Fix handling of -0 in the unary-op IC and avoid repeated patching/transitions.

src/ic.cc

Index: src/ic.cc
===================================================================
--- src/ic.cc	(revision 7936)
+++ src/ic.cc	(working copy)
@@ -2200,9 +2200,23 @@
 }
 
 
-TRUnaryOpIC::TypeInfo TRUnaryOpIC::JoinTypes(TRUnaryOpIC::TypeInfo x,
-                                             TRUnaryOpIC::TypeInfo y) {
-  return x >= y ? x : y;
+TRUnaryOpIC::TypeInfo TRUnaryOpIC::ComputeNewType(
+    TRUnaryOpIC::TypeInfo type,
+    TRUnaryOpIC::TypeInfo previous) {
+  switch (previous) {
+    case TRUnaryOpIC::UNINITIALIZED:
+      return type;
+    case TRUnaryOpIC::SMI:
+      return (type == TRUnaryOpIC::GENERIC)
+          ? TRUnaryOpIC::GENERIC
+          : TRUnaryOpIC::HEAP_NUMBER;
+    case TRUnaryOpIC::HEAP_NUMBER:
+      return TRUnaryOpIC::GENERIC;
+    case TRUnaryOpIC::GENERIC:
+      // We should never do patching if we are in GENERIC state.
+      UNREACHABLE();
+      return TRUnaryOpIC::GENERIC;
+  }
 }
 
 
@@ -2314,7 +2328,7 @@
       static_cast<TRUnaryOpIC::TypeInfo>(Smi::cast(args[3])->value());
 
   TRUnaryOpIC::TypeInfo type = TRUnaryOpIC::GetTypeInfo(operand);
-  type = TRUnaryOpIC::JoinTypes(type, previous_type);
+  type = TRUnaryOpIC::ComputeNewType(type, previous_type);
 
   Handle<Code> code = GetTypeRecordingUnaryOpStub(key, type);
   if (!code.is_null()) {