hw/xtensa/xtensa-isa.h

/* Interface definition for configurable Xtensa ISA support.
 *
 * Copyright (c) 2001-2013 Tensilica Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#ifndef XTENSA_LIBISA_H
#define XTENSA_LIBISA_H

#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif

/*
 * Version number: This is intended to help support code that works with
 * versions of this library from multiple Xtensa releases.
 */

#define XTENSA_ISA_VERSION 7000

/*
 * This file defines the interface to the Xtensa ISA library. This
 * library contains most of the ISA-specific information for a
 * particular Xtensa processor. For example, the set of valid
 * instructions, their opcode encodings and operand fields are all
 * included here.
 *
 * This interface basically defines a number of abstract data types.
 *
 * . an instruction buffer - for holding the raw instruction bits
 * . ISA info - information about the ISA as a whole
 * . instruction formats - instruction size and slot structure
 * . opcodes - information about individual instructions
 * . operands - information about register and immediate instruction operands
 * . stateOperands - information about processor state instruction operands
 * . interfaceOperands - information about interface instruction operands
 * . register files - register file information
 * . processor states - internal processor state information
 * . system registers - "special registers" and "user registers"
 * . interfaces - TIE interfaces that are external to the processor
 * . functional units - TIE shared functions
 *
 * The interface defines a set of functions to access each data type.
 * With the exception of the instruction buffer, the internal
 * representations of the data structures are hidden. All accesses must
 * be made through the functions defined here.
 */

typedef struct xtensa_isa_opaque { int unused; } *xtensa_isa;


/*
 * Most of the Xtensa ISA entities (e.g., opcodes, regfiles, etc.) are
 * represented here using sequential integers beginning with 0. The
 * specific values are only fixed for a particular instantiation of an
 * xtensa_isa structure, so these values should only be used
 * internally.
 */

typedef int xtensa_opcode;
typedef int xtensa_format;
typedef int xtensa_regfile;
typedef int xtensa_state;
typedef int xtensa_sysreg;
typedef int xtensa_interface;
typedef int xtensa_funcUnit;


/* Define a unique value for undefined items. */

#define XTENSA_UNDEFINED -1


/*
 * Overview of using this interface to decode/encode instructions:
 *
 * Each Xtensa instruction is associated with a particular instruction
 * format, where the format defines a fixed number of slots for
 * operations. The formats for the core Xtensa ISA have only one slot,
 * but FLIX instructions may have multiple slots. Within each slot,
 * there is a single opcode and some number of associated operands.
 *
 * The encoding and decoding functions operate on instruction buffers,
 * not on the raw bytes of the instructions. The same instruction
 * buffer data structure is used for both entire instructions and
 * individual slots in those instructions -- the contents of a slot need
 * to be extracted from or inserted into the buffer for the instruction
 * as a whole.
 *
 * Decoding an instruction involves first finding the format, which
 * identifies the number of slots, and then decoding each slot
 * separately. A slot is decoded by finding the opcode and then using
 * the opcode to determine how many operands there are. For example:
 *
 * xtensa_insnbuf_from_chars
 * xtensa_format_decode
 * for each slot {
 *   xtensa_format_get_slot
 *   xtensa_opcode_decode
 *   for each operand {
 *     xtensa_operand_get_field
 *     xtensa_operand_decode
 *   }
 * }
 *
 * Encoding an instruction is roughly the same procedure in reverse:
 *
 * xtensa_format_encode
 * for each slot {
 *   xtensa_opcode_encode
 *   for each operand {
 *     xtensa_operand_encode
 *     xtensa_operand_set_field
 *   }
 *   xtensa_format_set_slot
 * }
 * xtensa_insnbuf_to_chars
 */


/* Error handling. */

/*
 * Error codes. The code for the most recent error condition can be
 * retrieved with the "errno" function. For any result other than
 * xtensa_isa_ok, an error message containing additional information
 * about the problem can be retrieved using the "error_msg" function.
 * The error messages are stored in an internal buffer, which should
 * not be freed and may be overwritten by subsequent operations.
 */

typedef enum xtensa_isa_status_enum {
    xtensa_isa_ok = 0,
    xtensa_isa_bad_format,
    xtensa_isa_bad_slot,
    xtensa_isa_bad_opcode,
    xtensa_isa_bad_operand,
    xtensa_isa_bad_field,
    xtensa_isa_bad_iclass,
    xtensa_isa_bad_regfile,
    xtensa_isa_bad_sysreg,
    xtensa_isa_bad_state,
    xtensa_isa_bad_interface,
    xtensa_isa_bad_funcUnit,
    xtensa_isa_wrong_slot,
    xtensa_isa_no_field,
    xtensa_isa_out_of_memory,
    xtensa_isa_buffer_overflow,
    xtensa_isa_internal_error,
    xtensa_isa_bad_value
} xtensa_isa_status;

xtensa_isa_status xtensa_isa_errno(xtensa_isa isa);

char *xtensa_isa_error_msg(xtensa_isa isa);


/* Instruction buffers. */

typedef uint32_t xtensa_insnbuf_word;
typedef xtensa_insnbuf_word *xtensa_insnbuf;


/* Get the size in "insnbuf_words" of the xtensa_insnbuf array. */

int xtensa_insnbuf_size(xtensa_isa isa);


/* Allocate an xtensa_insnbuf of the right size. */

xtensa_insnbuf xtensa_insnbuf_alloc(xtensa_isa isa);


/* Release an xtensa_insnbuf. */

void xtensa_insnbuf_free(xtensa_isa isa, xtensa_insnbuf buf);


/*
 * Conversion between raw memory (char arrays) and our internal
 * instruction representation. This is complicated by the Xtensa ISA's
 * variable instruction lengths. When converting to chars, the buffer
 * must contain a valid instruction so we know how many bytes to copy;
 * thus, the "to_chars" function returns the number of bytes copied or
 * XTENSA_UNDEFINED on error. The "from_chars" function first reads the
 * minimal number of bytes required to decode the instruction length and
 * then proceeds to copy the entire instruction into the buffer; if the
 * memory does not contain a valid instruction, it copies the maximum
 * number of bytes required for the longest Xtensa instruction. The
 * "num_chars" argument may be used to limit the number of bytes that
 * can be read or written. Otherwise, if "num_chars" is zero, the
 * functions may read or write past the end of the code.
 */

int xtensa_insnbuf_to_chars(xtensa_isa isa, const xtensa_insnbuf insn,
                            unsigned char *cp, int num_chars);

void xtensa_insnbuf_from_chars(xtensa_isa isa, xtensa_insnbuf insn,
                               const unsigned char *cp, int num_chars);


/* ISA information. */

/* Initialize the ISA information. */

xtensa_isa xtensa_isa_init(void *xtensa_modules, xtensa_isa_status *errno_p,
                           char **error_msg_p);


/* Deallocate an xtensa_isa structure. */

void xtensa_isa_free(xtensa_isa isa);


/* Get the maximum instruction size in bytes. */

int xtensa_isa_maxlength(xtensa_isa isa);


/*
 * Decode the length in bytes of an instruction in raw memory (not an
 * insnbuf). This function reads only the minimal number of bytes
 * required to decode the instruction length. Returns
 * XTENSA_UNDEFINED on error.
 */

int xtensa_isa_length_from_chars(xtensa_isa isa, const unsigned char *cp);


/*
 * Get the number of stages in the processor's pipeline. The pipeline
 * stage values returned by other functions in this library will range
 * from 0 to N-1, where N is the value returned by this function.
 * Note that the stage numbers used here may not correspond to the
 * actual processor hardware, e.g., the hardware may have additional
 * stages before stage 0. Returns XTENSA_UNDEFINED on error.
 */

int xtensa_isa_num_pipe_stages(xtensa_isa isa);


/* Get the number of various entities that are defined for this processor. */

int xtensa_isa_num_formats(xtensa_isa isa);

int xtensa_isa_num_opcodes(xtensa_isa isa);

int xtensa_isa_num_regfiles(xtensa_isa isa);

int xtensa_isa_num_states(xtensa_isa isa);

int xtensa_isa_num_sysregs(xtensa_isa isa);

int xtensa_isa_num_interfaces(xtensa_isa isa);

int xtensa_isa_num_funcUnits(xtensa_isa isa);


/* Instruction formats. */

/* Get the name of a format. Returns null on error. */

const char *xtensa_format_name(xtensa_isa isa, xtensa_format fmt);


/*
 * Given a format name, return the format number. Returns
 * XTENSA_UNDEFINED if the name is not a valid format.
 */

xtensa_format xtensa_format_lookup(xtensa_isa isa, const char *fmtname);


/*
 * Decode the instruction format from a binary instruction buffer.
 * Returns XTENSA_UNDEFINED if the format is not recognized.
 */

xtensa_format xtensa_format_decode(xtensa_isa isa, const xtensa_insnbuf insn);


/*
 * Set the instruction format field(s) in a binary instruction buffer.
 * All the other fields are set to zero. Returns non-zero on error.
 */

int xtensa_format_encode(xtensa_isa isa, xtensa_format fmt,
                         xtensa_insnbuf insn);


/*
 * Find the length (in bytes) of an instruction. Returns
 * XTENSA_UNDEFINED on error.
 */

int xtensa_format_length(xtensa_isa isa, xtensa_format fmt);


/*
 * Get the number of slots in an instruction. Returns XTENSA_UNDEFINED
 * on error.
 */

int xtensa_format_num_slots(xtensa_isa isa, xtensa_format fmt);


/*
 * Get the opcode for a no-op in a particular slot.
 * Returns XTENSA_UNDEFINED on error.
 */

xtensa_opcode xtensa_format_slot_nop_opcode(xtensa_isa isa, xtensa_format fmt,
                                            int slot);


/*
 * Get the bits for a specified slot out of an insnbuf for the
 * instruction as a whole and put them into an insnbuf for that one
 * slot, and do the opposite to set a slot. Return non-zero on error.
 */

int xtensa_format_get_slot(xtensa_isa isa, xtensa_format fmt, int slot,
                           const xtensa_insnbuf insn, xtensa_insnbuf slotbuf);

int xtensa_format_set_slot(xtensa_isa isa, xtensa_format fmt, int slot,
                           xtensa_insnbuf insn, const xtensa_insnbuf slotbuf);


/* Opcode information. */

/*
 * Translate a mnemonic name to an opcode. Returns XTENSA_UNDEFINED if
 * the name is not a valid opcode mnemonic.
 */

xtensa_opcode xtensa_opcode_lookup(xtensa_isa isa, const char *opname);


/*
 * Decode the opcode for one instruction slot from a binary instruction
 * buffer. Returns the opcode or XTENSA_UNDEFINED if the opcode is
 * illegal.
 */

xtensa_opcode xtensa_opcode_decode(xtensa_isa isa, xtensa_format fmt, int slot,
                                   const xtensa_insnbuf slotbuf);


/*
 * Set the opcode field(s) for an instruction slot. All other fields
 * in the slot are set to zero. Returns non-zero if the opcode cannot
 * be encoded.
 */

int xtensa_opcode_encode(xtensa_isa isa, xtensa_format fmt, int slot,
                         xtensa_insnbuf slotbuf, xtensa_opcode opc);


/* Get the mnemonic name for an opcode. Returns null on error. */

const char *xtensa_opcode_name(xtensa_isa isa, xtensa_opcode opc);


/* Check various properties of opcodes. These functions return 0 if
 * the condition is false, 1 if the condition is true, and
 * XTENSA_UNDEFINED on error. The instructions are classified as
 * follows:
 *
 * branch: conditional branch; may fall through to next instruction (B*)
 * jump: unconditional branch (J, JX, RET*, RF*)
 * loop: zero-overhead loop (LOOP*)
 * call: unconditional call; control returns to next instruction (CALL*)
 *
 * For the opcodes that affect control flow in some way, the branch
 * target may be specified by an immediate operand or it may be an
 * address stored in a register. You can distinguish these by
 * checking if the instruction has a PC-relative immediate
 * operand.
 */

int xtensa_opcode_is_branch(xtensa_isa isa, xtensa_opcode opc);

int xtensa_opcode_is_jump(xtensa_isa isa, xtensa_opcode opc);

int xtensa_opcode_is_loop(xtensa_isa isa, xtensa_opcode opc);

int xtensa_opcode_is_call(xtensa_isa isa, xtensa_opcode opc);


/*
 * Find the number of ordinary operands, state operands, and interface
 * operands for an instruction. These return XTENSA_UNDEFINED on
 * error.
 */

int xtensa_opcode_num_operands(xtensa_isa isa, xtensa_opcode opc);

int xtensa_opcode_num_stateOperands(xtensa_isa isa, xtensa_opcode opc);

int xtensa_opcode_num_interfaceOperands(xtensa_isa isa, xtensa_opcode opc);


/*
 * Get functional unit usage requirements for an opcode. Each "use"
 * is identified by a <functional unit, pipeline stage> pair. The
 * "num_funcUnit_uses" function returns the number of these "uses" or
 * XTENSA_UNDEFINED on error. The "funcUnit_use" function returns
 * a pointer to a "use" pair or null on error.
 */

typedef struct xtensa_funcUnit_use_struct {
    xtensa_funcUnit unit;
    int stage;
} xtensa_funcUnit_use;

int xtensa_opcode_num_funcUnit_uses(xtensa_isa isa, xtensa_opcode opc);

xtensa_funcUnit_use *xtensa_opcode_funcUnit_use(xtensa_isa isa,
                                                xtensa_opcode opc, int u);


/* Operand information. */

/* Get the name of an operand. Returns null on error. */

const char *xtensa_operand_name(xtensa_isa isa, xtensa_opcode opc, int opnd);


/*
 * Some operands are "invisible", i.e., not explicitly specified in
 * assembly language. When assembling an instruction, you need not set
 * the values of invisible operands, since they are either hardwired or
 * derived from other field values. The values of invisible operands
 * can be examined in the same way as other operands, but remember that
 * an invisible operand may get its value from another visible one, so
 * the entire instruction must be available before examining the
 * invisible operand values. This function returns 1 if an operand is
 * visible, 0 if it is invisible, or XTENSA_UNDEFINED on error. Note
 * that whether an operand is visible is orthogonal to whether it is
 * "implicit", i.e., whether it is encoded in a field in the
 * instruction.
 */

int xtensa_operand_is_visible(xtensa_isa isa, xtensa_opcode opc, int opnd);


/*
 * Check if an operand is an input ('i'), output ('o'), or inout ('m')
 * operand. Note: The output operand of a conditional assignment
 * (e.g., movnez) appears here as an inout ('m') even if it is declared
 * in the TIE code as an output ('o'); this allows the compiler to
 * properly handle register allocation for conditional assignments.
 * Returns 0 on error.
 */

char xtensa_operand_inout(xtensa_isa isa, xtensa_opcode opc, int opnd);


/*
 * Get and set the raw (encoded) value of the field for the specified
 * operand. The "set" function does not check if the value fits in the
 * field; that is done by the "encode" function below. Both of these
 * functions return non-zero on error, e.g., if the field is not defined
 * for the specified slot.
 */

int xtensa_operand_get_field(xtensa_isa isa, xtensa_opcode opc, int opnd,
                             xtensa_format fmt, int slot,
                             const xtensa_insnbuf slotbuf, uint32_t *valp);

int xtensa_operand_set_field(xtensa_isa isa, xtensa_opcode opc, int opnd,
                             xtensa_format fmt, int slot,
                             xtensa_insnbuf slotbuf, uint32_t val);


/*
 * Encode and decode operands. The raw bits in the operand field may
 * be encoded in a variety of different ways. These functions hide
 * the details of that encoding. The result values are returned through
 * the argument pointer. The return value is non-zero on error.
 */

int xtensa_operand_encode(xtensa_isa isa, xtensa_opcode opc, int opnd,
                          uint32_t *valp);

int xtensa_operand_decode(xtensa_isa isa, xtensa_opcode opc, int opnd,
                          uint32_t *valp);


/*
 * An operand may be either a register operand or an immediate of some
 * sort (e.g., PC-relative or not). The "is_register" function returns
 * 0 if the operand is an immediate, 1 if it is a register, and
 * XTENSA_UNDEFINED on error. The "regfile" function returns the
 * regfile for a register operand, or XTENSA_UNDEFINED on error.
 */

int xtensa_operand_is_register(xtensa_isa isa, xtensa_opcode opc, int opnd);

xtensa_regfile xtensa_operand_regfile(xtensa_isa isa, xtensa_opcode opc,
                                      int opnd);


/*
 * Register operands may span multiple consecutive registers, e.g., a
 * 64-bit data type may occupy two 32-bit registers. Only the first
 * register is encoded in the operand field. This function specifies
 * the number of consecutive registers occupied by this operand. For
 * non-register operands, the return value is undefined. Returns
 * XTENSA_UNDEFINED on error.
 */

int xtensa_operand_num_regs(xtensa_isa isa, xtensa_opcode opc, int opnd);


/*
 * Some register operands do not completely identify the register being
 * accessed. For example, the operand value may be added to an internal
 * state value. By definition, this implies that the corresponding
 * regfile is not allocatable. Unknown registers should generally be
 * treated with worst-case assumptions. The function returns 0 if the
 * register value is unknown, 1 if known, and XTENSA_UNDEFINED on
 * error.
 */

int xtensa_operand_is_known_reg(xtensa_isa isa, xtensa_opcode opc, int opnd);


/*
 * Check if an immediate operand is PC-relative. Returns 0 for register
 * operands and non-PC-relative immediates, 1 for PC-relative
 * immediates, and XTENSA_UNDEFINED on error.
 */

int xtensa_operand_is_PCrelative(xtensa_isa isa, xtensa_opcode opc, int opnd);


/*
 * For PC-relative offset operands, the interpretation of the offset may
 * vary between opcodes, e.g., is it relative to the current PC or that
 * of the next instruction?  The following functions are defined to
 * perform PC-relative relocations and to undo them (as in the
 * disassembler). The "do_reloc" function takes the desired address
 * value and the PC of the current instruction and sets the value to the
 * corresponding PC-relative offset (which can then be encoded and
 * stored into the operand field). The "undo_reloc" function takes the
 * unencoded offset value and the current PC and sets the value to the
 * appropriate address. The return values are non-zero on error. Note
 * that these functions do not replace the encode/decode functions; the
 * operands must be encoded/decoded separately and the encode functions
 * are responsible for detecting invalid operand values.
 */

int xtensa_operand_do_reloc(xtensa_isa isa, xtensa_opcode opc, int opnd,
                            uint32_t *valp, uint32_t pc);

int xtensa_operand_undo_reloc(xtensa_isa isa, xtensa_opcode opc, int opnd,
                              uint32_t *valp, uint32_t pc);


/* State Operands. */

/*
 * Get the state accessed by a state operand. Returns XTENSA_UNDEFINED
 * on error.
 */

xtensa_state xtensa_stateOperand_state(xtensa_isa isa, xtensa_opcode opc,
                                       int stOp);


/*
 * Check if a state operand is an input ('i'), output ('o'), or inout
 * ('m') operand. Returns 0 on error.
 */

char xtensa_stateOperand_inout(xtensa_isa isa, xtensa_opcode opc, int stOp);


/* Interface Operands. */

/*
 * Get the external interface accessed by an interface operand.
 * Returns XTENSA_UNDEFINED on error.
 */

xtensa_interface xtensa_interfaceOperand_interface(xtensa_isa isa,
                                                   xtensa_opcode opc,
                                                   int ifOp);


/* Register Files. */

/*
 * Regfiles include both "real" regfiles and "views", where a view
 * allows a group of adjacent registers in a real "parent" regfile to be
 * viewed as a single register. A regfile view has all the same
 * properties as its parent except for its (long) name, bit width, number
 * of entries, and default ctype. You can use the parent function to
 * distinguish these two classes.
 */

/*
 * Look up a regfile by either its name or its abbreviated "short name".
 * Returns XTENSA_UNDEFINED on error. The "lookup_shortname" function
 * ignores "view" regfiles since they always have the same shortname as
 * their parents.
 */

xtensa_regfile xtensa_regfile_lookup(xtensa_isa isa, const char *name);

xtensa_regfile xtensa_regfile_lookup_shortname(xtensa_isa isa,
                                               const char *shortname);


/*
 * Get the name or abbreviated "short name" of a regfile.
 * Returns null on error.
 */

const char *xtensa_regfile_name(xtensa_isa isa, xtensa_regfile rf);

const char *xtensa_regfile_shortname(xtensa_isa isa, xtensa_regfile rf);


/*
 * Get the parent regfile of a "view" regfile. If the regfile is not a
 * view, the result is the same as the input parameter. Returns
 * XTENSA_UNDEFINED on error.
 */

xtensa_regfile xtensa_regfile_view_parent(xtensa_isa isa, xtensa_regfile rf);


/*
 * Get the bit width of a regfile or regfile view.
 * Returns XTENSA_UNDEFINED on error.
 */

int xtensa_regfile_num_bits(xtensa_isa isa, xtensa_regfile rf);


/*
 * Get the number of regfile entries. Returns XTENSA_UNDEFINED on
 * error.
 */

int xtensa_regfile_num_entries(xtensa_isa isa, xtensa_regfile rf);


/* Processor States. */

/* Look up a state by name. Returns XTENSA_UNDEFINED on error. */

xtensa_state xtensa_state_lookup(xtensa_isa isa, const char *name);


/* Get the name for a processor state. Returns null on error. */

const char *xtensa_state_name(xtensa_isa isa, xtensa_state st);


/*
 * Get the bit width for a processor state.
 * Returns XTENSA_UNDEFINED on error.
 */

int xtensa_state_num_bits(xtensa_isa isa, xtensa_state st);


/*
 * Check if a state is exported from the processor core. Returns 0 if
 * the condition is false, 1 if the condition is true, and
 * XTENSA_UNDEFINED on error.
 */

int xtensa_state_is_exported(xtensa_isa isa, xtensa_state st);


/*
 * Check for a "shared_or" state. Returns 0 if the condition is false,
 * 1 if the condition is true, and XTENSA_UNDEFINED on error.
 */

int xtensa_state_is_shared_or(xtensa_isa isa, xtensa_state st);


/* Sysregs ("special registers" and "user registers"). */

/*
 * Look up a register by its number and whether it is a "user register"
 * or a "special register". Returns XTENSA_UNDEFINED if the sysreg does
 * not exist.
 */

xtensa_sysreg xtensa_sysreg_lookup(xtensa_isa isa, int num, int is_user);


/*
 * Check if there exists a sysreg with a given name.
 * If not, this function returns XTENSA_UNDEFINED.
 */

xtensa_sysreg xtensa_sysreg_lookup_name(xtensa_isa isa, const char *name);


/* Get the name of a sysreg. Returns null on error. */

const char *xtensa_sysreg_name(xtensa_isa isa, xtensa_sysreg sysreg);


/* Get the register number. Returns XTENSA_UNDEFINED on error. */

int xtensa_sysreg_number(xtensa_isa isa, xtensa_sysreg sysreg);


/*
 * Check if a sysreg is a "special register" or a "user register".
 * Returns 0 for special registers, 1 for user registers and
 * XTENSA_UNDEFINED on error.
 */

int xtensa_sysreg_is_user(xtensa_isa isa, xtensa_sysreg sysreg);


/* Interfaces. */

/*
 * Find an interface by name. The return value is XTENSA_UNDEFINED if
 * the specified interface is not found.
 */

xtensa_interface xtensa_interface_lookup(xtensa_isa isa, const char *ifname);


/* Get the name of an interface. Returns null on error. */

const char *xtensa_interface_name(xtensa_isa isa, xtensa_interface intf);


/*
 * Get the bit width for an interface.
 * Returns XTENSA_UNDEFINED on error.
 */

int xtensa_interface_num_bits(xtensa_isa isa, xtensa_interface intf);


/*
 * Check if an interface is an input ('i') or output ('o') with respect
 * to the Xtensa processor core. Returns 0 on error.
 */

char xtensa_interface_inout(xtensa_isa isa, xtensa_interface intf);


/*
 * Check if accessing an interface has potential side effects.
 * Currently "data" interfaces have side effects and "control"
 * interfaces do not. Returns 1 if there are side effects, 0 if not,
 * and XTENSA_UNDEFINED on error.
 */

int xtensa_interface_has_side_effect(xtensa_isa isa, xtensa_interface intf);


/*
 * Some interfaces may be related such that accessing one interface
 * has side effects on a set of related interfaces. The interfaces
 * are partitioned into equivalence classes of related interfaces, and
 * each class is assigned a unique identifier number. This function
 * returns the class identifier for an interface, or XTENSA_UNDEFINED
 * on error. These identifiers can be compared to determine if two
 * interfaces are related; the specific values of the identifiers have
 * no particular meaning otherwise.
 */

int xtensa_interface_class_id(xtensa_isa isa, xtensa_interface intf);


/* Functional Units. */

/*
 * Find a functional unit by name. The return value is XTENSA_UNDEFINED if
 * the specified unit is not found.
 */

xtensa_funcUnit xtensa_funcUnit_lookup(xtensa_isa isa, const char *fname);


/* Get the name of a functional unit. Returns null on error. */

const char *xtensa_funcUnit_name(xtensa_isa isa, xtensa_funcUnit fun);


/*
 * Functional units may be replicated. See how many instances of a
 * particular function unit exist. Returns XTENSA_UNDEFINED on error.
 */

int xtensa_funcUnit_num_copies(xtensa_isa isa, xtensa_funcUnit fun);


#ifdef __cplusplus
}
#endif
#endif /* XTENSA_LIBISA_H */