Range info propagation through HBoundsCheck.

src/hydrogen-instructions.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 929 matching lines @@
     length_rep = Representation::Smi();
   }
   Representation r = index_rep.generalize(length_rep);
   if (r.is_more_general_than(Representation::Integer32())) {
     r = Representation::Integer32();
   }
   UpdateRepresentation(r, h_infer, "boundscheck");
 }
 
 
+Range* HBoundsCheck::InferRange(Zone* zone) {
+  Representation r = representation();
+  if (r.IsSmiOrInteger32() && length()->HasRange()) {
+    int upper = length()->range()->upper() - (allow_equality() ? 0 : 1);
+    int lower = 0;
+
+    Range* result = new(zone) Range(lower, upper);
+    if (index()->HasRange()) {
+      result->Intersect(index()->range());
+    }
+
+    // In case of Smi representation, clamp result to Smi::kMaxValue.
+    if (r.IsSmi()) result->ClampToSmi();
+    return result;
+  }
+  return HValue::InferRange(zone);
+}
+
+
 void HBoundsCheckBaseIndexInformation::PrintDataTo(StringStream* stream) {
   stream->Add("base: ");
   base_index()->PrintNameTo(stream);
   stream->Add(", check: ");
   base_index()->PrintNameTo(stream);
 }
 
 
 void HCallConstantFunction::PrintDataTo(StringStream* stream) {
   if (IsApplyFunction()) {
@@ skipping 3414 matching lines @@
       break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal