Improve internal compiler API so that OSR code is never installed on function.

runtime/vm/code_generator.cc

Index: runtime/vm/code_generator.cc
diff --git a/runtime/vm/code_generator.cc b/runtime/vm/code_generator.cc
index 22005f0796f98f707b0e57f508a8c723680c9222..bf44083dd4dfe08bde5dc7d37fcc1598a6cea7bf 100644
--- a/runtime/vm/code_generator.cc
+++ b/runtime/vm/code_generator.cc
@@ -658,10 +658,10 @@ DEFINE_RUNTIME_ENTRY(PatchStaticCall, 0) {
   const Function& target_function = Function::Handle(
       zone, caller_code.GetStaticCallTargetFunctionAt(caller_frame->pc()));
   if (!target_function.HasCode()) {
-    const Error& error =
-        Error::Handle(zone, Compiler::CompileFunction(thread, target_function));
-    if (!error.IsNull()) {
-      Exceptions::PropagateError(error);
+    const Object& result = Object::Handle(
+        zone, Compiler::CompileFunction(thread, target_function));
+    if (result.IsError()) {
+      Exceptions::PropagateError(Error::Cast(result));
     }
   }
   const Code& target_code = Code::Handle(zone, target_function.CurrentCode());
@@ -941,10 +941,10 @@ DEFINE_RUNTIME_ENTRY(StaticCallMissHandlerOneArg, 2) {
   ASSERT(ic_data.NumberOfChecksIs(1));
   const Function& target = Function::Handle(ic_data.GetTargetAt(0));
   if (!target.HasCode()) {
-    const Error& error =
-        Error::Handle(Compiler::CompileFunction(thread, target));
-    if (!error.IsNull()) {
-      Exceptions::PropagateError(error);
+    const Object& result =
+        Object::Handle(Compiler::CompileFunction(thread, target));
+    if (result.IsError()) {
+      Exceptions::PropagateError(Error::Cast(result));
     }
   }
   ASSERT(!target.IsNull() && target.HasCode());
@@ -973,10 +973,10 @@ DEFINE_RUNTIME_ENTRY(StaticCallMissHandlerTwoArgs, 3) {
   ASSERT(!ic_data.NumberOfChecksIs(0));
   const Function& target = Function::Handle(ic_data.GetTargetAt(0));
   if (!target.HasCode()) {
-    const Error& error =
-        Error::Handle(Compiler::CompileFunction(thread, target));
-    if (!error.IsNull()) {
-      Exceptions::PropagateError(error);
+    const Object& result =
+        Object::Handle(Compiler::CompileFunction(thread, target));
+    if (result.IsError()) {
+      Exceptions::PropagateError(Error::Cast(result));
     }
   }
   ASSERT(!target.IsNull() && target.HasCode());
@@ -1322,10 +1322,10 @@ DEFINE_RUNTIME_ENTRY(MegamorphicCacheMissHandler, 3) {
       // treeshaker.
 
       if (!target_function.HasCode()) {
-        const Error& error =
-            Error::Handle(Compiler::CompileFunction(thread, target_function));
-        if (!error.IsNull()) {
-          Exceptions::PropagateError(error);
+        const Object& result =
+            Object::Handle(Compiler::CompileFunction(thread, target_function));
+        if (result.IsError()) {
+          Exceptions::PropagateError(Error::Cast(result));
         }
       }
 
@@ -1706,28 +1706,20 @@ DEFINE_RUNTIME_ENTRY(StackOverflow, 0) {
                 function.usage_counter());
     }
 
-    const Code& original_code = Code::Handle(function.CurrentCode());
     // Since the code is referenced from the frame and the ZoneHandle,
     // it cannot have been removed from the function.
-    ASSERT(!original_code.IsNull());
-    const Error& error = Error::Handle(
+    const Object& result = Object::Handle(
         Compiler::CompileOptimizedFunction(thread, function, osr_id));
-    if (!error.IsNull()) {
-      Exceptions::PropagateError(error);
+    if (result.IsError()) {
+      Exceptions::PropagateError(Error::Cast(result));
     }
 
-    const Code& optimized_code = Code::Handle(function.CurrentCode());
-    // The current code will not be changed in the case that the compiler
-    // bailed out during OSR compilation.
-    if (optimized_code.raw() != original_code.raw()) {
-      // The OSR code does not work for calling the function, so restore the
-      // unoptimized code.  Patch the stack frame to return into the OSR
-      // code.
+    if (!result.IsNull()) {
+      const Code& code = Code::Cast(result);
       uword optimized_entry =
-          Instructions::UncheckedEntryPoint(optimized_code.instructions());
-      function.AttachCode(original_code);
+          Instructions::UncheckedEntryPoint(code.instructions());
       frame->set_pc(optimized_entry);
-      frame->set_pc_marker(optimized_code.raw());
+      frame->set_pc_marker(code.raw());
     }
   }
 }
@@ -1800,13 +1792,11 @@ DEFINE_RUNTIME_ENTRY(OptimizeInvokedFunction, 1) {
                   function.ToFullyQualifiedCString());
       }
     }
-    const Error& error = Error::Handle(
+    const Object& result = Object::Handle(
         zone, Compiler::CompileOptimizedFunction(thread, function));
-    if (!error.IsNull()) {
-      Exceptions::PropagateError(error);
+    if (result.IsError()) {
+      Exceptions::PropagateError(Error::Cast(result));
     }
-    const Code& optimized_code = Code::Handle(zone, function.CurrentCode());
-    ASSERT(!optimized_code.IsNull());
   }
   arguments.SetReturn(function);
 #else
@@ -1836,10 +1826,10 @@ DEFINE_RUNTIME_ENTRY(FixCallersTarget, 0) {
   const Function& target_function = Function::Handle(
       zone, caller_code.GetStaticCallTargetFunctionAt(frame->pc()));
   if (!target_function.HasCode()) {
-    const Error& error =
-        Error::Handle(zone, Compiler::CompileFunction(thread, target_function));
-    if (!error.IsNull()) {
-      Exceptions::PropagateError(error);
+    const Object& result =
+        Object::Handle(Compiler::CompileFunction(thread, target_function));
+    if (result.IsError()) {
+      Exceptions::PropagateError(Error::Cast(result));
     }
   }
   ASSERT(target_function.HasCode());