Add DoubleTestOp instruction

runtime/vm/intrinsifier_arm64.cc

Index: runtime/vm/intrinsifier_arm64.cc
diff --git a/runtime/vm/intrinsifier_arm64.cc b/runtime/vm/intrinsifier_arm64.cc
index f9cade23e23862b21a0e420bfca5e49edc80bee3..050ae7361cdaac8d2c7ee73dfc3c6982d9a89c90 100644
--- a/runtime/vm/intrinsifier_arm64.cc
+++ b/runtime/vm/intrinsifier_arm64.cc
@@ -1507,7 +1507,6 @@ void Intrinsifier::DoubleFromInteger(Assembler* assembler) {
 
 
 void Intrinsifier::Double_getIsNaN(Assembler* assembler) {
-  Label is_true;
   __ ldr(R0, Address(SP, 0 * kWordSize));
   __ LoadDFieldFromOffset(V0, R0, Double::value_offset());
   __ fcmpd(V0, V0);
@@ -1518,6 +1517,20 @@ void Intrinsifier::Double_getIsNaN(Assembler* assembler) {
 }
 
 
+void Intrinsifier::Double_getIsInfinite(Assembler* assembler) {
+  __ ldr(R0, Address(SP, 0 * kWordSize));
+  __ LoadFieldFromOffset(R0, R0, Double::value_offset());
+  // Mask off the sign.
+  __ AndImmediate(R0, R0, 0x7FFFFFFFFFFFFFFFLL);
+  // Compare with +infinity.
+  __ CompareImmediate(R0, 0x7FF0000000000000LL);
+  __ LoadObject(R0, Bool::False());
+  __ LoadObject(TMP, Bool::True());
+  __ csel(R0, TMP, R0, EQ);
+  __ ret();
+}
+
+
 void Intrinsifier::Double_getIsNegative(Assembler* assembler) {
   const Register false_reg = R0;
   const Register true_reg = R2;