Implemented FastAsciiStringJoin in X64 full codegen.

src/x64/full-codegen-x64.cc

Index: src/x64/full-codegen-x64.cc
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index 3b491525d2d09a676452e33c65262f8985c915d3..21879f28962debe202628301344d0dfda783c2e2 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -3231,7 +3231,288 @@ void FullCodeGenerator::EmitGetCachedArrayIndex(ZoneList<Expression*>* args) {
 
 
 void FullCodeGenerator::EmitFastAsciiArrayJoin(ZoneList<Expression*>* args) {
-  context()->Plug(Heap::kUndefinedValueRootIndex);
+  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;
+  ASSERT(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.
+  __ subq(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.
+  __ testb(FieldOperand(scratch, Map::kBitField2Offset),
+           Immediate(1 << Map::kHasFastElements));
+  __ j(zero, &bailout);
+
+  // Array has fast elements, so its length must be a smi.
+  // If the array has length zero, return the empty string.
+  __ movq(array_length, FieldOperand(array, JSArray::kLengthOffset));
+  __ SmiCompare(array_length, Smi::FromInt(0));
+  __ j(not_zero, &non_trivial_array);
+  __ LoadRoot(rax, Heap::kEmptyStringRootIndex);
+  __ 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;
+  __ movq(elements, FieldOperand(array, JSArray::kElementsOffset));
+  array = no_reg;
+
+
+  // Check that all array elements are sequential ASCII 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 (FLAG_debug_code) {
+    __ cmpq(index, array_length);
+    __ Assert(below, "No empty arrays here in EmitFastAsciiArrayJoin");
+  }
+  __ bind(&loop);
+  __ movq(string, FieldOperand(elements,
+                               index,
+                               times_pointer_size,
+                               FixedArray::kHeaderSize));
+  __ JumpIfSmi(string, &bailout);
+  __ movq(scratch, FieldOperand(string, HeapObject::kMapOffset));
+  __ movzxbl(scratch, FieldOperand(scratch, Map::kInstanceTypeOffset));
+  __ andb(scratch, Immediate(
+      kIsNotStringMask | kStringEncodingMask | kStringRepresentationMask));
+  __ cmpb(scratch, Immediate(kStringTag | kAsciiStringTag | kSeqStringTag));
+  __ j(not_equal, &bailout);
+  __ AddSmiField(string_length,
+                 FieldOperand(string, SeqAsciiString::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);
+  __ movq(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 flat ASCII string.

[William Hesse, 2011/03/24 12:02:21]

sequential ASCII string?

[Lasse Reichstein, 2011/03/24 12:14:08]

Done.

+  __ movq(string, separator_operand);
+  __ JumpIfSmi(string, &bailout);
+  __ movq(scratch, FieldOperand(string, HeapObject::kMapOffset));
+  __ movzxbl(scratch, FieldOperand(scratch, Map::kInstanceTypeOffset));
+  __ andb(scratch, Immediate(
+      kIsNotStringMask | kStringEncodingMask | kStringRepresentationMask));
+  __ cmpb(scratch, Immediate(ASCII_STRING_TYPE));

[William Hesse, 2011/03/24 12:02:21]

Why don't we use ASCII_STRING_TYPE above?  And why not ASCII_SEQ_STRING_TYPE?

[Lasse Reichstein, 2011/03/24 12:14:08]

No idea. I'll just make it use the or-of-three-things like above.

+  __ 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, SeqAsciiString::kLengthOffset));
+  __ decl(index);
+  __ imull(scratch, index);
+  __ j(overflow, &bailout);
+  __ addl(string_length, scratch);
+  __ j(overflow, &bailout);
+
+  // Live registers and stack values:
+  //   string_length: Total length of result string.
+  //   elements: FixedArray of strings.
+  __ AllocateAsciiString(result_pos, string_length, scratch,
+                         index, string, &bailout);
+  __ movq(result_operand, result_pos);
+  __ lea(result_pos, FieldOperand(result_pos, SeqAsciiString::kHeaderSize));
+
+  __ movq(string, separator_operand);
+  __ SmiCompare(FieldOperand(string, SeqAsciiString::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].
+  __ movq(string, FieldOperand(elements, index,
+                               times_pointer_size,
+                               FixedArray::kHeaderSize));
+  __ SmiToInteger32(string_length,
+                    FieldOperand(string, String::kLengthOffset));
+  __ lea(string,
+         FieldOperand(string, SeqAsciiString::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 ascii character value.
+  // Register "string" holds the separator.
+  __ movzxbl(scratch, FieldOperand(string, SeqAsciiString::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);
+  __ incq(result_pos);
+
+  __ bind(&loop_2_entry);
+  // Get string = array[index].
+  __ movq(string, FieldOperand(elements, index,
+                               times_pointer_size,
+                               FixedArray::kHeaderSize));
+  __ SmiToInteger32(string_length,
+                    FieldOperand(string, String::kLengthOffset));
+  __ lea(string,
+         FieldOperand(string, SeqAsciiString::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.

[William Hesse, 2011/03/24 12:02:21]

You should try this change on ia32, to see if it makes a difference.  Or else
just use another register for the loop limit.

[Lasse Reichstein, 2011/03/24 12:14:08]

Good idea for another CL.

+  __ movl(index, array_length_operand);
+  __ lea(elements, FieldOperand(elements, index, times_pointer_size,
+                                FixedArray::kHeaderSize));
+  __ neg(index);
+
+  // Replace separator string with pointer to its first character, and
+  // make scratch be its length.
+  __ movq(string, separator_operand);
+  __ SmiToInteger32(scratch,
+                    FieldOperand(string, String::kLengthOffset));
+  __ lea(string,
+         FieldOperand(string, SeqAsciiString::kHeaderSize));
+  __ movq(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.
+  //   rsp[0x10] (separator_operand): Address of first char of separator.

[William Hesse, 2011/03/24 12:02:21]

why not separator_operand (rsp[0x10])?

[Lasse Reichstein, 2011/03/24 12:14:08]

That's better, thanks.

+
+  // Copy the separator to the result.
+  __ movq(string, separator_operand);
+  __ movl(string_length, scratch);
+  __ CopyBytes(result_pos, string, string_length, 2);
+
+  __ bind(&loop_3_entry);
+  // Get string = array[index].
+  __ movq(string, Operand(elements, index, times_pointer_size, 0));
+  __ SmiToInteger32(string_length,
+                    FieldOperand(string, String::kLengthOffset));
+  __ lea(string,
+         FieldOperand(string, SeqAsciiString::kHeaderSize));
+  __ CopyBytes(result_pos, string, string_length);
+  __ addq(index, Immediate(1));
+  __ j(less, &loop_3);  // Loop while (index < 0).

[William Hesse, 2011/03/24 12:02:21]

I think if you use not_equal for the condition, you can use incq, since inc sets
the zero flag.

[Lasse Reichstein, 2011/03/24 12:14:08]

Done.

+
+  __ bind(&done);
+  __ movq(rax, result_operand);
+
+  __ bind(&return_result);
+  // Drop temp values from the stack, and restore context register.
+  __ addq(rsp, Immediate(3 * kPointerSize));
+  __ movq(rsi, Operand(rbp, StandardFrameConstants::kContextOffset));
+  context()->Plug(rax);
 }