Expand the class id to 32 bits and size field to 16 bits on 64-bit platforms.

runtime/vm/intermediate_language_mips.cc

Index: runtime/vm/intermediate_language_mips.cc
diff --git a/runtime/vm/intermediate_language_mips.cc b/runtime/vm/intermediate_language_mips.cc
index dc934ebe1e5b2f38a47fd1e10955e3ad99f869e4..39dd3c036c3b56056513c64325499b395f9fd0d0 100644
--- a/runtime/vm/intermediate_language_mips.cc
+++ b/runtime/vm/intermediate_language_mips.cc
@@ -1606,6 +1606,7 @@ LocationSummary* GuardFieldClassInstr::MakeLocationSummary(Zone* zone,
 
 
 void GuardFieldClassInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+  ASSERT(sizeof(classid_t) == kInt16Size);
   __ Comment("GuardFieldClassInstr");
 
   const intptr_t value_cid = value()->Type()->ToCid();
@@ -1947,6 +1948,7 @@ static void EnsureMutableBox(FlowGraphCompiler* compiler,
 
 
 void StoreInstanceFieldInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+  ASSERT(sizeof(classid_t) == kInt16Size);
   Label skip_store;
 
   Register instance_reg = locs()->in(0).reg();
@@ -2285,6 +2287,8 @@ LocationSummary* LoadFieldInstr::MakeLocationSummary(Zone* zone,
 
 
 void LoadFieldInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+  ASSERT(sizeof(classid_t) == kInt16Size);
+
   Register instance_reg = locs()->in(0).reg();
   if (IsUnboxedLoad() && compiler->is_optimizing()) {
     DRegister result = locs()->out(0).fpu_reg();