/*

 * Copyright (c) 1997, 2009, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

// Optimization - Graph Style

class Block;

class CFGLoop;

class MachCallNode;

class Matcher;

class RootNode;

class VectorSet;

struct Tarjan;

//------------------------------Block_Array------------------------------------

// Map dense integer indices to Blocks.  Uses classic doubling-array trick.

// Abstractly provides an infinite array of Block*'s, initialized to NULL.

// Note that the constructor just zeros things, and since I use Arena

// allocation I do not need a destructor to reclaim storage.

class Block_Array : public ResourceObj {

  uint _size;                   // allocated size, as opposed to formal limit

  debug_only(uint _limit;)      // limit to formal domain

protected:

  Block **_blocks;

  void grow( uint i );          // Grow array node to fit

public:

  Arena *_arena;                // Arena to allocate in

  Block_Array(Arena *a) : _arena(a), _size(OptoBlockListSize) {

    debug_only(_limit=0);

    _blocks = NEW_ARENA_ARRAY( a, Block *, OptoBlockListSize );

    for( int i = 0; i < OptoBlockListSize; i++ ) {

      _blocks[i] = NULL;

    }

  }

  Block *lookup( uint i ) const // Lookup, or NULL for not mapped

  { return (i<Max()) ? _blocks[i] : (Block*)NULL; }

  Block *operator[] ( uint i ) const // Lookup, or assert for not mapped

  { assert( i < Max(), "oob" ); return _blocks[i]; }

  // Extend the mapping: index i maps to Block *n.

  void map( uint i, Block *n ) { if( i>=Max() ) grow(i); _blocks[i] = n; }

  uint Max() const { debug_only(return _limit); return _size; }

};

class Block_List : public Block_Array {

public:

  uint _cnt;

  Block_List() : Block_Array(Thread::current()->resource_area()), _cnt(0) {}

  void push( Block *b ) { map(_cnt++,b); }

  Block *pop() { return _blocks[--_cnt]; }

  Block *rpop() { Block *b = _blocks[0]; _blocks[0]=_blocks[--_cnt]; return b;}

  void remove( uint i );

  void insert( uint i, Block *n );

  uint size() const { return _cnt; }

  void reset() { _cnt = 0; }

  void print();

};

class CFGElement : public ResourceObj {

 public:

  float _freq; // Execution frequency (estimate)

  CFGElement() : _freq(0.0f) {}

  virtual bool is_block() { return false; }

  virtual bool is_loop()  { return false; }

  Block*   as_Block() { assert(is_block(), "must be block"); return (Block*)this; }

  CFGLoop* as_CFGLoop()  { assert(is_loop(),  "must be loop");  return (CFGLoop*)this;  }

};

//------------------------------Block------------------------------------------

// This class defines a Basic Block.

// Basic blocks are used during the output routines, and are not used during

// any optimization pass.  They are created late in the game.

class Block : public CFGElement {

 public:

  // Nodes in this block, in order

  Node_List _nodes;

  // Basic blocks have a Node which defines Control for all Nodes pinned in

  // this block.  This Node is a RegionNode.  Exception-causing Nodes

  // (division, subroutines) and Phi functions are always pinned.  Later,

  // every Node will get pinned to some block.

  Node *head() const { return _nodes[0]; }

  // CAUTION: num_preds() is ONE based, so that predecessor numbers match

  // input edges to Regions and Phis.

  uint num_preds() const { return head()->req(); }

  Node *pred(uint i) const { return head()->in(i); }

  // Array of successor blocks, same size as projs array

  Block_Array _succs;

  // Basic blocks have some number of Nodes which split control to all

  // following blocks.  These Nodes are always Projections.  The field in

  // the Projection and the block-ending Node determine which Block follows.

  uint _num_succs;

  // Basic blocks also carry all sorts of good old fashioned DFS information

  // used to find loops, loop nesting depth, dominators, etc.

  uint _pre_order;              // Pre-order DFS number

  // Dominator tree

  uint _dom_depth;              // Depth in dominator tree for fast LCA

  Block* _idom;                 // Immediate dominator block

  CFGLoop *_loop;               // Loop to which this block belongs

  uint _rpo;                    // Number in reverse post order walk

  virtual bool is_block() { return true; }

  float succ_prob(uint i);      // return probability of i'th successor

  int num_fall_throughs();      // How many fall-through candidate this block has

  void update_uncommon_branch(Block* un); // Lower branch prob to uncommon code

  bool succ_fall_through(uint i); // Is successor "i" is a fall-through candidate

  Block* lone_fall_through();   // Return lone fall-through Block or null

  Block* dom_lca(Block* that);  // Compute LCA in dominator tree.

#ifdef ASSERT

  bool dominates(Block* that) {

    int dom_diff = this->_dom_depth - that->_dom_depth;

    if (dom_diff > 0)  return false;

    for (; dom_diff < 0; dom_diff++)  that = that->_idom;

    return this == that;

  }

#endif

  // Report the alignment required by this block.  Must be a power of 2.

  // The previous block will insert nops to get this alignment.

  uint code_alignment();

  uint compute_loop_alignment();

  // BLOCK_FREQUENCY is a sentinel to mark uses of constant block frequencies.

  // It is currently also used to scale such frequencies relative to

  // FreqCountInvocations relative to the old value of 1500.

#define BLOCK_FREQUENCY(f) ((f * (float) 1500) / FreqCountInvocations)

  // Register Pressure (estimate) for Splitting heuristic

  uint _reg_pressure;

  uint _ihrp_index;

  uint _freg_pressure;

  uint _fhrp_index;

  // Mark and visited bits for an LCA calculation in insert_anti_dependences.

  // Since they hold unique node indexes, they do not need reinitialization.

  node_idx_t _raise_LCA_mark;

  void    set_raise_LCA_mark(node_idx_t x)    { _raise_LCA_mark = x; }

  node_idx_t  raise_LCA_mark() const          { return _raise_LCA_mark; }

  node_idx_t _raise_LCA_visited;

  void    set_raise_LCA_visited(node_idx_t x) { _raise_LCA_visited = x; }

  node_idx_t  raise_LCA_visited() const       { return _raise_LCA_visited; }

  // Estimated size in bytes of first instructions in a loop.

  uint _first_inst_size;

  uint first_inst_size() const     { return _first_inst_size; }

  void set_first_inst_size(uint s) { _first_inst_size = s; }

  // Compute the size of first instructions in this block.

  uint compute_first_inst_size(uint& sum_size, uint inst_cnt, PhaseRegAlloc* ra);

  // Compute alignment padding if the block needs it.

  // Align a loop if loop's padding is less or equal to padding limit

  // or the size of first instructions in the loop > padding.

  uint alignment_padding(int current_offset) {

    int block_alignment = code_alignment();

    int max_pad = block_alignment-relocInfo::addr_unit();

    if( max_pad > 0 ) {

      assert(is_power_of_2(max_pad+relocInfo::addr_unit()), "");

      int current_alignment = current_offset & max_pad;

      if( current_alignment != 0 ) {

        uint padding = (block_alignment-current_alignment) & max_pad;

        if( has_loop_alignment() &&

            padding > (uint)MaxLoopPad &&

            first_inst_size() <= padding ) {

          return 0;

        }

        return padding;

      }

    }

    return 0;

  }

  // Connector blocks. Connector blocks are basic blocks devoid of

  // instructions, but may have relevant non-instruction Nodes, such as

  // Phis or MergeMems. Such blocks are discovered and marked during the

  // RemoveEmpty phase, and elided during Output.

  bool _connector;

  void set_connector() { _connector = true; }

  bool is_connector() const { return _connector; };

  // Loop_alignment will be set for blocks which are at the top of loops.

  // The block layout pass may rotate loops such that the loop head may not

  // be the sequentially first block of the loop encountered in the linear

  // list of blocks.  If the layout pass is not run, loop alignment is set

  // for each block which is the head of a loop.

  uint _loop_alignment;

  void set_loop_alignment(Block *loop_top) {

    uint new_alignment = loop_top->compute_loop_alignment();

    if (new_alignment > _loop_alignment) {

      _loop_alignment = new_alignment;

    }

  }

  uint loop_alignment() const { return _loop_alignment; }

  bool has_loop_alignment() const { return loop_alignment() > 0; }

  // Create a new Block with given head Node.

  // Creates the (empty) predecessor arrays.

  Block( Arena *a, Node *headnode )

    : CFGElement(),

      _nodes(a),

      _succs(a),

      _num_succs(0),

      _pre_order(0),

      _idom(0),

      _loop(NULL),

      _reg_pressure(0),

      _ihrp_index(1),

      _freg_pressure(0),

      _fhrp_index(1),

      _raise_LCA_mark(0),

      _raise_LCA_visited(0),

      _first_inst_size(999999),

      _connector(false),

      _loop_alignment(0) {

    _nodes.push(headnode);

  }

  // Index of 'end' Node

  uint end_idx() const {

    // %%%%% add a proj after every goto

    // so (last->is_block_proj() != last) always, then simplify this code

    // This will not give correct end_idx for block 0 when it only contains root.

    int last_idx = _nodes.size() - 1;

    Node *last  = _nodes[last_idx];

    assert(last->is_block_proj() == last || last->is_block_proj() == _nodes[last_idx - _num_succs], "");

    return (last->is_block_proj() == last) ? last_idx : (last_idx - _num_succs);

  }

  // Basic blocks have a Node which ends them.  This Node determines which

  // basic block follows this one in the program flow.  This Node is either an

  // IfNode, a GotoNode, a JmpNode, or a ReturnNode.

  Node *end() const { return _nodes[end_idx()]; }

  // Add an instruction to an existing block.  It must go after the head

  // instruction and before the end instruction.

  void add_inst( Node *n ) { _nodes.insert(end_idx(),n); }

  // Find node in block

  uint find_node( const Node *n ) const;

  // Find and remove n from block list

  void find_remove( const Node *n );

  // Schedule a call next in the block

  uint sched_call(Matcher &matcher, Block_Array &bbs, uint node_cnt, Node_List &worklist, int *ready_cnt, MachCallNode *mcall, VectorSet &next_call);

  // Perform basic-block local scheduling

  Node *select(PhaseCFG *cfg, Node_List &worklist, int *ready_cnt, VectorSet &next_call, uint sched_slot);

  void set_next_call( Node *n, VectorSet &next_call, Block_Array &bbs );

  void needed_for_next_call(Node *this_call, VectorSet &next_call, Block_Array &bbs);

  bool schedule_local(PhaseCFG *cfg, Matcher &m, int *ready_cnt, VectorSet &next_call);

  // Cleanup if any code lands between a Call and his Catch

  void call_catch_cleanup(Block_Array &bbs);

  // Detect implicit-null-check opportunities.  Basically, find NULL checks

  // with suitable memory ops nearby.  Use the memory op to do the NULL check.

  // I can generate a memory op if there is not one nearby.

  void implicit_null_check(PhaseCFG *cfg, Node *proj, Node *val, int allowed_reasons);

  // Return the empty status of a block

  enum { not_empty, empty_with_goto, completely_empty };

  int is_Empty() const;

  // Forward through connectors

  Block* non_connector() {

    Block* s = this;

    while (s->is_connector()) {

      s = s->_succs[0];

    }

    return s;

  }

  // Return true if b is a successor of this block

  bool has_successor(Block* b) const {

    for (uint i = 0; i < _num_succs; i++ ) {

      if (non_connector_successor(i) == b) {

        return true;

      }

    }

    return false;

  }

  // Successor block, after forwarding through connectors

  Block* non_connector_successor(int i) const {

    return _succs[i]->non_connector();

  }

  // Examine block's code shape to predict if it is not commonly executed.

  bool has_uncommon_code() const;

  // Use frequency calculations and code shape to predict if the block

  // is uncommon.

  bool is_uncommon( Block_Array &bbs ) const;

#ifndef PRODUCT

  // Debugging print of basic block

  void dump_bidx(const Block* orig) const;

  void dump_pred(const Block_Array *bbs, Block* orig) const;

  void dump_head( const Block_Array *bbs ) const;

  void dump( ) const;

  void dump( const Block_Array *bbs ) const;

#endif

};

//------------------------------PhaseCFG---------------------------------------

// Build an array of Basic Block pointers, one per Node.

class PhaseCFG : public Phase {

 private:

  // Build a proper looking cfg.  Return count of basic blocks

  uint build_cfg();

  // Perform DFS search.

  // Setup 'vertex' as DFS to vertex mapping.

  // Setup 'semi' as vertex to DFS mapping.

  // Set 'parent' to DFS parent.

  uint DFS( Tarjan *tarjan );

  // Helper function to insert a node into a block

  void schedule_node_into_block( Node *n, Block *b );

  void replace_block_proj_ctrl( Node *n );

  // Set the basic block for pinned Nodes

  void schedule_pinned_nodes( VectorSet &visited );

  // I'll need a few machine-specific GotoNodes.  Clone from this one.

  MachNode *_goto;

  Block* insert_anti_dependences(Block* LCA, Node* load, bool verify = false);

  void verify_anti_dependences(Block* LCA, Node* load) {

    assert(LCA == _bbs[load->_idx], "should already be scheduled");

    insert_anti_dependences(LCA, load, true);

  }

 public:

  PhaseCFG( Arena *a, RootNode *r, Matcher &m );

  uint _num_blocks;             // Count of basic blocks

  Block_List _blocks;           // List of basic blocks

  RootNode *_root;              // Root of whole program

  Block_Array _bbs;             // Map Nodes to owning Basic Block

  Block *_broot;                // Basic block of root

  uint _rpo_ctr;

  CFGLoop* _root_loop;

  float _outer_loop_freq;       // Outmost loop frequency

  // Per node latency estimation, valid only during GCM

#ifndef PRODUCT

  bool _trace_opto_pipelining;  // tracing flag

#endif

#ifdef ASSERT

  Unique_Node_List _raw_oops;

#endif

  // Build dominators

  void Dominators();

  // Estimate block frequencies based on IfNode probabilities

  void Estimate_Block_Frequency();

  // Global Code Motion.  See Click's PLDI95 paper.  Place Nodes in specific

  // basic blocks; i.e. _bbs now maps _idx for all Nodes to some Block.

  void GlobalCodeMotion( Matcher &m, uint unique, Node_List &proj_list );

  // Compute the (backwards) latency of a node from the uses

  void latency_from_uses(Node *n);

  // Compute the (backwards) latency of a node from a single use

  int latency_from_use(Node *n, const Node *def, Node *use);

  // Compute the (backwards) latency of a node from the uses of this instruction

  void partial_latency_of_defs(Node *n);

  // Schedule Nodes early in their basic blocks.

  bool schedule_early(VectorSet &visited, Node_List &roots);

  // For each node, find the latest block it can be scheduled into

  // and then select the cheapest block between the latest and earliest

  // block to place the node.

  void schedule_late(VectorSet &visited, Node_List &stack);

  // Pick a block between early and late that is a cheaper alternative

  // to late. Helper for schedule_late.

  Block* hoist_to_cheaper_block(Block* LCA, Block* early, Node* self);

  // Compute the instruction global latency with a backwards walk

  void ComputeLatenciesBackwards(VectorSet &visited, Node_List &stack);

  // Set loop alignment

  void set_loop_alignment();

  // Remove empty basic blocks

  void remove_empty();

  void fixup_flow();

  bool move_to_next(Block* bx, uint b_index);

  void move_to_end(Block* bx, uint b_index);

  void insert_goto_at(uint block_no, uint succ_no);

  // Check for NeverBranch at block end.  This needs to become a GOTO to the

  // true target.  NeverBranch are treated as a conditional branch that always

  // goes the same direction for most of the optimizer and are used to give a

  // fake exit path to infinite loops.  At this late stage they need to turn

  // into Goto's so that when you enter the infinite loop you indeed hang.

  void convert_NeverBranch_to_Goto(Block *b);

  CFGLoop* create_loop_tree();

  // Insert a node into a block, and update the _bbs

  void insert( Block *b, uint idx, Node *n ) {

    b->_nodes.insert( idx, n );

    _bbs.map( n->_idx, b );

  }

#ifndef PRODUCT

  bool trace_opto_pipelining() const { return _trace_opto_pipelining; }

  // Debugging print of CFG

  void dump( ) const;           // CFG only

  void _dump_cfg( const Node *end, VectorSet &visited  ) const;

  void verify() const;

  void dump_headers();

#else

  bool trace_opto_pipelining() const { return false; }

#endif

};

//------------------------------UnionFind--------------------------------------

// Map Block indices to a block-index for a cfg-cover.

// Array lookup in the optimized case.

class UnionFind : public ResourceObj {

  uint _cnt, _max;

  uint* _indices;

  ReallocMark _nesting;  // assertion check for reallocations

public:

  UnionFind( uint max );

  void reset( uint max );  // Reset to identity map for [0..max]

  uint lookup( uint nidx ) const {

    return _indices[nidx];

  }

  uint operator[] (uint nidx) const { return lookup(nidx); }

  void map( uint from_idx, uint to_idx ) {

    assert( from_idx < _cnt, "oob" );

    _indices[from_idx] = to_idx;

  }

  void extend( uint from_idx, uint to_idx );

  uint Size() const { return _cnt; }

  uint Find( uint idx ) {

    assert( idx < 65536, "Must fit into uint");

    uint uf_idx = lookup(idx);

    return (uf_idx == idx) ? uf_idx : Find_compress(idx);

  }

  uint Find_compress( uint idx );

  uint Find_const( uint idx ) const;

  void Union( uint idx1, uint idx2 );

};

//----------------------------BlockProbPair---------------------------

// Ordered pair of Node*.

class BlockProbPair VALUE_OBJ_CLASS_SPEC {

protected:

  Block* _target;      // block target

  float  _prob;        // probability of edge to block

public:

  BlockProbPair() : _target(NULL), _prob(0.0) {}

  BlockProbPair(Block* b, float p) : _target(b), _prob(p) {}

  Block* get_target() const { return _target; }

  float get_prob() const { return _prob; }

};

//------------------------------CFGLoop-------------------------------------------

class CFGLoop : public CFGElement {

  int _id;

  int _depth;

  CFGLoop *_parent;      // root of loop tree is the method level "pseudo" loop, it's parent is null

  CFGLoop *_sibling;     // null terminated list

  CFGLoop *_child;       // first child, use child's sibling to visit all immediately nested loops

  GrowableArray<CFGElement*> _members; // list of members of loop

  GrowableArray<BlockProbPair> _exits; // list of successor blocks and their probabilities

  float _exit_prob;       // probability any loop exit is taken on a single loop iteration

  void update_succ_freq(Block* b, float freq);

 public:

  CFGLoop(int id) :