[turbofan] Reduce Float64 comparison to Float32.

src/compiler/machine-operator-reducer.cc

Index: src/compiler/machine-operator-reducer.cc
diff --git a/src/compiler/machine-operator-reducer.cc b/src/compiler/machine-operator-reducer.cc
index 3ce59733ebaea08485912703ea8b498e84e56686..86e677d8ee69e501218eee8f24a5806e590db84b 100644
--- a/src/compiler/machine-operator-reducer.cc
+++ b/src/compiler/machine-operator-reducer.cc
@@ -439,6 +439,10 @@ Reduction MachineOperatorReducer::Reduce(Node* node) {
       return ReduceFloat64InsertHighWord32(node);
     case IrOpcode::kStore:
       return ReduceStore(node);
+    case IrOpcode::kFloat64Equal:
+    case IrOpcode::kFloat64LessThan:
+    case IrOpcode::kFloat64LessThanOrEqual:
+      return ReduceFloat64Compare(node);
     default:
       break;
   }
@@ -1004,6 +1008,37 @@ Reduction MachineOperatorReducer::ReduceFloat64InsertHighWord32(Node* node) {
 }
 
 
+Reduction MachineOperatorReducer::ReduceFloat64Compare(Node* node) {
+  DCHECK((IrOpcode::kFloat64Equal == node->opcode()) ||
+         (IrOpcode::kFloat64LessThan == node->opcode()) ||
+         (IrOpcode::kFloat64LessThanOrEqual == node->opcode()));
+  // As all Float32 values have an exact representation in Float64, comparing
+  // two Float64 values both converted from Float32 is equivalent to comparing
+  // the original Float32s, so we can ignore the conversions.
+  Float64BinopMatcher m(node);
+  if (m.left().IsChangeFloat32ToFloat64() &&
+      m.right().IsChangeFloat32ToFloat64()) {
+    switch (node->opcode()) {
+      case IrOpcode::kFloat64Equal:
+        node->set_op(machine()->Float32Equal());
+        break;
+      case IrOpcode::kFloat64LessThan:
+        node->set_op(machine()->Float32LessThan());
+        break;
+      case IrOpcode::kFloat64LessThanOrEqual:
+        node->set_op(machine()->Float32LessThanOrEqual());
+        break;
+      default:
+        return NoChange();
+    }
+    node->ReplaceInput(0, m.left().InputAt(0));
+    node->ReplaceInput(1, m.right().InputAt(0));
+    return Changed(node);
+  }
+  return NoChange();
+}
+
+
 CommonOperatorBuilder* MachineOperatorReducer::common() const {
   return jsgraph()->common();
 }