Expose SIMD.Float32x4 type to Javascript.

src/x64/full-codegen-x64.cc

Index: src/x64/full-codegen-x64.cc
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index a84a8e6d9c6675f511324edccb91d8bcc3c223b3..d2cd5a5dd26d8a2cabddaabb4af9fc7c6fe36089 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -5178,6 +5178,10 @@ void FullCodeGenerator::EmitLiteralCompareTypeof(Expression* expr,
     __ JumpIfSmi(rax, if_false);
     __ CmpObjectType(rax, SYMBOL_TYPE, rdx);
     Split(equal, if_true, if_false, fall_through);
+  } else if (String::Equals(check, factory->float32x4_string())) {
+    __ JumpIfSmi(rax, if_false);
+    __ CmpObjectType(rax, FLOAT32X4_TYPE, rdx);
+    Split(equal, if_true, if_false, fall_through);
   } else if (String::Equals(check, factory->boolean_string())) {
     __ CompareRoot(rax, Heap::kTrueValueRootIndex);
     __ j(equal, if_true);