Skeleton of a linear scan register allocator.

runtime/vm/flow_graph_compiler.h

Index: runtime/vm/flow_graph_compiler.h
diff --git a/runtime/vm/flow_graph_compiler.h b/runtime/vm/flow_graph_compiler.h
index 4184ecdb1453a280dea64de6039dfc769532ca4a..5d64d404d80a9368a0d8cb0866b4b774b9cb2bd0 100644
--- a/runtime/vm/flow_graph_compiler.h
+++ b/runtime/vm/flow_graph_compiler.h
@@ -32,11 +32,13 @@ class DeoptimizationStub;
 class FrameRegisterAllocator : public ValueObject {
  public:
   FrameRegisterAllocator(FlowGraphCompiler* compiler,
-                         bool keep_values_in_registers)
+                         bool keep_values_in_registers,
+                         bool is_ssa)
       : compiler_(compiler),
         stack_(kNumberOfCpuRegisters),
         registers_(),
-        keep_values_in_registers_(keep_values_in_registers) {
+        keep_values_in_registers_(keep_values_in_registers && !is_ssa),
+        is_ssa_(is_ssa) {
     for (int i = 0; i < kNumberOfCpuRegisters; i++) {
       registers_[i] = NULL;
     }
@@ -90,10 +92,44 @@ class FrameRegisterAllocator : public ValueObject {
   BindInstr* registers_[kNumberOfCpuRegisters];
 
   const bool keep_values_in_registers_;
+  const bool is_ssa_;
 
   DISALLOW_COPY_AND_ASSIGN(FrameRegisterAllocator);
 };
 
+
+class ParallelMoveResolver : public ValueObject {
+ public:
+  explicit ParallelMoveResolver(FlowGraphCompiler* compiler);
+
+  // Resolve a set of parallel moves, emitting assembler instructions.
+  void EmitNativeCode(ParallelMoveInstr* parallel_move);
+
+ private:
+  // Build the initial list of moves.
+  void BuildInitialMoveList(ParallelMoveInstr* parallel_move);
+
+  // Perform the move at the moves_ index in question (possibly requiring
+  // other moves to satisfy dependencies).
+  void PerformMove(int index);
+
+  // Emit a move and remove it from the move graph.
+  void EmitMove(int index);
+
+  // Execute a move by emitting a swap of two operands.  The move from
+  // source to destination is removed from the move graph.
+  void EmitSwap(int index);
+
+  // Verify the move list before performing moves.
+  void Verify();
+
+  FlowGraphCompiler* compiler_;
+
+  // List of moves not yet resolved.
+  GrowableArray<MoveOperands> moves_;
+};
+
+
 }  // namespace dart
 
 #if defined(TARGET_ARCH_IA32)