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

runtime/vm/intermediate_language_x64.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/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intermediate_language.h"
 
 #include "lib/error.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/locations.h"
 #include "vm/object_store.h"
 #include "vm/parser.h"
 #include "vm/stack_frame.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
 
 #define __ compiler->assembler()->
 
 namespace dart {
 
 DECLARE_FLAG(int, optimization_counter_threshold);
 DECLARE_FLAG(bool, propagate_ic_data);
 DECLARE_FLAG(bool, throw_on_javascript_int_overflow);
+DECLARE_FLAG(bool, use_osr);
 
 // Generic summary for call instructions that have all arguments pushed
 // on the stack and return the result in a fixed register RAX.
 LocationSummary* Instruction::MakeCallSummary() {
   LocationSummary* result = new LocationSummary(0, 0, LocationSummary::kCall);
   result->set_out(Location::RegisterLocation(RAX));
   return result;
 }
 
 
@@ skipping 2061 matching lines @@
     __ Bind(entry_label());
     compiler->SaveLiveRegisters(instruction_->locs());
     // pending_deoptimization_env_ is needed to generate a runtime call that
     // may throw an exception.
     ASSERT(compiler->pending_deoptimization_env_ == NULL);
     compiler->pending_deoptimization_env_ = instruction_->env();
     compiler->GenerateCallRuntime(instruction_->token_pos(),
                                   instruction_->deopt_id(),
                                   kStackOverflowRuntimeEntry,
                                   instruction_->locs());
+
+    if (FLAG_use_osr && !compiler->is_optimizing() && instruction_->in_loop()) {
+      // In unoptimized code, record loop stack checks as possible OSR entries.
+      compiler->AddCurrentDescriptor(PcDescriptors::kOsrEntry,
+                                     instruction_->deopt_id(),
+                                     0);  // No token position.
+    }
     compiler->pending_deoptimization_env_ = NULL;
     compiler->RestoreLiveRegisters(instruction_->locs());
     __ jmp(exit_label());
   }
 
  private:
   CheckStackOverflowInstr* instruction_;
 };
 
 
 void CheckStackOverflowInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   CheckStackOverflowSlowPath* slow_path = new CheckStackOverflowSlowPath(this);
   compiler->AddSlowPathCode(slow_path);
 
   Register temp = locs()->temp(0).reg();
   // Generate stack overflow check.
   __ movq(temp, Immediate(Isolate::Current()->stack_limit_address()));
   __ cmpq(RSP, Address(temp, 0));
   __ j(BELOW_EQUAL, slow_path->entry_label());
+  if (FLAG_use_osr && !compiler->is_optimizing() && in_loop()) {
+    // In unoptimized code check the usage counter to trigger OSR at loop
+    // stack checks.
+    __ LoadObject(temp, compiler->parsed_function().function());
+    __ cmpq(FieldAddress(temp, Function::usage_counter_offset()),
+            Immediate(2 * FLAG_optimization_counter_threshold));
+    __ j(GREATER_EQUAL, slow_path->entry_label());
+  }
   __ Bind(slow_path->exit_label());
 }
 
 
 static void Emit53BitOverflowCheck(FlowGraphCompiler* compiler,
                                    Label* overflow,
                                    Register result) {
   if (FLAG_throw_on_javascript_int_overflow) {
     ASSERT(overflow != NULL);
     __ movq(TMP, result);  // result is a tagged Smi.
@@ skipping 2276 matching lines @@
                          PcDescriptors::kOther,
                          locs());
   __ Drop(2);  // Discard type arguments and receiver.
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64