gas/doc/c-rx.texi

   1 @c Copyright 2008, 2009, 2011
   2 @c Free Software Foundation, Inc.
   3 @c This is part of the GAS manual.
   4 @c For copying conditions, see the file as.texinfo.
   5 @ifset GENERIC
   6 @page
   7 @node RX-Dependent
   8 @chapter RX Dependent Features
   9 @end ifset
  10 @ifclear GENERIC
  11 @node Machine Dependencies
  12 @chapter RX Dependent Features
  13 @end ifclear
  14
  15 @cindex RX support
  16 @menu
  17 * RX-Opts::                   RX Assembler Command Line Options
  18 * RX-Modifiers::              Symbolic Operand Modifiers
  19 * RX-Directives::             Assembler Directives
  20 * RX-Float::                  Floating Point
  21 * RX-Syntax::                 Syntax
  22 @end menu
  23
  24 @node RX-Opts
  25 @section RX Options
  26 @cindex options, RX
  27 @cindex RX options
  28
  29 The Renesas RX port of @code{@value{AS}} has a few target specfic
  30 command line options:
  31
  32 @table @code
  33
  34 @cindex @samp{-m32bit-doubles}
  35 @item -m32bit-doubles
  36 This option controls the ABI and indicates to use a 32-bit float ABI.
  37 It has no effect on the assembled instructions, but it does influence
  38 the behaviour of the @samp{.double} pseudo-op.
  39 This is the default.
  40
  41 @cindex @samp{-m64bit-doubles}
  42 @item -m64bit-doubles
  43 This option controls the ABI and indicates to use a 64-bit float ABI.
  44 It has no effect on the assembled instructions, but it does influence
  45 the behaviour of the @samp{.double} pseudo-op.
  46
  47 @cindex @samp{-mbig-endian}
  48 @item -mbig-endian
  49 This option controls the ABI and indicates to use a big-endian data
  50 ABI.  It has no effect on the assembled instructions, but it does
  51 influence the behaviour of the @samp{.short}, @samp{.hword}, @samp{.int},
  52 @samp{.word}, @samp{.long}, @samp{.quad} and @samp{.octa} pseudo-ops.
  53
  54 @cindex @samp{-mlittle-endian}
  55 @item -mlittle-endian
  56 This option controls the ABI and indicates to use a little-endian data
  57 ABI.  It has no effect on the assembled instructions, but it does
  58 influence the behaviour of the @samp{.short}, @samp{.hword}, @samp{.int},
  59 @samp{.word}, @samp{.long}, @samp{.quad} and @samp{.octa} pseudo-ops.
  60 This is the default.
  61
  62 @cindex @samp{-muse-conventional-section-names}
  63 @item -muse-conventional-section-names
  64 This option controls the default names given to the code (.text),
  65 initialised data (.data) and uninitialised data sections (.bss).
  66
  67 @cindex @samp{-muse-renesas-section-names}
  68 @item -muse-renesas-section-names
  69 This option controls the default names given to the code (.P),
  70 initialised data (.D_1) and uninitialised data sections (.B_1).
  71 This is the default.
  72
  73 @cindex @samp{-msmall-data-limit}
  74 @item -msmall-data-limit
  75 This option tells the assembler that the small data limit feature of
  76 the RX port of GCC is being used.  This results in the assembler
  77 generating an undefined reference to a symbol called @code{__gp} for
  78 use by the relocations that are needed to support the small data limit
  79 feature.   This option is not enabled by default as it would otherwise
  80 pollute the symbol table.
  81
  82 @cindex @samp{-mpid}
  83 @item -mpid
  84 This option tells the assembler that the position independent data of the
  85 RX port of GCC is being used.  This results in the assembler
  86 generating an undefined reference to a symbol called @code{__pid_base},
  87 and also setting the RX_PID flag bit in the e_flags field of the ELF
  88 header of the object file.
  89
  90 @cindex @samp{-mint-register}
  91 @item -mint-register=@var{num}
  92 This option tells the assembler how many registers have been reserved
  93 for use by interrupt handlers.  This is needed in order to compute the
  94 correct values for the @code{%gpreg} and @code{%pidreg} meta registers.
  95
  96 @end table
  97
  98 @node RX-Modifiers
  99 @section Symbolic Operand Modifiers
 100
 101 @cindex RX modifiers
 102 @cindex syntax, RX
 103 @cindex %gp
 104
 105 The assembler supports one modifier when using symbol addresses
 106 in RX instruction operands.  The general syntax is the following:
 107
 108 @smallexample
 109 %gp(symbol)
 110 @end smallexample
 111
 112 The modifier returns the offset from the @var{__gp} symbol to the
 113 specified symbol as a 16-bit value.  The intent is that this offset
 114 should be used in a register+offset move instruction when generating
 115 references to small data.  Ie, like this:
 116
 117 @smallexample
 118   mov.W  %gp(_foo)[%gpreg], r1
 119 @end smallexample
 120
 121 The assembler also supports two meta register names which can be used
 122 to refer to registers whose values may not be known to the
 123 programmer.  These meta register names are:
 124
 125 @table @code
 126
 127 @cindex @samp{%gpreg}
 128 @item %gpreg
 129 The small data address register.
 130
 131 @cindex @samp{%pidreg}
 132 @item %pidreg
 133 The PID base address register.
 134
 135 @end table
 136
 137 Both registers normally have the value r13, but this can change if
 138 some registers have been reserved for use by interrupt handlers or if
 139 both the small data limit and position independent data features are
 140 being used at the same time.
 141
 142 @node RX-Directives
 143 @section Assembler Directives
 144
 145 @cindex assembler directives, RX
 146 @cindex RX assembler directives
 147
 148 The RX version of @code{@value{AS}} has the following specific
 149 assembler directives:
 150
 151 @table @code
 152
 153 @item .3byte
 154 @cindex assembler directive .3byte, RX
 155 @cindex RX assembler directive .3byte
 156 Inserts a 3-byte value into the output file at the current location.
 157
 158 @item .fetchalign
 159 @cindex assembler directive .fetchalign, RX
 160 @cindex RX assembler directive .fetchalign
 161 If the next opcode following this directive spans a fetch line
 162 boundary (8 byte boundary), the opcode is aligned to that boundary.
 163 If the next opcode does not span a fetch line, this directive has no
 164 effect.  Note that one or more labels may be between this directive
 165 and the opcode; those labels are aligned as well.  Any inserted bytes
 166 due to alignment will form a NOP opcode.
 167
 168 @end table
 169
 170 @node RX-Float
 171 @section Floating Point
 172
 173 @cindex floating point, RX
 174 @cindex RX floating point
 175
 176 The floating point formats generated by directives are these.
 177
 178 @table @code
 179 @cindex @code{float} directive, RX
 180
 181 @item .float
 182 @code{Single} precision (32-bit) floating point constants.
 183
 184 @cindex @code{double} directive, RX
 185 @item .double
 186 If the @option{-m64bit-doubles} command line option has been specified
 187 then then @code{double} directive generates @code{double} precision
 188 (64-bit) floating point constants, otherwise it generates
 189 @code{single} precision (32-bit) floating point constants.  To force
 190 the generation of 64-bit floating point constants used the @code{dc.d}
 191 directive instead.
 192
 193 @end table
 194
 195 @node RX-Syntax
 196 @section Syntax for the RX
 197 @menu
 198 * RX-Chars::                Special Characters
 199 @end menu
 200
 201 @node RX-Chars
 202 @subsection Special Characters
 203
 204 @cindex line comment character, RX
 205 @cindex RX line comment character
 206 The presence of a @samp{;} appearing anywhere on a line indicates the
 207 start of a comment that extends to the end of that line.
 208
 209 If a @samp{#} appears as the first character of a line then the whole
 210 line is treated as a comment, but in this case the line can also be a
 211 logical line number directive (@pxref{Comments}) or a preprocessor
 212 control command (@pxref{Preprocessing}).
 213
 214 @cindex line separator, RX
 215 @cindex statement separator, RX
 216 @cindex RX line separator
 217 The @samp{!} character can be used to separate statements on the same
 218 line.