Disconnects code objects from infrequently used unoptimized functions.

runtime/vm/flow_graph_compiler_mips.cc

Index: runtime/vm/flow_graph_compiler_mips.cc
===================================================================
--- runtime/vm/flow_graph_compiler_mips.cc	(revision 28803)
+++ runtime/vm/flow_graph_compiler_mips.cc	(working copy)
@@ -8,6 +8,7 @@
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
+#include "vm/compiler.h"
 #include "vm/dart_entry.h"
 #include "vm/deopt_instructions.h"
 #include "vm/il_printer.h"
@@ -1126,6 +1127,28 @@
     ASSERT(StackSize() >= 0);
     __ EnterDartFrame(StackSize() * kWordSize);
   }
+
+  // TODO(zra): maybe do this only before we try to optimize?
+  if (FLAG_collect_code) {
+    // If we are collecting code, make sure this function still has a pointer
+    // to the code object.
+    // TODO(zra): Is it cheaper just to write the Function fields with the
+    // code object without doing the test?
+    Label is_connected;
+    const Register function_reg = T0;
+    __ LoadObject(function_reg, function);
+    __ lw(T1, FieldAddress(function_reg, Function::code_offset()));
+    __ BranchNotEqual(T1, reinterpret_cast<intptr_t>(Object::null()),
+                      &is_connected);
+    __ lw(T1, Address(FP, kPcMarkerSlotFromFp * kWordSize));
+    const intptr_t code_pc_dist =
+      Instructions::HeaderSize() - Instructions::code_offset() +
+      Assembler::kEntryPointToPcMarkerOffset;
+    __ lw(T1, Address(T1, -code_pc_dist));
+    __ sw(T1, FieldAddress(function_reg, Function::code_offset()));
+    __ sw(T1, FieldAddress(function_reg, Function::unoptimized_code_offset()));
+    __ Bind(&is_connected);
+  }
 }
 
 
@@ -1412,11 +1435,30 @@
   // proper target for the given name and arguments descriptor.  If the
   // illegal class id was found, the target is a cache miss handler that can
   // be invoked as a normal Dart function.
-  __ sll(TMP1, T3, 2);
-  __ addu(TMP1, T2, TMP1);
-  __ lw(T0, FieldAddress(TMP, base + kWordSize));
-  __ lw(T0, FieldAddress(T0, Function::code_offset()));
-  __ lw(T0, FieldAddress(T0, Code::instructions_offset()));
+  __ sll(T1, T3, 2);
+  __ addu(T1, T2, T1);
+  __ lw(T0, FieldAddress(T1, base + kWordSize));
+  __ lw(T1, FieldAddress(T0, Function::code_offset()));
+  if (FLAG_collect_code) {
+    // If we are collecting code, the code object may be null.
+    Label is_compiled;
+    __ BranchNotEqual(T1, reinterpret_cast<int32_t>(Object::null()),
+                      &is_compiled);
+    __ EnterStubFrame();
+    __ addiu(SP, SP, Immediate(-3 * kWordSize));
+    __ sw(S5, Address(SP, 2 * kWordSize));  // Preserve IC data.
+    __ sw(S4, Address(SP, 1 * kWordSize));  // Preserve arg desc.
+    __ sw(T0, Address(SP, 0 * kWordSize));  // Function argument.
+    __ CallRuntime(kCompileFunctionRuntimeEntry, 1);
+    __ lw(T0, Address(SP, 0 * kWordSize));  // Restore function.
+    __ lw(S4, Address(SP, 1 * kWordSize));  // Restore arg desc.
+    __ lw(S5, Address(SP, 2 * kWordSize));  // Restore IC data.
+    __ addiu(SP, SP, Immediate(3 * kWordSize));
+    __ LeaveStubFrame();
+    __ lw(T1, FieldAddress(T0, Function::code_offset()));
+    __ Bind(&is_compiled);
+  }
+  __ lw(T0, FieldAddress(T1, Code::instructions_offset()));
   __ LoadObject(S5, ic_data);
   __ LoadObject(S4, arguments_descriptor);
   __ AddImmediate(T0, Instructions::HeaderSize() - kHeapObjectTag);