Initial support for count-based profiling

src/ia32/builtins-ia32.cc

Index: src/ia32/builtins-ia32.cc
diff --git a/src/ia32/builtins-ia32.cc b/src/ia32/builtins-ia32.cc
index efa3456d8e0698de66e0e5d58eddd3452ca2d62e..531d1779bf1c213f3167aed13e7a36701c65f98f 100644
--- a/src/ia32/builtins-ia32.cc
+++ b/src/ia32/builtins-ia32.cc
@@ -1663,12 +1663,34 @@ void Builtins::Generate_OnStackReplacement(MacroAssembler* masm) {
   // stack guard check to enable interrupts.

[Erik Corry, 2012/02/10 13:01:42]

This should read "to trigger any pending interrupt".

[Jakob Kummerow, 2012/02/10 13:59:20]

Done.

   __ bind(&stack_check);
   Label ok;
-  ExternalReference stack_limit =
-      ExternalReference::address_of_stack_limit(masm->isolate());
-  __ cmp(esp, Operand::StaticVariable(stack_limit));
-  __ j(above_equal, &ok, Label::kNear);
-  StackCheckStub stub;
-  __ TailCallStub(&stub);
+  if (FLAG_count_based_interrupts) {

[Erik Corry, 2012/02/10 13:01:42]

Don't think we need this complexity.

[Jakob Kummerow, 2012/02/10 13:59:20]

Done.

+    // Fetch the function's profiling counter cell from the code surrounding
+    // the call site.
+    __ mov(ebx, Operand(esp, 0));  // return address
+    // These offsets are only correct if the 'weight' immediate in the
+    // 'sub' instruction fits into a single byte.
+    static const int kCellOffset = -12;
+    static const int kWeightOffset = -8;
+    if (FLAG_debug_code) {
+      static const uint8_t kSubImm8Byte = 0x83;  // "sub ..., <imm8>"
+      __ cmpb(Operand(ebx, kCellOffset - 2), kSubImm8Byte);
+      __ Assert(equal, "sub <imm8> instruction not found before cell offset");
+      STATIC_ASSERT(kCellOffset - 2 == kWeightOffset - 6);
+    }
+    __ movsx_b(ecx, Operand(ebx, kWeightOffset));
+    __ mov(ebx, Operand(ebx, kCellOffset));
+    __ sub(Operand(ebx, 0), ecx);
+    __ j(positive, &ok, Label::kNear);
+    InterruptStub stub;
+    __ TailCallStub(&stub);
+  } else {
+    ExternalReference stack_limit =
+        ExternalReference::address_of_stack_limit(masm->isolate());
+    __ cmp(esp, Operand::StaticVariable(stack_limit));
+    __ j(above_equal, &ok, Label::kNear);
+    StackCheckStub stub;
+    __ TailCallStub(&stub);
+  }
   if (FLAG_debug_code) {
     __ Abort("Unreachable code: returned from tail call.");
   }