Ensure that BoxInt32 input is correctly preserved on the slow-path.

runtime/vm/locations.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/locations.h"
 
 #include "vm/assembler.h"
 #include "vm/il_printer.h"
 #include "vm/intermediate_language.h"
 #include "vm/flow_graph_compiler.h"
@@ skipping 14 matching lines @@
 
 LocationSummary::LocationSummary(Isolate* isolate,
                                  intptr_t input_count,
                                  intptr_t temp_count,
                                  LocationSummary::ContainsCall contains_call)
     : num_inputs_(input_count),
       num_temps_(temp_count),
       stack_bitmap_(NULL),
       contains_call_(contains_call),
       live_registers_() {
+#if defined(DEBUG)
+  writable_inputs_ = 0;
+#endif
   input_locations_ = isolate->current_zone()->Alloc<Location>(num_inputs_);
   temp_locations_ = isolate->current_zone()->Alloc<Location>(num_temps_);
 }
 
 
 LocationSummary* LocationSummary::Make(
     Isolate* isolate,
     intptr_t input_count,
     Location out,
     LocationSummary::ContainsCall contains_call) {
@@ skipping 205 matching lines @@
   }
 
   if (!out(0).IsInvalid()) {
     f->Print(" => ");
     out(0).PrintTo(f);
   }
 
   if (always_calls()) f->Print(" C");
 }
 
+
+#if defined(DEBUG)
+void LocationSummary::DiscoverWritableInputs() {
+  if (!HasCallOnSlowPath()) {
+    return;
+  }
+
+  for (intptr_t i = 0; i < input_count(); i++) {
+    if (in(i).IsUnallocated() &&
+        (in(i).policy() == Location::kWritableRegister)) {
+      writable_inputs_ |= 1 << i;
+    }
+  }
+}
+
+
+void LocationSummary::CheckWritableInputs() {
+  ASSERT(HasCallOnSlowPath());
+  for (intptr_t i = 0; i < input_count(); i++) {
+    if ((writable_inputs_ & (1 << i)) != 0) {
+      // Writable registers have to be manually preserved because
+      // with the right representation because register allocator does not know
+      // how they are used within the instruction template.
+      ASSERT(in(i).IsMachineRegister());
+      ASSERT(live_registers()->Contains(in(i)));
+    }
+  }
+}
+#endif
+
 }  // namespace dart