[turbofan] decouple register allocation from schedule and graph

src/compiler/instruction-selector.cc

Index: src/compiler/instruction-selector.cc
diff --git a/src/compiler/instruction-selector.cc b/src/compiler/instruction-selector.cc
index bd3bfd73c9a7969a9dca3412945bb486d507b27d..157509310ba844c974dbe1aa8b35f96f7f79f1e0 100644
--- a/src/compiler/instruction-selector.cc
+++ b/src/compiler/instruction-selector.cc
@@ -853,8 +853,17 @@ void InstructionSelector::VisitParameter(Node* node) {
 
 void InstructionSelector::VisitPhi(Node* node) {
   // TODO(bmeurer): Emit a PhiInstruction here.
-  for (InputIter i = node->inputs().begin(); i != node->inputs().end(); ++i) {
-    MarkAsUsed(*i);
+  PhiInstruction* phi = new (instruction_zone())
+      PhiInstruction(instruction_zone(), sequence()->GetVirtualRegister(node));
+  sequence()->InstructionBlockAt(current_block_->GetRpoNumber())->AddPhi(phi);
+  Node::Inputs inputs = node->inputs();
+  size_t j = 0;
+  for (Node::Inputs::iterator iter(inputs.begin()); iter != inputs.end();
+       ++iter, ++j) {
+    MarkAsUsed(*iter);
+    // TODO(mstarzinger): Use a ValueInputIterator instead.
+    if (j >= current_block_->PredecessorCount()) continue;
+    phi->operands().push_back(sequence()->GetVirtualRegister(*iter));
   }
 }