[builtins] Introduce proper Float64Tan operator.

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 f0032d7d05bb31037f2a7b2c02a6f1dec14e9a2f..cfdfa3637b535172e462966973c98a4298b953f4 100644
--- a/src/compiler/machine-operator-reducer.cc
+++ b/src/compiler/machine-operator-reducer.cc
@@ -446,6 +446,11 @@ Reduction MachineOperatorReducer::Reduce(Node* node) {
       if (m.HasValue()) return ReplaceFloat64(base::ieee754::sin(m.Value()));
       break;
     }
+    case IrOpcode::kFloat64Tan: {
+      Float64Matcher m(node->InputAt(0));
+      if (m.HasValue()) return ReplaceFloat64(base::ieee754::tan(m.Value()));
+      break;
+    }
     case IrOpcode::kChangeFloat32ToFloat64: {
       Float32Matcher m(node->InputAt(0));
       if (m.HasValue()) return ReplaceFloat64(m.Value());