Revert "Initial implementation of on-stack replacement (OSR)."

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 8d78a52150d1fc3a41259fcfba4b82750d2bd4ab..0b49f5978c34baf945525dcc7fc1ff29b17e9412 100644
--- a/runtime/vm/stub_code_x64.cc
+++ b/runtime/vm/stub_code_x64.cc
@@ -1418,7 +1418,18 @@ void StubCode::GenerateOptimizedUsageCounterIncrement(Assembler* assembler) {
     __ popq(func_reg);     // Restore.
     __ LeaveFrame();
   }
+  Label is_hot;
+  if (FlowGraphCompiler::CanOptimize()) {
+    ASSERT(FLAG_optimization_counter_threshold > 1);
+    __ cmpq(FieldAddress(func_reg, Function::usage_counter_offset()),
+        Immediate(FLAG_optimization_counter_threshold));
+    __ j(GREATER_EQUAL, &is_hot, Assembler::kNearJump);
+    // As long as VM has no OSR do not optimize in the middle of the function
+    // but only at exit so that we have collected all type feedback before
+    // optimizing.
+  }
   __ incq(FieldAddress(func_reg, Function::usage_counter_offset()));
+  __ Bind(&is_hot);
 }
 
 
@@ -1429,10 +1440,22 @@ void StubCode::GenerateUsageCounterIncrement(Assembler* assembler,
   Register func_reg = temp_reg;
   ASSERT(ic_reg != func_reg);
   __ movq(func_reg, FieldAddress(ic_reg, ICData::function_offset()));
+  Label is_hot;
+  if (FlowGraphCompiler::CanOptimize()) {
+    ASSERT(FLAG_optimization_counter_threshold > 1);
+    // The usage_counter is always less than FLAG_optimization_counter_threshold
+    // except when the function gets optimized.
+    __ cmpq(FieldAddress(func_reg, Function::usage_counter_offset()),
+        Immediate(FLAG_optimization_counter_threshold));
+    __ j(EQUAL, &is_hot, Assembler::kNearJump);
+    // As long as VM has no OSR do not optimize in the middle of the function
+    // but only at exit so that we have collected all type feedback before
+    // optimizing.
+  }
   __ incq(FieldAddress(func_reg, Function::usage_counter_offset()));
+  __ Bind(&is_hot);
 }
 
-
 // Generate inline cache check for 'num_args'.
 //  RBX: Inline cache data object.
 //  R10: Arguments descriptor array.