Profiler experiments: interrupt check at function exit

Review URL: https://chromiumcodereview.appspot.com/9432026

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10795 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/flag-definitions.h

@@ -177,6 +177,8 @@ DEFINE_bool(self_optimization, false,
             "primitive functions trigger their own optimization")
 DEFINE_bool(count_based_interrupts, false,
             "trigger profiler ticks based on counting instead of timing")
+DEFINE_bool(interrupt_at_exit, false,
+            "insert an interrupt check at function exit")
 DEFINE_bool(weighted_back_edges, false,
             "weight back edges by jump distance for interrupt triggering")
 DEFINE_int(interrupt_budget, 10000,
@@ -187,6 +189,7 @@ DEFINE_int(type_info_threshold, 0,
 DEFINE_implication(experimental_profiler, watch_ic_patching)
 DEFINE_implication(experimental_profiler, self_optimization)
 DEFINE_implication(experimental_profiler, count_based_interrupts)
+DEFINE_implication(experimental_profiler, interrupt_at_exit)
 DEFINE_implication(experimental_profiler, weighted_back_edges)
 
 DEFINE_bool(trace_opt_verbose, false, "extra verbose compilation tracing")

src/ia32/full-codegen-ia32.cc

@@ -332,7 +332,7 @@ void FullCodeGenerator::EmitStackCheck(IterationStatement* stmt,
     int weight = 1;
     if (FLAG_weighted_back_edges) {
       ASSERT(back_edge_target->is_bound());
-      int distance = masm_->pc_offset() - back_edge_target->pos();
+      int distance = masm_->SizeOfCodeGeneratedSince(back_edge_target);
       weight = Min(127, Max(1, distance / 100));
     }
     __ sub(Operand::Cell(profiling_counter_), Immediate(Smi::FromInt(weight)));
@@ -389,6 +389,26 @@ void FullCodeGenerator::EmitReturnSequence() {
       __ push(eax);
       __ CallRuntime(Runtime::kTraceExit, 1);
     }
+    if (FLAG_interrupt_at_exit) {
+      // Pretend that the exit is a backwards jump to the entry.
+      int weight = 1;
+      if (FLAG_weighted_back_edges) {
+        int distance = masm_->pc_offset();
+        weight = Min(127, Max(1, distance / 100));
+      }
+      __ sub(Operand::Cell(profiling_counter_),
+             Immediate(Smi::FromInt(weight)));
+      Label ok;
+      __ j(positive, &ok, Label::kNear);
+      __ push(eax);
+      InterruptStub stub;
+      __ CallStub(&stub);
+      __ pop(eax);
+      // Reset the countdown.
+      __ mov(Operand::Cell(profiling_counter_),
+             Immediate(Smi::FromInt(FLAG_interrupt_budget)));
+      __ bind(&ok);
+    }
 #ifdef DEBUG
     // Add a label for checking the size of the code used for returning.
     Label check_exit_codesize;