Change the way sampler / profiler handle external callbacks.

test/cctest/test-log-stack-tracer.cc

 // Copyright 2010 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 285 matching lines @@
       "true;");
   CHECK(!result.IsEmpty());
   // When stack tracer is invoked, the stack should look as follows:
   // script [JS]
   //   JSTrace() [JS]
   //     JSFuncDoTrace() [JS] [captures EBP value and encodes it as Smi]
   //       trace(EBP) [native (extension)]
   //         DoTrace(EBP) [native]
   //           StackTracer::Trace
 
-  // The VM state tracking keeps track of external callbacks and puts
-  // them at the top of the sample stack.
-  int base = 0;
-  CHECK(sample.stack[0] == FUNCTION_ADDR(TraceExtension::Trace));
-  base++;
+  CHECK(sample.has_external_callback);
+  CHECK_EQ(FUNCTION_ADDR(TraceExtension::Trace), sample.external_callback);
 
   // Stack tracing will start from the first JS function, i.e. "JSFuncDoTrace"
+  int base = 0;
   CHECK_GT(sample.frames_count, base + 1);
   CHECK(IsAddressWithinFuncCode("JSFuncDoTrace", sample.stack[base + 0]));
   CHECK(IsAddressWithinFuncCode("JSTrace", sample.stack[base + 1]));
 }
 
 
 // This test verifies that stack tracing works when called during
 // execution of JS code. However, as calling StackTracer requires
 // entering native code, we can only emulate pure JS by erasing
 // Isolate::c_entry_fp value. In this case, StackTracer uses passed frame
@@ skipping 24 matching lines @@
   // When stack tracer is invoked, the stack should look as follows:
   // script [JS]
   //   OuterJSTrace() [JS]
   //     JSTrace() [JS]
   //       JSFuncDoTrace() [JS]
   //         js_trace(EBP) [native (extension)]
   //           DoTraceHideCEntryFPAddress(EBP) [native]
   //             StackTracer::Trace
   //
 
-  // The VM state tracking keeps track of external callbacks and puts
-  // them at the top of the sample stack.
-  int base = 0;
-  CHECK(sample.stack[0] == FUNCTION_ADDR(TraceExtension::JSTrace));
-  base++;
+  CHECK(sample.has_external_callback);
+  CHECK_EQ(FUNCTION_ADDR(TraceExtension::JSTrace), sample.external_callback);
 
   // Stack sampling will start from the caller of JSFuncDoTrace, i.e. "JSTrace"
+  int base = 0;
   CHECK_GT(sample.frames_count, base + 1);
   CHECK(IsAddressWithinFuncCode("JSTrace", sample.stack[base + 0]));
   CHECK(IsAddressWithinFuncCode("OuterJSTrace", sample.stack[base + 1]));
 }
 
 
 static void CFuncDoTrace(byte dummy_parameter) {
   Address fp;
 #ifdef __GNUC__
   fp = reinterpret_cast<Address>(__builtin_frame_address(0));
@@ skipping 36 matching lines @@
   CHECK_EQ(0, GetJsEntrySp());
   CompileRun("a = 1; b = a + 1;");
   CHECK_EQ(0, GetJsEntrySp());
   CompileRun("js_entry_sp();");
   CHECK_EQ(0, GetJsEntrySp());
   CompileRun("js_entry_sp_level2();");
   CHECK_EQ(0, GetJsEntrySp());
 }
 
 #endif  // ENABLE_LOGGING_AND_PROFILING