Retry background compilation if an assumption is invalidated

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
diff --git a/runtime/vm/compiler.cc b/runtime/vm/compiler.cc
index cc3b69161b382adfc552185160f65bb74e610fc2..1bc179cdd3f696979ca6d252f09ef86522b1d08d 100644
--- a/runtime/vm/compiler.cc
+++ b/runtime/vm/compiler.cc
@@ -1167,8 +1167,10 @@ bool CompileParsedFunctionHelper::Compile(CompilationPipeline* pipeline) {
         done = true;
       }
 
-      // Clear the error if it was not a real error, but just a bailout.
-      if (error.IsLanguageError() &&
+      // If is is not a background compilation, clear the error if it was not a
+      // real error, but just a bailout. If we're it a background compilation
+      // this will be dealt with in the caller.
+      if (!Compiler::IsBackgroundCompilation() && error.IsLanguageError() &&
           (LanguageError::Cast(error).kind() == Report::kBailout)) {
         thread()->clear_sticky_error();
       }
@@ -1277,6 +1279,21 @@ static RawError* CompileFunctionHelper(CompilationPipeline* pipeline,
             THR_Print("Aborted background compilation: %s\n",
                 function.ToFullyQualifiedCString());
           }
+          {
+            // If it was a bailout, then disable optimization.
+            Error& error = Error::Handle();
+            // We got an error during compilation.
+            error = thread->sticky_error();
+            thread->clear_sticky_error();
+            if (error.IsLanguageError() &&
+                LanguageError::Cast(error).kind() == Report::kBailout) {
+              if (FLAG_trace_compiler) {
+                THR_Print("--> disabling optimizations for '%s'\n",
+                          function.ToFullyQualifiedCString());
+              }
+              function.SetIsOptimizable(false);
+            }
+          }
           return Error::null();
         }
         // Optimizer bailed out. Disable optimizations and never try again.
@@ -1295,6 +1312,7 @@ static RawError* CompileFunctionHelper(CompilationPipeline* pipeline,
         // We got an error during compilation.
         error = thread->sticky_error();
         thread->clear_sticky_error();
+        // The non-optimizing compiler should not bail out.
         ASSERT(error.IsLanguageError() &&
                LanguageError::Cast(error).kind() != Report::kBailout);
         return error.raw();
@@ -1870,8 +1888,9 @@ void BackgroundCompiler::Run() {
             function = Function::null();
           } else {
             qelem = function_queue()->Remove();
-            if (FLAG_stress_test_background_compilation) {
-              const Function& old = Function::Handle(qelem->Function());
+            const Function& old = Function::Handle(qelem->Function());
+            if ((!old.HasOptimizedCode() && old.IsOptimizable()) ||
+                 FLAG_stress_test_background_compilation) {
               if (Compiler::CanOptimizeFunction(thread, old)) {
                 QueueElement* repeat_qelem = new QueueElement(old);
                 function_queue()->Add(repeat_qelem);