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 @cindex @samp{-mgcc-abi}
  97 @item -mgcc-abi
  98 This option tells the assembler that the old GCC ABI is being used by
  99 the assembled code.  With this version of the ABI function arguments
 100 that are passed on the stack are aligned to a 32-bit boundary.
 101
 102 @cindex @samp{-mrx-abi}
 103 @item -mrx-abi
 104 This option tells the assembler that the official RX ABI is being used
 105 by the assembled code.  With this version of the ABI function
 106 arguments that are passed on the stack are aligned to their natural
 107 alignments.  This option is the default.
 108
 109 @end table
 110
 111 @node RX-Modifiers
 112 @section Symbolic Operand Modifiers
 113
 114 @cindex RX modifiers
 115 @cindex syntax, RX
 116 @cindex %gp
 117
 118 The assembler supports one modifier when using symbol addresses
 119 in RX instruction operands.  The general syntax is the following:
 120
 121 @smallexample
 122 %gp(symbol)
 123 @end smallexample
 124
 125 The modifier returns the offset from the @var{__gp} symbol to the
 126 specified symbol as a 16-bit value.  The intent is that this offset
 127 should be used in a register+offset move instruction when generating
 128 references to small data.  Ie, like this:
 129
 130 @smallexample
 131   mov.W  %gp(_foo)[%gpreg], r1
 132 @end smallexample
 133
 134 The assembler also supports two meta register names which can be used
 135 to refer to registers whose values may not be known to the
 136 programmer.  These meta register names are:
 137
 138 @table @code
 139
 140 @cindex @samp{%gpreg}
 141 @item %gpreg
 142 The small data address register.
 143
 144 @cindex @samp{%pidreg}
 145 @item %pidreg
 146 The PID base address register.
 147
 148 @end table
 149
 150 Both registers normally have the value r13, but this can change if
 151 some registers have been reserved for use by interrupt handlers or if
 152 both the small data limit and position independent data features are
 153 being used at the same time.
 154
 155 @node RX-Directives
 156 @section Assembler Directives
 157
 158 @cindex assembler directives, RX
 159 @cindex RX assembler directives
 160
 161 The RX version of @code{@value{AS}} has the following specific
 162 assembler directives:
 163
 164 @table @code
 165
 166 @item .3byte
 167 @cindex assembler directive .3byte, RX
 168 @cindex RX assembler directive .3byte
 169 Inserts a 3-byte value into the output file at the current location.
 170
 171 @item .fetchalign
 172 @cindex assembler directive .fetchalign, RX
 173 @cindex RX assembler directive .fetchalign
 174 If the next opcode following this directive spans a fetch line
 175 boundary (8 byte boundary), the opcode is aligned to that boundary.
 176 If the next opcode does not span a fetch line, this directive has no
 177 effect.  Note that one or more labels may be between this directive
 178 and the opcode; those labels are aligned as well.  Any inserted bytes
 179 due to alignment will form a NOP opcode.
 180
 181 @end table
 182
 183 @node RX-Float
 184 @section Floating Point
 185
 186 @cindex floating point, RX
 187 @cindex RX floating point
 188
 189 The floating point formats generated by directives are these.
 190
 191 @table @code
 192 @cindex @code{float} directive, RX
 193
 194 @item .float
 195 @code{Single} precision (32-bit) floating point constants.
 196
 197 @cindex @code{double} directive, RX
 198 @item .double
 199 If the @option{-m64bit-doubles} command line option has been specified
 200 then then @code{double} directive generates @code{double} precision
 201 (64-bit) floating point constants, otherwise it generates
 202 @code{single} precision (32-bit) floating point constants.  To force
 203 the generation of 64-bit floating point constants used the @code{dc.d}
 204 directive instead.
 205
 206 @end table
 207
 208 @node RX-Syntax
 209 @section Syntax for the RX
 210 @menu
 211 * RX-Chars::                Special Characters
 212 @end menu
 213
 214 @node RX-Chars
 215 @subsection Special Characters
 216
 217 @cindex line comment character, RX
 218 @cindex RX line comment character
 219 The presence of a @samp{;} appearing anywhere on a line indicates the
 220 start of a comment that extends to the end of that line.
 221
 222 If a @samp{#} appears as the first character of a line then the whole
 223 line is treated as a comment, but in this case the line can also be a
 224 logical line number directive (@pxref{Comments}) or a preprocessor
 225 control command (@pxref{Preprocessing}).
 226
 227 @cindex line separator, RX
 228 @cindex statement separator, RX
 229 @cindex RX line separator
 230 The @samp{!} character can be used to separate statements on the same
 231 line.