[turbofan] Introduce dedicated ObjectIsNaN operator.

src/compiler/simplified-lowering.cc

Index: src/compiler/simplified-lowering.cc
diff --git a/src/compiler/simplified-lowering.cc b/src/compiler/simplified-lowering.cc
index 4acc77f22f3668fcee5dc4e7d911a2b853709bba..82d2e1d29590f0aa9510a2ea817d7f2b5f9cf8e4 100644
--- a/src/compiler/simplified-lowering.cc
+++ b/src/compiler/simplified-lowering.cc
@@ -2545,6 +2545,36 @@ class RepresentationSelector {
         VisitObjectIs(node, Type::DetectableCallable(), lowering);
         return;
       }
+      case IrOpcode::kObjectIsNaN: {
+        Type* const input_type = TypeOf(node->InputAt(0));
+        if (input_type->Is(Type::NaN())) {
+          VisitUnop(node, UseInfo::None(), MachineRepresentation::kBit);

[Jarin, 2017/02/27 15:15:49]

Are you sure it is ok to change the use infos based on the type, here?

If you really want to keep it this way, please write mjsunit tests that test the
paths through here, especially all the possible changes from one path to
another.

[Benedikt Meurer, 2017/03/03 08:42:15]

Changed to GetUpperBound now, and added tests.

+          if (lower()) {
+            DeferReplacement(node, lowering->jsgraph()->Int32Constant(1));
+          }
+        } else if (!input_type->Maybe(Type::NaN())) {
+          VisitUnop(node, UseInfo::Any(), MachineRepresentation::kBit);
+          if (lower()) {
+            DeferReplacement(node, lowering->jsgraph()->Int32Constant(0));
+          }
+        } else if (input_type->Is(Type::Number())) {
+          VisitUnop(node, UseInfo::TruncatingFloat64(),
+                    MachineRepresentation::kBit);
+          if (lower()) {
+            // ObjectIsNaN(x:kRepFloat64) => Word32Equal(Float64Equal(x,x),#0)
+            Node* const input = node->InputAt(0);
+            node->ReplaceInput(
+                0,
+                jsgraph_->graph()->NewNode(lowering->machine()->Float64Equal(),
+                                           input, input));
+            node->AppendInput(jsgraph_->zone(), jsgraph_->Int32Constant(0));
+            NodeProperties::ChangeOp(node, lowering->machine()->Word32Equal());
+          }
+        } else {
+          VisitUnop(node, UseInfo::AnyTagged(), MachineRepresentation::kBit);
+        }
+        return;
+      }
       case IrOpcode::kObjectIsNonCallable: {
         VisitObjectIs(node, Type::NonCallable(), lowering);
         return;