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1 /*
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2 * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 // Optimization - Graph Style
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26
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27 class Block;
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28 class CFGLoop;
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29 class MachCallNode;
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30 class Matcher;
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31 class RootNode;
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32 class VectorSet;
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33 struct Tarjan;
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34
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35 //------------------------------Block_Array------------------------------------
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36 // Map dense integer indices to Blocks. Uses classic doubling-array trick.
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37 // Abstractly provides an infinite array of Block*'s, initialized to NULL.
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38 // Note that the constructor just zeros things, and since I use Arena
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39 // allocation I do not need a destructor to reclaim storage.
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40 class Block_Array : public ResourceObj {
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41 uint _size; // allocated size, as opposed to formal limit
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42 debug_only(uint _limit;) // limit to formal domain
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43 protected:
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44 Block **_blocks;
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45 void grow( uint i ); // Grow array node to fit
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46
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47 public:
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48 Arena *_arena; // Arena to allocate in
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49
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50 Block_Array(Arena *a) : _arena(a), _size(OptoBlockListSize) {
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51 debug_only(_limit=0);
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52 _blocks = NEW_ARENA_ARRAY( a, Block *, OptoBlockListSize );
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53 for( int i = 0; i < OptoBlockListSize; i++ ) {
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54 _blocks[i] = NULL;
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55 }
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56 }
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57 Block *lookup( uint i ) const // Lookup, or NULL for not mapped
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58 { return (i<Max()) ? _blocks[i] : (Block*)NULL; }
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59 Block *operator[] ( uint i ) const // Lookup, or assert for not mapped
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60 { assert( i < Max(), "oob" ); return _blocks[i]; }
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61 // Extend the mapping: index i maps to Block *n.
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62 void map( uint i, Block *n ) { if( i>=Max() ) grow(i); _blocks[i] = n; }
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63 uint Max() const { debug_only(return _limit); return _size; }
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64 };
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65
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66
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67 class Block_List : public Block_Array {
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68 public:
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69 uint _cnt;
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70 Block_List() : Block_Array(Thread::current()->resource_area()), _cnt(0) {}
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71 void push( Block *b ) { map(_cnt++,b); }
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72 Block *pop() { return _blocks[--_cnt]; }
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73 Block *rpop() { Block *b = _blocks[0]; _blocks[0]=_blocks[--_cnt]; return b;}
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74 void remove( uint i );
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75 void insert( uint i, Block *n );
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76 uint size() const { return _cnt; }
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77 void reset() { _cnt = 0; }
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78 };
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79
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80
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81 class CFGElement : public ResourceObj {
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82 public:
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83 float _freq; // Execution frequency (estimate)
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84
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85 CFGElement() : _freq(0.0f) {}
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86 virtual bool is_block() { return false; }
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87 virtual bool is_loop() { return false; }
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88 Block* as_Block() { assert(is_block(), "must be block"); return (Block*)this; }
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89 CFGLoop* as_CFGLoop() { assert(is_loop(), "must be loop"); return (CFGLoop*)this; }
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90 };
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91
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92 //------------------------------Block------------------------------------------
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93 // This class defines a Basic Block.
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94 // Basic blocks are used during the output routines, and are not used during
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95 // any optimization pass. They are created late in the game.
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96 class Block : public CFGElement {
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97 public:
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98 // Nodes in this block, in order
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99 Node_List _nodes;
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100
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101 // Basic blocks have a Node which defines Control for all Nodes pinned in
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102 // this block. This Node is a RegionNode. Exception-causing Nodes
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103 // (division, subroutines) and Phi functions are always pinned. Later,
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104 // every Node will get pinned to some block.
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105 Node *head() const { return _nodes[0]; }
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106
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107 // CAUTION: num_preds() is ONE based, so that predecessor numbers match
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108 // input edges to Regions and Phis.
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109 uint num_preds() const { return head()->req(); }
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110 Node *pred(uint i) const { return head()->in(i); }
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111
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112 // Array of successor blocks, same size as projs array
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113 Block_Array _succs;
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114
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115 // Basic blocks have some number of Nodes which split control to all
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116 // following blocks. These Nodes are always Projections. The field in
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117 // the Projection and the block-ending Node determine which Block follows.
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118 uint _num_succs;
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119
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120 // Basic blocks also carry all sorts of good old fashioned DFS information
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121 // used to find loops, loop nesting depth, dominators, etc.
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122 uint _pre_order; // Pre-order DFS number
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123
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124 // Dominator tree
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125 uint _dom_depth; // Depth in dominator tree for fast LCA
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126 Block* _idom; // Immediate dominator block
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127
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128 CFGLoop *_loop; // Loop to which this block belongs
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129 uint _rpo; // Number in reverse post order walk
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130
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131 virtual bool is_block() { return true; }
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132 float succ_prob(uint i); // return probability of i'th successor
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133
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134 Block* dom_lca(Block* that); // Compute LCA in dominator tree.
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135 #ifdef ASSERT
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136 bool dominates(Block* that) {
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137 int dom_diff = this->_dom_depth - that->_dom_depth;
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138 if (dom_diff > 0) return false;
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139 for (; dom_diff < 0; dom_diff++) that = that->_idom;
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140 return this == that;
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141 }
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142 #endif
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143
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144 // Report the alignment required by this block. Must be a power of 2.
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145 // The previous block will insert nops to get this alignment.
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146 uint code_alignment();
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147
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148 // BLOCK_FREQUENCY is a sentinel to mark uses of constant block frequencies.
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149 // It is currently also used to scale such frequencies relative to
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150 // FreqCountInvocations relative to the old value of 1500.
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151 #define BLOCK_FREQUENCY(f) ((f * (float) 1500) / FreqCountInvocations)
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152
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153 // Register Pressure (estimate) for Splitting heuristic
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154 uint _reg_pressure;
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155 uint _ihrp_index;
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156 uint _freg_pressure;
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157 uint _fhrp_index;
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158
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159 // Mark and visited bits for an LCA calculation in insert_anti_dependences.
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160 // Since they hold unique node indexes, they do not need reinitialization.
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161 node_idx_t _raise_LCA_mark;
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162 void set_raise_LCA_mark(node_idx_t x) { _raise_LCA_mark = x; }
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163 node_idx_t raise_LCA_mark() const { return _raise_LCA_mark; }
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164 node_idx_t _raise_LCA_visited;
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165 void set_raise_LCA_visited(node_idx_t x) { _raise_LCA_visited = x; }
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166 node_idx_t raise_LCA_visited() const { return _raise_LCA_visited; }
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167
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168 // Estimated size in bytes of first instructions in a loop.
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169 uint _first_inst_size;
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170 uint first_inst_size() const { return _first_inst_size; }
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171 void set_first_inst_size(uint s) { _first_inst_size = s; }
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172
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173 // Compute the size of first instructions in this block.
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174 uint compute_first_inst_size(uint& sum_size, uint inst_cnt, PhaseRegAlloc* ra);
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175
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176 // Compute alignment padding if the block needs it.
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177 // Align a loop if loop's padding is less or equal to padding limit
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178 // or the size of first instructions in the loop > padding.
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179 uint alignment_padding(int current_offset) {
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180 int block_alignment = code_alignment();
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181 int max_pad = block_alignment-relocInfo::addr_unit();
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182 if( max_pad > 0 ) {
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183 assert(is_power_of_2(max_pad+relocInfo::addr_unit()), "");
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184 int current_alignment = current_offset & max_pad;
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185 if( current_alignment != 0 ) {
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186 uint padding = (block_alignment-current_alignment) & max_pad;
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187 if( !head()->is_Loop() ||
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188 padding <= (uint)MaxLoopPad ||
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189 first_inst_size() > padding ) {
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190 return padding;
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191 }
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192 }
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193 }
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194 return 0;
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195 }
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196
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197 // Connector blocks. Connector blocks are basic blocks devoid of
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198 // instructions, but may have relevant non-instruction Nodes, such as
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199 // Phis or MergeMems. Such blocks are discovered and marked during the
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200 // RemoveEmpty phase, and elided during Output.
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201 bool _connector;
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202 void set_connector() { _connector = true; }
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203 bool is_connector() const { return _connector; };
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204
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205 // Create a new Block with given head Node.
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206 // Creates the (empty) predecessor arrays.
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207 Block( Arena *a, Node *headnode )
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208 : CFGElement(),
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209 _nodes(a),
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210 _succs(a),
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211 _num_succs(0),
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212 _pre_order(0),
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213 _idom(0),
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214 _loop(NULL),
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215 _reg_pressure(0),
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216 _ihrp_index(1),
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217 _freg_pressure(0),
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218 _fhrp_index(1),
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219 _raise_LCA_mark(0),
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220 _raise_LCA_visited(0),
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221 _first_inst_size(999999),
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222 _connector(false) {
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223 _nodes.push(headnode);
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224 }
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225
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226 // Index of 'end' Node
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227 uint end_idx() const {
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228 // %%%%% add a proj after every goto
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229 // so (last->is_block_proj() != last) always, then simplify this code
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230 // This will not give correct end_idx for block 0 when it only contains root.
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231 int last_idx = _nodes.size() - 1;
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232 Node *last = _nodes[last_idx];
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233 assert(last->is_block_proj() == last || last->is_block_proj() == _nodes[last_idx - _num_succs], "");
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234 return (last->is_block_proj() == last) ? last_idx : (last_idx - _num_succs);
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235 }
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236
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237 // Basic blocks have a Node which ends them. This Node determines which
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238 // basic block follows this one in the program flow. This Node is either an
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239 // IfNode, a GotoNode, a JmpNode, or a ReturnNode.
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240 Node *end() const { return _nodes[end_idx()]; }
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241
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242 // Add an instruction to an existing block. It must go after the head
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243 // instruction and before the end instruction.
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244 void add_inst( Node *n ) { _nodes.insert(end_idx(),n); }
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245 // Find node in block
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246 uint find_node( const Node *n ) const;
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247 // Find and remove n from block list
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248 void find_remove( const Node *n );
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249
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250 // Schedule a call next in the block
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251 uint sched_call(Matcher &matcher, Block_Array &bbs, uint node_cnt, Node_List &worklist, int *ready_cnt, MachCallNode *mcall, VectorSet &next_call);
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252
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253 // Perform basic-block local scheduling
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254 Node *select(PhaseCFG *cfg, Node_List &worklist, int *ready_cnt, VectorSet &next_call, uint sched_slot);
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255 void set_next_call( Node *n, VectorSet &next_call, Block_Array &bbs );
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256 void needed_for_next_call(Node *this_call, VectorSet &next_call, Block_Array &bbs);
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257 bool schedule_local(PhaseCFG *cfg, Matcher &m, int *ready_cnt, VectorSet &next_call);
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258 // Cleanup if any code lands between a Call and his Catch
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259 void call_catch_cleanup(Block_Array &bbs);
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260 // Detect implicit-null-check opportunities. Basically, find NULL checks
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261 // with suitable memory ops nearby. Use the memory op to do the NULL check.
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262 // I can generate a memory op if there is not one nearby.
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263 void implicit_null_check(PhaseCFG *cfg, Node *proj, Node *val, int allowed_reasons);
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264
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265 // Return the empty status of a block
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266 enum { not_empty, empty_with_goto, completely_empty };
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267 int is_Empty() const;
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268
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269 // Forward through connectors
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270 Block* non_connector() {
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271 Block* s = this;
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272 while (s->is_connector()) {
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273 s = s->_succs[0];
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274 }
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275 return s;
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276 }
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277
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278 // Successor block, after forwarding through connectors
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279 Block* non_connector_successor(int i) const {
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280 return _succs[i]->non_connector();
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281 }
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282
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283 // Examine block's code shape to predict if it is not commonly executed.
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284 bool has_uncommon_code() const;
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285
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286 // Use frequency calculations and code shape to predict if the block
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287 // is uncommon.
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288 bool is_uncommon( Block_Array &bbs ) const;
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289
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290 #ifndef PRODUCT
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291 // Debugging print of basic block
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292 void dump_bidx(const Block* orig) const;
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293 void dump_pred(const Block_Array *bbs, Block* orig) const;
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294 void dump_head( const Block_Array *bbs ) const;
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295 void dump( ) const;
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296 void dump( const Block_Array *bbs ) const;
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297 #endif
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298 };
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299
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300
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301 //------------------------------PhaseCFG---------------------------------------
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302 // Build an array of Basic Block pointers, one per Node.
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303 class PhaseCFG : public Phase {
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304 private:
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305 // Build a proper looking cfg. Return count of basic blocks
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306 uint build_cfg();
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307
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308 // Perform DFS search.
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309 // Setup 'vertex' as DFS to vertex mapping.
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310 // Setup 'semi' as vertex to DFS mapping.
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311 // Set 'parent' to DFS parent.
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312 uint DFS( Tarjan *tarjan );
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313
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314 // Helper function to insert a node into a block
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315 void schedule_node_into_block( Node *n, Block *b );
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316
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317 // Set the basic block for pinned Nodes
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318 void schedule_pinned_nodes( VectorSet &visited );
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319
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320 // I'll need a few machine-specific GotoNodes. Clone from this one.
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321 MachNode *_goto;
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322 void insert_goto_at(uint block_no, uint succ_no);
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323
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324 Block* insert_anti_dependences(Block* LCA, Node* load, bool verify = false);
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325 void verify_anti_dependences(Block* LCA, Node* load) {
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326 assert(LCA == _bbs[load->_idx], "should already be scheduled");
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327 insert_anti_dependences(LCA, load, true);
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328 }
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329
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330 public:
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331 PhaseCFG( Arena *a, RootNode *r, Matcher &m );
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332
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333 uint _num_blocks; // Count of basic blocks
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334 Block_List _blocks; // List of basic blocks
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335 RootNode *_root; // Root of whole program
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336 Block_Array _bbs; // Map Nodes to owning Basic Block
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337 Block *_broot; // Basic block of root
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338 uint _rpo_ctr;
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339 CFGLoop* _root_loop;
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340
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341 // Per node latency estimation, valid only during GCM
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342 GrowableArray<uint> _node_latency;
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343
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344 #ifndef PRODUCT
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345 bool _trace_opto_pipelining; // tracing flag
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346 #endif
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347
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348 // Build dominators
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349 void Dominators();
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350
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351 // Estimate block frequencies based on IfNode probabilities
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352 void Estimate_Block_Frequency();
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353
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354 // Global Code Motion. See Click's PLDI95 paper. Place Nodes in specific
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355 // basic blocks; i.e. _bbs now maps _idx for all Nodes to some Block.
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356 void GlobalCodeMotion( Matcher &m, uint unique, Node_List &proj_list );
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357
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358 // Compute the (backwards) latency of a node from the uses
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359 void latency_from_uses(Node *n);
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360
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361 // Compute the (backwards) latency of a node from a single use
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362 int latency_from_use(Node *n, const Node *def, Node *use);
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363
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364 // Compute the (backwards) latency of a node from the uses of this instruction
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365 void partial_latency_of_defs(Node *n);
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366
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367 // Schedule Nodes early in their basic blocks.
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368 bool schedule_early(VectorSet &visited, Node_List &roots);
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369
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370 // For each node, find the latest block it can be scheduled into
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371 // and then select the cheapest block between the latest and earliest
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372 // block to place the node.
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373 void schedule_late(VectorSet &visited, Node_List &stack);
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374
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375 // Pick a block between early and late that is a cheaper alternative
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376 // to late. Helper for schedule_late.
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377 Block* hoist_to_cheaper_block(Block* LCA, Block* early, Node* self);
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378
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379 // Compute the instruction global latency with a backwards walk
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380 void ComputeLatenciesBackwards(VectorSet &visited, Node_List &stack);
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381
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382 // Remove empty basic blocks
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383 void RemoveEmpty();
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384 bool MoveToNext(Block* bx, uint b_index);
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385 void MoveToEnd(Block* bx, uint b_index);
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386
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387 // Check for NeverBranch at block end. This needs to become a GOTO to the
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388 // true target. NeverBranch are treated as a conditional branch that always
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389 // goes the same direction for most of the optimizer and are used to give a
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390 // fake exit path to infinite loops. At this late stage they need to turn
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391 // into Goto's so that when you enter the infinite loop you indeed hang.
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392 void convert_NeverBranch_to_Goto(Block *b);
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393
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394 CFGLoop* create_loop_tree();
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395
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396 // Insert a node into a block, and update the _bbs
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397 void insert( Block *b, uint idx, Node *n ) {
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398 b->_nodes.insert( idx, n );
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399 _bbs.map( n->_idx, b );
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400 }
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401
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402 #ifndef PRODUCT
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403 bool trace_opto_pipelining() const { return _trace_opto_pipelining; }
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404
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405 // Debugging print of CFG
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406 void dump( ) const; // CFG only
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407 void _dump_cfg( const Node *end, VectorSet &visited ) const;
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408 void verify() const;
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409 void dump_headers();
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410 #else
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411 bool trace_opto_pipelining() const { return false; }
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412 #endif
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413 };
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414
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415
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416 //------------------------------UnionFindInfo----------------------------------
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417 // Map Block indices to a block-index for a cfg-cover.
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418 // Array lookup in the optimized case.
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419 class UnionFind : public ResourceObj {
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420 uint _cnt, _max;
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421 uint* _indices;
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422 ReallocMark _nesting; // assertion check for reallocations
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423 public:
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424 UnionFind( uint max );
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425 void reset( uint max ); // Reset to identity map for [0..max]
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426
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427 uint lookup( uint nidx ) const {
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428 return _indices[nidx];
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429 }
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430 uint operator[] (uint nidx) const { return lookup(nidx); }
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431
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432 void map( uint from_idx, uint to_idx ) {
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433 assert( from_idx < _cnt, "oob" );
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434 _indices[from_idx] = to_idx;
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435 }
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436 void extend( uint from_idx, uint to_idx );
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437
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438 uint Size() const { return _cnt; }
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439
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440 uint Find( uint idx ) {
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441 assert( idx < 65536, "Must fit into uint");
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442 uint uf_idx = lookup(idx);
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443 return (uf_idx == idx) ? uf_idx : Find_compress(idx);
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444 }
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445 uint Find_compress( uint idx );
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446 uint Find_const( uint idx ) const;
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447 void Union( uint idx1, uint idx2 );
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448
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449 };
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450
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451 //----------------------------BlockProbPair---------------------------
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452 // Ordered pair of Node*.
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453 class BlockProbPair VALUE_OBJ_CLASS_SPEC {
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454 protected:
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455 Block* _target; // block target
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456 float _prob; // probability of edge to block
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457 public:
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458 BlockProbPair() : _target(NULL), _prob(0.0) {}
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459 BlockProbPair(Block* b, float p) : _target(b), _prob(p) {}
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460
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461 Block* get_target() const { return _target; }
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462 float get_prob() const { return _prob; }
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463 };
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464
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465 //------------------------------CFGLoop-------------------------------------------
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466 class CFGLoop : public CFGElement {
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467 int _id;
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468 int _depth;
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469 CFGLoop *_parent; // root of loop tree is the method level "pseudo" loop, it's parent is null
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470 CFGLoop *_sibling; // null terminated list
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471 CFGLoop *_child; // first child, use child's sibling to visit all immediately nested loops
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472 GrowableArray<CFGElement*> _members; // list of members of loop
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473 GrowableArray<BlockProbPair> _exits; // list of successor blocks and their probabilities
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474 float _exit_prob; // probability any loop exit is taken on a single loop iteration
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475 void update_succ_freq(Block* b, float freq);
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476
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477 public:
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478 CFGLoop(int id) :
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479 CFGElement(),
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480 _id(id),
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481 _depth(0),
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482 _parent(NULL),
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483 _sibling(NULL),
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484 _child(NULL),
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485 _exit_prob(1.0f) {}
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486 CFGLoop* parent() { return _parent; }
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487 void push_pred(Block* blk, int i, Block_List& worklist, Block_Array& node_to_blk);
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488 void add_member(CFGElement *s) { _members.push(s); }
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489 void add_nested_loop(CFGLoop* cl);
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490 Block* head() {
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491 assert(_members.at(0)->is_block(), "head must be a block");
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492 Block* hd = _members.at(0)->as_Block();
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493 assert(hd->_loop == this, "just checking");
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494 assert(hd->head()->is_Loop(), "must begin with loop head node");
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495 return hd;
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496 }
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497 Block* backedge_block(); // Return the block on the backedge of the loop (else NULL)
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498 void compute_loop_depth(int depth);
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499 void compute_freq(); // compute frequency with loop assuming head freq 1.0f
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500 void scale_freq(); // scale frequency by loop trip count (including outer loops)
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501 bool in_loop_nest(Block* b);
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502 float trip_count() const { return 1.0f / _exit_prob; }
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503 virtual bool is_loop() { return true; }
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504 int id() { return _id; }
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505
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506 #ifndef PRODUCT
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507 void dump( ) const;
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508 void dump_tree() const;
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509 #endif
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510 };
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