tighten invariants of HValue::InferRange

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 2be2a032574b6bf9af1f8560e19fe95d1694bab7..f9f48ae019ef39f6da4f6d67277540c86832de71 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -862,18 +862,15 @@ void HInstanceOf::PrintDataTo(StringStream* stream) {
 
 
 Range* HValue::InferRange() {
-  if (representation().IsTagged()) {
-    // Tagged values are always in int32 range when converted to integer,
-    // but they can contain -0.
+  if (representation().IsInteger32()) {
+    // Untagged integer32 cannot be -0.
+    return new Range();
+  } else {
+    // Tagged values, untagged doubles, and values with unknown representation
+    // can contain -0.
     Range* result = new Range();
     result->set_can_be_minus_zero(true);
     return result;
-  } else if (representation().IsNone()) {
-    return NULL;
-  } else {
-    // Untagged integer32 cannot be -0 and we don't compute ranges for
-    // untagged doubles.
-    return new Range();
   }
 }