Fix smi-based math floor.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index f977a750d946a6b24d657b08229fc4a238c368b2..a03faca5c85ff989f6c35449e24b41e82b2b5ce3 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -2430,6 +2430,21 @@ class HUnaryMathOperation: public HTemplateInstruction<2> {
     }
   }
 
+  virtual void UpdateRepresentation(Representation new_rep,
+                                    HInferRepresentationPhase* h_infer,
+                                    const char* reason) {
+    if (flexible_int() && !new_rep.IsSmi()) {
+      new_rep = Representation::Integer32();
+    }
+    HValue::UpdateRepresentation(new_rep, h_infer, reason);
+  }
+
+  virtual void RepresentationChanged(Representation new_rep) {
+    if (flexible_int() && new_rep.IsInteger32()) {
+      ClearFlag(kFlexibleRepresentation);
+    }
+  }
+
   virtual Range* InferRange(Zone* zone);
 
   virtual HValue* Canonicalize();
@@ -2447,6 +2462,10 @@ class HUnaryMathOperation: public HTemplateInstruction<2> {
   }
 
  private:
+  bool flexible_int() {
+    return op_ == kMathFloor || op_ == kMathRound;
+  }
+
   HUnaryMathOperation(HValue* context, HValue* value, BuiltinFunctionId op)
       : HTemplateInstruction<2>(HType::TaggedNumber()), op_(op) {
     SetOperandAt(0, context);
@@ -2454,8 +2473,8 @@ class HUnaryMathOperation: public HTemplateInstruction<2> {
     switch (op) {
       case kMathFloor:
       case kMathRound:
-        // TODO(verwaest): Set representation to flexible int starting as smi.
-        set_representation(Representation::Integer32());
+        set_representation(Representation::Smi());
+        SetFlag(kFlexibleRepresentation);
         break;
       case kMathAbs:
         // Not setting representation here: it is None intentionally.