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

src/ia32/codegen-ia32.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 337 matching lines @@
   // Call into runtime if GC is required.
   __ bind(&gc_required);
   // Restore registers before jumping into runtime.
   __ mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
   __ pop(ebx);
   __ pop(eax);
   __ jmp(fail);
 
   // Convert and copy elements
   // esi: source FixedArray
   // edi: number of elements to convert/copy

[Michael Starzinger, 2011/10/27 13:33:07]

At this point %edi is actually the index of the last element to be converted.
The above comment should be fixed.

   __ 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
   __ JumpIfNotSmi(ebx, &convert_hole);
 
   // Normal smi, convert it to double and store.
   __ SmiUntag(ebx);
   if (CpuFeatures::IsSupported(SSE2)) {
     CpuFeatures::Scope fscope(SSE2);
     __ cvtsi2sd(xmm0, ebx);
@@ skipping 12 matching lines @@
   if (CpuFeatures::IsSupported(SSE2)) {
     CpuFeatures::Scope use_sse2(SSE2);
     __ movdbl(FieldOperand(eax, edi, times_4, FixedDoubleArray::kHeaderSize),
               the_hole_nan);
   } else {
     __ fld_d(Operand::StaticVariable(canonical_the_hole_nan_reference));
     __ fstp_d(FieldOperand(eax, edi, times_4, FixedDoubleArray::kHeaderSize));
   }
 
   __ bind(&entry);
-  __ test(edi, edi);
-  __ j(not_zero, &loop);
+  __ sub(edi, Immediate(Smi::FromInt(1)));
+  __ j(not_sign, &loop);
 
   __ pop(ebx);
   __ pop(eax);
   // eax: value
   // ebx: target map
   // Set transitioned map.
   __ mov(FieldOperand(edx, HeapObject::kMapOffset), ebx);
   __ RecordWriteField(edx,
                       HeapObject::kMapOffset,
                       ebx,
@@ skipping 42 matching lines @@
   __ mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
   __ pop(ebx);
   __ pop(edx);
   __ pop(eax);
   __ jmp(fail);
 
   // Box doubles into heap numbers.
   // 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));
   __ j(equal, &convert_hole);
 
   // Non-hole double, copy value into a heap number.
   __ AllocateHeapNumber(edx, esi, no_reg, &gc_required);
   // edx: new heap number
   if (CpuFeatures::IsSupported(SSE2)) {
     CpuFeatures::Scope fscope(SSE2);
@@ skipping 15 matching lines @@
                       EMIT_REMEMBERED_SET,
                       OMIT_SMI_CHECK);
   __ jmp(&entry, Label::kNear);
 
   // Replace the-hole NaN with the-hole pointer.
   __ bind(&convert_hole);
   __ mov(FieldOperand(eax, ebx, times_2, FixedArray::kHeaderSize),
          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);
   // ebx: target map
   // edx: receiver
   // Set transitioned map.
   __ mov(FieldOperand(edx, HeapObject::kMapOffset), ebx);
   __ RecordWriteField(edx,
                       HeapObject::kMapOffset,
                       ebx,
@@ skipping 14 matching lines @@
   // Restore registers.
   __ pop(eax);
   __ mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32