[compiler] Make --code-comments include inlining info on main thread.

In my previous CL, I completely disabled the processing of inlining stacks
when generating code comments. This CL restores the feature at least for
runs without concurrent recompilation.

In other words, if you use --code-comments and want to see nice source positions,
you must also use --no-concurrent-recompilation.

Bug: v8:6048
Change-Id: Ief7e52a4046cb74e02b1783dbace19534093c588
Reviewed-on: https://chromium-review.googlesource.com/570021
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46643}

src/compiler/code-generator.cc

@@ -506,12 +506,14 @@ void CodeGenerator::AssembleSourcePosition(SourcePosition source_position) {
     if (!info->parse_info()) return;
     std::ostringstream buffer;
     buffer << "-- ";
-    if (FLAG_trace_turbo) {
+    if (FLAG_trace_turbo ||
+        tasm()->isolate()->concurrent_recompilation_enabled()) {
       buffer << source_position;
     } else {
-      buffer << source_position;
-      // TODO(neis): Figure out if/how to print InliningStack(info) from a
-      // background thread.
+      AllowHeapAllocation allocation;
+      AllowHandleAllocation handles;
+      AllowHandleDereference deref;
+      buffer << source_position.InliningStack(info);
     }
     buffer << " --";
     tasm()->RecordComment(StrDup(buffer.str().c_str()));

src/flag-definitions.h

@@ -699,7 +699,9 @@ DEFINE_BOOL(fast_promotion_new_space, false,
 // assembler-ia32.cc / assembler-arm.cc / assembler-x64.cc
 DEFINE_BOOL(debug_code, DEBUG_BOOL,
             "generate extra code (assertions) for debugging")
-DEFINE_BOOL(code_comments, false, "emit comments in code disassembly")
+DEFINE_BOOL(code_comments, false,
+            "emit comments in code disassembly; for more readable source "
+            "positions you should add --no-concurrent_recompilation")
 DEFINE_BOOL(enable_sse3, true, "enable use of SSE3 instructions if available")
 DEFINE_BOOL(enable_ssse3, true, "enable use of SSSE3 instructions if available")
 DEFINE_BOOL(enable_sse4_1, true,