Initial support for count-based profiling

src/ia32/builtins-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 1642 matching lines @@
   }
 
   // If the result was -1 it means that we couldn't optimize the
   // function. Just return and continue in the unoptimized version.
   Label skip;
   __ cmp(eax, Immediate(Smi::FromInt(-1)));
   __ j(not_equal, &skip, Label::kNear);
   __ ret(0);
 
   // If we decide not to perform on-stack replacement we perform a
   // 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.");
   }
   __ bind(&ok);
   __ ret(0);
 
   __ bind(&skip);
   // Untag the AST id and push it on the stack.
   __ SmiUntag(eax);
   __ push(eax);
 
   // Generate the code for doing the frame-to-frame translation using
   // the deoptimizer infrastructure.
   Deoptimizer::EntryGenerator generator(masm, Deoptimizer::OSR);
   generator.Generate();
 }
 
 
 #undef __
 }
 }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32