Add support for Motorola XGATE embedded CPU

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+@c Copyright 2012
+@c Free Software Foundation, Inc.
+@c This is part of the GAS manual.
+@c For copying conditions, see the file as.texinfo.
+@ifset GENERIC
+@page
+@node XGATE-Dependent
+@chapter XGATE Dependent Features
+@end ifset
+@ifclear GENERIC
+@node Machine Dependencies
+@chapter XGATE Dependent Features
+@end ifclear
+
+@cindex XGATE support
+@menu
+* XGATE-Opts::                   XGATE Options
+* XGATE-Syntax::                 Syntax
+* XGATE-Directives::             Assembler Directives
+* XGATE-Float::                  Floating Point
+* XGATE-opcodes::                Opcodes
+@end menu
+
+@node XGATE-Opts
+@section XGATE Options
+
+@cindex options, XGATE
+@cindex XGATE options
+The Freescale XGATE version of @code{@value{AS}} has a few machine
+dependent options.
+
+@table @code
+
+@cindex @samp{-mshort}
+@item -mshort
+This option controls the ABI and indicates to use a 16-bit integer ABI.
+It has no effect on the assembled instructions.
+This is the default.
+
+@cindex @samp{-mlong}
+@item -mlong
+This option controls the ABI and indicates to use a 32-bit integer ABI.
+
+@cindex @samp{-mshort-double}
+@item -mshort-double
+This option controls the ABI and indicates to use a 32-bit float ABI.
+This is the default.
+
+@cindex @samp{-mlong-double}
+@item -mlong-double
+This option controls the ABI and indicates to use a 64-bit float ABI.
+
+@cindex @samp{--print-insn-syntax}
+@item --print-insn-syntax
+You can use the @samp{--print-insn-syntax} option to obtain the
+syntax description of the instruction when an error is detected.
+
+@cindex @samp{--print-opcodes}
+@item --print-opcodes
+The @samp{--print-opcodes} option prints the list of all the
+instructions with their syntax. Once the list is printed
+@code{@value{AS}} exits.
+
+@end table
+
+@node XGATE-Syntax
+@section Syntax
+
+@cindex XGATE syntax
+@cindex syntax, XGATE
+
+In XGATE RISC syntax, the instruction name comes first and it may
+be followed by up to three operands. Operands are separated by commas
+(@samp{,}). @code{@value{AS}} will complain if too many operands are specified
+for a given instruction. The same will happen if you specified too few
+ operands.
+
+@smallexample
+nop
+ldl  #23
+CMP  R1, R2
+@end smallexample
+
+@cindex line comment character, XGATE
+@cindex XGATE line comment character
+The presence of a @samp{;} character or a @samp{!} character anywhere
+on a line indicates the start of a comment that extends to the end of
+that line.
+
+A @samp{*} or a @samp{#} character at the start of a line also
+introduces a line comment, but these characters do not work elsewhere
+on the line.  If the first character of the line is a @samp{#} then as
+well as starting a comment, the line could also be logical line number
+directive (@pxref{Comments}) or a preprocessor control command
+(@pxref{Preprocessing}).
+
+@cindex line separator, XGATE
+@cindex statement separator, XGATE
+@cindex XGATE line separator
+The XGATE assembler does not currently support a line separator
+character.
+
+@cindex XGATE addressing modes
+@cindex addressing modes, XGATE
+The following addressing modes are understood for XGATE:
+@table @dfn
+@item Inherent
+@samp{}
+
+@item Immediate 3 Bit Wide
+@samp{#@var{number}}
+
+@item Immediate 4 Bit Wide
+@samp{#@var{number}}
+
+@item Immediate 8 Bit Wide
+@samp{#@var{number}}
+
+@item Monadic Addressing
+@samp{@var{reg}}
+
+@item Dyadic Addressing
+@samp{@var{reg}, @var{reg}}
+
+@item Triadic Addressing
+@samp{@var{reg}, @var{reg}, @var{reg}}
+
+@item Relative Addressing 9 Bit Wide
+@samp{*@var{symbol}}
+
+@item Relative Addressing 10 Bit Wide
+@samp{*@var{symbol}}
+
+@item Index Register plus Immediate Offset
+@samp{@var{reg}, (@var{reg}, #@var{number})}
+
+@item Index Register plus Register Offset
+@samp{@var{reg}, @var{reg}, @var{reg}}
+
+@item Index Register plus Register Offset with Post-increment
+@samp{@var{reg}, @var{reg}, @var{reg}+}
+
+@item Index Register plus Register Offset with Pre-decrement
+@samp{@var{reg}, @var{reg}, -@var{reg}}
+
+The register can be either @samp{R0}, @samp{R1}, @samp{R2}, @samp{R3},
+@samp{R4}, @samp{R5}, @samp{R6} or @samp{R7}.
+
+@end table
+
+Convience macro opcodes to deal with 16-bit values have been added.  
+
+@table @dfn
+
+@item Immediate 16 Bit Wide
+@samp{#@var{number}}, or @samp{*@var{symbol}}
+
+For example:
+
+@smallexample
+ldw R1, #1024
+ldw R3, timer
+ldw R1, (R1, #0)
+COM R1
+stw R2, (R1, #0)
+@end smallexample
+@end table
+
+@node XGATE-Directives
+@section Assembler Directives
+
+@cindex assembler directives, XGATE
+@cindex XGATE assembler directives
+
+The XGATE version of @code{@value{AS}} have the following
+specific assembler directives:
+
+@node XGATE-Float
+@section Floating Point
+
+@cindex floating point, XGATE
+@cindex XGATE floating point
+Packed decimal (P) format floating literals are not supported(yet).
+
+The floating point formats generated by directives are these.
+
+@table @code
+@cindex @code{float} directive, XGATE
+@item .float
+@code{Single} precision floating point constants.
+
+@cindex @code{double} directive, XGATE
+@item .double
+@code{Double} precision floating point constants.
+
+@cindex @code{extend} directive XGATE
+@cindex @code{ldouble} directive XGATE
+@item .extend
+@itemx .ldouble
+@code{Extended} precision (@code{long double}) floating point constants.
+@end table
+
+@need 2000
+@node XGATE-opcodes
+@section Opcodes
+
+@cindex XGATE opcodes
+@cindex instruction set, XGATE
+