DFG SSA stack accesses shouldn't speak of VariableAccessDatas
[WebKit-https.git] / Source / JavaScriptCore / dfg / DFGVirtualRegisterAllocationPhase.cpp
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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             for (size_t indexInBlock = 0; indexInBlock < block->size(); ++indexInBlock) {
59                 Node* node = block->at(indexInBlock);
60         
61                 if (!node->shouldGenerate())
62                     continue;
63                 
64                 switch (node->op()) {
65                 case Phi:
66                 case Flush:
67                 case PhantomLocal:
68                     continue;
69                 case GetLocal:
70                     ASSERT(!node->child1()->hasResult());
71                     break;
72                 default:
73                     break;
74                 }
75                 
76                 // First, call use on all of the current node's children, then
77                 // allocate a VirtualRegister for this node. We do so in this
78                 // order so that if a child is on its last use, and a
79                 // VirtualRegister is freed, then it may be reused for node.
80                 if (node->flags() & NodeHasVarArgs) {
81                     for (unsigned childIdx = node->firstChild(); childIdx < node->firstChild() + node->numChildren(); childIdx++)
82                         scoreBoard.useIfHasResult(m_graph.m_varArgChildren[childIdx]);
83                 } else {
84                     scoreBoard.useIfHasResult(node->child1());
85                     scoreBoard.useIfHasResult(node->child2());
86                     scoreBoard.useIfHasResult(node->child3());
87                 }
88
89                 if (!node->hasResult())
90                     continue;
91
92                 VirtualRegister virtualRegister = scoreBoard.allocate();
93                 node->setVirtualRegister(virtualRegister);
94                 // 'mustGenerate' nodes have their useCount artificially elevated,
95                 // call use now to account for this.
96                 if (node->mustGenerate())
97                     scoreBoard.use(node);
98             }
99             scoreBoard.assertClear();
100         }
101         
102         // Record the number of virtual registers we're using. This is used by calls
103         // to figure out where to put the parameters.
104         m_graph.m_nextMachineLocal = scoreBoard.highWatermark();
105
106         return true;
107     }
108 };
109
110 bool performVirtualRegisterAllocation(Graph& graph)
111 {
112     SamplingRegion samplingRegion("DFG Virtual Register Allocation Phase");
113     return runPhase<VirtualRegisterAllocationPhase>(graph);
114 }
115
116 } } // namespace JSC::DFG
117
118 #endif // ENABLE(DFG_JIT)