gcc/rtl.def

   1 /* This file contains the definitions and documentation for the
   2    Register Transfer Expressions (rtx's) that make up the
   3    Register Transfer Language (rtl) used in the Back End of the GNU compiler.
   4    Copyright (C) 1987, 88, 92, 94, 95, 97, 98, 1999, 2000
   5    Free Software Foundation, Inc.
   6
   7 This file is part of GNU CC.
   8
   9 GNU CC is free software; you can redistribute it and/or modify
  10 it under the terms of the GNU General Public License as published by
  11 the Free Software Foundation; either version 2, or (at your option)
  12 any later version.
  13
  14 GNU CC is distributed in the hope that it will be useful,
  15 but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 GNU General Public License for more details.
  18
  19 You should have received a copy of the GNU General Public License
  20 along with GNU CC; see the file COPYING.  If not, write to
  21 the Free Software Foundation, 59 Temple Place - Suite 330,
  22 Boston, MA 02111-1307, USA.  */
  23
  24
  25 /* Expression definitions and descriptions for all targets are in this file.
  26    Some will not be used for some targets.
  27
  28    The fields in the cpp macro call "DEF_RTL_EXPR()"
  29    are used to create declarations in the C source of the compiler.
  30
  31    The fields are:
  32
  33    1.  The internal name of the rtx used in the C source.
  34    It is a tag in the enumeration "enum rtx_code" defined in "rtl.h".
  35    By convention these are in UPPER_CASE.
  36
  37    2.  The name of the rtx in the external ASCII format read by
  38    read_rtx(), and printed by print_rtx().
  39    These names are stored in rtx_name[].
  40    By convention these are the internal (field 1) names in lower_case.
  41
  42    3.  The print format, and type of each rtx->fld[] (field) in this rtx.
  43    These formats are stored in rtx_format[].
  44    The meaning of the formats is documented in front of this array in rtl.c
  45
  46    4.  The class of the rtx.  These are stored in rtx_class and are accessed
  47    via the GET_RTX_CLASS macro.  They are defined as follows:
  48
  49      "o" an rtx code that can be used to represent an object (e.g, REG, MEM)
  50      "<" an rtx code for a comparison (e.g, EQ, NE, LT)
  51      "1" an rtx code for a unary arithmetic expression (e.g, NEG, NOT)
  52      "c" an rtx code for a commutative binary operation (e.g,, PLUS, MULT)
  53      "3" an rtx code for a non-bitfield three input operation (IF_THEN_ELSE)
  54      "2" an rtx code for a non-commutative binary operation (e.g., MINUS, DIV)
  55      "b" an rtx code for a bit-field operation (ZERO_EXTRACT, SIGN_EXTRACT)
  56      "i" an rtx code for a machine insn (INSN, JUMP_INSN, CALL_INSN)
  57      "m" an rtx code for something that matches in insns (e.g, MATCH_DUP)
  58      "g" an rtx code for grouping insns together (e.g, GROUP_PARALLEL)
  59      "x" everything else
  60
  61    */
  62
  63 /* ---------------------------------------------------------------------
  64    Expressions (and "meta" expressions) used for structuring the
  65    rtl representation of a program.
  66    --------------------------------------------------------------------- */
  67
  68 /* an expression code name unknown to the reader */
  69 DEF_RTL_EXPR(UNKNOWN, "UnKnown", "*", 'x')
  70
  71 /* (NIL) is used by rtl reader and printer to represent a null pointer.  */
  72
  73 DEF_RTL_EXPR(NIL, "nil", "*", 'x')
  74
  75 /* ---------------------------------------------------------------------
  76    Expressions used in constructing lists.
  77    --------------------------------------------------------------------- */
  78
  79 /* a linked list of expressions */
  80 DEF_RTL_EXPR(EXPR_LIST, "expr_list", "ee", 'x')
  81
  82 /* a linked list of instructions.
  83    The insns are represented in print by their uids.  */
  84 DEF_RTL_EXPR(INSN_LIST, "insn_list", "ue", 'x')
  85
  86 /* ----------------------------------------------------------------------
  87    Expression types for machine descriptions.
  88    These do not appear in actual rtl code in the compiler.
  89    ---------------------------------------------------------------------- */
  90
  91 /* Appears only in machine descriptions.
  92    Means use the function named by the second arg (the string)
  93    as a predicate; if matched, store the structure that was matched
  94    in the operand table at index specified by the first arg (the integer).
  95    If the second arg is the null string, the structure is just stored.
  96
  97    A third string argument indicates to the register allocator restrictions
  98    on where the operand can be allocated.
  99
 100    If the target needs no restriction on any instruction this field should
 101    be the null string.
 102
 103    The string is prepended by:
 104    '=' to indicate the operand is only written to.
 105    '+' to indicate the operand is both read and written to.
 106
 107    Each character in the string represents an allocable class for an operand.
 108    'g' indicates the operand can be any valid class.
 109    'i' indicates the operand can be immediate (in the instruction) data.
 110    'r' indicates the operand can be in a register.
 111    'm' indicates the operand can be in memory.
 112    'o' a subset of the 'm' class.  Those memory addressing modes that
 113        can be offset at compile time (have a constant added to them).
 114
 115    Other characters indicate target dependent operand classes and
 116    are described in each target's machine description.
 117
 118    For instructions with more than one operand, sets of classes can be
 119    separated by a comma to indicate the appropriate multi-operand constraints.
 120    There must be a 1 to 1 correspondence between these sets of classes in
 121    all operands for an instruction.
 122    */
 123 DEF_RTL_EXPR(MATCH_OPERAND, "match_operand", "iss", 'm')
 124
 125 /* Appears only in machine descriptions.
 126    Means match a SCRATCH or a register.  When used to generate rtl, a
 127    SCRATCH is generated.  As for MATCH_OPERAND, the mode specifies
 128    the desired mode and the first argument is the operand number.
 129    The second argument is the constraint.  */
 130 DEF_RTL_EXPR(MATCH_SCRATCH, "match_scratch", "is", 'm')
 131
 132 /* Appears only in machine descriptions.
 133    Means match only something equal to what is stored in the operand table
 134    at the index specified by the argument.  */
 135 DEF_RTL_EXPR(MATCH_DUP, "match_dup", "i", 'm')
 136
 137 /* Appears only in machine descriptions.
 138    Means apply a predicate, AND match recursively the operands of the rtx.
 139    Operand 0 is the operand-number, as in match_operand.
 140    Operand 1 is a predicate to apply (as a string, a function name).
 141    Operand 2 is a vector of expressions, each of which must match
 142    one subexpression of the rtx this construct is matching.  */
 143 DEF_RTL_EXPR(MATCH_OPERATOR, "match_operator", "isE", 'm')
 144
 145 /* Appears only in machine descriptions.
 146    Means to match a PARALLEL of arbitrary length.  The predicate is applied
 147    to the PARALLEL and the initial expressions in the PARALLEL are matched.
 148    Operand 0 is the operand-number, as in match_operand.
 149    Operand 1 is a predicate to apply to the PARALLEL.
 150    Operand 2 is a vector of expressions, each of which must match the
 151    corresponding element in the PARALLEL.  */
 152 DEF_RTL_EXPR(MATCH_PARALLEL, "match_parallel", "isE", 'm')
 153
 154 /* Appears only in machine descriptions.
 155    Means match only something equal to what is stored in the operand table
 156    at the index specified by the argument.  For MATCH_OPERATOR.  */
 157 DEF_RTL_EXPR(MATCH_OP_DUP, "match_op_dup", "iE", 'm')
 158
 159 /* Appears only in machine descriptions.
 160    Means match only something equal to what is stored in the operand table
 161    at the index specified by the argument.  For MATCH_PARALLEL.  */
 162 DEF_RTL_EXPR(MATCH_PAR_DUP, "match_par_dup", "iE", 'm')
 163
 164 /* Appears only in machine descriptions.
 165    Operand 0 is the operand number, as in match_operand.
 166    Operand 1 is the predicate to apply to the insn.  */
 167 DEF_RTL_EXPR(MATCH_INSN, "match_insn", "is", 'm')
 168
 169 /* Appears only in machine descriptions.
 170    Defines the pattern for one kind of instruction.
 171    Operand:
 172    0: names this instruction.
 173       If the name is the null string, the instruction is in the
 174       machine description just to be recognized, and will never be emitted by
 175       the tree to rtl expander.
 176    1: is the pattern.
 177    2: is a string which is a C expression
 178       giving an additional condition for recognizing this pattern.
 179       A null string means no extra condition.
 180    3: is the action to execute if this pattern is matched.
 181       If this assembler code template starts with a * then it is a fragment of
 182       C code to run to decide on a template to use.  Otherwise, it is the
 183       template to use.
 184    4: optionally, a vector of attributes for this insn.
 185      */
 186 DEF_RTL_EXPR(DEFINE_INSN, "define_insn", "sEssV", 'x')
 187
 188 /* Definition of a peephole optimization.
 189    1st operand: vector of insn patterns to match
 190    2nd operand: C expression that must be true
 191    3rd operand: template or C code to produce assembler output.
 192    4: optionally, a vector of attributes for this insn.
 193      */
 194 DEF_RTL_EXPR(DEFINE_PEEPHOLE, "define_peephole", "EssV", 'x')
 195
 196 /* Definition of a split operation.
 197    1st operand: insn pattern to match
 198    2nd operand: C expression that must be true
 199    3rd operand: vector of insn patterns to place into a SEQUENCE
 200    4th operand: optionally, some C code to execute before generating the
 201         insns.  This might, for example, create some RTX's and store them in
 202         elements of `recog_operand' for use by the vector of insn-patterns.
 203         (`operands' is an alias here for `recog_operand').   */
 204 DEF_RTL_EXPR(DEFINE_SPLIT, "define_split", "EsES", 'x')
 205
 206 /* Definition of an RTL peephole operation.
 207    Follows the same arguments as define_split.  */
 208 DEF_RTL_EXPR(DEFINE_PEEPHOLE2, "define_peephole2", "EsES", 'x')
 209
 210 /* Definition of a combiner pattern.
 211    Operands not defined yet.  */
 212 DEF_RTL_EXPR(DEFINE_COMBINE, "define_combine", "Ess", 'x')
 213
 214 /* Define how to generate multiple insns for a standard insn name.
 215    1st operand: the insn name.
 216    2nd operand: vector of insn-patterns.
 217         Use match_operand to substitute an element of `recog_operand'.
 218    3rd operand: C expression that must be true for this to be available.
 219         This may not test any operands.
 220    4th operand: Extra C code to execute before generating the insns.
 221         This might, for example, create some RTX's and store them in
 222         elements of `recog_operand' for use by the vector of insn-patterns.
 223         (`operands' is an alias here for `recog_operand').  */
 224 DEF_RTL_EXPR(DEFINE_EXPAND, "define_expand", "sEss", 'x')
 225
 226 /* Define a requirement for delay slots.
 227    1st operand: Condition involving insn attributes that, if true,
 228                 indicates that the insn requires the number of delay slots
 229                 shown.
 230    2nd operand: Vector whose length is the three times the number of delay
 231                 slots required.
 232                 Each entry gives three conditions, each involving attributes.
 233                 The first must be true for an insn to occupy that delay slot
 234                 location.  The second is true for all insns that can be
 235                 annulled if the branch is true and the third is true for all
 236                 insns that can be annulled if the branch is false.
 237
 238    Multiple DEFINE_DELAYs may be present.  They indicate differing
 239    requirements for delay slots.  */
 240 DEF_RTL_EXPR(DEFINE_DELAY, "define_delay", "eE", 'x')
 241
 242 /* Define a set of insns that requires a function unit.  This means that
 243    these insns produce their result after a delay and that there may be
 244    restrictions on the number of insns of this type that can be scheduled
 245    simultaneously.
 246
 247    More than one DEFINE_FUNCTION_UNIT can be specified for a function unit.
 248    Each gives a set of operations and associated delays.  The first three
 249    operands must be the same for each operation for the same function unit.
 250
 251    All delays are specified in cycles.
 252
 253    1st operand: Name of function unit (mostly for documentation)
 254    2nd operand: Number of identical function units in CPU
 255    3rd operand: Total number of simultaneous insns that can execute on this
 256                 function unit; 0 if unlimited.
 257    4th operand: Condition involving insn attribute, that, if true, specifies
 258                 those insns that this expression applies to.
 259    5th operand: Constant delay after which insn result will be
 260                 available.
 261    6th operand: Delay until next insn can be scheduled on the function unit
 262                 executing this operation.  The meaning depends on whether or
 263                 not the next operand is supplied.
 264    7th operand: If this operand is not specified, the 6th operand gives the
 265                 number of cycles after the instruction matching the 4th
 266                 operand begins using the function unit until a subsequent
 267                 insn can begin.  A value of zero should be used for a
 268                 unit with no issue constraints.  If only one operation can
 269                 be executed a time and the unit is busy for the entire time,
 270                 the 3rd operand should be specified as 1, the 6th operand
 271                 should be specified as 0, and the 7th operand should not
 272                 be specified.
 273
 274                 If this operand is specified, it is a list of attribute
 275                 expressions.  If an insn for which any of these expressions
 276                 is true is currently executing on the function unit, the
 277                 issue delay will be given by the 6th operand.  Otherwise,
 278                 the insn can be immediately scheduled (subject to the limit
 279                 on the number of simultaneous operations executing on the
 280                 unit.)  */
 281 DEF_RTL_EXPR(DEFINE_FUNCTION_UNIT, "define_function_unit", "siieiiV", 'x')
 282
 283 /* Define attribute computation for `asm' instructions.  */
 284 DEF_RTL_EXPR(DEFINE_ASM_ATTRIBUTES, "define_asm_attributes", "V", 'x' )
 285
 286 /* SEQUENCE appears in the result of a `gen_...' function
 287    for a DEFINE_EXPAND that wants to make several insns.
 288    Its elements are the bodies of the insns that should be made.
 289    `emit_insn' takes the SEQUENCE apart and makes separate insns.  */
 290 DEF_RTL_EXPR(SEQUENCE, "sequence", "E", 'x')
 291
 292 /* Refers to the address of its argument.  This is only used in alias.c.  */
 293 DEF_RTL_EXPR(ADDRESS, "address", "e", 'm')
 294
 295 /* ----------------------------------------------------------------------
 296    Expressions used for insn attributes.  These also do not appear in
 297    actual rtl code in the compiler.
 298    ---------------------------------------------------------------------- */
 299
 300 /* Definition of an insn attribute.
 301    1st operand: name of the attribute
 302    2nd operand: comma-separated list of possible attribute values
 303    3rd operand: expression for the default value of the attribute. */
 304 DEF_RTL_EXPR(DEFINE_ATTR, "define_attr", "sse", 'x')
 305
 306 /* Marker for the name of an attribute. */
 307 DEF_RTL_EXPR(ATTR, "attr", "s", 'x')
 308
 309 /* For use in the last (optional) operand of DEFINE_INSN or DEFINE_PEEPHOLE and
 310    in DEFINE_ASM_INSN to specify an attribute to assign to insns matching that
 311    pattern.
 312
 313    (set_attr "name" "value") is equivalent to
 314    (set (attr "name") (const_string "value"))  */
 315 DEF_RTL_EXPR(SET_ATTR, "set_attr", "ss", 'x')
 316
 317 /* In the last operand of DEFINE_INSN and DEFINE_PEEPHOLE, this can be used to
 318    specify that attribute values are to be assigned according to the
 319    alternative matched.
 320
 321    The following three expressions are equivalent:
 322
 323    (set (attr "att") (cond [(eq_attrq "alternative" "1") (const_string "a1")
 324                             (eq_attrq "alternative" "2") (const_string "a2")]
 325                            (const_string "a3")))
 326    (set_attr_alternative "att" [(const_string "a1") (const_string "a2")
 327                                  (const_string "a3")])
 328    (set_attr "att" "a1,a2,a3")
 329  */
 330 DEF_RTL_EXPR(SET_ATTR_ALTERNATIVE, "set_attr_alternative", "sE", 'x')
 331
 332 /* A conditional expression true if the value of the specified attribute of
 333    the current insn equals the specified value.  The first operand is the
 334    attribute name and the second is the comparison value.  */
 335 DEF_RTL_EXPR(EQ_ATTR, "eq_attr", "ss", 'x')
 336
 337 /* A conditional expression which is true if the specified flag is
 338    true for the insn being scheduled in reorg.
 339
 340    genattr.c defines the following flags which can be tested by
 341    (attr_flag "foo") expressions in eligible_for_delay.
 342
 343    forward, backward, very_likely, likely, very_unlikely, and unlikely.  */
 344
 345 DEF_RTL_EXPR (ATTR_FLAG, "attr_flag", "s", 'x')
 346
 347 /* ----------------------------------------------------------------------
 348    Expression types used for things in the instruction chain.
 349
 350    All formats must start with "iuu" to handle the chain.
 351    Each insn expression holds an rtl instruction and its semantics
 352    during back-end processing.
 353    See macros's in "rtl.h" for the meaning of each rtx->fld[].
 354
 355    ---------------------------------------------------------------------- */
 356
 357 /* An instruction that cannot jump.  */
 358 DEF_RTL_EXPR(INSN, "insn", "iuueiee", 'i')
 359
 360 /* An instruction that can possibly jump.
 361    Fields ( rtx->fld[] ) have exact same meaning as INSN's.  */
 362 DEF_RTL_EXPR(JUMP_INSN, "jump_insn", "iuueiee0", 'i')
 363
 364 /* An instruction that can possibly call a subroutine
 365    but which will not change which instruction comes next
 366    in the current function.
 367    Field ( rtx->fld[7] ) is CALL_INSN_FUNCTION_USAGE.
 368    All other fields ( rtx->fld[] ) have exact same meaning as INSN's.  */
 369 DEF_RTL_EXPR(CALL_INSN, "call_insn", "iuueieee", 'i')
 370
 371 /* A marker that indicates that control will not flow through.  */
 372 DEF_RTL_EXPR(BARRIER, "barrier", "iuu", 'x')
 373
 374 /* Holds a label that is followed by instructions.
 375    Operand:
 376    3: is a number that is unique in the entire compilation.
 377    4: is the user-given name of the label, if any.
 378    5: is used in jump.c for the use-count of the label.
 379    6: is used in flow.c to point to the chain of label_ref's to this label.
 380    7: is the alternate label name.  */
 381 DEF_RTL_EXPR(CODE_LABEL, "code_label", "iuuis00s", 'x')
 382
 383 /* Say where in the code a source line starts, for symbol table's sake.
 384    Contains a filename and a line number.  Line numbers <= 0 are special:
 385    0 is used in a dummy placed at the front of every function
 386       just so there will never be a need to delete the first insn;
 387    -1 indicates a dummy; insns to be deleted by flow analysis and combining
 388       are really changed to NOTEs with a number of -1.
 389    -2 means beginning of a name binding contour; output N_LBRAC.
 390    -3 means end of a contour; output N_RBRAC.  */
 391 DEF_RTL_EXPR(NOTE, "note", "iuu0n", 'x')
 392
 393 /* ----------------------------------------------------------------------
 394    Top level constituents of INSN, JUMP_INSN and CALL_INSN.
 395    ---------------------------------------------------------------------- */
 396
 397 /* Several operations to be done in parallel.  */
 398 DEF_RTL_EXPR(PARALLEL, "parallel", "E", 'x')
 399
 400 /* A string that is passed through to the assembler as input.
 401      One can obviously pass comments through by using the
 402      assembler comment syntax.
 403      These occur in an insn all by themselves as the PATTERN.
 404      They also appear inside an ASM_OPERANDS
 405      as a convenient way to hold a string.  */
 406 DEF_RTL_EXPR(ASM_INPUT, "asm_input", "s", 'x')
 407
 408 /* An assembler instruction with operands.
 409    1st operand is the instruction template.
 410    2nd operand is the constraint for the output.
 411    3rd operand is the number of the output this expression refers to.
 412      When an insn stores more than one value, a separate ASM_OPERANDS
 413      is made for each output; this integer distinguishes them.
 414    4th is a vector of values of input operands.
 415    5th is a vector of modes and constraints for the input operands.
 416      Each element is an ASM_INPUT containing a constraint string
 417      and whose mode indicates the mode of the input operand.
 418    6th is the name of the containing source file.
 419    7th is the source line number.  */
 420 DEF_RTL_EXPR(ASM_OPERANDS, "asm_operands", "ssiEEsi", 'x')
 421
 422 /* A machine-specific operation.
 423    1st operand is a vector of operands being used by the operation so that
 424      any needed reloads can be done.
 425    2nd operand is a unique value saying which of a number of machine-specific
 426      operations is to be performed.
 427    (Note that the vector must be the first operand because of the way that
 428    genrecog.c record positions within an insn.)
 429    This can occur all by itself in a PATTERN, as a component of a PARALLEL,
 430    or inside an expression.  */
 431 DEF_RTL_EXPR(UNSPEC, "unspec", "Ei", 'x')
 432
 433 /* Similar, but a volatile operation and one which may trap.  */
 434 DEF_RTL_EXPR(UNSPEC_VOLATILE, "unspec_volatile", "Ei", 'x')
 435
 436 /* Vector of addresses, stored as full words.  */
 437 /* Each element is a LABEL_REF to a CODE_LABEL whose address we want.  */
 438 DEF_RTL_EXPR(ADDR_VEC, "addr_vec", "E", 'x')
 439
 440 /* Vector of address differences X0 - BASE, X1 - BASE, ...
 441    First operand is BASE; the vector contains the X's.
 442    The machine mode of this rtx says how much space to leave
 443    for each difference and is adjusted by branch shortening if
 444    CASE_VECTOR_SHORTEN_MODE is defined.
 445    The third and fourth operands store the target labels with the
 446    minimum and maximum addresses respectively.
 447    The fifth operand stores flags for use by branch shortening.
 448   Set at the start of shorten_branches:
 449    min_align: the minimum alignment for any of the target labels.
 450    base_after_vec: true iff BASE is after the ADDR_DIFF_VEC.
 451    min_after_vec: true iff minimum addr target label is after the ADDR_DIFF_VEC.
 452    max_after_vec: true iff maximum addr target label is after the ADDR_DIFF_VEC.
 453    min_after_base: true iff minimum address target label is after BASE.
 454    max_after_base: true iff maximum address target label is after BASE.
 455   Set by the actual branch shortening process:
 456    offset_unsigned: true iff offsets have to be treated as unsigned.
 457    scale: scaling that is necessary to make offsets fit into the mode.
 458
 459    The third, fourth and fifth operands are only valid when
 460    CASE_VECTOR_SHORTEN_MODE is defined, and only in an optimizing
 461    compilations.  */
 462
 463 DEF_RTL_EXPR(ADDR_DIFF_VEC, "addr_diff_vec", "eEee0", 'x')
 464
 465 /* ----------------------------------------------------------------------
 466    At the top level of an instruction (perhaps under PARALLEL).
 467    ---------------------------------------------------------------------- */
 468
 469 /* Assignment.
 470    Operand 1 is the location (REG, MEM, PC, CC0 or whatever) assigned to.
 471    Operand 2 is the value stored there.
 472    ALL assignment must use SET.
 473    Instructions that do multiple assignments must use multiple SET,
 474    under PARALLEL.  */
 475 DEF_RTL_EXPR(SET, "set", "ee", 'x')
 476
 477 /* Indicate something is used in a way that we don't want to explain.
 478    For example, subroutine calls will use the register
 479    in which the static chain is passed.  */
 480 DEF_RTL_EXPR(USE, "use", "e", 'x')
 481
 482 /* Indicate something is clobbered in a way that we don't want to explain.
 483    For example, subroutine calls will clobber some physical registers
 484    (the ones that are by convention not saved).  */
 485 DEF_RTL_EXPR(CLOBBER, "clobber", "e", 'x')
 486
 487 /* Call a subroutine.
 488    Operand 1 is the address to call.
 489    Operand 2 is the number of arguments.  */
 490
 491 DEF_RTL_EXPR(CALL, "call", "ee", 'x')
 492
 493 /* Return from a subroutine.  */
 494
 495 DEF_RTL_EXPR(RETURN, "return", "", 'x')
 496
 497 /* Conditional trap.
 498    Operand 1 is the condition.
 499    Operand 2 is the trap code.
 500    For an unconditional trap, make the condition (const_int 1).  */
 501 DEF_RTL_EXPR(TRAP_IF, "trap_if", "ee", 'x')
 502
 503 /* ----------------------------------------------------------------------
 504    Primitive values for use in expressions.
 505    ---------------------------------------------------------------------- */
 506
 507 /* numeric integer constant */
 508 DEF_RTL_EXPR(CONST_INT, "const_int", "w", 'o')
 509
 510 /* numeric floating point constant.
 511    Operand 0 ('e') is the MEM that stores this constant in memory, or
 512    various other things (see comments at immed_double_const in
 513    varasm.c).
 514    Operand 1 ('0') is a chain of all CONST_DOUBLEs in use in the
 515    current function.
 516    Remaining operands hold the actual value.  They are all 'w' and
 517    there may be from 1 to 4; see rtl.c.  */
 518 DEF_RTL_EXPR(CONST_DOUBLE, "const_double", CONST_DOUBLE_FORMAT, 'o')
 519
 520 /* String constant.  Used only for attributes right now.  */
 521 DEF_RTL_EXPR(CONST_STRING, "const_string", "s", 'o')
 522
 523 /* This is used to encapsulate an expression whose value is constant
 524    (such as the sum of a SYMBOL_REF and a CONST_INT) so that it will be
 525    recognized as a constant operand rather than by arithmetic instructions.  */
 526
 527 DEF_RTL_EXPR(CONST, "const", "e", 'o')
 528
 529 /* program counter.  Ordinary jumps are represented
 530    by a SET whose first operand is (PC).  */
 531 DEF_RTL_EXPR(PC, "pc", "", 'o')
 532
 533 /* Used in the cselib routines to describe a value.  */
 534 DEF_RTL_EXPR(VALUE, "value", "0", 'o')
 535
 536 /* A register.  The "operand" is the register number, accessed with
 537    the REGNO macro.  If this number is less than FIRST_PSEUDO_REGISTER
 538    than a hardware register is being referred to.  The second operand
 539    doesn't really exist.  Unfortunately, however, the compiler
 540    implicitly assumes that a REG can be transformed in place into a
 541    MEM, and therefore that a REG is at least as big as a MEM.  To
 542    avoid this memory overhead, which is likely to be substantial,
 543    search for uses of PUT_CODE that turn REGs into MEMs, and fix them
 544    somehow.  Then, the trailing `0' can be removed here.  */
 545 DEF_RTL_EXPR(REG, "reg", "i0", 'o')
 546
 547 /* A scratch register.  This represents a register used only within a
 548    single insn.  It will be turned into a REG during register allocation
 549    or reload unless the constraint indicates that the register won't be
 550    needed, in which case it can remain a SCRATCH.  This code is
 551    marked as having one operand so it can be turned into a REG.  */
 552 DEF_RTL_EXPR(SCRATCH, "scratch", "0", 'o')
 553
 554 /* One word of a multi-word value.
 555    The first operand is the complete value; the second says which word.
 556    The WORDS_BIG_ENDIAN flag controls whether word number 0
 557    (as numbered in a SUBREG) is the most or least significant word.
 558
 559    This is also used to refer to a value in a different machine mode.
 560    For example, it can be used to refer to a SImode value as if it were
 561    Qimode, or vice versa.  Then the word number is always 0.  */
 562 DEF_RTL_EXPR(SUBREG, "subreg", "ei", 'x')
 563
 564 /* This one-argument rtx is used for move instructions
 565    that are guaranteed to alter only the low part of a destination.
 566    Thus, (SET (SUBREG:HI (REG...)) (MEM:HI ...))
 567    has an unspecified effect on the high part of REG,
 568    but (SET (STRICT_LOW_PART (SUBREG:HI (REG...))) (MEM:HI ...))
 569    is guaranteed to alter only the bits of REG that are in HImode.
 570
 571    The actual instruction used is probably the same in both cases,
 572    but the register constraints may be tighter when STRICT_LOW_PART
 573    is in use.  */
 574
 575 DEF_RTL_EXPR(STRICT_LOW_PART, "strict_low_part", "e", 'x')
 576
 577 /* (CONCAT a b) represents the virtual concatenation of a and b
 578    to make a value that has as many bits as a and b put together.
 579    This is used for complex values.  Normally it appears only
 580    in DECL_RTLs and during RTL generation, but not in the insn chain.  */
 581 DEF_RTL_EXPR(CONCAT, "concat", "ee", 'o')
 582
 583 /* A memory location; operand is the address.  Can be nested inside a
 584    VOLATILE.  The second operand is the alias set to which this MEM
 585    belongs.  We use `0' instead of `i' for this field so that the
 586    field need not be specified in machine descriptions.  */
 587 DEF_RTL_EXPR(MEM, "mem", "e0", 'o')
 588
 589 /* Reference to an assembler label in the code for this function.
 590    The operand is a CODE_LABEL found in the insn chain.
 591    The unprinted fields 1 and 2 are used in flow.c for the
 592    LABEL_NEXTREF and CONTAINING_INSN.  */
 593 DEF_RTL_EXPR(LABEL_REF, "label_ref", "u00", 'o')
 594
 595 /* Reference to a named label: the string that is the first operand,
 596    with `_' added implicitly in front.
 597    Exception: if the first character explicitly given is `*',
 598    to give it to the assembler, remove the `*' and do not add `_'.  */
 599 DEF_RTL_EXPR(SYMBOL_REF, "symbol_ref", "s", 'o')
 600
 601 /* The condition code register is represented, in our imagination,
 602    as a register holding a value that can be compared to zero.
 603    In fact, the machine has already compared them and recorded the
 604    results; but instructions that look at the condition code
 605    pretend to be looking at the entire value and comparing it.  */
 606 DEF_RTL_EXPR(CC0, "cc0", "", 'o')
 607
 608 /* Reference to the address of a register.  Removed by purge_addressof after
 609    CSE has elided as many as possible.
 610    1st operand: the register we may need the address of.
 611    2nd operand: the original pseudo regno we were generated for.
 612    3rd operand: the decl for the object in the register, for
 613      put_reg_in_stack.  */
 614
 615 DEF_RTL_EXPR(ADDRESSOF, "addressof", "eit", 'o')
 616
 617 /* =====================================================================
 618    A QUEUED expression really points to a member of the queue of instructions
 619    to be output later for postincrement/postdecrement.
 620    QUEUED expressions never become part of instructions.
 621    When a QUEUED expression would be put into an instruction,
 622    instead either the incremented variable or a copy of its previous
 623    value is used.
 624
 625    Operands are:
 626    0. the variable to be incremented (a REG rtx).
 627    1. the incrementing instruction, or 0 if it hasn't been output yet.
 628    2. A REG rtx for a copy of the old value of the variable, or 0 if none yet.
 629    3. the body to use for the incrementing instruction
 630    4. the next QUEUED expression in the queue.
 631    ====================================================================== */
 632
 633 DEF_RTL_EXPR(QUEUED, "queued", "eeeee", 'x')
 634
 635 /* ----------------------------------------------------------------------
 636    Expressions for operators in an rtl pattern
 637    ---------------------------------------------------------------------- */
 638
 639 /* if_then_else.  This is used in representing ordinary
 640    conditional jump instructions.
 641      Operand:
 642      0:  condition
 643      1:  then expr
 644      2:  else expr */
 645 DEF_RTL_EXPR(IF_THEN_ELSE, "if_then_else", "eee", '3')
 646
 647 /* General conditional. The first operand is a vector composed of pairs of
 648    expressions.  The first element of each pair is evaluated, in turn.
 649    The value of the conditional is the second expression of the first pair
 650    whose first expression evaluates non-zero.  If none of the expressions is
 651    true, the second operand will be used as the value of the conditional.
 652
 653    This should be replaced with use of IF_THEN_ELSE.  */
 654 DEF_RTL_EXPR(COND, "cond", "Ee", 'x')
 655
 656 /* Comparison, produces a condition code result.  */
 657 DEF_RTL_EXPR(COMPARE, "compare", "ee", '2')
 658
 659 /* plus */
 660 DEF_RTL_EXPR(PLUS, "plus", "ee", 'c')
 661
 662 /* Operand 0 minus operand 1.  */
 663 DEF_RTL_EXPR(MINUS, "minus", "ee", '2')
 664
 665 /* Minus operand 0.  */
 666 DEF_RTL_EXPR(NEG, "neg", "e", '1')
 667
 668 DEF_RTL_EXPR(MULT, "mult", "ee", 'c')
 669
 670 /* Operand 0 divided by operand 1.  */
 671 DEF_RTL_EXPR(DIV, "div", "ee", '2')
 672 /* Remainder of operand 0 divided by operand 1.  */
 673 DEF_RTL_EXPR(MOD, "mod", "ee", '2')
 674
 675 /* Unsigned divide and remainder.  */
 676 DEF_RTL_EXPR(UDIV, "udiv", "ee", '2')
 677 DEF_RTL_EXPR(UMOD, "umod", "ee", '2')
 678
 679 /* Bitwise operations.  */
 680 DEF_RTL_EXPR(AND, "and", "ee", 'c')
 681
 682 DEF_RTL_EXPR(IOR, "ior", "ee", 'c')
 683
 684 DEF_RTL_EXPR(XOR, "xor", "ee", 'c')
 685
 686 DEF_RTL_EXPR(NOT, "not", "e", '1')
 687
 688 /* Operand:
 689      0:  value to be shifted.
 690      1:  number of bits.  */
 691 DEF_RTL_EXPR(ASHIFT, "ashift", "ee", '2') /* shift left */
 692 DEF_RTL_EXPR(ROTATE, "rotate", "ee", '2') /* rotate left */
 693 DEF_RTL_EXPR(ASHIFTRT, "ashiftrt", "ee", '2') /* arithmetic shift right */
 694 DEF_RTL_EXPR(LSHIFTRT, "lshiftrt", "ee", '2') /* logical shift right */
 695 DEF_RTL_EXPR(ROTATERT, "rotatert", "ee", '2') /* rotate right */
 696
 697 /* Minimum and maximum values of two operands.  We need both signed and
 698    unsigned forms.  (We cannot use MIN for SMIN because it conflicts
 699    with a macro of the same name.) */
 700
 701 DEF_RTL_EXPR(SMIN, "smin", "ee", 'c')
 702 DEF_RTL_EXPR(SMAX, "smax", "ee", 'c')
 703 DEF_RTL_EXPR(UMIN, "umin", "ee", 'c')
 704 DEF_RTL_EXPR(UMAX, "umax", "ee", 'c')
 705
 706 /* These unary operations are used to represent incrementation
 707    and decrementation as they occur in memory addresses.
 708    The amount of increment or decrement are not represented
 709    because they can be understood from the machine-mode of the
 710    containing MEM.  These operations exist in only two cases:
 711    1. pushes onto the stack.
 712    2. created automatically by the life_analysis pass in flow.c.  */
 713 DEF_RTL_EXPR(PRE_DEC, "pre_dec", "e", 'x')
 714 DEF_RTL_EXPR(PRE_INC, "pre_inc", "e", 'x')
 715 DEF_RTL_EXPR(POST_DEC, "post_dec", "e", 'x')
 716 DEF_RTL_EXPR(POST_INC, "post_inc", "e", 'x')
 717
 718 /* These binary operations are used to represent generic address
 719    side-effects in memory addresses, except for simple incrementation
 720    or decrementation which use the above operations.  They are
 721    created automatically by the life_analysis pass in flow.c.
 722    (Note that these operators are currently placeholders.)  */
 723 DEF_RTL_EXPR(PRE_MODIFY, "pre_modify", "ee", 'x')
 724 DEF_RTL_EXPR(POST_MODIFY, "post_modify", "ee", 'x')
 725
 726 /* Comparison operations.  The ordered comparisons exist in two
 727    flavors, signed and unsigned.  */
 728 DEF_RTL_EXPR(NE, "ne", "ee", '<')
 729 DEF_RTL_EXPR(EQ, "eq", "ee", '<')
 730 DEF_RTL_EXPR(GE, "ge", "ee", '<')
 731 DEF_RTL_EXPR(GT, "gt", "ee", '<')
 732 DEF_RTL_EXPR(LE, "le", "ee", '<')
 733 DEF_RTL_EXPR(LT, "lt", "ee", '<')
 734 DEF_RTL_EXPR(GEU, "geu", "ee", '<')
 735 DEF_RTL_EXPR(GTU, "gtu", "ee", '<')
 736 DEF_RTL_EXPR(LEU, "leu", "ee", '<')
 737 DEF_RTL_EXPR(LTU, "ltu", "ee", '<')
 738
 739 /* Additional floating point unordered comparision flavors.  */
 740 DEF_RTL_EXPR(UNORDERED, "unordered", "ee", '<')
 741 DEF_RTL_EXPR(ORDERED, "ordered", "ee", '<')
 742
 743 /* These are equivalent to unordered or ... */
 744 DEF_RTL_EXPR(UNEQ, "uneq", "ee", '<')
 745 DEF_RTL_EXPR(UNGE, "unge", "ee", '<')
 746 DEF_RTL_EXPR(UNGT, "ungt", "ee", '<')
 747 DEF_RTL_EXPR(UNLE, "unle", "ee", '<')
 748 DEF_RTL_EXPR(UNLT, "unlt", "ee", '<')
 749
 750 /* This is an ordered NE, ie !UNEQ, ie false for NaN.  */
 751 DEF_RTL_EXPR(LTGT, "ltgt", "ee", '<')
 752
 753 /* Represents the result of sign-extending the sole operand.
 754    The machine modes of the operand and of the SIGN_EXTEND expression
 755    determine how much sign-extension is going on.  */
 756 DEF_RTL_EXPR(SIGN_EXTEND, "sign_extend", "e", '1')
 757
 758 /* Similar for zero-extension (such as unsigned short to int).  */
 759 DEF_RTL_EXPR(ZERO_EXTEND, "zero_extend", "e", '1')
 760
 761 /* Similar but here the operand has a wider mode.  */
 762 DEF_RTL_EXPR(TRUNCATE, "truncate", "e", '1')
 763
 764 /* Similar for extending floating-point values (such as SFmode to DFmode).  */
 765 DEF_RTL_EXPR(FLOAT_EXTEND, "float_extend", "e", '1')
 766 DEF_RTL_EXPR(FLOAT_TRUNCATE, "float_truncate", "e", '1')
 767
 768 /* Conversion of fixed point operand to floating point value.  */
 769 DEF_RTL_EXPR(FLOAT, "float", "e", '1')
 770
 771 /* With fixed-point machine mode:
 772    Conversion of floating point operand to fixed point value.
 773    Value is defined only when the operand's value is an integer.
 774    With floating-point machine mode (and operand with same mode):
 775    Operand is rounded toward zero to produce an integer value
 776    represented in floating point.  */
 777 DEF_RTL_EXPR(FIX, "fix", "e", '1')
 778
 779 /* Conversion of unsigned fixed point operand to floating point value.  */
 780 DEF_RTL_EXPR(UNSIGNED_FLOAT, "unsigned_float", "e", '1')
 781
 782 /* With fixed-point machine mode:
 783    Conversion of floating point operand to *unsigned* fixed point value.
 784    Value is defined only when the operand's value is an integer.  */
 785 DEF_RTL_EXPR(UNSIGNED_FIX, "unsigned_fix", "e", '1')
 786
 787 /* Absolute value */
 788 DEF_RTL_EXPR(ABS, "abs", "e", '1')
 789
 790 /* Square root */
 791 DEF_RTL_EXPR(SQRT, "sqrt", "e", '1')
 792
 793 /* Find first bit that is set.
 794    Value is 1 + number of trailing zeros in the arg.,
 795    or 0 if arg is 0.  */
 796 DEF_RTL_EXPR(FFS, "ffs", "e", '1')
 797
 798 /* Reference to a signed bit-field of specified size and position.
 799    Operand 0 is the memory unit (usually SImode or QImode) which
 800    contains the field's first bit.  Operand 1 is the width, in bits.
 801    Operand 2 is the number of bits in the memory unit before the
 802    first bit of this field.
 803    If BITS_BIG_ENDIAN is defined, the first bit is the msb and
 804    operand 2 counts from the msb of the memory unit.
 805    Otherwise, the first bit is the lsb and operand 2 counts from
 806    the lsb of the memory unit.  */
 807 DEF_RTL_EXPR(SIGN_EXTRACT, "sign_extract", "eee", 'b')
 808
 809 /* Similar for unsigned bit-field.  */
 810 DEF_RTL_EXPR(ZERO_EXTRACT, "zero_extract", "eee", 'b')
 811
 812 /* For RISC machines.  These save memory when splitting insns.  */
 813
 814 /* HIGH are the high-order bits of a constant expression.  */
 815 DEF_RTL_EXPR(HIGH, "high", "e", 'o')
 816
 817 /* LO_SUM is the sum of a register and the low-order bits
 818    of a constant expression.  */
 819 DEF_RTL_EXPR(LO_SUM, "lo_sum", "ee", 'o')
 820
 821 /* Header for range information.  Operand 0 is the NOTE_INSN_RANGE_START insn.
 822    Operand 1 is the NOTE_INSN_RANGE_END insn.  Operand 2 is a vector of all of
 823    the registers that can be substituted within this range.  Operand 3 is the
 824    number of calls in the range.  Operand 4 is the number of insns in the
 825    range.  Operand 5 is the unique range number for this range.  Operand 6 is
 826    the basic block # of the start of the live range.  Operand 7 is the basic
 827    block # of the end of the live range.  Operand 8 is the loop depth.  Operand
 828    9 is a bitmap of the registers live at the start of the range.  Operand 10
 829    is a bitmap of the registers live at the end of the range.  Operand 11 is
 830    marker number for the start of the range.  Operand 12 is the marker number
 831    for the end of the range.  */
 832 DEF_RTL_EXPR(RANGE_INFO, "range_info", "uuEiiiiiibbii", 'x')
 833
 834 /* Registers that can be substituted within the range.  Operand 0 is the
 835    original pseudo register number.  Operand 1 will be filled in with the
 836    pseudo register the value is copied for the duration of the range.  Operand
 837    2 is the number of references within the range to the register.  Operand 3
 838    is the number of sets or clobbers of the register in the range.  Operand 4
 839    is the number of deaths the register has.  Operand 5 is the copy flags that
 840    give the status of whether a copy is needed from the original register to
 841    the new register at the beginning of the range, or whether a copy from the
 842    new register back to the original at the end of the range.  Operand 6 is the
 843    live length.  Operand 7 is the number of calls that this register is live
 844    across.  Operand 8 is the symbol node of the variable if the register is a
 845    user variable.  Operand 9 is the block node that the variable is declared
 846    in if the register is a user variable. */
 847 DEF_RTL_EXPR(RANGE_REG, "range_reg", "iiiiiiiitt", 'x')
 848
 849 /* Information about a local variable's ranges.  Operand 0 is an EXPR_LIST of
 850    the different ranges a variable is in where it is copied to a different
 851    pseudo register.  Operand 1 is the block that the variable is declared in.
 852    Operand 2 is the number of distinct ranges.  */
 853 DEF_RTL_EXPR(RANGE_VAR, "range_var", "eti", 'x')
 854
 855 /* Information about the registers that are live at the current point.  Operand
 856    0 is the live bitmap.  Operand 1 is the original block number.  */
 857 DEF_RTL_EXPR(RANGE_LIVE, "range_live", "bi", 'x')
 858
 859 /* A unary `__builtin_constant_p' expression.  These are only emitted
 860    during RTL generation, and then only if optimize > 0.  They are
 861    eliminated by the first CSE pass. */
 862 DEF_RTL_EXPR(CONSTANT_P_RTX, "constant_p_rtx", "e", 'x')
 863
 864 /* A placeholder for a CALL_INSN which may be turned into a normal call,
 865    a sibling (tail) call or tail recursion.
 866
 867    Immediately after RTL generation, this placeholder will be replaced
 868    by the insns to perform the call, sibcall or tail recursion.
 869
 870    This RTX has 4 operands.  The first three are lists of instructions to
 871    perform the call as a normal call, sibling call and tail recursion
 872    respectively.  The latter two lists may be NULL, the first may never
 873    be NULL.
 874
 875    The last operand is the tail recursion CODE_LABEL, which may be NULL if no
 876    potential tail recursive calls were found.
 877
 878    The tail recursion label is needed so that we can clear LABEL_PRESERVE_P
 879    after we select a call method.
 880
 881    This method of tail-call elimination is intended to be replaced by
 882    tree-based optimizations once front-end conversions are complete.  */
 883 DEF_RTL_EXPR(CALL_PLACEHOLDER, "call_placeholder", "uuuu", 'x')
 884
 885 /* The SSA phi operator.
 886
 887    The argument is a vector of 2N rtxes.  Element 2N+1 is a CONST_INT
 888    containing the block number of the predecessor through which control
 889    has passed when the register at element 2N is used.
 890
 891    Note that PHI may only appear at the beginning of a basic block.
 892
 893    ??? There may be multiple PHI insns, but they are all evaluated
 894    in parallel.  This probably ought to be changed to use a real
 895    PARALLEL, as that would be less confusing and more in the spirit
 896    of canonical RTL.  It is, however, easier to manipulate this way.  */
 897 DEF_RTL_EXPR(PHI, "phi", "E", 'x')
 898
 899 /* Conditionally execute code.
 900    Operand 0 is the condition that if true, the code is executed.
 901    Operand 1 is the code to be executed (typically a SET).
 902
 903    Semantics are that there are no side effects if the condition
 904    is false.  */
 905 DEF_RTL_EXPR(COND_EXEC, "cond_exec", "ee", 'x')
 906
 907 /*
 908 Local variables:
 909 mode:c
 910 End:
 911 */