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

runtime/vm/code_generator.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/code_generator.h"
 
 #include "vm/assembler.h"
 #include "vm/ast.h"
 #include "vm/bigint_operations.h"
 #include "vm/code_patcher.h"
@@ skipping 36 matching lines @@
 DEFINE_FLAG(charp, optimization_filter, NULL, "Optimize only named function");
 DEFINE_FLAG(bool, trace_failed_optimization_attempts, false,
     "Traces all failed optimization attempts");
 DEFINE_FLAG(bool, trace_optimized_ic_calls, false,
     "Trace IC calls in optimized code.");
 DEFINE_FLAG(int, reoptimization_counter_threshold, 2000,
     "Counter threshold before a function gets reoptimized.");
 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() ==
       kTraceFunctionEntryRuntimeEntry.argument_count());
   const Function& function = Function::CheckedHandle(arguments.ArgAt(0));
   const String& function_name = String::Handle(function.name());
   const String& class_name =
       String::Handle(Class::Handle(function.Owner()).Name());
   OS::PrintErr("> Entering '%s.%s'\n",
       class_name.ToCString(), function_name.ToCString());
@@ skipping 1191 matching lines @@
         UNIMPLEMENTED();
       }
     }
   }
   if (interrupt_bits & Isolate::kVmStatusInterrupt) {
     Dart_IsolateInterruptCallback callback = isolate->VmStatsCallback();
     if (callback) {
       (*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 Code& original_code = Code::Handle(function.CurrentCode());
+    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 changed in the case that the compiler
+    // bailed out during OSR compilation.
+    if (optimized_code.raw() != original_code.raw()) {
+      // 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.
+      uword optimized_entry =
+          Instructions::Handle(optimized_code.instructions()).EntryPoint();
+      function.SetCode(original_code);
+      frame->set_pc(optimized_entry);
+    }
+  }
 }
 
 
 DEFINE_RUNTIME_ENTRY(TraceICCall, 2) {
   ASSERT(arguments.ArgCount() ==
          kTraceICCallRuntimeEntry.argument_count());
   const ICData& ic_data = ICData::CheckedHandle(arguments.ArgAt(0));
   const Function& function = Function::CheckedHandle(arguments.ArgAt(1));
   DartFrameIterator iterator;
   StackFrame* frame = iterator.NextFrame();
@@ skipping 43 matching lines @@
     return;
   }
   if (function.is_optimizable()) {
     const Error& error =
         Error::Handle(Compiler::CompileOptimizedFunction(function));
     if (!error.IsNull()) {
       Exceptions::PropagateError(error);
     }
     const Code& optimized_code = Code::Handle(function.CurrentCode());
     ASSERT(!optimized_code.IsNull());
-    // Set usage counter for reoptimization.
-    function.set_usage_counter(
-        function.usage_counter() - FLAG_reoptimization_counter_threshold);
+    // Reset usage counter for reoptimization.
+    function.set_usage_counter(0);
   } else {
     if (FLAG_trace_failed_optimization_attempts) {
       OS::PrintErr("Not Optimizable: %s\n", function.ToFullyQualifiedCString());
     }
     // TODO(5442338): Abort as this should not happen.
     function.set_usage_counter(kLowInvocationCount);
   }
   arguments.SetReturn(Code::Handle(function.CurrentCode()));
 }
 
@@ skipping 417 matching lines @@
 //   Arg1: Value that is being stored.
 DEFINE_RUNTIME_ENTRY(UpdateFieldCid, 2) {
   ASSERT(arguments.ArgCount() == kUpdateFieldCidRuntimeEntry.argument_count());
   const Field& field = Field::CheckedHandle(arguments.ArgAt(0));
   const Object& value = Object::Handle(arguments.ArgAt(1));
 
   field.UpdateCid(value.GetClassId());
 }
 
 }  // namespace dart