dfg/DFGVirtualRegisterAllocationPhase.cpp

   1 /*
   2  * Copyright (C) 2011, 2013 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "config.h"
  27 #include "DFGVirtualRegisterAllocationPhase.h"
  28
  29 #if ENABLE(DFG_JIT)
  30
  31 #include "DFGGraph.h"
  32 #include "DFGScoreBoard.h"
  33 #include "JSCInlines.h"
  34 #include "StackAlignment.h"
  35 #include <wtf/StdLibExtras.h>
  36
  37 namespace JSC { namespace DFG {
  38
  39 class VirtualRegisterAllocationPhase : public Phase {
  40 public:
  41     VirtualRegisterAllocationPhase(Graph& graph)
  42         : Phase(graph, "virtual register allocation")
  43     {
  44     }
  45
  46     bool run()
  47     {
  48         DFG_ASSERT(m_graph, nullptr, m_graph.m_form == ThreadedCPS);
  49
  50         ScoreBoard scoreBoard(m_graph.m_nextMachineLocal);
  51         scoreBoard.assertClear();
  52         for (size_t blockIndex = 0; blockIndex < m_graph.numBlocks(); ++blockIndex) {
  53             BasicBlock* block = m_graph.block(blockIndex);
  54             if (!block)
  55                 continue;
  56             if (!block->isReachable)
  57                 continue;
  58             if (!ASSERT_DISABLED) {
  59                 // Force usage of highest-numbered virtual registers.
  60                 scoreBoard.sortFree();
  61             }
  62             for (size_t indexInBlock = 0; indexInBlock < block->size(); ++indexInBlock) {
  63                 Node* node = block->at(indexInBlock);
  64
  65                 if (!node->shouldGenerate())
  66                     continue;
  67
  68                 switch (node->op()) {
  69                 case Phi:
  70                 case Flush:
  71                 case PhantomLocal:
  72                     continue;
  73                 case GetLocal:
  74                     ASSERT(!node->child1()->hasResult());
  75                     break;
  76                 default:
  77                     break;
  78                 }
  79
  80                 // First, call use on all of the current node's children, then
  81                 // allocate a VirtualRegister for this node. We do so in this
  82                 // order so that if a child is on its last use, and a
  83                 // VirtualRegister is freed, then it may be reused for node.
  84                 if (node->flags() & NodeHasVarArgs) {
  85                     for (unsigned childIdx = node->firstChild(); childIdx < node->firstChild() + node->numChildren(); childIdx++)
  86                         scoreBoard.useIfHasResult(m_graph.m_varArgChildren[childIdx]);
  87                 } else {
  88                     scoreBoard.useIfHasResult(node->child1());
  89                     scoreBoard.useIfHasResult(node->child2());
  90                     scoreBoard.useIfHasResult(node->child3());
  91                 }
  92
  93                 if (!node->hasResult())
  94                     continue;
  95
  96                 VirtualRegister virtualRegister = scoreBoard.allocate();
  97                 node->setVirtualRegister(virtualRegister);
  98                 // 'mustGenerate' nodes have their useCount artificially elevated,
  99                 // call use now to account for this.
 100                 if (node->mustGenerate())
 101                     scoreBoard.use(node);
 102             }
 103             scoreBoard.assertClear();
 104         }
 105
 106         // Record the number of virtual registers we're using. This is used by calls
 107         // to figure out where to put the parameters.
 108         m_graph.m_nextMachineLocal = scoreBoard.highWatermark();
 109
 110         return true;
 111     }
 112 };
 113
 114 bool performVirtualRegisterAllocation(Graph& graph)
 115 {
 116     SamplingRegion samplingRegion("DFG Virtual Register Allocation Phase");
 117     return runPhase<VirtualRegisterAllocationPhase>(graph);
 118 }
 119
 120 } } // namespace JSC::DFG
 121
 122 #endif // ENABLE(DFG_JIT)