Fix Smi vs. HeapObject confusion in HConstants.

Representation and HType should agree with each other.

BUG=chromium:412215
LOG=y
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/556563005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23901 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/conversions.h

@@ -153,6 +153,12 @@ static inline bool IsMinusZero(double value) {
 }
 
 
+static inline bool IsSmiDouble(double value) {
+  return !IsMinusZero(value) && value >= Smi::kMinValue &&
+         value <= Smi::kMaxValue && value == FastI2D(FastD2I(value));
+}
+
+
 // Integer32 is an integer that can be represented as a signed 32-bit
 // integer. It has to be in the range [-2^31, 2^31 - 1].
 // We also have to check for negative 0 as it is not an Integer32.

src/hydrogen-instructions.cc

@@ -2815,6 +2815,13 @@ void HConstant::Initialize(Representation r) {
       r = Representation::Tagged();
     }
   }
+  if (r.IsSmi()) {
+    // If we have an existing handle, zap it, because it might be a heap
+    // number which we must not re-use when copying this HConstant to
+    // Tagged representation later, because having Smi representation now
+    // could cause heap object checks not to get emitted.
+    object_ = Unique<Object>(Handle<Object>::null());
+  }
   set_representation(r);
   SetFlag(kUseGVN);
 }

src/hydrogen-types.cc

@@ -42,7 +42,10 @@ HType HType::FromType<HeapType>(Handle<HeapType> type);
 HType HType::FromValue(Handle<Object> value) {
   if (value->IsSmi()) return HType::Smi();
   if (value->IsNull()) return HType::Null();
-  if (value->IsHeapNumber()) return HType::HeapNumber();
+  if (value->IsHeapNumber()) {
+    double n = Handle<v8::internal::HeapNumber>::cast(value)->value();
+    return IsSmiDouble(n) ? HType::Smi() : HType::HeapNumber();
+  }
   if (value->IsString()) return HType::String();
   if (value->IsBoolean()) return HType::Boolean();
   if (value->IsUndefined()) return HType::Undefined();

test/mjsunit/regress/regress-crbug-412215.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+var dummy = {foo: "true"};
+
+var a = {y:0.5};
+a.y = 357;
+var b = a.y;
+
+var d;
+function f(  )  {
+  d = 357;
+  return {foo: b};
+}
+f();
+f();
+%OptimizeFunctionOnNextCall(f);
+var x = f();
+
+// With the bug, x is now an invalid object; the code below
+// triggers a crash.
+
+function g(obj) {
+  return obj.foo.length;
+}
+
+g(dummy);
+g(dummy);
+%OptimizeFunctionOnNextCall(g);
+g(x);