Disconnects code objects from infrequently used unoptimized functions.

runtime/vm/flow_graph_compiler_ia32.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #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"
 #include "vm/locations.h"
 #include "vm/object_store.h"
 #include "vm/parser.h"
 #include "vm/stack_frame.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
 
@@ skipping 1070 matching lines @@
   if (flow_graph().IsCompiledForOsr()) {
     intptr_t extra_slots = StackSize()
         - flow_graph().num_stack_locals()
         - flow_graph().num_copied_params();
     ASSERT(extra_slots >= 0);
     __ EnterOsrFrame(extra_slots * kWordSize);
   } else {
     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 Immediate& raw_null =
+        Immediate(reinterpret_cast<intptr_t>(Object::null()));
+    const Register function_reg = EDI;
+    __ LoadObject(function_reg, function);
+    __ movl(EAX, FieldAddress(function_reg, Function::code_offset()));
+    __ cmpl(EAX, raw_null);
+    __ j(NOT_EQUAL, &is_connected, Assembler::kNearJump);

[srdjan, 2013/10/18 17:16:07]

Add comment what you are doing: add the code object back to function?

[zra, 2013/10/22 16:13:24]

Code obsolete.

+    __ movl(EAX, Address(EBP, kPcMarkerSlotFromFp * kWordSize));
+    const intptr_t code_pc_dist =
+      Instructions::HeaderSize() - Instructions::code_offset() +
+      Assembler::kEntryPointToPcMarkerOffset;

[srdjan, 2013/10/18 17:16:07]

Indent 4 chars the two lines above

[zra, 2013/10/22 16:13:24]

Code obsolete

+    __ movl(EAX, Address(EAX, -code_pc_dist));
+    __ movl(FieldAddress(function_reg, Function::code_offset()), EAX);
+    __ movl(
+        FieldAddress(function_reg, Function::unoptimized_code_offset()), EAX);
+    __ Bind(&is_connected);
+  }
 }
 
 
 void FlowGraphCompiler::CompileGraph() {
   InitCompiler();
 
   TryIntrinsify();
 
   EmitFrameEntry();
 
@@ skipping 294 matching lines @@
   __ j(ZERO, &call_target_function, Assembler::kNearJump);
   __ cmpl(EDX, EAX);
   __ j(NOT_EQUAL, &update, Assembler::kNearJump);
 
   __ Bind(&call_target_function);
   // Call the target found in the cache.  For a class id match, this is a
   // 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.
   __ movl(EAX, FieldAddress(EDI, ECX, TIMES_4, base + kWordSize));
-  __ movl(EAX, FieldAddress(EAX, Function::code_offset()));
-  __ movl(EAX, FieldAddress(EAX, Code::instructions_offset()));
+  __ movl(EBX, FieldAddress(EAX, Function::code_offset()));
+  if (FLAG_collect_code) {
+    // If we are collecting code, the code object may be null.
+    Label is_compiled;
+    const Immediate& raw_null =
+        Immediate(reinterpret_cast<intptr_t>(Object::null()));
+    __ cmpl(EBX, raw_null);
+    __ j(NOT_EQUAL, &is_compiled, Assembler::kNearJump);
+    __ EnterStubFrame();
+    __ pushl(EDX);  // Preserve arguments descriptor array.
+    __ pushl(ECX);  // Preserve IC data object.
+    __ pushl(EAX);  // Pass function.
+    __ CallRuntime(kCompileFunctionRuntimeEntry, 1);
+    __ popl(EAX);  // Restore function.

[srdjan, 2013/10/18 17:16:07]

The argument can be modified in the callee, therefore you need to do extra
saving/restoring of function.

[zra, 2013/10/22 16:13:24]

At other call-sites of CompileFunction (e.g. around stub_code_ia32.cc:720) there
are comments indicating the argument is read-only. If this is actually not true,
I'll preserve the function, and edit the comments at all call-sites.

+    __ popl(ECX);  // Restore IC data array.
+    __ popl(EDX);  // Restore arguments descriptor array.
+    __ LeaveFrame();
+    __ movl(EBX, FieldAddress(EAX, Function::code_offset()));
+    __ Bind(&is_compiled);
+  }
+  __ movl(EAX, FieldAddress(EBX, Code::instructions_offset()));
   __ LoadObject(ECX, ic_data);
   __ LoadObject(EDX, arguments_descriptor);
   __ addl(EAX, Immediate(Instructions::HeaderSize() - kHeapObjectTag));
   __ call(EAX);
   AddCurrentDescriptor(PcDescriptors::kOther, Isolate::kNoDeoptId, token_pos);
   RecordSafepoint(locs);
   AddDeoptIndexAtCall(Isolate::ToDeoptAfter(deopt_id), token_pos);
   __ Drop(argument_count);
 }
 
@@ skipping 488 matching lines @@
   __ movups(reg, Address(ESP, 0));
   __ addl(ESP, Immediate(kFpuRegisterSize));
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32