Disconnects code objects from infrequently used unoptimized functions.

runtime/vm/stub_code_arm.cc

Index: runtime/vm/stub_code_arm.cc
===================================================================
--- runtime/vm/stub_code_arm.cc	(revision 28803)
+++ runtime/vm/stub_code_arm.cc	(working copy)
@@ -1589,8 +1589,25 @@
 
   __ Bind(&call_target_function);
   // R0: target function.
-  __ ldr(R0, FieldAddress(R0, Function::code_offset()));
-  __ ldr(R0, FieldAddress(R0, Code::instructions_offset()));
+  __ ldr(R1, FieldAddress(R0, Function::code_offset()));
+  if (FLAG_collect_code) {
+    // If we are collecting code, the code object may be null.
+    Label is_compiled;
+    __ CompareImmediate(R1, reinterpret_cast<intptr_t>(Object::null()));
+    __ b(&is_compiled, NE);
+    __ EnterStubFrame();
+    // Preserve arg desc. and IC data object.
+    __ PushList((1 << R4) | (1 << R5));
+    __ Push(R0);  // Pass function.
+    __ CallRuntime(kCompileFunctionRuntimeEntry, 1);
+    __ Pop(R0);  // Discard argument.
+    __ PopList((1 << R4) | (1 << R5));  // Restore arg desc. and IC data.
+    __ LeaveStubFrame();
+    // R0: target function.
+    __ ldr(R1, FieldAddress(R0, Function::code_offset()));
+    __ Bind(&is_compiled);
+  }
+  __ ldr(R0, FieldAddress(R1, Code::instructions_offset()));
   __ AddImmediate(R0, Instructions::HeaderSize() - kHeapObjectTag);
   __ bx(R0);