex-prefix @samp{0x}, a hexadecimal number
+ can also be specified by the prefix character @samp{#}.
+ After all operands to an MMIX instruction or directive have been
+ specified, the rest of the line is ignored, treated as a comment.
+ @menu
+ * MMIX-Chars::		        Special Characters
+ * MMIX-Symbols::		Symbols
+ * MMIX-Regs::			Register Names
+ * MMIX-Pseudos::		Assembler Directives
+ @end menu
+ @node MMIX-Chars
+ @subsection Special Characters
+ @cindex line comment characters, MMIX
+ @cindex MMIX line comment characters
+ The characters @samp{*} and @samp{#} are line comment characters; each
+ start a comment at the beginning of a line, but only at the beginning of a
+ line.  A @samp{#} prefixes a hexadecimal number if found elsewhere on a
+ line.
+ Two other characters, @samp{%} and @samp{!}, each start a comment anywhere
+ on the line.  Thus you can't use the @samp{modulus} and @samp{not}
+ operators in expressions normally associated with these two characters.
+ A @samp{;} is a line separator, treated as a new-line, so separate
+ instructions can be specified on a single line.
+ @node MMIX-Symbols
+ @subsection Symbols
+ The character @samp{:} is permitted in identifiers.  There are two
+ exceptions to it being treated as any other symbol character: if a symbol
+ begins with @samp{:}, it means that the symbol is in the global namespace
+ and that the current prefix should not be prepended to that symbol
+ (@pxref{MMIX-prefix}).  The @samp{:} is then not considered part of the
+ symbol.  For a symbol in the label position (first on a line), a @samp{:}
+ at the end of a symbol is silently stripped off.  A label is permitted,
+ but not required, to be followed by a @samp{:}, as with many other
+ assembly formats.
+ The character @samp{@@} in an expression, is a synonym for @samp{.}, the
+ current location.
+ In addition to the common forward and backward local symbol formats
+ (@pxref{Symbol Names}), they can be specified with upper-case @samp{B} and
+ @samp{F}, as in @samp{8B} and @samp{9F}.  A local label defined for the
+ current position is written with a @samp{H} appended to the number:
+ @smallexample
+ 3H LDB $0,$1,2
+ @end smallexample
+ This and traditional local-label formats cannot be mixed: a label must be
+ defined and referred to using the same format.
+ There's a minor caveat: just as for the ordinary local symbols, the local
+ symbols are translated into ordinary symbols using control characters are
+ to hide the ordinal number of the symbol.  Unfortunately, these symbols
+ are not translated back in error messages.  Thus you may see confusing
+ error messages when local symbols are used.  Control characters
+ @samp{\003} (control-C) and @samp{\004} (control-D) are used for the
+ MMIX-specific local-symbol syntax.
+ The symbol @samp{Main} is handled specially; it is always global.
+ By defining the symbols @samp{__.MMIX.start..text} and
+ @samp{}, the address of respectively the @samp{.text}
+ and @samp{.data} segments of the final program can be defined, though when
+ linking more than one object file, the code or data in the object file
+ containing the symbol is not guaranteed to be start at that position; just
+ the final executable.  @xref{MMIX-loc}.
+ @node MMIX-Regs
+ @subsection Register names
+ @cindex register names, MMIX
+ @cindex MMIX register names
+ Local and global registers are specified as @samp{$0} to @samp{$255}.
+ The recognized special register names are @samp{rJ}, @samp{rA}, @samp{rB},
+ @samp{rC}, @samp{rD}, @samp{rE}, @samp{rF}, @samp{rG}, @samp{rH},
+ @samp{rI}, @samp{rK}, @samp{rL}, @samp{rM}, @samp{rN}, @samp{rO},
+ @samp{rP}, @samp{rQ}, @samp{rR}, @samp{rS}, @samp{rT}, @samp{rU},
+ @samp{rV}, @samp{rW}, @samp{rX}, @samp{rY}, @samp{rZ}, @samp{rBB},
+ @samp{rTT}, @samp{rWW}, @samp{rXX}, @samp{rYY} and @samp{rZZ}.  A leading
+ @samp{:} is optional for special register names.
+ Local and global symbols can be equated to register names and used in
+ place of ordinary registers.
+ Similarly for special registers, local and global symbols can be used.
+ Also, symbols equated from numbers and constant expressions are allowed in
+ place of a special register, except when either of the options
+ @code{--no-predefined-syms} and @code{--fixed-special-register-names} are
+ specified.  Then only the special register names above are allowed for the
+ instructions having a special register operand; @code{GET} and @code{PUT}.
+ @node MMIX-Pseudos
+ @subsection Assembler Directives
+ @cindex assembler directives, MMIX
+ @cindex pseudo-ops, MMIX
+ @cindex MMIX assembler directives
+ @cindex MMIX pseudo-ops
+ @table @code
+ @item LOC
+ @cindex assembler directive LOC, MMIX
+ @cindex pseudo-op LOC, MMIX
+ @cindex MMIX assembler directive LOC
+ @cindex MMIX pseudo-op LOC
+ @anchor{MMIX-loc}
+ The @code{LOC} directive sets the current location to the value of the
+ operand field, which may include changing sections.  If the operand is a
+ constant, the section is set to either @code{.data} if the value is
+ @code{0x2000000000000000} or larger, else it is set to @code{.text}.
+ Within a section, the current location may only be changed to
+ monotonically higher addresses.  A LOC expression must be a previously
+ defined symbol or a ``pure'' constant.
+ An example, which sets the label @var{prev} to the current location, and
+ updates the current location to eight bytes forward:
+ @smallexample
+ prev LOC @@+8
+ @end smallexample
+ When a LOC has a constant as its operand, a symbol
+ @code{__.MMIX.start..text} or @code{} is defined
+ depending on the address as mentioned above.  Each such symbol is
+ interpreted as special by the linker, locating the section at that
+ address.  Note that if multiple files are linked, the first object file
+ with that section will be mapped to that address (not necessarily the file
+ with the LOC definition).
+ @item LOCAL
+ @cindex assembler directive LOCAL, MMIX
+ @cindex pseudo-op LOCAL, MMIX
+ @cindex MMIX assembler directive LOCAL
+ @cindex MMIX pseudo-op LOCAL
+ @anchor{MMIX-local}
+ Example:
+ @smallexample
+  LOCAL external_symbol
+  LOCAL 42
+  .local asymbol
+ @end smallexample
+ This directive-operation generates a link-time assertion that the operand
+ does not correspond to a global register.  The operand is an expression
+ that at link-time resolves to a register symbol or a number.  A number is
+ treated as the register having that number.  There is one restriction on
+ the use of this directive: the pseudo-directive must be placed in a
+ section with contents, code or data.
+ @item IS
+ @cindex assembler directive IS, MMIX
+ @cindex pseudo-op IS, MMIX
+ @cindex MMIX assembler directive IS
+ @cindex MMIX pseudo-op IS
+ @anchor{MMIX-is}
+ The @code{IS} directive:
+ @smallexample
+ asymbol IS an_expression
+ @end smallexample
+ sets the symbol @samp{asymbol} to @samp{an_expression}.  A symbol may not
+ be set more than once using this directive.  Local labels may be set using
+ this directive, for example:
+ @smallexample
+ 5H IS @@+4
+ @end smallexample
+ @item GREG
+ @cindex assembler directive GREG, MMIX
+ @cindex pseudo-op GREG, MMIX
+ @cindex MMIX assembler directive GREG
+ @cindex MMIX pseudo-op GREG
+ @anchor{MMIX-greg}
+ This directive reserves a global register, gives it an initial value and
+ optionally gives it a symbolic name.  Some examples:
+ @smallexample
+ areg GREG
+ breg GREG data_value
+      GREG data_buffer
+      .greg creg, another_data_value
+ @end smallexample
+ The symbolic register name can be used in place of a (non-special)
+ register.  If a value isn't provided, it defaults to zero.  Unless the
+ option @samp{--no-merge-gregs} is specified, non-zero registers allocated
+ with this directive may be eliminated by @code{@value{AS}}; another
+ register with the same value used in its place.
+ Any of the instructions
+ @samp{CSWAP},
+ @samp{GO},
+ @samp{LDA},
+ @samp{LDBU},
+ @samp{LDB},
+ @samp{LDHT},
+ @samp{LDOU},
+ @samp{LDO},
+ @samp{LDSF},
+ @samp{LDTU},
+ @samp{LDT},
+ @samp{LDUNC},
+ @samp{LDVTS},
+ @samp{LDWU},
+ @samp{LDW},
+ @samp{PREGO},
+ @samp{PRELD},
+ @samp{PREST},
+ @samp{PUSHGO},
+ @samp{STBU},
+ @samp{STB},
+ @samp{STCO},
+ @samp{STHT},
+ @samp{STOU},
+ @samp{STSF},
+ @samp{STTU},
+ @samp{STT},
+ @samp{STUNC},
+ @samp{SYNCD},
+ @samp{SYNCID},
+ can have a value nearby @anchor{GREG-base}an initial value in place of its
+ second and third operands.  Here, ``nearby'' is defined as within the
+ range 0@dots{}255 from the initial value of such an allocated register.
+ @smallexample
+ buffer1 BYTE 0,0,0,0,0
+ buffer2 BYTE 0,0,0,0,0
+  @dots{}
+  GREG buffer1
+  LDOU $42,buffer2
+ @end smallexample
+ In the example above, the @samp{Y} field of the @code{LDOUI} instruction
+ (LDOU with a constant Z) will be replaced with the global register
+ allocated for @samp{buffer1}, and the @samp{Z} field will have the value
+ 5, the offset from @samp{buffer1} to @samp{buffer2}.  The result is
+ equivalent to this code:
+ @smallexample
+ buffer1 BYTE 0,0,0,0,0
+ buffer2 BYTE 0,0,0,0,0
+  @dots{}
+ tmpreg GREG buffer1
+  LDOU $42,tmpreg,(buffer2-buffer1)
+ @end smallexample
+ Global registers allocated with this directive are allocated in order
+ higher-to-lower within a file.  Other than that, the exact order of
+ register allocation and elimination is undefined.  For example, the order
+ is undefined when more than one file with such directives are linked
+ together.
+ @item BYTE
+ @cindex assembler directive BYTE, MMIX
+ @cindex pseudo-op BYTE, MMIX
+ @cindex MMIX assembler directive BYTE
+ @cindex MMIX pseudo-op BYTE
+ @anchor{MMIX-byte}
+ The @samp{BYTE} directive takes a series of operands separated by a comma.
+ If an operand is a string (@pxref{Strings}), each character of that string
+ is emitted as a byte.  Other operands must be constant expressions without
+ forward references, in the range 0@dots{}255.  If you need operands having
+ expressions with forward references, use @samp{.byte} (@pxref{Byte}).  An
+ operand can be omitted, defaulting to a zero value.
+ @item WYDE
+ @itemx TETRA
+ @itemx OCTA
+ @cindex assembler directive WYDE, MMIX
+ @cindex pseudo-op WYDE, MMIX
+ @cindex MMIX assembler directive WYDE
+ @cindex MMIX pseudo-op WYDE
+ @cindex assembler directive TETRA, MMIX
+ @cindex pseudo-op TETRA, MMIX
+ @cindex MMIX assembler directive TETRA
+ @cindex MMIX pseudo-op TETRA
+ @cindex assembler directive OCTA, MMIX
+ @cindex pseudo-op OCTA, MMIX
+ @cindex MMIX assembler directive OCTA
+ @cindex MMIX pseudo-op OCTA
+ @anchor{MMIX-constants}
+ The directives @samp{WYDE}, @samp{TETRA} and @samp{OCTA} emit constants of
+ two, four and eight bytes size respectively.  Before anything else happens
+ for the directive, the current location is aligned to the respective
+ constant-size bondary.  If a label is defined at the beginning of the
+ line, its value will be that after the alignment.  A single operand can be
+ omitted, defaulting to a zero value emitted for the directive.  Operands
+ can be expressed as strings (@pxref{Strings}), in which case each
+ character in the string is emitted as a separate constant of the size
+ indicated by the directive.
+ @item PREFIX
+ @cindex assembler directive PREFIX, MMIX
+ @cindex pseudo-op PREFIX, MMIX
+ @cindex MMIX assembler directive PREFIX
+ @cindex MMIX pseudo-op PREFIX
+ @anchor{MMIX-prefix}
+ The @samp{PREFIX} directive sets a symbol name prefix to be prepended to
+ all symbols (except local symbols, @pxref{MMIX-Symbols}), that are not
+ prefixed with @samp{:}, until the next @samp{PREFIX} directive.  Such
+ prefixes accumulate.  For example,
+ @smallexample
+ c IS 0
+ @end smallexample
+ defines a symbol @samp{abc} with the value 0.
+ @item BSPEC
+ @itemx ESPEC
+ @cindex assembler directive BSPEC, MMIX
+ @cindex pseudo-op BSPEC, MMIX
+ @cindex MMIX assembler directive BSPEC
+ @cindex MMIX pseudo-op BSPEC
+ @cindex assembler directive ESPEC, MMIX
+ @cindex pseudo-op ESPEC, MMIX
+ @cindex MMIX assembler directive ESPEC
+ @cindex MMIX pseudo-op ESPEC
+ @anchor{MMIX-spec}
+ A pair of @samp{BSPEC} and @samp{ESPEC} directives delimit a section of
+ special contents (without specified semantics).  Example:
+ @smallexample
+  BSPEC 42
+  TETRA 1,2,3
+ @end smallexample
+ The single operand to @samp{BSPEC} must be number in the range
+ 0@dots{}255.  The @samp{BSPEC} number 80 is used by the GNU binutils
+ implementation.
+ @end table
+ @node MMIX-mmixal
+ @section Differences to @code{mmixal}
+ @cindex mmixal differences
+ @cindex differences, mmixal
+ The binutils @code{@value{AS}} and @code{@value{LD}} combination has a few
+ differences in function compared to @code{mmixal} (@pxref{mmixsite}).
+ The replacement of a symbol with a GREG-allocated register
+ (@pxref{GREG-base}) is not handled the exactly same way in
+ @code{@value{AS}} as in @code{mmixal}.  This is apparent in the
+ @code{mmixal} example file @code{inout.mms}, where different registers
+ with different offsets, eventually yielding the same address, are used in
+ the first instruction.  This type of difference should however not affect
+ the function of any program unless it has specific assumptions about the
+ allocated register number.
+ Line numbers (in the @samp{mmo} object format) are currently not
+ supported.
+ Expression operator precedence is not that of mmixal: operator precedence
+ is that of the C programming language.  It's recommended to use
+ parentheses to explicitly specify wanted operator precedence whenever more
+ than one type of operators are used.
+ The serialize unary operator @code{&}, the fractional division operator
+ @samp{//}, the logical not operator @code{!} and the modulus operator
+ @samp{%} are not available.
+ Symbols are not global by default, unless the option
+ @samp{--globalize-symbols} is passed.  Use the @samp{.global} directive to
+ globalize symbols (@pxref{Global}).
+ Operand syntax is a bit stricter with @code{@value{AS}} than
+ @code{mmixal}.  For example, you can't say @code{addu 1,2,3}, instead you
+ must write @code{addu $1,$2,3}.
+ You can't LOC to a lower address than those already visited
+ (i.e. ``backwards'').
+ A LOC directive must come before any emitted code.
+ Predefined symbols are visible as file-local symbols after use.  (In the
+ ELF file, that is---the linked mmo file has no notion of a file-local
+ symbol.)
+ Some mapping of constant expressions to sections in LOC expressions is
+ attempted, but that functionality is easily confused and should be avoided
+ unless compatibility with @code{mmixal} is required.  A LOC expression to
+ @samp{0x2000000000000000} or higher, maps to the @samp{.data} section and
+ lower addresses map to the @samp{.text} section (@pxref{MMIX-loc}).
+ The code and data areas are each contiguous.  Sparse programs with
+ far-away LOC directives will take up the same amount of space as a
+ contiguous program with zeros filled in the gaps between the LOC
+ directives.  If you need sparse programs, you might try and get the wanted
+ effect with a linker script and splitting up the code parts into sections
+ (@pxref{Section}).  Assembly code for this, to be compatible with
+ @code{mmixal}, would look something like:
+ @smallexample
+  .if 0
+  LOC away_expression
+  .else
+  .section away,"ax"
+  .fi
+ @end smallexample
+ @code{@value{AS}} will not execute the LOC directive and @code{mmixal}
+ ignores the lines with @code{.}.  This construct can be used generally to
+ help compatibility.
+ Symbols can't be defined twice--not even to the same value.
+ Instruction mnemonics are recognized case-insensitive, though the
+ @samp{IS} and @samp{GREG} pseudo-operations must be specified in
+ upper-case characters.
+ There's no unicode support.
+ The following is a list of programs in
+ @url{} dated
+ 2001-08-25 (md5sum c393470cfc86fac040487d22d2bf0172) that assembles with
+ @code{mmixal} but don't with @code{@value{AS}}:
+ @table @code
+ @item silly.mms
+ LOC to a previous address.
+ @item sim.mms
+ Redefines symbol @samp{Done}.
+ @item test.mms
+ Uses the serial operator @samp{&}.
+ @end table

brgds, H-P

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]