Cache IC handlers on the prototype's map if possible

src/arm64/stub-cache-arm64.cc

Index: src/arm64/stub-cache-arm64.cc
diff --git a/src/arm64/stub-cache-arm64.cc b/src/arm64/stub-cache-arm64.cc
index c3b48a5815e6037c390e5367a7ad254eed9b4d39..d66224f3adf76d5eca37ed9f53eca17e5bd68998 100644
--- a/src/arm64/stub-cache-arm64.cc
+++ b/src/arm64/stub-cache-arm64.cc
@@ -823,13 +823,14 @@ Register StubCompiler::CheckPrototypes(Handle<HeapType> type,
       reg = holder_reg;  // From now on the object will be in holder_reg.
       __ Ldr(reg, FieldMemOperand(scratch1, Map::kPrototypeOffset));
     } else {
-      bool need_map = (depth != 1 || check == CHECK_ALL_MAPS) ||
-                      heap()->InNewSpace(*prototype);
-      Register map_reg = NoReg;
-      if (need_map) {
-        map_reg = scratch1;
-        __ Ldr(map_reg, FieldMemOperand(reg, HeapObject::kMapOffset));
-      }
+      // Two possible reasons for loading the prototype from the map:
+      // (1) Can't store references to new space in code.
+      // (2) Handler is shared for all receivers with the same prototype
+      //     map (but not necessarily the same prototype instance).
+      bool load_prototype_from_map =
+          heap()->InNewSpace(*prototype) || depth == 1;
+      Register map_reg = scratch1;
+      __ Ldr(map_reg, FieldMemOperand(reg, HeapObject::kMapOffset));
 
       if (depth != 1 || check == CHECK_ALL_MAPS) {
         __ CheckMap(map_reg, current_map, miss, DONT_DO_SMI_CHECK);
@@ -849,12 +850,9 @@ Register StubCompiler::CheckPrototypes(Handle<HeapType> type,
 
       reg = holder_reg;  // From now on the object will be in holder_reg.
 
-      if (heap()->InNewSpace(*prototype)) {
-        // The prototype is in new space; we cannot store a reference to it
-        // in the code.  Load it from the map.
+      if (load_prototype_from_map) {
         __ Ldr(reg, FieldMemOperand(map_reg, Map::kPrototypeOffset));
       } else {
-        // The prototype is in old space; load it directly.
         __ Mov(reg, Operand(prototype));
       }
     }