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95008a8828
Add a new machine dependent option to set a prefix for register names. gas/ * config/tc-s12z.c (register_prefix): New variable. (md_show_usage, md_parse_option): parse the new option. (lex_reg_name): Scan the prefix if one is set. * doc/c-s12z.texi (S12Z-Opts): Document the new option. * testsuite/gas/s12z/reg-prefix.d: New file. * testsuite/gas/s12z/reg-prefix.s: New file. * testsuite/gas/s12z/s12z.exp: Add them.
281 lines
8.2 KiB
Plaintext
281 lines
8.2 KiB
Plaintext
@c Copyright (C) 2018-2019 Free Software Foundation, Inc.
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@c This is part of the GAS manual.
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@c For copying conditions, see the file as.texinfo.
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@ifset GENERIC
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@page
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@node S12Z-Dependent
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@chapter S12Z Dependent Features
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@end ifset
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@ifclear GENERIC
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@node Machine Dependencies
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@chapter S12Z Dependent Features
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@end ifclear
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The Freescale S12Z version of @code{@value{AS}} has a few machine
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dependent features.
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@cindex S12Z support
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@menu
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* S12Z-Opts:: S12Z Options
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* S12Z-Syntax:: Syntax
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* S12Z-Directives:: Assembler Directives
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* S12Z-Opcodes:: Opcodes
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@end menu
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@node S12Z-Opts
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@section S12Z Options
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@cindex options, S12Z
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@cindex S12Z options
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The S12Z version of @code{@value{AS}} has the following options:
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@cindex @samp{-mreg-prefix=@var{prefix}} option, reg-prefix
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You can use the @samp{-mreg-prefix=@var{pfx}} option to indicate
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that the assembler expects each register name to be prefixed with the
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string @var{pfx}.
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For an explanation of what this means and why it might be needed,
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see @ref{Register Notation}.
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@node S12Z-Syntax
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@section Syntax
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@menu
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* Register Notation:: How to refer to registers
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@end menu
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@cindex S12Z syntax
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@cindex syntax, S12Z
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In the S12Z syntax, the instruction name comes first and it may
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be followed by one or by several operands.
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In most cases the maximum number of operands is three.
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Some instructions accept and (in certain situations require) a suffix
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indicating the size of the operand.
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The suffix is separated from the instruction name by a period (@samp{.})
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and may be one of @samp{b}, @samp{w}, @samp{p} or @samp{l} indicating
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`byte' (a single byte), `word' (2 bytes), `pointer' (3 bytes) or `long' (4 bytes)
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respectively.
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Operands are separated by a comma (@samp{,}).
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A comma however does not act as a separator if it appears within parentheses
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(@samp{()}) or within square brackets (@samp{[]}).
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@code{@value{AS}} will complain if too many, too few or inappropriate operands
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are specified for a given instruction.
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The MRI mode is not supported for this architecture.
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Example:
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@smallexample
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bset.b 0xA98, #5
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mov.b #6, 0x2409
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ld d0, #4
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mov.l (d0, x), 0x2409
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inc d0
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cmp d0, #12
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blt *-4
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lea x, 0x2409
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st y, (1, x)
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@end smallexample
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@cindex line comment character, S12Z
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@cindex S12Z line comment character
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The presence of a @samp{;} character anywhere
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on a line indicates the start of a comment that extends to the end of
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that line.
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A @samp{*} or a @samp{#} character at the start of a line also
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introduces a line comment, but these characters do not work elsewhere
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on the line. If the first character of the line is a @samp{#} then as
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well as starting a comment, the line could also be logical line number
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directive (@pxref{Comments}) or a preprocessor control command
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(@pxref{Preprocessing}).
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@cindex line separator, S12Z
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@cindex statement separator, S12Z
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@cindex S12Z line separator
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The S12Z assembler does not currently support a line separator
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character.
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@cindex S12Z addressing modes
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@cindex addressing modes, S12Z
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The following addressing modes are understood for the S12Z.
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@table @dfn
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@item Immediate
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@samp{#@var{number}}
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@item Immediate Bit Field
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@samp{#@var{width}:@var{offset}}
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Bit field instructions in the immediate mode require the width and offset to
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be specified.
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The @var{width} pararmeter specifies the number of bits in the field.
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It should be a number in the range [1,32].
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@var{Offset} determines the position within the field where the operation
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should start.
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It should be a number in the range [0,31].
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@item Relative
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@samp{*@var{symbol}}, or @samp{*[+-]@var{digits}}
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Program counter relative addresses have a width of 15 bits.
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Thus, they must be within the range [-32768, 32767].
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@item Register
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@samp{@var{reg}}
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@cindex register names, S12Z
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Some instructions accept a register as an operand.
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In general, @var{reg} may be a
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data register (@samp{D0}, @samp{D1} @dots{} @samp{D7}),
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the @samp{X} register or the @samp{Y} register.
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A few instructions accept as an argument the stack pointer
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register (@samp{S}), and/or the program counter (@samp{P}).
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Some very special instructions accept arguments which refer to the
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condition code register. For these arguments the syntax is
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@samp{CCR}, @samp{CCH} or @samp{CCL} which refer to the complete
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condition code register, the condition code register high byte
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and the condition code register low byte respectively.
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@item Absolute Direct
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@samp{@var{symbol}}, or @samp{@var{digits}}
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@item Absolute Indirect
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@samp{[@var{symbol}}, or @samp{@var{digits}]}
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@item Constant Offset Indexed
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@samp{(@var{number},@var{reg})}
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@var{Reg} may be either @samp{X}, @samp{Y}, @samp{S} or
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@samp{P} or one of the data registers @samp{D0}, @samp{D1} @dots{}
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@samp{D7}.
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If any of the registers @samp{D2} @dots{} @samp{D5} are specified, then the
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register value is treated as a signed value.
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Otherwise it is treated as unsigned.
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@var{Number} may be any integer in the range [-8388608,8388607].
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@item Offset Indexed Indirect
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@samp{[@var{number},@var{reg}]}
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@var{Reg} may be either @samp{X}, @samp{Y}, @samp{S} or
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@samp{P}.
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@var{Number} may be any integer in the range [-8388608,8388607].
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@item Auto Pre-Increment/Pre-Decrement/Post-Increment/Post-Decrement
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@samp{-@var{reg}},
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@samp{+@var{reg}},
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@samp{@var{reg}-} or
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@samp{@var{reg}+}
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This addressing mode is typically used to access a value at an address,
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and simultaneously to increment/decrement the register pointing to that
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address.
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Thus @var{reg} may be any of the 24 bit registers @samp{X}, @samp{Y}, or
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@samp{S}.
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Pre-increment and post-decrement are not available for
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register @samp{S} (only post-increment and pre-decrement are available).
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@item Register Offset Direct
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@samp{(@var{data-reg},@var{reg})}
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@var{Reg} can be either @samp{X}, @samp{Y}, or @samp{S}.
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@var{Data-reg}
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must be one of the data registers @samp{D0}, @samp{D1} @dots{} @samp{D7}.
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If any of the registers @samp{D2} @dots{} @samp{D5} are specified, then
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the register value is treated as a signed value.
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Otherwise it is treated as unsigned.
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@item Register Offset Indirect
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@samp{[@var{data-reg},@var{reg}]}
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@var{Reg} can be either @samp{X} or @samp{Y}.
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@var{Data-reg}
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must be one of the data registers @samp{D0}, @samp{D1} @dots{} @samp{D7}.
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If any of the registers @samp{D2} @dots{} @samp{D5} are specified, then
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the register value is treated as a signed value.
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Otherwise it is treated as unsigned.
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@end table
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For example:
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@smallexample
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trap #197
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bra *+49
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bra .L0
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jmp 0xFE0034
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jmp [0xFD0012]
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inc.b (4,x)
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dec.w [4,y]
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clr.p (-s)
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neg.l (d0, s)
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com.b [d1, x]
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jsr (45, d0)
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psh cch
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@end smallexample
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@node Register Notation
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@subsection Register Notation
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@cindex register notation, S12Z
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Without a register prefix (@pxref{S12Z-Opts}), S12Z assembler code is expected in the traditional
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format like this:
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@smallexample
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lea s, (-2,s)
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st d2, (0,s)
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ld x, symbol
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tfr d2, d6
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cmp d6, #1532
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@end smallexample
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@noindent
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However, if @code{@value{AS}} is started with (for example) @samp{-mreg-prefix=%}
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then all register names must be prefixed with @samp{%} as follows:
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@smallexample
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lea %s, (-2,%s)
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st %d2, (0,%s)
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ld %x, symbol
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tfr %d2, %d6
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cmp %d6, #1532
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@end smallexample
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The register prefix feature is intended to be used by compilers
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to avoid ambiguity between symbols and register names.
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Consider the following assembler instruction:
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@smallexample
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st d0, d1
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@end smallexample
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@noindent
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This instruction is most likely to
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mean ``Store the value in the register D0 into the register D1'' and that is the
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default way in which @code{@value{AS}} interprets it.
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However it could also be intended to mean
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``Store the value in the register D0 into the memory referenced by the symbol
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named @samp{d1}''.
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If that is what is intended then @code{@value{AS}} must be invoked with
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@samp{-mreg-prefix=@var{pfx}} and the code written as
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@smallexample
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st @var{pfx}d0, d1
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@end smallexample
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@noindent
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where @var{pfx} is the chosen register prefix.
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For this reason, compiler back-ends should choose a register prefix which
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cannot be confused with a symbol name.
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@node S12Z-Directives
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@section Assembler Directives
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@cindex assembler directives, S12Z
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@node S12Z-Opcodes
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@section Opcodes
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@cindex S12Z opcodes
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@cindex opcodes, S12Z
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@cindex instruction set, S12Z
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