Add LoadTaggedClassIdMayBeSmi to assembly and improve performance of inline cache stubs.

runtime/vm/stub_code_mips.cc

Index: runtime/vm/stub_code_mips.cc
===================================================================
--- runtime/vm/stub_code_mips.cc	(revision 37007)
+++ runtime/vm/stub_code_mips.cc	(working copy)
@@ -1445,7 +1445,7 @@
   // Preserve return address, since RA is needed for subroutine call.
   __ mov(T2, RA);
   // Loop that checks if there is an IC data match.
-  Label loop, update, test, found, get_class_id_as_smi;
+  Label loop, update, test, found;
   // S5: IC data object (preserved).
   __ lw(T0, FieldAddress(S5, ICData::ic_data_offset()));
   // T0: ic_data_array with check entries: classes and target functions.
@@ -1459,8 +1459,9 @@
   __ subu(T1, T1, TMP);
   __ sll(T3, T1, 1);  // T1 (argument_count - 1) is smi.
   __ addu(T3, T3, SP);
-  __ bal(&get_class_id_as_smi);
-  __ delay_slot()->lw(T3, Address(T3));
+  __ lw(T3, Address(T3));
+  __ LoadTaggedClassIdMayBeSmi(T3, T3);
+
   // T1: argument_count - 1 (smi).
   // T3: receiver's class ID (smi).
   __ b(&test);
@@ -1474,8 +1475,8 @@
       __ addu(T3, T1, T3);
       __ sll(T3, T3, 1);
       __ addu(T3, SP, T3);
-      __ bal(&get_class_id_as_smi);
-      __ delay_slot()->lw(T3, Address(T3));
+      __ lw(T3, Address(T3));
+      __ LoadTaggedClassIdMayBeSmi(T3, T3);
       // T3: next argument class ID (smi).
       __ lw(T4, Address(T0, i * kWordSize));
       // T4: next class ID to check (smi).
@@ -1496,8 +1497,8 @@
   if (num_args > 1) {
     __ sll(T3, T1, 1);
     __ addu(T3, T3, SP);
-    __ bal(&get_class_id_as_smi);
-    __ delay_slot()->lw(T3, Address(T3));
+    __ lw(T3, Address(T3));
+    __ LoadTaggedClassIdMayBeSmi(T3, T3);
   }
 
   const intptr_t entry_size = ICData::TestEntryLengthFor(num_args) * kWordSize;
@@ -1572,20 +1573,6 @@
   __ lw(T4, FieldAddress(T0, Function::instructions_offset()));
   __ AddImmediate(T4, Instructions::HeaderSize() - kHeapObjectTag);
   __ jr(T4);
-
-  // Instance in T3, return its class-id in T3 as Smi.
-  __ Bind(&get_class_id_as_smi);
-  Label not_smi;
-  // Test if Smi -> load Smi class for comparison.
-  __ andi(CMPRES1, T3, Immediate(kSmiTagMask));
-  __ bne(CMPRES1, ZR, &not_smi);
-  __ jr(RA);
-  __ delay_slot()->addiu(T3, ZR, Immediate(Smi::RawValue(kSmiCid)));
-
-  __ Bind(&not_smi);
-  __ LoadClassId(T3, T3);
-  __ jr(RA);
-  __ delay_slot()->SmiTag(T3);
 }