[compiler] Whenever we want source positions, record that in the CompilationInfo.

With this CL, we set the is_source_positions_enabled flag on CompilationInfo when
- a command line flag is enabled that requires Turbofan to preserve source position
  information (e.g. --trace-deopt), and
- when profiling is enabled.

This also removes the --turbo-source-positions flag.

The goal is to eventually only track source position information when needed.

R=mstarzinger@chromium.org
BUG=v8:5439

Review-Url: https://codereview.chromium.org/2484163003
Cr-Commit-Position: refs/heads/master@{#40836}

src/compilation-info.cc

@@ -65,8 +65,12 @@ CompilationInfo::CompilationInfo(ParseInfo* parse_info,
   if (isolate_->serializer_enabled()) EnableDeoptimizationSupport();
 
   if (FLAG_function_context_specialization) MarkAsFunctionContextSpecializing();
-  if (FLAG_turbo_source_positions) MarkAsSourcePositionsEnabled();
   if (FLAG_turbo_splitting) MarkAsSplittingEnabled();
+
+  if (FLAG_trace_deopt || FLAG_trace_turbo || FLAG_trace_turbo_graph ||
+      FLAG_turbo_profiling || isolate_->is_profiling()) {
+    MarkAsSourcePositionsEnabled();
+  }
 }
 
 CompilationInfo::CompilationInfo(Vector<const char> debug_name,

src/flag-definitions.h

@@ -447,9 +447,6 @@ DEFINE_BOOL(turbo_stats_nvp, false,
 DEFINE_BOOL(turbo_splitting, true, "split nodes during scheduling in TurboFan")
 DEFINE_BOOL(turbo_type_feedback, true,
             "use typed feedback for representation inference in Turbofan")
-DEFINE_BOOL(turbo_source_positions, false,
-            "track source code positions when building TurboFan IR")
-DEFINE_IMPLICATION(trace_turbo, turbo_source_positions)
 DEFINE_BOOL(function_context_specialization, false,
             "enable function context specialization in TurboFan")
 DEFINE_BOOL(turbo_inlining, true, "enable inlining in TurboFan")

test/cctest/test-cpu-profiler.cc

@@ -1030,7 +1030,6 @@ static void TickLines(bool optimize) {
   CcTest::InitializeVM();
   LocalContext env;
   i::FLAG_allow_natives_syntax = true;
-  i::FLAG_turbo_source_positions = true;
   i::Isolate* isolate = CcTest::i_isolate();
   i::Factory* factory = isolate->factory();
   i::HandleScope scope(isolate);