Initial support for count-based profiling

src/ia32/full-codegen-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 101 matching lines @@
 //   o esp: stack pointer (pointing to return address)
 //
 // The function builds a JS frame.  Please see JavaScriptFrameConstants in
 // frames-ia32.h for its layout.
 void FullCodeGenerator::Generate(CompilationInfo* info) {
   ASSERT(info_ == NULL);
   info_ = info;
   scope_ = info->scope();
   handler_table_ =
       isolate()->factory()->NewFixedArray(function()->handler_count(), TENURED);
+  profiling_counter_ = isolate()->factory()->NewJSGlobalPropertyCell(
+      Handle<Smi>(Smi::FromInt(FLAG_interrupt_budget)));
   SetFunctionPosition(function());
   Comment cmnt(masm_, "[ function compiled by full code generator");
 
 #ifdef DEBUG
   if (strlen(FLAG_stop_at) > 0 &&
       info->function()->name()->IsEqualTo(CStrVector(FLAG_stop_at))) {
     __ int3();
   }
 #endif
 
@@ skipping 184 matching lines @@
     EmitReturnSequence();
   }
 }
 
 
 void FullCodeGenerator::ClearAccumulator() {
   __ Set(eax, Immediate(Smi::FromInt(0)));
 }
 
 
-void FullCodeGenerator::EmitStackCheck(IterationStatement* stmt) {
+void FullCodeGenerator::EmitStackCheck(IterationStatement* stmt,
+                                       Label* back_edge_target) {
   Comment cmnt(masm_, "[ Stack check");
   Label ok;
-  ExternalReference stack_limit =
-      ExternalReference::address_of_stack_limit(isolate());
-  __ cmp(esp, Operand::StaticVariable(stack_limit));
-  __ j(above_equal, &ok, Label::kNear);
-  StackCheckStub stub;
-  __ CallStub(&stub);
+
+  if (FLAG_count_based_interrupts) {
+    if (FLAG_weighted_back_edges) {
+      ASSERT(back_edge_target->is_bound());
+      int distance = masm_->pc_offset() - back_edge_target->pos();
+      __ sub(Operand::Cell(profiling_counter_),

[Vyacheslav Egorov (Chromium), 2012/02/14 12:52:47]

generation of the sub can be moved out of the if and inside the if you can just
compute int step

[Jakob Kummerow, 2012/02/14 13:54:45]

Done.

+             // weight: ceil(distance/100).
+             Immediate(Smi::FromInt(Min(127, (distance + 99) / 100))));
+    } else {
+      __ sub(Operand::Cell(profiling_counter_), Immediate(Smi::FromInt(1)));
+    }
+    __ j(positive, &ok, Label::kNear);
+    InterruptStub stub;
+    __ CallStub(&stub);
+  } else {
+    ExternalReference stack_limit =

[Vyacheslav Egorov (Chromium), 2012/02/14 12:52:47]

It is not clear to me why stack check sits in the else branch. 

It is a conscious decision to postpone interrupts until countdown reaches zero?

If so please add a comment about it.

[Jakob Kummerow, 2012/02/14 13:54:45]

Done.

+        ExternalReference::address_of_stack_limit(isolate());
+    __ cmp(esp, Operand::StaticVariable(stack_limit));
+    __ j(above_equal, &ok, Label::kNear);
+    StackCheckStub stub;
+    __ CallStub(&stub);
+  }
+
   // Record a mapping of this PC offset to the OSR id.  This is used to find
   // the AST id from the unoptimized code in order to use it as a key into
   // the deoptimization input data found in the optimized code.
   RecordStackCheck(stmt->OsrEntryId());
 
   // Loop stack checks can be patched to perform on-stack replacement. In
   // order to decide whether or not to perform OSR we embed the loop depth
   // in a test instruction after the call so we can extract it from the OSR
   // builtin.
   ASSERT(loop_depth() > 0);
   __ test(eax, Immediate(Min(loop_depth(), Code::kMaxLoopNestingMarker)));
 
+  if (FLAG_count_based_interrupts) {
+    // Reset the countdown.
+    __ mov(Operand::Cell(profiling_counter_),
+           Immediate(Smi::FromInt(FLAG_interrupt_budget)));
+  }
+
   __ bind(&ok);
   PrepareForBailoutForId(stmt->EntryId(), NO_REGISTERS);
   // Record a mapping of the OSR id to this PC.  This is used if the OSR
   // entry becomes the target of a bailout.  We don't expect it to be, but
   // we want it to work if it is.
   PrepareForBailoutForId(stmt->OsrEntryId(), NO_REGISTERS);
 }
 
 
 void FullCodeGenerator::EmitReturnSequence() {
@@ skipping 697 matching lines @@
   }
 
   // Generate code for the body of the loop.
   Visit(stmt->body());
 
   // Generate code for going to the next element by incrementing the
   // index (smi) stored on top of the stack.
   __ bind(loop_statement.continue_label());
   __ add(Operand(esp, 0 * kPointerSize), Immediate(Smi::FromInt(1)));
 
-  EmitStackCheck(stmt);
+  EmitStackCheck(stmt, &loop);
   __ jmp(&loop);
 
   // Remove the pointers stored on the stack.
   __ bind(loop_statement.break_label());
   __ add(esp, Immediate(5 * kPointerSize));
 
   // Exit and decrement the loop depth.
   __ bind(&exit);
   decrement_loop_depth();
 }
@@ skipping 3326 matching lines @@
   *context_length = 0;
   return previous_;
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32