Save one branch for normal heap number un-tagging.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/23496041

Patch from Bangfu Tao <bangfu.tao@samsung.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16856 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-codegen-arm.cc

@@ -4868,36 +4868,20 @@ void LCodeGen::EmitNumberUntagD(Register input_reg,
   Register scratch = scratch0();
   SwVfpRegister flt_scratch = double_scratch0().low();
   ASSERT(!result_reg.is(double_scratch0()));
-
-  Label load_smi, heap_number, done;
-
+  Label convert, load_smi, done;
   if (mode == NUMBER_CANDIDATE_IS_ANY_TAGGED) {
     // Smi check.
     __ UntagAndJumpIfSmi(scratch, input_reg, &load_smi);
-
     // Heap number map check.
     __ ldr(scratch, FieldMemOperand(input_reg, HeapObject::kMapOffset));
     __ LoadRoot(ip, Heap::kHeapNumberMapRootIndex);
     __ cmp(scratch, Operand(ip));
-    if (!can_convert_undefined_to_nan) {
-      DeoptimizeIf(ne, env);
+    if (can_convert_undefined_to_nan) {
+      __ b(ne, &convert);
     } else {
-      Label heap_number, convert;
-      __ b(eq, &heap_number);
-
-      // Convert undefined (and hole) to NaN.
-      __ LoadRoot(ip, Heap::kUndefinedValueRootIndex);
-      __ cmp(input_reg, Operand(ip));
       DeoptimizeIf(ne, env);
-
-      __ bind(&convert);
-      __ LoadRoot(scratch, Heap::kNanValueRootIndex);
-      __ vldr(result_reg, scratch, HeapNumber::kValueOffset - kHeapObjectTag);
-      __ jmp(&done);
-
-      __ bind(&heap_number);
     }
-    // Heap number to double register conversion.
+    // load heap number
     __ vldr(result_reg, input_reg, HeapNumber::kValueOffset - kHeapObjectTag);
     if (deoptimize_on_minus_zero) {
       __ VmovLow(scratch, result_reg);
@@ -4908,11 +4892,20 @@ void LCodeGen::EmitNumberUntagD(Register input_reg,
       DeoptimizeIf(eq, env);
     }
     __ jmp(&done);
+    if (can_convert_undefined_to_nan) {
+      __ bind(&convert);
+      // Convert undefined (and hole) to NaN.
+      __ LoadRoot(ip, Heap::kUndefinedValueRootIndex);
+      __ cmp(input_reg, Operand(ip));
+      DeoptimizeIf(ne, env);
+      __ LoadRoot(scratch, Heap::kNanValueRootIndex);
+      __ vldr(result_reg, scratch, HeapNumber::kValueOffset - kHeapObjectTag);
+      __ jmp(&done);
+    }
   } else {
     __ SmiUntag(scratch, input_reg);
     ASSERT(mode == NUMBER_CANDIDATE_IS_SMI);
   }
-
   // Smi to double register conversion
   __ bind(&load_smi);
   // scratch: untagged value of input_reg