[wasm] Remove redundant tiering_completed_ flag

The flag was only there to tell whether the {AsyncCompileJob} needs to
be kept alive. We already have this information in all the other fields
of the {AsyncCompileJob}, thus remove it.

R=ahaas@chromium.org

Bug: v8:8238
Change-Id: I8d1d76ba8d622d1816c240e7a824ecf31c3b1ce5
Reviewed-on: https://chromium-review.googlesource.com/c/1297957Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56977}

src/wasm/module-compiler.cc

@@ -117,6 +117,8 @@ class CompilationState {
     return baseline_compilation_finished_;
   }
 
+  bool has_outstanding_units() const { return outstanding_units_ > 0; }
+
   WasmEngine* wasm_engine() const { return wasm_engine_; }
   CompileMode compile_mode() const { return compile_mode_; }
   WasmFeatures* detected_features() { return &detected_features_; }
@@ -2504,9 +2506,6 @@ class AsyncCompileJob::PrepareAndStartCompile : public CompileStep {
         module->functions.size() - module->num_imported_functions;
 
     if (num_functions == 0) {
-      // Tiering has nothing to do if module is empty.
-      job_->tiering_completed_ = true;
-
       // Degenerate case of an empty module.
       job_->FinishCompile(true);
       return;
@@ -2538,12 +2537,10 @@ class AsyncCompileJob::PrepareAndStartCompile : public CompileStep {
                 }
                 // If a foreground task or a finisher is pending, we rely on
                 // FinishModule to remove the job.
-                if (job->pending_foreground_task_ ||
-                    job->outstanding_finishers_.load() > 0) {
-                  job->tiering_completed_ = true;
-                  return;
+                if (!job->pending_foreground_task_ &&
+                    job->outstanding_finishers_.load() == 0) {
+                  job->isolate_->wasm_engine()->RemoveCompileJob(job);
                 }
-                job->isolate_->wasm_engine()->RemoveCompileJob(job);
                 return;
               case CompilationEvent::kFailedCompilation: {
                 // Tier-up compilation should not fail if baseline compilation
@@ -2630,12 +2627,9 @@ class AsyncCompileJob::FinishModule : public CompileStep {
       job_->isolate_->wasm_engine()->RemoveCompileJob(job_);
       return;
     }
-    // If background tiering compilation finished before we resolved the
-    // promise, switch to patching now. Otherwise, patching will be scheduled
-    // by a callback.
     DCHECK_EQ(CompileMode::kTiering,
               job_->native_module_->compilation_state()->compile_mode());
-    if (job_->tiering_completed_) {
+    if (!job_->native_module_->compilation_state()->has_outstanding_units()) {
       job_->isolate_->wasm_engine()->RemoveCompileJob(job_);
     }
   }
@@ -2830,9 +2824,6 @@ bool AsyncStreamingProcessor::Deserialize(Vector<const uint8_t> module_bytes,
   job_->wire_bytes_ = ModuleWireBytes(owned_wire_bytes.as_vector());
   job_->native_module_->set_wire_bytes(std::move(owned_wire_bytes));
 
-  // Job should now behave as if it's fully compiled.
-  job_->tiering_completed_ = true;
-
   SaveContext saved_context(job_->isolate_);
   job_->isolate_->set_context(*job_->native_context_);
   job_->FinishCompile(false);

src/wasm/module-compiler.h

@@ -173,8 +173,6 @@ class AsyncCompileJob {
   // compilation. The AsyncCompileJob does not actively use the
   // StreamingDecoder.
   std::shared_ptr<StreamingDecoder> stream_;
-
-  bool tiering_completed_ = false;
 };
 }  // namespace wasm
 }  // namespace internal