[Compiler] Remove unused background_compile flag.

We now unconditionally both parse and compile StreamedSource on the background
thread.

BUG=v8:5203

Change-Id: I42d6fe9059bc1745da3a415d270f46cf1c08b306
Reviewed-on: https://chromium-review.googlesource.com/948854Reviewed-by: Mythri Alle <mythria@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51758}

src/compiler.cc

@@ -960,7 +960,7 @@ void BackgroundCompileTask::Run() {
   source_->parser->set_stack_limit(stack_limit);
 
   source_->parser->ParseOnBackground(source_->info.get());
-  if (FLAG_background_compile && source_->info->literal() != nullptr) {
+  if (source_->info->literal() != nullptr) {
     // Parsing has succeeded, compile.
     source_->outer_function_job = CompileTopLevelOnBackgroundThread(
         source_->info.get(), allocator_, &source_->inner_function_jobs);
@@ -1780,21 +1780,14 @@ Compiler::GetSharedFunctionInfoForStreamedScript(
           isolate, script, parse_info->ast_value_factory());
     } else {
       // Parsing has succeeded - finalize compilation.
-      if (i::FLAG_background_compile) {
-        // Finalize background compilation.
-        if (streaming_data->outer_function_job) {
-          maybe_result = FinalizeTopLevel(
-              parse_info, isolate, streaming_data->outer_function_job.get(),
-              &streaming_data->inner_function_jobs);
-        } else {
-          // Compilation failed on background thread - throw an exception.
-          FailWithPendingException(
-              isolate, parse_info,
-              Compiler::ClearExceptionFlag::KEEP_EXCEPTION);
-        }
+      if (streaming_data->outer_function_job) {
+        maybe_result = FinalizeTopLevel(
+            parse_info, isolate, streaming_data->outer_function_job.get(),
+            &streaming_data->inner_function_jobs);
       } else {
-        // Compilation on main thread.
-        maybe_result = CompileToplevel(parse_info, isolate);
+        // Compilation failed on background thread - throw an exception.
+        FailWithPendingException(isolate, parse_info,
+                                 Compiler::ClearExceptionFlag::KEEP_EXCEPTION);
       }
     }
 

src/flag-definitions.h

@@ -975,9 +975,6 @@ DEFINE_BOOL(preparser_scope_analysis, true,
             "perform scope analysis for preparsed inner functions")
 DEFINE_IMPLICATION(preparser_scope_analysis, aggressive_lazy_inner_functions)
 
-// compiler.cc
-DEFINE_BOOL(background_compile, true, "enable background compilation")
-
 // simulator-arm.cc, simulator-arm64.cc and simulator-mips.cc
 DEFINE_BOOL(trace_sim, false, "Trace simulator execution")
 DEFINE_BOOL(debug_sim, false, "Enable debugging the simulator")

tools/testrunner/local/variants.py

@@ -17,7 +17,7 @@ ALL_VARIANT_FLAGS = {
   "nooptimization": [["--noopt"]],
   "slow_path": [["--force-slow-path"]],
   "stress": [["--stress-opt", "--always-opt"]],
-  "stress_background_compile": [["--background-compile", "--stress-background-compile"]],
+  "stress_background_compile": [["--stress-background-compile"]],
   "stress_incremental_marking":  [["--stress-incremental-marking"]],
   "stress_off_heap_code":  [["--stress-off-heap-code"]],
   # Trigger stress sampling allocation profiler with sample interval = 2^14