Inline ordered relative compares of mixed double/undefined values.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 074054ce1d0c414ce12c6e8230400a1acd798cba..2805d3983fb4af7473fd53c7730d269559ebf514 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -1457,7 +1457,17 @@ void HGoto::PrintDataTo(StringStream* stream) {
 void HCompareIDAndBranch::SetInputRepresentation(Representation r) {
   input_representation_ = r;
   if (r.IsDouble()) {
-    SetFlag(kDeoptimizeOnUndefined);
+    // ==, === and != have special handling of undefined, specifically undeifned

[fschneider, 2012/03/02 12:39:15]

s/undeifned/undefined

[danno, 2012/03/02 13:28:45]

Done.

+    // == undefined is 'true' but the standard Crankshaft tagged-to-double
+    // conversion to ensure the HCompareIDAndBranch's inputs, including
+    // undefined values, are doubles will convert undefined to NaN, and NaN ==
+    // NaN is 'false'. So all comparisons that aren't explicitly defined by the
+    // spec to call ToPrimitive() (i.e. anything not an ordered relational
+    // comparison) must deopt when one of the arguments is undefined.
+    // See v8:1434

[fschneider, 2012/03/02 12:39:15]

I'd also refer to the corresponding sections in the ES5 spec (11.9.3, 11.8.5)
and use the same terms "relational comparison" and "equality comparison".

[danno, 2012/03/02 13:28:45]

Done.

+    if (!Token::IsOrderedCompareOp(token_)) {

[fschneider, 2012/03/02 12:39:15]

maybe rename to IsRelationalCompareOp.

[danno, 2012/03/02 13:28:45]

Done.

+      SetFlag(kDeoptimizeOnUndefined);
+    }
   } else {
     ASSERT(r.IsInteger32());
   }