Fixes javascript integer overflow check.

runtime/vm/intermediate_language_x64.cc

Index: runtime/vm/intermediate_language_x64.cc
===================================================================
--- runtime/vm/intermediate_language_x64.cc	(revision 25633)
+++ runtime/vm/intermediate_language_x64.cc	(working copy)
@@ -2151,18 +2151,20 @@
 }
 
 
-static void Emit53BitOverflowCheck(FlowGraphCompiler* compiler,
+static void Emit54BitOverflowCheck(FlowGraphCompiler* compiler,
                                    Label* overflow,
                                    Register result) {
   if (FLAG_throw_on_javascript_int_overflow) {
     ASSERT(overflow != NULL);
     __ movq(TMP, result);  // result is a tagged Smi.
-    // Bits 54...64 must be all 0 or all 1. (It would be bit 53, but result
+    // Bits 55...64 must be all 0 or all 1. (It would be bit 54, but result
     // is tagged.)
-    __ shlq(result, Immediate(64 - 54));
-    __ sarq(result, Immediate(64 - 54));
+    __ shlq(result, Immediate(64 - 55));
+    __ sarq(result, Immediate(64 - 55));
     __ cmpq(result, TMP);
-    __ j(NOT_EQUAL, overflow);  // 53-bit overflow.
+    __ j(NOT_EQUAL, overflow);  // 54-bit overflow.
+    __ cmpq(result, Immediate(-0x1FFFFFFFFFFFFF-1));
+    __ j(EQUAL, overflow);  // The most negative 54-bit int is also disallowed.
   }
 }
 
@@ -2206,7 +2208,7 @@
       // Shift for result now we know there is no overflow.
       __ shlq(left, Immediate(value));
     }
-    Emit53BitOverflowCheck(compiler, deopt, result);
+    Emit54BitOverflowCheck(compiler, deopt, result);
     return;
   }
 
@@ -2236,7 +2238,7 @@
       __ SmiUntag(right);
       __ shlq(left, right);
     }
-    Emit53BitOverflowCheck(compiler, deopt, result);
+    Emit54BitOverflowCheck(compiler, deopt, result);
     return;
   }
 
@@ -2287,7 +2289,7 @@
     // Shift for result now we know there is no overflow.
     __ shlq(left, right);
   }
-  Emit53BitOverflowCheck(compiler, deopt, result);
+  Emit54BitOverflowCheck(compiler, deopt, result);
 }
 
 
@@ -2486,7 +2488,7 @@
         UNREACHABLE();
         break;
     }
-    Emit53BitOverflowCheck(compiler, deopt, result);
+    Emit54BitOverflowCheck(compiler, deopt, result);
     return;
   }  // locs()->in(1).IsConstant().
 
@@ -2529,7 +2531,7 @@
         UNREACHABLE();
         break;
     }
-    Emit53BitOverflowCheck(compiler, deopt, result);
+    Emit54BitOverflowCheck(compiler, deopt, result);
     return;
   }  // locs()->in(1).IsStackSlot().
 
@@ -2659,7 +2661,7 @@
       UNREACHABLE();
       break;
   }
-  Emit53BitOverflowCheck(compiler, deopt, result);
+  Emit54BitOverflowCheck(compiler, deopt, result);
 }
 
 
@@ -3840,7 +3842,7 @@
                                             kDeoptUnaryOp);
       __ negq(value);
       __ j(OVERFLOW, deopt);
-      Emit53BitOverflowCheck(compiler, deopt, value);
+      Emit54BitOverflowCheck(compiler, deopt, value);
       break;
     }
     case Token::kBIT_NOT:
@@ -3901,7 +3903,7 @@
   __ shlq(temp, Immediate(1));
   __ j(OVERFLOW, &do_call, Assembler::kNearJump);
   __ SmiTag(result);
-  Emit53BitOverflowCheck(compiler, &do_call, result);
+  Emit54BitOverflowCheck(compiler, &do_call, result);
   __ jmp(&done);
   __ Bind(&do_call);
   ASSERT(instance_call()->HasICData());
@@ -3947,7 +3949,7 @@
   __ shlq(temp, Immediate(1));
   __ j(OVERFLOW, deopt);
   __ SmiTag(result);
-  Emit53BitOverflowCheck(compiler, deopt, result);
+  Emit54BitOverflowCheck(compiler, deopt, result);
 }