Add support for XMM registers in SSA code generation pipeline.

runtime/vm/locations.cc

Index: runtime/vm/locations.cc
diff --git a/runtime/vm/locations.cc b/runtime/vm/locations.cc
index 9bf0325336fd73063971f7df2f3b5a6817bd30f8..2dafe8a07fef0c25502fdafdda32148197e84c87 100644
--- a/runtime/vm/locations.cc
+++ b/runtime/vm/locations.cc
@@ -49,6 +49,7 @@ const char* Location::Name() const {
   switch (kind()) {
     case kInvalid: return "?";
     case kRegister: return Assembler::RegisterName(reg());
+    case kXmmRegister: return Assembler::XmmRegisterName(xmm_reg());
     case kStackSlot: return "S";
     case kUnallocated:
       switch (policy()) {
@@ -58,6 +59,8 @@ const char* Location::Name() const {
           return "P";
         case kRequiresRegister:
           return "R";
+        case kRequiresXmmRegister:
+          return "D";
         case kSameAsFirstInput:
           return "0";
       }