[stubs] Introduce ToIntegerStub and unify the handling of %_ToInteger.

src/code-stubs.cc

Index: src/code-stubs.cc
diff --git a/src/code-stubs.cc b/src/code-stubs.cc
index 7ac1eb30ac0474f8985ffa02ef4102b254c68e12..da95296bb0f805b9cf847d41b70194fcc6c35113 100644
--- a/src/code-stubs.cc
+++ b/src/code-stubs.cc
@@ -2983,6 +2983,68 @@ void ToBooleanStub::GenerateAssembly(
   }
 }
 
+void ToIntegerStub::GenerateAssembly(
+    compiler::CodeStubAssembler* assembler) const {
+  typedef compiler::CodeStubAssembler::Label Label;
+  typedef compiler::Node Node;
+  typedef compiler::CodeStubAssembler::Variable Variable;
+
+  Node* context = assembler->Parameter(1);
+
+  // We might need to loop once for ToNumber conversion.
+  Variable var_arg(assembler, MachineRepresentation::kTagged);
+  Label loop(assembler, &var_arg);
+  var_arg.Bind(assembler->Parameter(0));
+  assembler->Goto(&loop);
+  assembler->Bind(&loop);
+  {
+    // Shared entry points.
+    Label return_arg(assembler), return_zero(assembler, Label::kDeferred);
+
+    // Load the current {arg} value.
+    Node* arg = var_arg.value();
+
+    // Check if {arg} is a Smi.
+    assembler->GotoIf(assembler->WordIsSmi(arg), &return_arg);
+
+    // Check if {arg} is a HeapNumber.
+    Label if_argisheapnumber(assembler),
+        if_argisnotheapnumber(assembler, Label::kDeferred);
+    assembler->Branch(assembler->WordEqual(assembler->LoadMap(arg),
+                                           assembler->HeapNumberMapConstant()),
+                      &if_argisheapnumber, &if_argisnotheapnumber);
+
+    assembler->Bind(&if_argisheapnumber);
+    {
+      // Load the floating-point value of {arg}.
+      Node* arg_value = assembler->LoadHeapNumberValue(arg);
+
+      // Check if {arg} is NaN.
+      assembler->GotoUnless(assembler->Float64Equal(arg_value, arg_value),
+                            &return_zero);
+
+      // Truncate {arg} towards zero.
+      Node* value = assembler->Float64Trunc(arg_value);
+      var_arg.Bind(assembler->ChangeFloat64ToTagged(value));
+      assembler->Goto(&return_arg);
+    }
+
+    assembler->Bind(&if_argisnotheapnumber);
+    {
+      // Need to convert {arg} to a Number first.
+      Callable callable = CodeFactory::NonNumberToNumber(assembler->isolate());
+      var_arg.Bind(assembler->CallStub(callable, context, arg));
+      assembler->Goto(&loop);
+    }
+
+    assembler->Bind(&return_arg);
+    assembler->Return(var_arg.value());
+
+    assembler->Bind(&return_zero);
+    assembler->Return(assembler->SmiConstant(Smi::FromInt(0)));
+  }
+}
+
 void StoreInterceptorStub::GenerateAssembly(
     compiler::CodeStubAssembler* assembler) const {
   typedef compiler::Node Node;