Tiny improvements on fast element conversion loops in ia32 and x64.

Review URL: http://codereview.chromium.org/8403035

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9820 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/ia32/codegen-ia32.cc

@@ -355,9 +355,7 @@ void ElementsTransitionGenerator::GenerateSmiOnlyToDouble(
 
   // Convert and copy elements
   // esi: source FixedArray
-  // edi: number of elements to convert/copy
   __ bind(&loop);
-  __ sub(edi, Immediate(Smi::FromInt(1)));
   __ mov(ebx, FieldOperand(esi, edi, times_2, FixedArray::kHeaderSize));
   // ebx: current element from source
   // edi: index of current element
@@ -390,8 +388,8 @@ void ElementsTransitionGenerator::GenerateSmiOnlyToDouble(
   }
 
   __ bind(&entry);
-  __ test(edi, edi);
-  __ j(not_zero, &loop);
+  __ sub(edi, Immediate(Smi::FromInt(1)));
+  __ j(not_sign, &loop);
 
   __ pop(ebx);
   __ pop(eax);
@@ -454,7 +452,6 @@ void ElementsTransitionGenerator::GenerateDoubleToObject(
   // edi: source FixedDoubleArray
   // eax: destination FixedArray
   __ bind(&loop);
-  __ sub(ebx, Immediate(Smi::FromInt(1)));
   // ebx: index of current element (smi-tagged)
   uint32_t offset = FixedDoubleArray::kHeaderSize + sizeof(kHoleNanLower32);
   __ cmp(FieldOperand(edi, ebx, times_4, offset), Immediate(kHoleNanUpper32));
@@ -490,8 +487,8 @@ void ElementsTransitionGenerator::GenerateDoubleToObject(
          masm->isolate()->factory()->the_hole_value());
 
   __ bind(&entry);
-  __ test(ebx, ebx);
-  __ j(not_zero, &loop);
+  __ sub(ebx, Immediate(Smi::FromInt(1)));
+  __ j(not_sign, &loop);
 
   __ pop(ebx);
   __ pop(edx);

src/x64/codegen-x64.cc

@@ -243,7 +243,6 @@ void ElementsTransitionGenerator::GenerateSmiOnlyToDouble(
 
   // Conversion loop.
   __ bind(&loop);
-  __ decq(r9);
   __ movq(rbx,
           FieldOperand(r8, r9, times_8, FixedArray::kHeaderSize));
   // r9 : current element's index
@@ -257,8 +256,8 @@ void ElementsTransitionGenerator::GenerateSmiOnlyToDouble(
   __ bind(&convert_hole);
   __ movq(FieldOperand(r14, r9, times_8, FixedDoubleArray::kHeaderSize), r15);
   __ bind(&entry);
-  __ testq(r9, r9);
-  __ j(not_zero, &loop);
+  __ decq(r9);
+  __ j(not_sign, &loop);
 }
 
 
@@ -301,7 +300,6 @@ void ElementsTransitionGenerator::GenerateDoubleToObject(
 
   // Box doubles into heap numbers.
   __ bind(&loop);
-  __ decq(r9);
   __ movq(r14, FieldOperand(r8,
                             r9,
                             times_pointer_size,
@@ -338,8 +336,8 @@ void ElementsTransitionGenerator::GenerateDoubleToObject(
           rdi);
 
   __ bind(&entry);
-  __ testq(r9, r9);
-  __ j(not_zero, &loop);
+  __ decq(r9);
+  __ j(not_sign, &loop);
 
   // Set transitioned map.
   __ movq(FieldOperand(rdx, HeapObject::kMapOffset), rbx);