Add more safe points in compiler

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..7295cf48f5a63e8a9295db87d769b6302534aebd 100644
--- a/runtime/vm/code_generator.cc
+++ b/runtime/vm/code_generator.cc
@@ -1706,7 +1706,12 @@ DEFINE_RUNTIME_ENTRY(StackOverflow, 0) {
                 function.usage_counter());
     }
 
+    // We need to save the original code because the way we check for the
+    // success of the compiler pipeline is to see if it installed the new code.
+    // We also need the original because the pipeline installs the code even
+    // though it is OSR code and not usable for normal entry.
     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());
@@ -1725,6 +1730,13 @@ DEFINE_RUNTIME_ENTRY(StackOverflow, 0) {
       // code.
       uword optimized_entry =
           Instructions::UncheckedEntryPoint(optimized_code.instructions());
+      // Unfortunately, while we were compiling, the background compiler may

[Vyacheslav Egorov (Google), 2017/03/27 14:11:51]

The comment is inaccurate: it is background compiler that disables the
unoptimized code. see Function::InstallOptimizedCode - there is a hack there
that prevents disabling of the unoptimized code when we are installing for OSR.

[erikcorry, 2017/03/30 14:10:19]

I now made more serious changes to this section in
https://codereview.chromium.org/2781483005/ so it should be more solid.

+      // have completed a non-OSR compilation of the same code. Our call to the
+      // compiler overwrote the optimized version with an unusable OSR version,
+      // which doesn't have the right entry point.  If it did that it also
+      // disabled the old version, so we have to reenable it before we install
+      // it.  See https://github.com/dart-lang/sdk/issues/29160
+      original_code.Enable();
       function.AttachCode(original_code);
       frame->set_pc(optimized_entry);
       frame->set_pc_marker(optimized_code.raw());