Migrate instance of deprecated maps in HCheckMaps.

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 25867adb4668efa7bfaf3e07ab912ead9b5353b1..abcf664876a71032a950f2f543b1e866b7ce504d 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -2061,11 +2061,24 @@ LInstruction* LChunkBuilder::DoCheckFunction(HCheckFunction* instr) {
 
 
 LInstruction* LChunkBuilder::DoCheckMaps(HCheckMaps* instr) {
+  LOperand* context = NULL;
   LOperand* value = NULL;
-  if (!instr->CanOmitMapChecks()) value = UseRegisterAtStart(instr->value());
-  LCheckMaps* result = new(zone()) LCheckMaps(value);
-  if (instr->CanOmitMapChecks()) return result;
-  return AssignEnvironment(result);
+  if (!instr->CanOmitMapChecks()) {
+    value = UseRegisterAtStart(instr->value());
+    if (instr->has_migration_target()) {
+      // The context is not actually required for instance migration, so clobber
+      // the context register to Smi::FromInt(0).
+      HConstant* clobber_value = graph()->GetConstant0();
+      context = UseConstant(clobber_value);

[danno, 2013/08/05 14:36:59]

I don't think you need any of this new logic, do you? The context register isn't
used, the code can stay the same, right?

[Toon Verwaest, 2013/08/05 15:03:26]

Done.

+      info()->MarkAsDeferredCalling();
+    }
+  }
+  LCheckMaps* result = new(zone()) LCheckMaps(context, value);
+  if (!instr->CanOmitMapChecks()) {
+    AssignEnvironment(result);
+    if (instr->has_migration_target()) return AssignPointerMap(result);
+  }
+  return result;
 }