Fixes javascript integer overflow check.

runtime/vm/object.cc

Index: runtime/vm/object.cc
===================================================================
--- runtime/vm/object.cc	(revision 25633)
+++ runtime/vm/object.cc	(working copy)
@@ -52,7 +52,7 @@
 DEFINE_FLAG(int, huge_method_cutoff_in_code_size, 200000,
     "Huge method cutoff in unoptimized code size (in bytes).");
 DEFINE_FLAG(bool, throw_on_javascript_int_overflow, false,
-    "Throw an exception when integer arithmetic exceeds 53 bits.");
+    "Throw an exception when integer arithmetic exceeds 54 bits.");
 DECLARE_FLAG(bool, trace_compiler);
 DECLARE_FLAG(bool, eliminate_type_checks);
 DECLARE_FLAG(bool, enable_type_checks);
@@ -11233,12 +11233,12 @@
 }
 
 
-// Throw FiftyThreeBitOverflow exception.
-static void ThrowFiftyThreeBitOverflow(const Integer& i) {
+// Throw FiftyFourBitOverflow exception.
+static void ThrowFiftyFourBitOverflow(const Integer& i) {
   const Array& exc_args = Array::Handle(Array::New(1));
   const String& i_str = String::Handle(String::New(i.ToCString()));
   exc_args.SetAt(0, i_str);
-  Exceptions::ThrowByType(Exceptions::kFiftyThreeBitOverflowError, exc_args);
+  Exceptions::ThrowByType(Exceptions::kFiftyFourBitOverflowError, exc_args);
 }
 
 
@@ -11251,7 +11251,7 @@
     ASSERT(!BigintOperations::FitsIntoSmi(big));
     ASSERT(!BigintOperations::FitsIntoInt64(big));
     if (FLAG_throw_on_javascript_int_overflow) {
-      ThrowFiftyThreeBitOverflow(big);
+      ThrowFiftyFourBitOverflow(big);
     }
     return big.raw();
   }
@@ -11260,7 +11260,7 @@
 
 
 // This is called from LiteralToken::New() in the parser, so we can't
-// raise an exception for 53-bit overflow here. Instead we do it in
+// raise an exception for 54-bit overflow here. Instead we do it in
 // Parser::CurrentIntegerLiteral(), which is the point in the parser where
 // integer literals escape, so we can call Parser::ErrorMsg().
 RawInteger* Integer::NewCanonical(const String& str) {
@@ -11280,13 +11280,20 @@
 }
 
 
+// Floating point has a sign bit and 53 bits of fraction. When the sign bit is
+// set, and the fraction is 0, the result is -0.0, not MIN_53BIT_INT.

[siva, 2013/07/31 16:08:28]

The comment here is a bit confusing as we are dealing with integers and
you refer to floating point. I presume you are referring to the
implementation by dart2js, maybe you should make that explicit.

[zra, 2013/07/31 17:46:31]

Done.

+static bool Is54BitNoMinInt(int64_t value) {
+  return (Utils::IsInt(54, value)) && (value != (-0x1FFFFFFFFFFFFF - 1));
+}
+
+
 RawInteger* Integer::New(int64_t value, Heap::Space space) {
   if ((value <= Smi::kMaxValue) && (value >= Smi::kMinValue)) {
     return Smi::New(value);
   }
-  if (FLAG_throw_on_javascript_int_overflow && !Utils::IsInt(53, value)) {
+  if (FLAG_throw_on_javascript_int_overflow && !Is54BitNoMinInt(value)) {
     const Integer &i = Integer::Handle(Mint::New(value));
-    ThrowFiftyThreeBitOverflow(i);
+    ThrowFiftyFourBitOverflow(i);
   }
   return Mint::New(value, space);
 }
@@ -11297,7 +11304,7 @@
     if (FLAG_throw_on_javascript_int_overflow) {
       const Integer &i =
           Integer::Handle(BigintOperations::NewFromUint64(value));
-      ThrowFiftyThreeBitOverflow(i);
+      ThrowFiftyFourBitOverflow(i);
     }
     return BigintOperations::NewFromUint64(value);
   } else {
@@ -11324,8 +11331,8 @@
 }
 
 
-// Returns true if the signed Integer requires more than 53 bits.
-bool Integer::CheckFiftyThreeBitOverflow() const {
+// Returns true if the signed Integer requires more than 54 bits.
+bool Integer::CheckFiftyFourBitOverflow() const {
   // Always overflow if the value doesn't fit into an int64_t.
   int64_t value = 1ULL << 63;
   if (IsSmi()) {
@@ -11342,14 +11349,14 @@
       value = BigintOperations::ToInt64(big_value);
     }
   }
-  return !Utils::IsInt(53, value);
+  return !Is54BitNoMinInt(value);
 }
 
 
 RawInteger* Integer::AsValidInteger() const {
   if (FLAG_throw_on_javascript_int_overflow &&
-      CheckFiftyThreeBitOverflow()) {
-    ThrowFiftyThreeBitOverflow(*this);
+      CheckFiftyFourBitOverflow()) {
+    ThrowFiftyFourBitOverflow(*this);
   }
   if (IsSmi()) return raw();
   if (IsMint()) {