Revert of [fullcodegen] Remove the hacky %_FastOneByteArrayJoin intrinsic.

src/full-codegen/x64/full-codegen-x64.cc

Index: src/full-codegen/x64/full-codegen-x64.cc
diff --git a/src/full-codegen/x64/full-codegen-x64.cc b/src/full-codegen/x64/full-codegen-x64.cc
index 69ca48ff0cbe05739a9218bd48335ca21e49803f..6b99d730c8e32a3bc6df415b1b863a9d33eeff5c 100644
--- a/src/full-codegen/x64/full-codegen-x64.cc
+++ b/src/full-codegen/x64/full-codegen-x64.cc
@@ -3305,6 +3305,296 @@
   __ AssertFunction(rax);
   __ movp(rax, FieldOperand(rax, HeapObject::kMapOffset));
   __ movp(rax, FieldOperand(rax, Map::kPrototypeOffset));
+  context()->Plug(rax);
+}
+
+
+void FullCodeGenerator::EmitFastOneByteArrayJoin(CallRuntime* expr) {
+  Label bailout, return_result, done, one_char_separator, long_separator,
+      non_trivial_array, not_size_one_array, loop,
+      loop_1, loop_1_condition, loop_2, loop_2_entry, loop_3, loop_3_entry;
+  ZoneList<Expression*>* args = expr->arguments();
+  DCHECK(args->length() == 2);
+  // We will leave the separator on the stack until the end of the function.
+  VisitForStackValue(args->at(1));
+  // Load this to rax (= array)
+  VisitForAccumulatorValue(args->at(0));
+  // All aliases of the same register have disjoint lifetimes.
+  Register array = rax;
+  Register elements = no_reg;  // Will be rax.
+
+  Register index = rdx;
+
+  Register string_length = rcx;
+
+  Register string = rsi;
+
+  Register scratch = rbx;
+
+  Register array_length = rdi;
+  Register result_pos = no_reg;  // Will be rdi.
+
+  Operand separator_operand =    Operand(rsp, 2 * kPointerSize);
+  Operand result_operand =       Operand(rsp, 1 * kPointerSize);
+  Operand array_length_operand = Operand(rsp, 0 * kPointerSize);
+  // Separator operand is already pushed. Make room for the two
+  // other stack fields, and clear the direction flag in anticipation
+  // of calling CopyBytes.
+  __ subp(rsp, Immediate(2 * kPointerSize));
+  __ cld();
+  // Check that the array is a JSArray
+  __ JumpIfSmi(array, &bailout);
+  __ CmpObjectType(array, JS_ARRAY_TYPE, scratch);
+  __ j(not_equal, &bailout);
+
+  // Check that the array has fast elements.
+  __ CheckFastElements(scratch, &bailout);
+
+  // Array has fast elements, so its length must be a smi.
+  // If the array has length zero, return the empty string.
+  __ movp(array_length, FieldOperand(array, JSArray::kLengthOffset));
+  __ SmiCompare(array_length, Smi::FromInt(0));
+  __ j(not_zero, &non_trivial_array);
+  __ LoadRoot(rax, Heap::kempty_stringRootIndex);
+  __ jmp(&return_result);
+
+  // Save the array length on the stack.
+  __ bind(&non_trivial_array);
+  __ SmiToInteger32(array_length, array_length);
+  __ movl(array_length_operand, array_length);
+
+  // Save the FixedArray containing array's elements.
+  // End of array's live range.
+  elements = array;
+  __ movp(elements, FieldOperand(array, JSArray::kElementsOffset));
+  array = no_reg;
+
+
+  // Check that all array elements are sequential one-byte strings, and
+  // accumulate the sum of their lengths, as a smi-encoded value.
+  __ Set(index, 0);
+  __ Set(string_length, 0);
+  // Loop condition: while (index < array_length).
+  // Live loop registers: index(int32), array_length(int32), string(String*),
+  //                      scratch, string_length(int32), elements(FixedArray*).
+  if (generate_debug_code_) {
+    __ cmpp(index, array_length);
+    __ Assert(below, kNoEmptyArraysHereInEmitFastOneByteArrayJoin);
+  }
+  __ bind(&loop);
+  __ movp(string, FieldOperand(elements,
+                               index,
+                               times_pointer_size,
+                               FixedArray::kHeaderSize));
+  __ JumpIfSmi(string, &bailout);
+  __ movp(scratch, FieldOperand(string, HeapObject::kMapOffset));
+  __ movzxbl(scratch, FieldOperand(scratch, Map::kInstanceTypeOffset));
+  __ andb(scratch, Immediate(
+      kIsNotStringMask | kStringEncodingMask | kStringRepresentationMask));
+  __ cmpb(scratch, Immediate(kStringTag | kOneByteStringTag | kSeqStringTag));
+  __ j(not_equal, &bailout);
+  __ AddSmiField(string_length,
+                 FieldOperand(string, SeqOneByteString::kLengthOffset));
+  __ j(overflow, &bailout);
+  __ incl(index);
+  __ cmpl(index, array_length);
+  __ j(less, &loop);
+
+  // Live registers:
+  // string_length: Sum of string lengths.
+  // elements: FixedArray of strings.
+  // index: Array length.
+  // array_length: Array length.
+
+  // If array_length is 1, return elements[0], a string.
+  __ cmpl(array_length, Immediate(1));
+  __ j(not_equal, &not_size_one_array);
+  __ movp(rax, FieldOperand(elements, FixedArray::kHeaderSize));
+  __ jmp(&return_result);
+
+  __ bind(&not_size_one_array);
+
+  // End of array_length live range.
+  result_pos = array_length;
+  array_length = no_reg;
+
+  // Live registers:
+  // string_length: Sum of string lengths.
+  // elements: FixedArray of strings.
+  // index: Array length.
+
+  // Check that the separator is a sequential one-byte string.
+  __ movp(string, separator_operand);
+  __ JumpIfSmi(string, &bailout);
+  __ movp(scratch, FieldOperand(string, HeapObject::kMapOffset));
+  __ movzxbl(scratch, FieldOperand(scratch, Map::kInstanceTypeOffset));
+  __ andb(scratch, Immediate(
+      kIsNotStringMask | kStringEncodingMask | kStringRepresentationMask));
+  __ cmpb(scratch, Immediate(kStringTag | kOneByteStringTag | kSeqStringTag));
+  __ j(not_equal, &bailout);
+
+  // Live registers:
+  // string_length: Sum of string lengths.
+  // elements: FixedArray of strings.
+  // index: Array length.
+  // string: Separator string.
+
+  // Add (separator length times (array_length - 1)) to string_length.
+  __ SmiToInteger32(scratch,
+                    FieldOperand(string, SeqOneByteString::kLengthOffset));
+  __ decl(index);
+  __ imull(scratch, index);
+  __ j(overflow, &bailout);
+  __ addl(string_length, scratch);
+  __ j(overflow, &bailout);
+  __ jmp(&bailout);
+
+  // Bailout for large object allocations.
+  __ cmpl(string_length, Immediate(Page::kMaxRegularHeapObjectSize));
+  __ j(greater, &bailout);
+
+  // Live registers and stack values:
+  //   string_length: Total length of result string.
+  //   elements: FixedArray of strings.
+  __ AllocateOneByteString(result_pos, string_length, scratch, index, string,
+                           &bailout);
+  __ movp(result_operand, result_pos);
+  __ leap(result_pos, FieldOperand(result_pos, SeqOneByteString::kHeaderSize));
+
+  __ movp(string, separator_operand);
+  __ SmiCompare(FieldOperand(string, SeqOneByteString::kLengthOffset),
+                Smi::FromInt(1));
+  __ j(equal, &one_char_separator);
+  __ j(greater, &long_separator);
+
+
+  // Empty separator case:
+  __ Set(index, 0);
+  __ movl(scratch, array_length_operand);
+  __ jmp(&loop_1_condition);
+  // Loop condition: while (index < array_length).
+  __ bind(&loop_1);
+  // Each iteration of the loop concatenates one string to the result.
+  // Live values in registers:
+  //   index: which element of the elements array we are adding to the result.
+  //   result_pos: the position to which we are currently copying characters.
+  //   elements: the FixedArray of strings we are joining.
+  //   scratch: array length.
+
+  // Get string = array[index].
+  __ movp(string, FieldOperand(elements, index,
+                               times_pointer_size,
+                               FixedArray::kHeaderSize));
+  __ SmiToInteger32(string_length,
+                    FieldOperand(string, String::kLengthOffset));
+  __ leap(string,
+         FieldOperand(string, SeqOneByteString::kHeaderSize));
+  __ CopyBytes(result_pos, string, string_length);
+  __ incl(index);
+  __ bind(&loop_1_condition);
+  __ cmpl(index, scratch);
+  __ j(less, &loop_1);  // Loop while (index < array_length).
+  __ jmp(&done);
+
+  // Generic bailout code used from several places.
+  __ bind(&bailout);
+  __ LoadRoot(rax, Heap::kUndefinedValueRootIndex);
+  __ jmp(&return_result);
+
+
+  // One-character separator case
+  __ bind(&one_char_separator);
+  // Get the separator one-byte character value.
+  // Register "string" holds the separator.
+  __ movzxbl(scratch, FieldOperand(string, SeqOneByteString::kHeaderSize));
+  __ Set(index, 0);
+  // Jump into the loop after the code that copies the separator, so the first
+  // element is not preceded by a separator
+  __ jmp(&loop_2_entry);
+  // Loop condition: while (index < length).
+  __ bind(&loop_2);
+  // Each iteration of the loop concatenates one string to the result.
+  // Live values in registers:
+  //   elements: The FixedArray of strings we are joining.
+  //   index: which element of the elements array we are adding to the result.
+  //   result_pos: the position to which we are currently copying characters.
+  //   scratch: Separator character.
+
+  // Copy the separator character to the result.
+  __ movb(Operand(result_pos, 0), scratch);
+  __ incp(result_pos);
+
+  __ bind(&loop_2_entry);
+  // Get string = array[index].
+  __ movp(string, FieldOperand(elements, index,
+                               times_pointer_size,
+                               FixedArray::kHeaderSize));
+  __ SmiToInteger32(string_length,
+                    FieldOperand(string, String::kLengthOffset));
+  __ leap(string,
+         FieldOperand(string, SeqOneByteString::kHeaderSize));
+  __ CopyBytes(result_pos, string, string_length);
+  __ incl(index);
+  __ cmpl(index, array_length_operand);
+  __ j(less, &loop_2);  // End while (index < length).
+  __ jmp(&done);
+
+
+  // Long separator case (separator is more than one character).
+  __ bind(&long_separator);
+
+  // Make elements point to end of elements array, and index
+  // count from -array_length to zero, so we don't need to maintain
+  // a loop limit.
+  __ movl(index, array_length_operand);
+  __ leap(elements, FieldOperand(elements, index, times_pointer_size,
+                                FixedArray::kHeaderSize));
+  __ negq(index);
+
+  // Replace separator string with pointer to its first character, and
+  // make scratch be its length.
+  __ movp(string, separator_operand);
+  __ SmiToInteger32(scratch,
+                    FieldOperand(string, String::kLengthOffset));
+  __ leap(string,
+         FieldOperand(string, SeqOneByteString::kHeaderSize));
+  __ movp(separator_operand, string);
+
+  // Jump into the loop after the code that copies the separator, so the first
+  // element is not preceded by a separator
+  __ jmp(&loop_3_entry);
+  // Loop condition: while (index < length).
+  __ bind(&loop_3);
+  // Each iteration of the loop concatenates one string to the result.
+  // Live values in registers:
+  //   index: which element of the elements array we are adding to the result.
+  //   result_pos: the position to which we are currently copying characters.
+  //   scratch: Separator length.
+  //   separator_operand (rsp[0x10]): Address of first char of separator.
+
+  // Copy the separator to the result.
+  __ movp(string, separator_operand);
+  __ movl(string_length, scratch);
+  __ CopyBytes(result_pos, string, string_length, 2);
+
+  __ bind(&loop_3_entry);
+  // Get string = array[index].
+  __ movp(string, Operand(elements, index, times_pointer_size, 0));
+  __ SmiToInteger32(string_length,
+                    FieldOperand(string, String::kLengthOffset));
+  __ leap(string,
+         FieldOperand(string, SeqOneByteString::kHeaderSize));
+  __ CopyBytes(result_pos, string, string_length);
+  __ incq(index);
+  __ j(not_equal, &loop_3);  // Loop while (index < 0).
+
+  __ bind(&done);
+  __ movp(rax, result_operand);
+
+  __ bind(&return_result);
+  // Drop temp values from the stack, and restore context register.
+  __ addp(rsp, Immediate(3 * kPointerSize));
+  __ movp(rsi, Operand(rbp, StandardFrameConstants::kContextOffset));
   context()->Plug(rax);
 }