ircons.h 71.3 KB
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/*
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 * Copyright (C) 1995-2010 University of Karlsruhe.  All right reserved.
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 *
 * This file is part of libFirm.
 *
 * This file may be distributed and/or modified under the terms of the
 * GNU General Public License version 2 as published by the Free Software
 * Foundation and appearing in the file LICENSE.GPL included in the
 * packaging of this file.
 *
 * Licensees holding valid libFirm Professional Edition licenses may use
 * this file in accordance with the libFirm Commercial License.
 * Agreement provided with the Software.
 *
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE.
 */

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/**
 * @file
 * @brief   Various irnode constructors. Automatic construction of SSA
 *          representation.
 * @author  Martin Trapp, Christian Schaefer, Goetz Lindenmaier, Boris Boesler,
 *          Michael Beck
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 */
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/**
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 *  @file
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 *
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 *  documentation no more supported since 2001
 *
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 *  IR node construction.
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 *
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 *    This file documents all datatypes and constructors needed to
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 *    build a FIRM representation of a procedure.  The constructors are
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 *    also implemented in this file.
 *
 *    The documentation also gives a short manual how to use the library.
 *
 *    For extensive documentation of FIRM see UKA Techreport 1999-14.
 *
 *
 *    Three kinds of nodes
 *    --------------------
 *
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 *      There are three kinds of nodes known to the IR:  entities,
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 *      types, and ir_nodes
 *
 *      + ir_nodes are the actual nodes of the FIRM intermediate representation.
 *        They represent operations on the data of the program and control flow
 *        operations.
 *
 *      + entity ==> implemented in entity.h
 *        Refers to a single entity of the compiled program, e.g. a field of a
 *        class or a method.  If a method or variable can not be assigned to
 *        a method or class or the like, it is a global object.
 *
 *      + types ==> implemented in type.h
 *        With types type information is represented.  There are several type
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 *       nodes.
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 *
 *    Implementation of the FIRM operations: ir_node
 *    ----------------------------------------------
 *
 *      Ir_nodes represent operations on the data of the program and control flow
 *      operations.  Examples of ir_nodes:  Add, Jmp, Cmp
 *
 *      FIRM is a dataflow graph.  A dataflow graph is a directed graph,
 *      so that every node has incoming and outgoing edges.  A node is
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 *      executable if every input at its incoming edges is available.
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 *      Execution of the dataflow graph is started at the Start node which
 *      has no incoming edges and ends when the End node executes, even if
 *      there are still executable or not executed nodes.  (Is this true,
 *      or must all executable nodes be executed?)  (There are exceptions
 *      to the dataflow paradigma that all inputs have to be available
 *      before a node can execute: Phi, Block.  See UKA Techreport
 *      1999-14.)
 *
 *      The implementation of FIRM differs from the view as a dataflow
 *      graph.  To allow fast traversion of the graph edges are
 *      implemented as C-pointers.  Inputs to nodes are not ambiguous, the
 *      results can be used by several other nodes.  Each input can be
 *      implemented as a single pointer to a predecessor node, outputs
 *      need to be lists of pointers to successors.  Therefore a node
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 *      contains pointers to its predecessors so that the implementation is a
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 *      dataflow graph with reversed edges.  It has to be traversed bottom
 *      up.
 *
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 *      All nodes of the IR have the same basic structure.  They are
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 *      distinguished by a field containing the opcode.
 *
 *      The fields of an ir_node:
 *
 *      kind             A firm_kind tag containing k_ir_node.  This is useful for
 *                       dynamically checking the type of a node.
 *
 *      *op              This ir_op gives the opcode as a tag and a string
 *                       and the number of attributes of an ir_node.  There is
 *                       one statically allocated struct ir_op for each opcode.
 *
 *      *mode            The ir_mode of the operation represented by this firm
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 *                       node.  The mode of the operation is the mode of its
 *                       result.  A Firm mode is a datatype as known to the
 *                       target, not a type of the source language.
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 *
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 *      visit            A flag for traversing the IR.
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 *
 *      **in             An array with pointers to the node's predecessors.
 *
 *      *link            A pointer to an ir_node.  With this pointer all Phi nodes
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 *                       are attached to a Block, i.e. a Block points to its
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 *                       first Phi node, this node points to the second Phi node
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 *                       in the Block and so forth.  Used in mature_immBlock
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 *                       to find all Phi nodes to be matured.  It's also used to
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 *                       annotate a node with a better, optimized version of it.
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 *
 *      attr             An attr struct containing the attributes of the nodes. The
 *                       attributes depend on the opcode of the node.  The number
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 *                       of these attributes is given in op.
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 *
 *    The struct ir_op
 *    ----------------
 *                       Not yet documented. See irop.h.
 *
 *    The struct ir_mode
 *    ------------------
 *                       Not yet documented. See irmode.h.
 *
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 *    GLOBAL VARIABLES -- now also fields of ir_graph.
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 *    ================
 *
 *    current_ir_graph   Points to the current ir_graph.  All constructors for
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 *                       nodes add nodes to this graph.
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 *
 *    ir_visited         An int used as flag to traverse the ir_graph.
 *
 *    block_visited      An int used as a flag to traverse block nodes in the
 *                       graph.
 *
 *                       Others not yet documented.
 *
 *
 *
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 *    CONSTRUCTOR FOR IR_GRAPH --> see irgraph.h
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 *    ========================
 *
 *
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 *    PROCEDURE TO CONSTRUCT AN IR GRAPH --> see also Firm tutorial
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 *    ==================================
 *
 *    This library supplies several interfaces to construct a FIRM graph for
 *    a program:
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 *    - A "comfortable" interface generating SSA automatically.  Automatically
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 *      computed predecessors of nodes need not be specified in the constructors.
 *      (new_<Node> constructurs and a set of additional routines.)
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 *    - A less comfortable interface where all predecessors except the block
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 *      an operation belongs to need to be specified.  SSA must be constructed
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 *      by hand.  (new_<Node> constructors and set_cur_block()).  This interface
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 *      is called "block oriented".  It automatically calles the local optimizations
 *      for each new node.
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 *    - An even less comfortable interface where the block needs to be specified
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 *      explicitly.  This is called the "raw" interface. (new_r_<Node>
 *      constructors).  These nodes are not optimized.
 *
 *    To use the functionality of the comfortable interface correctly the Front
 *    End needs to follow certain protocols.  This is explained in the following.
 *    To build a correct IR with the other interfaces study the semantics of
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 *    the firm node (See tech-reprot UKA 1999-14).  For the construction of
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 *    types and entities see the documentation in those modules.
 *
 *    First the Frontend needs to decide which variables and values used in
 *    a procedure can be represented by dataflow edges.  These are variables
 *    that need not be saved to memory as they cause no side effects visible
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 *    out of the procedure.  Often these are all compiler generated
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 *    variables and simple local variables of the procedure as integers,
 *    reals and pointers.  The frontend has to count and number these variables.
 *
 *    First an ir_graph needs to be constructed with new_ir_graph.  The
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 *    constructor gets the number of local variables.  The graph is held in the
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 *    global variable irg.
 *
 *    Now the construction of the procedure can start.  Several basic blocks can
 *    be constructed in parallel, but the code within each block needs to
 *    be constructed (almost) in program order.
 *
 *    A global variable holds the current basic block.  All (non block) nodes
 *    generated are added to this block.  The current block can be set with
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 *    set_cur_block(block).  If several blocks are constructed in parallel block
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 *    switches need to be performed constantly.
 *
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 *    To generate a Block node (with the comfortable interface), its predecessor
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 *    control flow nodes need not be known.  In case of cyclic control flow these
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 *    can not be known when the block is constructed.  With add_immBlock_pred(block,
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 *    cfnode) predecessors can be added to the block.  If all predecessors are
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 *    added to the block mature_immBlock(b) needs to be called.  Calling mature_immBlock
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 *    early improves the efficiency of the Phi node construction algorithm.
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 *    But if several  blocks are constructed at once, mature_immBlock must only
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 *    be called after performing all set_values and set_stores in the block!
 *    (See documentation of new_immBlock constructor.)
 *
 *    The constructors of arithmetic nodes require that their predecessors
 *    are mentioned.  Sometimes these are available in the Frontend as the
 *    predecessors have just been generated by the frontend.  If they are local
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 *    values, the predecessors can be obtained from the library with a call to
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 *    get_value(local_val_nr).  (local_val_nr needs to be administered by
 *    the Frontend.)  A call to get_value triggers the generation of Phi nodes.
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 *    If an arithmetic operation produces a local value, this value needs to be
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 *    passed to the library by set_value(node, local_val_nr).
 *    In straight line code these two operations just remember and return the
 *    pointer to nodes producing the value.  If the value passes block boundaries
 *    Phi nodes can be inserted.
 *    Similar routines exist to manage the Memory operands: set_store and
 *    get_store.
 *
 *    Several nodes produce more than one result.  An example is the Div node.
 *    Such nodes return tuples of values.  From these individual values can be
 *    extracted by proj nodes.
 *
 *    The following example illustrates the construction of a simple basic block
 *    with two predecessors stored in variables cf_pred1 and cf_pred2, containing
 *    the code
 *      a = a div a;
 *    and finally jumping to an other block.  The variable a got the local_val_nr
 *    42 by the frontend.
 *
 *    ir_node *this_block, *cf_pred1, *cf_pred2, *a_val, *mem, *div, *res, *cf_op;
 *
 *    this_block = new_immBlock();
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 *    add_immBlock_pred(this_block, cf_pred1);
 *    add_immBlock_pred(this_block, cf_pred2);
 *    mature_immBlock(this_block);
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 *    a_val = get_value(42, mode_Iu);
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 *    mem = get_store();
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 *    div = new_Div(mem, a_val, a_val, mode_Iu);
 *    mem = new_Proj(div, mode_M, pn_Div_M);   * for the numbers for Proj see docu *
 *    res = new_Proj(div, mode_Iu, pn_Div_res);
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 *    set_store(mem);
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 *    set_value(res, 42);
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 *    cf_op = new_Jmp();
 *
 *    For further information look at the documentation of the nodes and
 *    constructors and at the paragraph COPING WITH DATA OBJECTS at the
 *    end of this documentation.
 *
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 *    The comfortable interface contains the following routines further explained
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 *    below:
 *
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 *    ir_node *new_immBlock (void);
 *    ir_node *new_Start    (void);
 *    ir_node *new_End      (void);
 *    ir_node *new_Jmp      (void);
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 *    ir_node *new_IJmp     (ir_node *tgt);
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 *    ir_node *new_Cond     (ir_node *c);
 *    ir_node *new_Return   (ir_node *store, int arity, ir_node **in);
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 *    ir_node *new_Const    (ir_tarval *con);
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 *    ir_node *new_SymConst (ir_mode *mode, symconst_symbol value, symconst_kind kind);
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 *    ir_node *new_simpleSel (ir_node *store, ir_node *objptr, ir_entity *ent);
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 *    ir_node *new_Sel    (ir_node *store, ir_node *objptr, int arity,
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 *                         ir_node **in, ir_entity *ent);
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 *    ir_node *new_Call   (ir_node *store, ir_node *callee, int arity,
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 *                         ir_node **in, type_method *type);
 *    ir_node *new_Builtin(ir_node *store, ir_builtin_kind kind, int arity,
 *                         ir_node **in, type_method *type);
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 *    ir_node *new_Add    (ir_node *op1, ir_node *op2, ir_mode *mode);
 *    ir_node *new_Sub    (ir_node *op1, ir_node *op2, ir_mode *mode);
 *    ir_node *new_Minus  (ir_node *op,  ir_mode *mode);
 *    ir_node *new_Mul    (ir_node *op1, ir_node *op2, ir_mode *mode);
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 *    ir_node *new_Mulh   (ir_node *op1, ir_node *op2, ir_mode *mode);
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 *    ir_node *new_Div    (ir_node *memop, ir_node *op1, ir_node *op2, ir_mode *mode, op_pin_state state);
 *    ir_node *new_Mod    (ir_node *memop, ir_node *op1, ir_node *op2, ir_mode *mode, op_pin_state state;
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 *    ir_node *new_And    (ir_node *op1, ir_node *op2, ir_mode *mode);
 *    ir_node *new_Or     (ir_node *op1, ir_node *op2, ir_mode *mode);
 *    ir_node *new_Eor    (ir_node *op1, ir_node *op2, ir_mode *mode);
 *    ir_node *new_Not    (ir_node *op,                ir_mode *mode);
 *    ir_node *new_Shl    (ir_node *op,  ir_node *k,   ir_mode *mode);
 *    ir_node *new_Shr    (ir_node *op,  ir_node *k,   ir_mode *mode);
 *    ir_node *new_Shrs   (ir_node *op,  ir_node *k,   ir_mode *mode);
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 *    ir_node *new_Rotl   (ir_node *op,  ir_node *k,   ir_mode *mode);
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 *    ir_node *new_Cmp    (ir_node *op1, ir_node *op2);
 *    ir_node *new_Conv   (ir_node *op, ir_mode *mode);
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 *    ir_node *new_Cast   (ir_node *op, ir_type *to_tp);
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 *    ir_node *new_Carry  (ir_node *op1, ir_node *op2, ir_mode *mode);
 *    ir_node *new_Borrow (ir_node *op1, ir_node *op2, ir_mode *mode);
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 *    ir_node *new_Load   (ir_node *store, ir_node *addr, ir_mode *mode, ir_cons_flags flags);
 *    ir_node *new_Store  (ir_node *store, ir_node *addr, ir_node *val, ir_cons_flags flags);
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 *    ir_node *new_Alloc  (ir_node *store, ir_node *count, ir_type *alloc_type,
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 *                         where_alloc where);
 *    ir_node *new_Free   (ir_node *store, ir_node *ptr, ir_node *size,
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 *               ir_type *free_type, where_alloc where);
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 *    ir_node *new_Proj   (ir_node *arg, ir_mode *mode, long proj);
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 *    ir_node *new_NoMem  (void);
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 *    ir_node *new_Mux    (ir_node *sel, ir_node *ir_false, ir_node *ir_true, ir_mode *mode);
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 *    ir_node *new_CopyB  (ir_node *store, ir_node *dst, ir_node *src, ir_type *data_type);
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 *    ir_node *new_InstOf (ir_node *store, ir_node obj, ir_type *ent);
 *    ir_node *new_Raise  (ir_node *store, ir_node *obj);
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 *    ir_node *new_Bound  (ir_node *store, ir_node *idx, ir_node *lower, ir_node *upper);
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 *    ir_node *new_Pin    (ir_node *node);
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 *
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 *    void add_immBlock_pred (ir_node *block, ir_node *jmp);
 *    void mature_immBlock (ir_node *block);
 *    void set_cur_block (ir_node *target);
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 *    ir_node *get_value (int pos, ir_mode *mode);
 *    void set_value (int pos, ir_node *value);
 *    ir_node *get_store (void);
 *    void set_store (ir_node *store);
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 *    keep_alive (ir_node ka)
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 *
 *    IR_NODES AND CONSTRUCTORS FOR IR_NODES
 *    =======================================
 *
 *    All ir_nodes are defined by a common data structure.  They are distinguished
 *    by their opcode and differ in the number of their attributes.
 *
 *    Const nodes are always added to the start block.
 *    All other constructors add the created node to the current_block.
 *    swich_block(block) allows to set the current block to block.
 *
 *    Watch for my inconsistent use of input and predecessor (dataflow view)
 *    and `the node points to' (implementation view).
 *
 *    The following description of the nodes lists four properties them if these
 *    are of interest:
 *     - the parameters to the constructor
 *     - the inputs of the Firm node
 *     - the outputs of the Firm node
 *     - attributes to the node
 *
 *    ------------
 *
 *    ir_node *new_immBlock (void)
 *    ----------------------------
 *
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 *    Creates a new block. When a new block is created it cannot be known how
 *    many predecessors this block will have in the control flow graph.
 *    Therefore the list of inputs can not be fixed at creation.  Predecessors
 *    can be added with add_immBlock_pred (block, control flow operation).
 *    With every added predecessor the number of inputs to Phi nodes also
 *    changes.
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 *
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 *    The block can be completed by mature_immBlock(block) if all predecessors are
 *    known.  If several blocks are built at once, mature_immBlock can only be called
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 *    after set_value has been called for all values that are life at the end
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 *    of the block.  This is necessary so that Phi nodes created mature_immBlock
 *    get the right predecessors in case of cyclic dependencies.  If all set_values
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 *    of this block are called after maturing it and before calling get_value
 *    in some block that is control flow dependent on this block, the construction
 *    is correct.
 *
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 *    Example for faulty IR construction:  (draw the graph on a paper and you'll
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 *                                          get it ;-)
 *
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 *      block_before_loop = new_immBlock();
 *      set_cur_block(block_before_loop);
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 *      set_value(x);
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 *      mature_immBlock(block_before_loop);
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 *      before2header = new_Jmp;
 *
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 *      loop_header = new_immBlock ();
 *      set_cur_block(loop_header);
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 *      header2body - new_Jmp();
 *
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 *      loop_body = new_immBlock ();
 *      set_cur_block(loop_body);
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 *      body2header = new_Jmp();
 *
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 *      add_immBlock_pred(loop_header, before2header);
 *      add_immBlock_pred(loop_header, body2header);
 *      add_immBlock_pred(loop_body, header2body);
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 *
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 *      mature_immBlock(loop_header);
 *      mature_immBlock(loop_body);
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 *
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 *      get_value(loop_body, x);   //  gets the Phi in loop_header
 *      set_value(loop_header, x); //  sets the value the above get_value should
 *                                 //  have returned!!!
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 *
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 *    Mature_immBlock also fixes the number of inputs to the Phi nodes.  Mature_immBlock
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 *    should be called as early as possible, as afterwards the generation of Phi
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 *    nodes is more efficient.
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 *
 *    Inputs:
 *      There is an input for each control flow predecessor of the block.
 *      The input points to an instruction producing an output of type X.
 *      Possible predecessors:  Start, Jmp, Cond, Raise or Return or any node
 *      possibly causing an exception.  (Often the real predecessors are Projs.)
 *    Output:
 *      Mode BB (R), all nodes belonging to this block should consume this output.
 *      As they are strict (except Block and Phi node) it is a necessary condition
 *      that the block node executed before any other node in this block executes.
 *    Attributes:
 *      block.matured  Indicates whether the block is mature.
 *      block.**graph_arr
 *                      This attribute contains all local values valid in this
 *                      block. This is needed to build the Phi nodes and removed
 *                      if the graph is complete.  This field is used by the
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 *              internal construction algorithm and should not be accessed
 *              from outside.
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 *
 *
 *    ir_node *new_Block (int arity, ir_node **in)
 *    --------------------------------------------
 *
 *    Creates a new Block with the given list of predecessors.  This block
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 *    is mature.  As other constructors calls optimization and verify for the
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 *    block.  If one of the predecessors is Unknown (as it has to be filled in
 *    later) optimizations are skipped.  This is necessary to
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 *    construct Blocks in loops.
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 *
 *
 *    CONTROL FLOW OPERATIONS
 *    -----------------------
 *
 *    In each block there must be exactly one of the control flow
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 *    operations Start, End, Jmp, Cond, Return or Raise.  The output of a
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 *    control flow operation points to the block to be executed next.
 *
 *    ir_node *new_Start (void)
 *    -------------------------
 *
 *    Creates a start node.  Not actually needed public.  There is only one such
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 *   node in each procedure which is automatically created by new_ir_graph.
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 *
 *    Inputs:
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 *      No inputs except the block it belongs to.
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 *    Output:
 *      A tuple of 4 (5, 6) distinct values. These are labeled by the following
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 *      projection numbers (pn_Start):
 *      * pn_Start_X_initial_exec    mode X, points to the first block to be exe *                                   cuted.
 *      * pn_Start_M                 mode M, the global store
 *      * pn_Start_P_frame_base      mode P, a pointer to the base of the proce  *                                   dures stack frame.
 *      * pn_Start_P_globals         mode P, a pointer to the part of the memory *                                   containing_all_ global things.
 *      * pn_Start_T_args            mode T, a tuple containing all arguments of *                                   the procedure.
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 *
 *
 *    ir_node *new_End (void)
 *    -----------------------
 *
 *    Creates an end node.  Not actually needed public.  There is only one such
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 *   node in each procedure which is automatically created by new_ir_graph.
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 *
 *    Inputs:
 *      No inputs except the block it belongs to.
 *    Output:
 *      No output.
 *
 *    ir_node *new_Jmp (void)
 *    -----------------------
 *
 *    Creates a Jmp node.
 *
 *    Inputs:
 *      The block the node belongs to
 *    Output:
 *      Control flow to the next block.
 *
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 *    ir_node *new_IJmp (ir_node *tgt)
 *    -----------------------
 *
 *    Creates an IJmp node.
 *
 *    Inputs:
 *      The node that represents the target jump address
 *    Output:
 *      Control flow to an unknown target, must be pinned by
 *      the End node.
 *
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 *    ir_node *new_Cond (ir_node *c)
 *    ------------------------------
 *
 *    Creates a Cond node.  There are two versions of this node.
 *
 *    The Boolean Cond:
 *    Input:
 *      A value of mode b.
 *    Output:
 *      A tuple of two control flows.  The first is taken if the input is
 *      false, the second if it is true.
 *
 *    The Switch Cond:
 *    Input:
 *      A value of mode I_u. (i)
 *    Output:
 *      A tuple of n control flows.  If the Cond's input is i, control
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 *      flow will proceed along output i. If the input is >= n control
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 *      flow proceeds along output n.
 *
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 *    ir_node *new_Return (ir_node *store, int arity, ir_node **in)
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 *    -------------------------------------------------------------
 *
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 *    The Return node has as inputs the results of the procedure.  It
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 *    passes the control flow to the end_block.
 *
 *    Inputs:
 *      The memory state.
 *      All results.
 *    Output
 *      Control flow to the end block.
 *
 *
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 *    ir_node *new_Const (ir_tarval *con)
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 *    -----------------------------------------------
 *
 *    Creates a constant in the constant table and adds a Const node
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 *    returning this value to the start block. The mode is derived
 *    from the tarval.
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 *
 *    Parameters:
 *      *con             Points to an entry in the constant table.
 *                       This pointer is added to the attributes of
 *                       the node (self->attr.con)
 *    Inputs:
 *      No inputs except the block it belogns to.
 *    Output:
 *      The constant value.
 *    Attribute:
 *      attr.con   A tarval* pointer to the proper entry in the constant
 *                 table.
 *
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 *    ir_node *new_SymConst (ir_mode *mode, union symconst_symbol value, symconst_addr_ent kind)
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 *    -----------------------------------------------------------------------------------------
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 *
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 *    There are several symbolic constants:
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 *     symconst_type_size  The symbolic constant represents the size of a type.
 *     symconst_type_align The symbolic constant represents the alignment of a type.
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 *     symconst_addr_ent   The symbolic constant represents the address of an entity.
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 *     symconst_ofs_ent    The symbolic constant represents the offset of an
 *                         entity in its owner type.
 *     symconst_enum_const The symbolic constant is a enumeration constant of an
 *                         enumeration type.
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 *
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 *    Parameters
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 *      mode        P for SymConsts representing addresses, Iu otherwise.
 *      value       The type, ident, entity or enum constant, depending on the
 *                  kind
 *      kind        The kind of the symbolic constant, see the list above.
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 *
 *    Inputs:
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 *      No inputs except the block it belongs to.
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 *    Output:
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 *      A symbolic constant.
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 *
 *    Attributes:
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 *      attr.i.num       The symconst_addr_ent, i.e. one of
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 *                        -symconst_type_size
 *                        -symconst_type_align
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 *                        -symconst_addr_ent
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 *
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 *    If the attr.i.num is symconst_type_size or symconst_type_align,
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 *    the node contains an attribute:
 *
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 *      attr.i.*type,    a pointer to a type_class.
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 *        if it is linkage_ptr_info it contains
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 *      attr.i.*ptrinfo,  an ident holding information for the linker.
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 *
 *    ---------------
 *
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 *    ir_node *new_simpleSel (ir_node *store, ir_node *frame, ir_entity *sel)
 *    -----------------------------------------------------------------------
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 *
 *
 *    Selects an entity from a compound type. This entity can be a field or
 *    a method.
 *
 *    Parameters:
 *      *store     The memory in which the object the entity should be selected
 *                 from is allocated.
 *      *frame     The pointer to the object.
 *      *sel       The entity to select.
 *
 *    Inputs:
 *      The memory containing the object.
 *      A pointer to the object.
 *      An unsigned integer.
 *    Output:
 *      A pointer to the selected entity.
 *    Attributes:
 *      attr.sel   Pointer to the entity
 *
 *
 *    ir_node *new_Sel (ir_node *store, ir_node *frame, int arity, ir_node **in,
 *    --------------------------------------------------------------------------
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 *                      ir_entity *sel)
 *                      ---------------
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 *
 *    Selects a field from an array type.  The entity has as owner the array, as
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 *    type the arrays element type.  The indices to access an array element are
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 *    given also.
 *
 *    Parameters:
 *      *store     The memory in which the object the entity should be selected from
 *                 is allocated.
 *      *frame     The pointer to the object.
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 *      *arity     number of array indices.
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 *      *in        array with index inputs to the node.
 *      *sel       The entity to select.
 *
 *    Inputs:
 *      The memory containing the object.
 *      A pointer to the object.
 *      As much unsigned integer as there are array expressions.
 *    Output:
 *      A pointer to the selected entity.
 *    Attributes:
 *      attr.sel   Pointer to the entity
 *
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 *    The constructors new_Sel and new_simpleSel generate the same IR nodes.
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 *    simpleSel just sets the arity of the index inputs to zero.
 *
 *
 *    ARITHMETIC OPERATIONS
 *    ---------------------
 *
 *    ir_node *new_Call (ir_node *store, ir_node *callee, int arity, ir_node **in,
 *    ----------------------------------------------------------------------------
 *                       type_method *type)
 *                       ------------------
 *
 *    Creates a procedure call.
 *
 *    Parameters
 *      *store           The actual store.
 *      *callee          A pointer to the called procedure.
 *      arity            The number of procedure parameters.
 *      **in             An array with the pointers to the parameters.
 *                       The constructor copies this array.
 *      *type            Type information of the procedure called.
 *
 *    Inputs:
 *      The store, the callee and the parameters.
 *    Output:
 *      A tuple containing the eventually changed store and the procedure
 *      results.
 *    Attributes:
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 *      attr.call        Contains the attributes for the procedure.
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 *
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 *    ir_node *new_Builtin(ir_node *store, ir_builtin_kind kind, int arity, ir_node **in,
 *    -----------------------------------------------------------------------------------
 *                       type_method *type)
 *                       ------------------
 *
 *    Creates a builtin call.
 *
 *    Parameters
 *      *store           The actual store.
 *      kind             Describes the called builtin.
 *      arity            The number of procedure parameters.
 *      **in             An array with the pointers to the parameters.
 *                       The constructor copies this array.
 *      *type            Type information of the procedure called.
 *
 *    Inputs:
 *      The store, the kind and the parameters.
 *    Output:
 *      A tuple containing the eventually changed store and the procedure
 *      results.
 *    Attributes:
 *      attr.builtin     Contains the attributes for the called builtin.
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 *
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 *    ir_node *new_Add (ir_node *op1, ir_node *op2, ir_mode *mode)
 *    ------------------------------------------------------------
 *
 *    Trivial.
 *
 *    ir_node *new_Sub (ir_node *op1, ir_node *op2, ir_mode *mode)
 *    ------------------------------------------------------------
 *
 *    Trivial.
 *
 *    ir_node *new_Minus (ir_node *op, ir_mode *mode)
 *    -----------------------------------------------
 *
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 *    Unary Minus operations on integer and floating point values.
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 *
 *    ir_node *new_Mul (ir_node *op1, ir_node *op2, ir_mode *mode)
 *    ------------------------------------------------------------
 *
 *    Trivial.
 *
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 *    ir_node *new_Mulh (ir_node *op1, ir_node *op2, ir_mode *mode)
 *    ------------------------------------------------------------
 *
 *    Returns the high order bits of a n*n=2n multiplication.
 *
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 *    ir_node *new_Div (ir_node *memop, ir_node *op1, ir_node *op2, ir_mode *mode, op_pin_state state)
 *    ------------------------------------------------------------------------------------------------
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 *
 *    Trivial.
 *
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 *    ir_node *new_Mod (ir_node *memop, ir_node *op1, ir_node *op2, ir_mode *mode, op_pin_state state)
 *    ------------------------------------------------------------------------------------------------
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 *
 *    Trivial.
 *
 *    ir_node *new_And (ir_node *op1, ir_node *op2, ir_mode *mode)
 *    ------------------------------------------------------------
 *
 *    Trivial.
 *
 *    ir_node *new_Or (ir_node *op1, ir_node *op2, ir_mode *mode)
 *    -----------------------------------------------------------
 *
 *    Trivial.
 *
 *    ir_node *new_Eor (ir_node *op1, ir_node *op2, ir_mode *mode)
 *    ------------------------------------------------------------
 *
 *    Trivial.
 *
 *    ir_node *new_Not (ir_node *op, ir_mode *mode)
 *    ---------------------------------------------
 *
 *    This node constructs a constant where all bits are set to one
 *    and a Eor of this constant and the operator.  This simulates a
 *    Not operation.
 *
 *    ir_node *new_Shl (ir_node *op, ir_node *k, ir_mode *mode)
 *    ---------------------------------------------------------
 *
 *    Trivial.
 *
 *    ir_node *new_Shr (ir_node *op, ir_node *k, ir_mode *mode)
 *    ---------------------------------------------------------
 *
 *    Logic shift right, i.e., zero extended.
 *
 *
 *    ir_node *new_Shrs (ir_node *op, ir_node *k, ir_mode *mode)
 *    ----------------------------------------------------------
 *
 *    Arithmetic shift right, i.e., sign extended.
 *
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 *    ir_node *new_Rotl (ir_node *op, ir_node *k, ir_mode *mode)
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 *    ---------------------------------------------------------
 *
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 *    Rotates the operand to the left by k bits.
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 *
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 *    ir_node *new_Carry (ir_node *op1, ir_node *op2, ir_mode *mode)
 *    ------------------------------------------------------------
 *
 *    Calculates the Carry value for integer addition. Used only
 *    in lowering code.
 *
 *    ir_node *new_Borrow (ir_node *op1, ir_node *op2, ir_mode *mode)
 *    ------------------------------------------------------------
 *
 *    Calculates the Borrow value for integer substraction. Used only
 *    in lowering code.
 *
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 *    ir_node *new_Conv (ir_node *op, ir_mode *mode)
 *    ---------------------------------------------
 *
 *    Mode conversion.  For allowed conversions see UKA Tech Report
 *    1999-14.
 *
 *    ir_node *new_Cmp (ir_node *op1, ir_node *op2)
 *    ---------------------------------------------
 *
 *    Input:
 *      The two values to be compared.
 *    Output:
 *      A 16-tuple containing the results of the 16 different comparisons.
 *      The following is a list giving the comparisons and a projection
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 *      number (pn_Cmp) to use in Proj nodes to extract the proper result.
 *        pn_Cmp_False false
 *        pn_Cmp_Eq    equal
 *        pn_Cmp_Lt    less
 *        pn_Cmp_Le    less or equal
 *        pn_Cmp_Gt    greater
 *        pn_Cmp_Ge    greater of equal
 *        pn_Cmp_Lg    less or greater
 *        pn_Cmp_Leg   less, equal or greater = ordered
 *        pn_Cmp_Uo    unordered
 *        pn_Cmp_Ue    unordered or equal
 *        pn_Cmp_Ul    unordered or less
 *        pn_Cmp_Ule   unordered, less or equal
 *        pn_Cmp_Ug    unordered or greater
 *        pn_Cmp_Uge   unordered, greater or equal
 *        pn_Cmp_Ne    unordered, less or greater = not equal
 *        pn_Cmp_True  true
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 *
 *
 *
 *    ------------
 *
 *    In general, Phi nodes are automaitcally inserted.  In some cases, if
 *    all predecessors of a block are known, an explicit Phi node constructor
 *    is needed.  E.g., to construct a FIRM graph for a statement as
 *      a = (b==c) ? 2 : 5;
 *
 *    ir_node *new_Phi (int arity, ir_node **in, ir_mode *mode)
 *    ---------------------------------------------------------
 *
 *    Creates a Phi node. The in's order has to correspond to the order
 *    of in's of current_block.  This is not checked by the library!
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 *    If one of the predecessors is Unknown (as it has to be filled in
 *    later) optimizations are skipped.  This is necessary to
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 *    construct Phi nodes in loops.
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 *
 *    Parameter
 *      arity            number of predecessors
 *      **in             array with predecessors
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 *      *mode            The mode of its inputs and output.
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 *    Inputs:
 *      A Phi node has as many inputs as the block it belongs to.
 *      Each input points to a definition of the same value on a
 *      different path in the control flow.
 *    Output
 *      The definition valid in this block.
 *
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 *    -----------------------------------------------------------------------------------
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 *
 *    Creates a Mux node. This node implements the following semantic:
 *    If the sel node (which must be of mode_b) evaluates to true, its value is
 *    ir_true, else ir_false;
 *
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 *
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 *    OPERATIONS TO MANAGE MEMORY EXPLICITLY
 *    --------------------------------------
 *
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 *    ir_node *new_Load (ir_node *store, ir_node *addr, ir_mode *mode, ir_cons_flags flags)
 *    -------------------------------------------------------------------------------------
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 *
 *    The Load operation reads a value from memory.
 *
 *    Parameters:
 *    *store        The current memory.
 *    *addr         A pointer to the variable to be read in this memory.
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 *    *mode         The mode of the value to be loaded.
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 *     flags        Additional flags for alignment, volatility and pin state.
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 *
 *    Inputs:
 *      The memory and a pointer to a variable in this memory.
 *    Output:
 *      A tuple of the memory, a control flow to be taken in case of
 *      an exception and the loaded value.
 *
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 *    ir_node *new_Store (ir_node *store, ir_node *addr, ir_node *val, ir_cons_flags flags)
 *    -------------------------------------------------------------------------------------
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 *
 *    The Store operation writes a value to a variable in memory.
 *
 *    Inputs:
 *      The memory, a pointer to a variable in this memory and the value
 *      to write to this variable.
 *    Output:
 *      A tuple of the changed memory and a control flow to be taken in
 *      case of an exception.
 *
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 *    ir_node *new_Alloc (ir_node *store, ir_node *count, ir_type *alloc_type,
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 *    -----------------------------------------------------------------------
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 *                        where_alloc where)
 *                        ------------------
 *
 *    The Alloc node allocates a new variable.  It can be specified whether the
 *    variable should be allocated to the stack or to the heap.
 *
 *    Parameters:
 *      *store       The memory which shall contain the new variable.
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 *      *count       This field is for allocating arrays, it specifies how
 *                   many array elements are to be allocated.
 *      *alloc_type  The type of the allocated variable. In case of allocating
 *                   arrays this has to be the array type, not the type of the
 *                   array elements.
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 *      where        Where to allocate the variable, either heap_alloc or stack_alloc.
 *
 *    Inputs:
 *      A memory and an unsigned integer.
 *    Output:
 *      A tuple of the changed memory, a control flow to be taken in
 *      case of an exception and the pointer to the new variable.
 *    Attributes:
 *      a.where          Indicates where the variable is allocated.
 *      a.*type          A pointer to the class the allocated data object
 *                       belongs to.
 *
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 *    ir_node *new_Free (ir_node *store, ir_node *ptr, ir_node *size, ir_type *free_type,
 *    -----------------------------------------------------------------------------------
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 *                        where_alloc where)
 *                        ------------------
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 *
 *    The Free node frees memory of the given variable.
 *
 *    Parameters:
 *      *store       The memory which shall contain the new variable.
 *      *ptr         The pointer to the object to free.
 *      *size        The number of objects of type free_type to free in a sequence.
 *      *free_type   The type of the freed variable.
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 *      where        Where the variable was allocated, either heap_alloc or stack_alloc.
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 *
 *    Inputs:
 *      A memory, a pointer and an unsigned integer.
 *    Output:
 *      The changed memory.
 *    Attributes:
 *      f.*type          A pointer to the type information of the freed data object.
 *
 *    Not Implemented!
 *
 *    ir_node *new_Sync (int arity, ir_node **in)
 *    -------------------------------------------
 *
 *    The Sync operation unifies several partial memory blocks.  These blocks
 *    have to be pairwise disjunct or the values in common locations have to
 *    be identical.  This operation allows to specify all operations that eventually
 *    need several partial memory blocks as input with a single entrance by
 *    unifying the memories with a preceding Sync operation.
 *
 *    Parameters
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 *      arity    The number of memories to synchronize.
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 *      **in     An array of pointers to nodes that produce an output of
 *               type memory.
 *    Inputs
 *      Several memories.
 *    Output
 *      The unified memory.
 *
 *
 *    SPECIAL OPERATIONS
 *    ------------------
 *
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 *    ir_node *new_NoMem (void)
 *    -----------------------------------------------------------------------------------
 *
 *    Returns the unique NoMem node current_ir_graph->no_mem.
 *    This node is used as input for operations that need a Memory, but do not
 *    change it like Div by const != 0, analyzed calls etc.
 *
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 *    ir_node *new_Proj (ir_node *arg, ir_mode *mode, long proj)
 *    ----------------------------------------------------------
 *
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 *    Selects one entry of a tuple.  This is a hidden edge with attributes.
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 *
 *    Parameters
 *      *arg      A node producing a tuple.
 *      *mode     The mode of the value to project.
 *      proj      The position of the value in the tuple.
 *    Input:
 *      The tuple.
 *    Output:
 *      The value.
 *
 *    ir_node *new_Tuple (int arity, ir_node **in)
 *    --------------------------------------------
 *
 *    Builds a Tuple from single values.  This is needed to implement
 *    optimizations that remove a node that produced a tuple.  The node can be
 *    replaced by the Tuple operation so that the following Proj nodes have not to
 *    be changed.  (They are hard to find due to the implementation with pointers
 *    in only one direction.)  The Tuple node is smaller than any other
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 *    node, so that a node can be changed into a Tuple by just changing its
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 *    opcode and giving it a new in array.
 *
 *    Parameters
 *      arity    The number of tuple elements.
 *      **in     An array containing pointers to the nodes producing the
 *               tuple elements.
 *
 *    ir_node *new_Id (ir_node *val, ir_mode *mode)
 *    ---------------------------------------------
 *
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 *    The single output of the Id operation is its input.  Also needed
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 *    for optimizations.
 *
 *
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 *    HIGH LEVEL OPERATIONS
 *    ---------------------
 *
 *    ir_node *new_CopyB (ir_node *store, ir_node *dst, ir_node *src, ir_type *data_type)
 *    -----------------------------------------------------------------------------------
 *
 *    Describes a high level block copy of a compound type from address src to
 *    address dst. Must be lowered to a Call to a runtime memory copy function.
 *
 *
 *    HIGH LEVEL OPERATIONS: Exception Support
 *    ----------------------------------------
 *    See TechReport 1999-14, chapter Exceptions.
 *
 *    ir_node *new_InstOf(ir_node *store, ir_node *ptr, ir_type *type);
 *    -----------------------------------------------------------------------------------
 *
 *    Describes a high level type check. Must be lowered to a Call to a runtime check
 *    function.
 *
 *    ir_node *new_Raise (ir_node *store, ir_node *obj)
 *    -------------------------------------------------
 *
 *    Raises an exception.  Unconditional change of control flow.  Writes
 *    an explicit Except variable to memory to pass it to the exception
 *    handler.  Must be lowered to a Call to a runtime check
 *    function.
 *
 *    Inputs:
 *      The memory state.
 *      A pointer to the Except variable.
 *    Output:
 *      A tuple of control flow and the changed memory state.  The control flow