Add Float64x2, Float64x2List, etc... with runtime and dart2js implementations

runtime/platform/globals.h

Index: runtime/platform/globals.h
diff --git a/runtime/platform/globals.h b/runtime/platform/globals.h
index 52adc16c79a292a586e918f525a852a65ddf28d3..b35c4f57e24fd1783d120216bed9b2d18b79b26f 100644
--- a/runtime/platform/globals.h
+++ b/runtime/platform/globals.h
@@ -76,6 +76,7 @@ struct simd128_value_t {
   union {
     float float_storage[4];
     int32_t int_storage[4];
+    double double_storage[2];
   };
   simd128_value_t& readFrom(const float* v) {
     float_storage[0] = v[0];
@@ -91,6 +92,11 @@ struct simd128_value_t {
     int_storage[3] = v[3];
     return *this;
   }
+  simd128_value_t& readFrom(const double* v) {
+    double_storage[0] = v[0];
+    double_storage[1] = v[1];
+    return *this;
+  }
   simd128_value_t& readFrom(const simd128_value_t* v) {
     *this = *v;
     return *this;
@@ -107,6 +113,10 @@ struct simd128_value_t {
     v[2] = int_storage[2];
     v[3] = int_storage[3];
   }
+  void writeTo(double* v) {
+    v[0] = double_storage[0];
+    v[1] = double_storage[1];
+  }
   void writeTo(simd128_value_t* v) {
     *v = *this;
   }