Merge r8237 to V8 3.2 branch. Fix bug v8:1434, optimized compare of undefined can fail.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
===================================================================
--- src/x64/lithium-codegen-x64.cc	(revision 8253)
+++ src/x64/lithium-codegen-x64.cc	(working copy)
@@ -3362,8 +3362,9 @@
 
 void LCodeGen::EmitNumberUntagD(Register input_reg,
                                 XMMRegister result_reg,
+                                bool deoptimize_on_undefined,
                                 LEnvironment* env) {
-  NearLabel load_smi, heap_number, done;
+  NearLabel load_smi, done;
 
   // Smi check.
   __ JumpIfSmi(input_reg, &load_smi);
@@ -3371,18 +3372,22 @@
   // Heap number map check.
   __ CompareRoot(FieldOperand(input_reg, HeapObject::kMapOffset),
                  Heap::kHeapNumberMapRootIndex);
-  __ j(equal, &heap_number);
+  if (deoptimize_on_undefined) {
+    DeoptimizeIf(not_equal, env);
+  } else {
+    NearLabel heap_number;
+    __ j(equal, &heap_number);
+    __ 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.
+    __ xorpd(result_reg, result_reg);
+    __ divsd(result_reg, result_reg);
+    __ jmp(&done);
 
-  // Convert undefined to NaN. Compute NaN as 0/0.
-  __ xorpd(result_reg, result_reg);
-  __ divsd(result_reg, result_reg);
-  __ jmp(&done);
-
+    __ bind(&heap_number);
+  }
   // Heap number to XMM conversion.
-  __ bind(&heap_number);
   __ movsd(result_reg, FieldOperand(input_reg, HeapNumber::kValueOffset));
   __ jmp(&done);
 
@@ -3473,7 +3478,9 @@
   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());
 }