Do not emit debug check in optimized IC stubs

runtime/vm/stub_code_x64.cc

Index: runtime/vm/stub_code_x64.cc
diff --git a/runtime/vm/stub_code_x64.cc b/runtime/vm/stub_code_x64.cc
index 5fd33a5b12ee54cea1dfd97f530d1570705362c2..70166680eac8a8e84c619be67db7edc0ca94e9f2 100644
--- a/runtime/vm/stub_code_x64.cc
+++ b/runtime/vm/stub_code_x64.cc
@@ -1334,7 +1334,8 @@ void StubCode::GenerateNArgsCheckInlineCacheStub(
     intptr_t num_args,
     const RuntimeEntry& handle_ic_miss,
     Token::Kind kind,
-    RangeCollectionMode range_collection_mode) {
+    RangeCollectionMode range_collection_mode,
+    bool optimized) {
   ASSERT(num_args > 0);
 #if defined(DEBUG)
   { Label ok;
@@ -1351,7 +1352,7 @@ void StubCode::GenerateNArgsCheckInlineCacheStub(
 #endif  // DEBUG
 
   Label stepping, done_stepping;
-  if (FLAG_support_debugger) {
+  if (FLAG_support_debugger && !optimized) {
     __ Comment("Check single stepping");
     __ LoadIsolate(RAX);
     __ cmpb(Address(RAX, Isolate::single_step_offset()), Immediate(0));
@@ -1511,7 +1512,7 @@ void StubCode::GenerateNArgsCheckInlineCacheStub(
     __ jmp(RCX);
   }
 
-  if (FLAG_support_debugger) {
+  if (FLAG_support_debugger && !optimized) {
     __ Bind(&stepping);
     __ EnterStubFrame();
     __ pushq(RBX);
@@ -1615,7 +1616,7 @@ void StubCode::GenerateOneArgOptimizedCheckInlineCacheStub(
   GenerateNArgsCheckInlineCacheStub(assembler, 1,
       kInlineCacheMissHandlerOneArgRuntimeEntry,
       Token::kILLEGAL,
-      kIgnoreRanges);
+      kIgnoreRanges, true /* optimized */);
 }
 
 
@@ -1625,7 +1626,7 @@ void StubCode::GenerateTwoArgsOptimizedCheckInlineCacheStub(
   GenerateNArgsCheckInlineCacheStub(assembler, 2,
       kInlineCacheMissHandlerTwoArgsRuntimeEntry,
       Token::kILLEGAL,
-      kIgnoreRanges);
+      kIgnoreRanges, true /* optimized */);
 }