Add fast Smi op version of switchable instance calls.

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 53429c8bda2bc2b539b327a3997b8030ee407e35..1dc370ce3b51bff3b333ddd137014be3e95456e4 100644
--- a/runtime/vm/flow_graph_compiler_arm64.cc
+++ b/runtime/vm/flow_graph_compiler_arm64.cc
@@ -1257,7 +1257,7 @@ void FlowGraphCompiler::EmitMegamorphicInstanceCall(
       MegamorphicCacheTable::Lookup(isolate(), name, arguments_descriptor));
 
   __ Comment("MegamorphicCall");
-  __ LoadFromOffset(R0, SP, (argument_count - 1) * kWordSize);
+  __ LoadFromOffset(R1, SP, (argument_count - 1) * kWordSize);
   __ LoadObject(R5, cache);
   if (FLAG_use_megamorphic_stub) {
     __ BranchLink(*StubCode::MegamorphicLookup_entry());
@@ -1288,23 +1288,35 @@ void FlowGraphCompiler::EmitSwitchableInstanceCall(
     intptr_t token_pos,
     LocationSummary* locs) {
   __ Comment("SwitchableCall");
-  __ LoadFromOffset(R0, SP, (argument_count - 1) * kWordSize);
+  __ LoadFromOffset(R1, SP, (argument_count - 1) * kWordSize);
   if (ic_data.NumArgsTested() == 1) {
     __ LoadUniqueObject(R5, ic_data);
     __ BranchLinkPatchable(*StubCode::ICLookup_entry());
   } else {
     const String& name = String::Handle(zone(), ic_data.target_name());
-    const Array& arguments_descriptor =
-        Array::ZoneHandle(zone(), ic_data.arguments_descriptor());
-    ASSERT(!arguments_descriptor.IsNull() &&
-           (arguments_descriptor.Length() > 0));
-    const MegamorphicCache& cache = MegamorphicCache::ZoneHandle(zone(),
-        MegamorphicCacheTable::Lookup(isolate(), name, arguments_descriptor));
-
-    __ LoadUniqueObject(R5, cache);
-    __ BranchLinkPatchable(*StubCode::MegamorphicLookup_entry());
+
+    if (name.raw() == Symbols::Plus().raw()) {
+      __ LoadUniqueObject(R5, ic_data);
+      __ BranchLinkPatchable(*StubCode::ICSmiAddLookup_entry());
+    } else if (name.raw() == Symbols::Minus().raw()) {
+      __ LoadUniqueObject(R5, ic_data);
+      __ BranchLinkPatchable(*StubCode::ICSmiSubLookup_entry());
+    } else if (name.raw() == Symbols::Equals().raw()) {
+      __ LoadUniqueObject(R5, ic_data);
+      __ BranchLinkPatchable(*StubCode::ICSmiEqualLookup_entry());
+    } else {
+      const Array& arguments_descriptor =
+          Array::ZoneHandle(zone(), ic_data.arguments_descriptor());
+      ASSERT(!arguments_descriptor.IsNull() &&
+             (arguments_descriptor.Length() > 0));
+      const MegamorphicCache& cache = MegamorphicCache::ZoneHandle(zone(),
+          MegamorphicCacheTable::Lookup(isolate(), name, arguments_descriptor));
+
+      __ LoadUniqueObject(R5, cache);
+      __ BranchLinkPatchable(*StubCode::MegamorphicLookup_entry());
+    }
   }
-  __ blr(R1);
+  __ blr(R1);  // A fast Smi operation may return past this call.
 
   AddCurrentDescriptor(RawPcDescriptors::kOther,
       Thread::kNoDeoptId, token_pos);