Add a fast case to Array.join when all the elements and the separator are fla...

src/ia32/macro-assembler-ia32.cc

 // Copyright 2006-2009 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 871 matching lines @@
                      scratch1,
                      scratch2,
                      gc_required,
                      TAG_OBJECT);
 
   // Set the map. The other fields are left uninitialized.
   mov(FieldOperand(result, HeapObject::kMapOffset),
       Immediate(Factory::cons_ascii_string_map()));
 }
 
+// All registers must be distinct.  Only current_string needs valid contents
+// on entry.  All registers may be invalid on exit.  result_operand is
+// unchanged, padding_chars is updated correctly.
+void MacroAssembler::AppendStringToTopOfNewSpace(
+    Register current_string,  // Tagged pointer to string to copy.
+    Register current_string_length,
+    Register result_pos,
+    Register scratch,
+    Register new_padding_chars,
+    Operand operand_result,
+    Operand operand_padding_chars,
+    Label* bailout) {
+  mov(current_string_length,
+      FieldOperand(current_string, String::kLengthOffset));
+  shr(current_string_length, 1);
+  sub(current_string_length, operand_padding_chars);
+  mov(new_padding_chars, current_string_length);
+  add(Operand(current_string_length), Immediate(kObjectAlignmentMask));
+  and_(Operand(current_string_length), Immediate(~kObjectAlignmentMask));
+  sub(new_padding_chars, Operand(current_string_length));
+  neg(new_padding_chars);
+  // We need an allocation even if current_string_length is 0, to fetch
+  // result_pos.  Consider using a faster fetch of result_pos in that case.
+  AllocateInNewSpace(current_string_length, result_pos, scratch, no_reg,
+                     bailout, NO_ALLOCATION_FLAGS);
+  sub(result_pos, operand_padding_chars);
+  mov(operand_padding_chars, new_padding_chars);
+
+  Register scratch_2 = new_padding_chars;  // Used to compute total length.
+  // Copy string to the end of result.
+  mov(current_string_length,
+      FieldOperand(current_string, String::kLengthOffset));
+  mov(scratch, operand_result);
+  mov(scratch_2, current_string_length);
+  add(scratch_2, FieldOperand(scratch, String::kLengthOffset));
+  mov(FieldOperand(scratch, String::kLengthOffset), scratch_2);
+  shr(current_string_length, 1);
+  lea(current_string,
+      FieldOperand(current_string, SeqAsciiString::kHeaderSize));
+  // Loop condition: while (--current_string_length >= 0).
+  Label copy_loop;
+  Label copy_loop_entry;
+  jmp(&copy_loop_entry);
+  bind(&copy_loop);
+  mov_b(scratch, Operand(current_string, current_string_length, times_1, 0));
+  mov_b(Operand(result_pos, current_string_length, times_1, 0), scratch);
+  bind(&copy_loop_entry);
+  sub(Operand(current_string_length), Immediate(1));
+  j(greater_equal, &copy_loop);
+}
+
 
 void MacroAssembler::NegativeZeroTest(CodeGenerator* cgen,
                                       Register result,
                                       Register op,
                                       JumpTarget* then_target) {
   JumpTarget ok;
   test(result, Operand(result));
   ok.Branch(not_zero, taken);
   test(op, Operand(op));
   then_target->Branch(sign, not_taken);
@@ skipping 906 matching lines @@
 
   // Check that the code was patched as expected.
   ASSERT(masm_.pc_ == address_ + size_);
   ASSERT(masm_.reloc_info_writer.pos() == address_ + size_ + Assembler::kGap);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32