Add boolean flag to HChange and LNumberUntagD to not convert undefined to NaN.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index e4cd8c3519aecf531581c22b749eb1a066839d4b..15542147e7bec85624ccd357ed754728e9efabdc 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -3559,8 +3559,9 @@ void LCodeGen::DoSmiUntag(LSmiUntag* instr) {
 
 void LCodeGen::EmitNumberUntagD(Register input_reg,
                                 XMMRegister result_reg,
+                                bool deoptimize_on_undefined,
                                 LEnvironment* env) {
-  Label load_smi, heap_number, done;
+  Label load_smi, done;
 
   // Smi check.
   __ JumpIfSmi(input_reg, &load_smi, Label::kNear);
@@ -3568,18 +3569,23 @@ void LCodeGen::EmitNumberUntagD(Register input_reg,
   // Heap number map check.
   __ CompareRoot(FieldOperand(input_reg, HeapObject::kMapOffset),
                  Heap::kHeapNumberMapRootIndex);
-  __ j(equal, &heap_number, Label::kNear);
+  if (deoptimize_on_undefined) {
+    DeoptimizeIf(not_equal, env);
+  } else {
+    Label heap_number;
+    __ j(equal, &heap_number, Label::kNear);
 
-  __ CompareRoot(input_reg, Heap::kUndefinedValueRootIndex);
-  DeoptimizeIf(not_equal, env);
+    __ CompareRoot(input_reg, Heap::kUndefinedValueRootIndex);
+    DeoptimizeIf(not_equal, env);
 
-  // Convert undefined to NaN. Compute NaN as 0/0.
-  __ xorps(result_reg, result_reg);
-  __ divsd(result_reg, result_reg);
-  __ jmp(&done, Label::kNear);
+    // Convert undefined to NaN. Compute NaN as 0/0.
+    __ xorps(result_reg, result_reg);
+    __ divsd(result_reg, result_reg);
+    __ jmp(&done, Label::kNear);
 
+    __ bind(&heap_number);
+  }
   // Heap number to XMM conversion.
-  __ bind(&heap_number);
   __ movsd(result_reg, FieldOperand(input_reg, HeapNumber::kValueOffset));
   __ jmp(&done, Label::kNear);
 
@@ -3670,7 +3676,9 @@ void LCodeGen::DoNumberUntagD(LNumberUntagD* instr) {
   Register input_reg = ToRegister(input);
   XMMRegister result_reg = ToDoubleRegister(result);
 
-  EmitNumberUntagD(input_reg, result_reg, instr->environment());
+  EmitNumberUntagD(input_reg, result_reg,
+                   instr->hydrogen()->deoptimize_on_undefined(),
+                   instr->environment());
 }