Introduce %_IsMinusZero.

src/arm/full-codegen-arm.cc

Index: src/arm/full-codegen-arm.cc
diff --git a/src/arm/full-codegen-arm.cc b/src/arm/full-codegen-arm.cc
index 8fb1e15585bffc4bcf303f67834baeb49145ae48..276d8ec167a3367bc5fe9e6eb845574b414425d9 100644
--- a/src/arm/full-codegen-arm.cc
+++ b/src/arm/full-codegen-arm.cc
@@ -3104,6 +3104,32 @@ void FullCodeGenerator::EmitIsFunction(CallRuntime* expr) {
 }
 
 
+void FullCodeGenerator::EmitIsMinusZero(CallRuntime* expr) {
+  ZoneList<Expression*>* args = expr->arguments();
+  ASSERT(args->length() == 1);
+
+  VisitForAccumulatorValue(args->at(0));
+
+  Label materialize_true, materialize_false;
+  Label* if_true = NULL;
+  Label* if_false = NULL;
+  Label* fall_through = NULL;
+  context()->PrepareTest(&materialize_true, &materialize_false,
+                         &if_true, &if_false, &fall_through);
+
+  __ CheckMap(r0, r1, Heap::kHeapNumberMapRootIndex, if_false, DO_SMI_CHECK);
+  __ ldr(r2, FieldMemOperand(r0, HeapNumber::kExponentOffset));
+  __ ldr(r1, FieldMemOperand(r0, HeapNumber::kMantissaOffset));
+  __ cmp(r2, Operand(0x80000000));
+  __ cmp(r1, Operand(0x00000000), eq);
+
+  PrepareForBailoutBeforeSplit(expr, true, if_true, if_false);
+  Split(eq, if_true, if_false, fall_through);
+
+  context()->Plug(if_true, if_false);
+}
+
+
 void FullCodeGenerator::EmitIsArray(CallRuntime* expr) {
   ZoneList<Expression*>* args = expr->arguments();
   ASSERT(args->length() == 1);