CTX and TMP registers may not be allocated.

runtime/vm/intermediate_language_x64.cc

 // Copyright (c) 2012, 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_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/flow_graph_compiler.h"
 #include "vm/locations.h"
 #include "vm/stub_code.h"
@@ skipping 40 matching lines @@
 }
 
 
 void CurrentContextComp::EmitNativeCode(FlowGraphCompiler* compiler) {
   __ movq(locs()->out().reg(), CTX);
 }
 
 
 LocationSummary* StoreContextComp::MakeLocationSummary() {
   LocationSummary* summary = new LocationSummary(1);
-  summary->set_in(0, Location::RegisterLocation(CTX));

[Vyacheslav Egorov (Google), 2012/05/22 23:25:23]

I don't think this change is necessary. 

This is not a register allocated register, this is known fixed register.

[srdjan, 2012/05/22 23:45:38]

How is it known? The register allocator attempts to allocate any register,
including the one holding context, unless we block it from being allocatable.

[srdjan, 2012/05/22 23:57:21]

Discussed offline and  reverted the changes here by moving the blocking of
registers after the input registers locking and before allocating a register.

+  summary->set_in(0, Location::RequiresRegister());
   return summary;
 }
 
 
 void StoreContextComp::EmitNativeCode(FlowGraphCompiler* compiler) {
-  // Nothing to do.  Context register were loaded by register allocator.
-  ASSERT(locs()->in(0).reg() == CTX);

[Vyacheslav Egorov (Google), 2012/05/22 23:25:23]

Ditto.

+  __ movq(CTX, locs()->in(0).reg());
 }
 
 
 LocationSummary* StrictCompareComp::MakeLocationSummary() {
   return MakeSimpleLocationSummary(2, Location::SameAsFirstInput());
 }
 
 
 void StrictCompareComp::EmitNativeCode(FlowGraphCompiler* compiler) {
   const Bool& bool_true = Bool::ZoneHandle(Bool::True());
@@ skipping 127 matching lines @@
     __ LoadObject(result, value());
   }
 }
 
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64