[WIP][turbofan] Instruction scheduler for Turbofan.

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 7200bf0e7a210e11016ff6e50e42a73bcd32710b..009d386d8303ac72692e206d69dd5711f892254c 100644
--- a/src/compiler/instruction-selector.cc
+++ b/src/compiler/instruction-selector.cc
@@ -34,7 +34,8 @@ InstructionSelector::InstructionSelector(
       defined_(node_count, false, zone),
       used_(node_count, false, zone),
       virtual_registers_(node_count,
-                         InstructionOperand::kInvalidVirtualRegister, zone) {
+                         InstructionOperand::kInvalidVirtualRegister, zone),
+      scheduler_(nullptr) {
   instructions_.reserve(node_count);
 }
 
@@ -61,17 +62,48 @@ void InstructionSelector::SelectInstructions() {
   }
 
   // Schedule the selected instructions.
+  if (FLAG_turbo_instruction_scheduling) {
+    scheduler_ = new (zone()) InstructionScheduler(zone(), sequence());
+  }
+
   for (auto const block : *blocks) {
     InstructionBlock* instruction_block =
         sequence()->InstructionBlockAt(RpoNumber::FromInt(block->rpo_number()));
     size_t end = instruction_block->code_end();
     size_t start = instruction_block->code_start();
     DCHECK_LE(end, start);
-    sequence()->StartBlock(RpoNumber::FromInt(block->rpo_number()));
+    StartBlock(RpoNumber::FromInt(block->rpo_number()));
     while (start-- > end) {
-      sequence()->AddInstruction(instructions_[start]);
+      AddInstruction(instructions_[start]);
     }
-    sequence()->EndBlock(RpoNumber::FromInt(block->rpo_number()));
+    EndBlock(RpoNumber::FromInt(block->rpo_number()));
+  }
+}
+
+
+void InstructionSelector::StartBlock(RpoNumber rpo) {
+  if (FLAG_turbo_instruction_scheduling) {
+    scheduler_->StartBlock(rpo);
+  } else {
+    sequence()->StartBlock(rpo);
+  }
+}
+
+
+void InstructionSelector::EndBlock(RpoNumber rpo) {
+  if (FLAG_turbo_instruction_scheduling) {
+    scheduler_->EndBlock(rpo);
+  } else {
+    sequence()->EndBlock(rpo);
+  }
+}
+
+
+void InstructionSelector::AddInstruction(Instruction* instr) {
+  if (FLAG_turbo_instruction_scheduling) {
+    scheduler_->AddInstruction(instr);
+  } else {
+    sequence()->AddInstruction(instr);
   }
 }