Optimize AOT's switchable calls for the monomorphic case.

runtime/vm/flow_graph_compiler_arm64.cc

Index: runtime/vm/flow_graph_compiler_arm64.cc
diff --git a/runtime/vm/flow_graph_compiler_arm64.cc b/runtime/vm/flow_graph_compiler_arm64.cc
index 178482ab4a727eaa2c62db958671b6ebd3f1dffb..5dd2308580d4db556a76e8adddb9f7df989ae81c 100644
--- a/runtime/vm/flow_graph_compiler_arm64.cc
+++ b/runtime/vm/flow_graph_compiler_arm64.cc
@@ -1314,9 +1314,8 @@ void FlowGraphCompiler::EmitMegamorphicInstanceCall(
   }
 
   __ LoadObject(R5, cache);
-  __ ldr(LR, Address(THR, Thread::megamorphic_lookup_entry_point_offset()));
+  __ ldr(LR, Address(THR, Thread::megamorphic_lookup_checked_entry_offset()));
   __ blr(LR);
-  __ blr(R1);
 
   __ Bind(&done);
   RecordSafepoint(locs, slow_path_argument_count);
@@ -1353,12 +1352,16 @@ void FlowGraphCompiler::EmitSwitchableInstanceCall(
     intptr_t deopt_id,
     TokenPosition token_pos,
     LocationSummary* locs) {
+  ASSERT(ic_data.NumArgsTested() == 1);
+  const Code& initial_stub = Code::ZoneHandle(
+      StubCode::ICLookupThroughFunction_entry()->code());
   __ Comment("SwitchableCall");
+
   __ LoadFromOffset(R0, SP, (argument_count - 1) * kWordSize);
-  ASSERT(ic_data.NumArgsTested() == 1);
   __ LoadUniqueObject(R5, ic_data);
-  __ BranchLinkPatchable(*StubCode::ICLookupThroughFunction_entry());
-  __ blr(R1);
+  __ LoadUniqueObject(CODE_REG, initial_stub);
+  __ ldr(TMP, FieldAddress(CODE_REG, Code::checked_entry_point_offset()));
+  __ blr(TMP);
 
   AddCurrentDescriptor(RawPcDescriptors::kOther,
       Thread::kNoDeoptId, token_pos);