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

runtime/vm/code_generator.cc

Index: runtime/vm/code_generator.cc
diff --git a/runtime/vm/code_generator.cc b/runtime/vm/code_generator.cc
index 697d51cc7ba38f28c5b207c2c8f179f824c9d35c..68e167f5b05af6a3dde3535e8a83d0fdc445945d 100644
--- a/runtime/vm/code_generator.cc
+++ b/runtime/vm/code_generator.cc
@@ -54,13 +54,6 @@ DEFINE_FLAG(int, reoptimization_counter_threshold, 2000,
 DEFINE_FLAG(int, max_subtype_cache_entries, 100,
     "Maximum number of subtype cache entries (number of checks cached).");
 
-#if defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_X64)
-DEFINE_FLAG(bool, use_osr, true, "Use on-stack replacement.");
-#else
-DEFINE_FLAG(bool, use_osr, false, "Use on-stack replacement.");
-#endif
-DEFINE_FLAG(bool, trace_osr, false, "Trace attempts at on-stack replacement.");
-
 
 DEFINE_RUNTIME_ENTRY(TraceFunctionEntry, 1) {
   ASSERT(arguments.ArgCount() ==
@@ -1272,38 +1265,6 @@ DEFINE_RUNTIME_ENTRY(StackOverflow, 0) {
       (*callback)();
     }
   }
-
-  if (FLAG_use_osr && (interrupt_bits == 0)) {
-    DartFrameIterator iterator;
-    StackFrame* frame = iterator.NextFrame();
-    const Function& function = Function::Handle(frame->LookupDartFunction());
-    ASSERT(!function.IsNull());
-    if (!function.is_optimizable()) return;
-    intptr_t osr_id =
-        Code::Handle(function.unoptimized_code()).GetDeoptIdForOsr(frame->pc());
-    if (FLAG_trace_osr) {
-      OS::Print("Attempting OSR for %s at id=%"Pd"\n",
-                function.ToFullyQualifiedCString(),
-                osr_id);
-    }
-
-    const Error& error =
-        Error::Handle(Compiler::CompileOptimizedFunction(function, osr_id));
-    if (!error.IsNull()) Exceptions::PropagateError(error);
-
-    const Code& optimized_code = Code::Handle(function.CurrentCode());
-    // The current code will not be optimized in the case that the compiler
-    // bailed out (not an error) during OSR compilation.
-    if (optimized_code.is_optimized()) {
-      // The OSR code does not work for calling the function, so restore the
-      // unoptimized code.  Patch the stack frame to return into the OSR
-      // code.
-      intptr_t optimized_entry =
-          Instructions::Handle(optimized_code.instructions()).EntryPoint();
-      function.SetCode(Code::Handle(function.unoptimized_code()));
-      frame->set_pc(optimized_entry);
-    }
-  }
 }
 
 
@@ -1367,8 +1328,9 @@ DEFINE_RUNTIME_ENTRY(OptimizeInvokedFunction, 1) {
     }
     const Code& optimized_code = Code::Handle(function.CurrentCode());
     ASSERT(!optimized_code.IsNull());
-    // Reset usage counter for reoptimization.
-    function.set_usage_counter(0);
+    // Set usage counter for reoptimization.
+    function.set_usage_counter(
+        function.usage_counter() - FLAG_reoptimization_counter_threshold);
   } else {
     if (FLAG_trace_failed_optimization_attempts) {
       OS::PrintErr("Not Optimizable: %s\n", function.ToFullyQualifiedCString());