Fix smi-based math floor.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 997b7c2fda9b29455d03faac59c5a49a60d18d5c..5fc65ce8034ca6d7e764e41da2f447dced9aef61 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -1285,6 +1285,15 @@ static HValue* SimplifiedDividendForMathFloorOfDiv(HValue* dividend) {
 
 
 HValue* HUnaryMathOperation::Canonicalize() {
+  if (op() == kMathRound) {
+    HValue* val = value();
+    if (val->IsChange()) val = HChange::cast(val)->value();
+
+    // If the input is integer32 then we replace the round instruction
+    // with its input.
+    if (val->representation().IsSmiOrInteger32()) return val;
+  }
+
   if (op() == kMathFloor) {
     HValue* val = value();
     if (val->IsChange()) val = HChange::cast(val)->value();
@@ -3313,7 +3322,11 @@ Representation HUnaryMathOperation::RepresentationFromInputs() {
   // If any of the actual input representation is more general than what we
   // have so far but not Tagged, use that representation instead.
   Representation input_rep = value()->representation();
-  if (!input_rep.IsTagged()) rep = rep.generalize(input_rep);
+  if (!input_rep.IsTagged()) {
+    rep = rep.generalize(input_rep);
+  } else if (flexible_int()) {
+    rep = Representation::Integer32();
+  }
   return rep;
 }