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

src/full-codegen/arm/full-codegen-arm.cc

Index: src/full-codegen/arm/full-codegen-arm.cc
diff --git a/src/full-codegen/arm/full-codegen-arm.cc b/src/full-codegen/arm/full-codegen-arm.cc
index c0e91a591c30be470d23a37e11bbb0a8ef044e51..c7efef6d32b5e136d80d84360f68c27900a4a32c 100644
--- a/src/full-codegen/arm/full-codegen-arm.cc
+++ b/src/full-codegen/arm/full-codegen-arm.cc
@@ -3432,6 +3432,243 @@
   __ AssertFunction(r0);
   __ ldr(r0, FieldMemOperand(r0, HeapObject::kMapOffset));
   __ ldr(r0, FieldMemOperand(r0, Map::kPrototypeOffset));
+  context()->Plug(r0);
+}
+
+
+void FullCodeGenerator::EmitFastOneByteArrayJoin(CallRuntime* expr) {
+  Label bailout, done, one_char_separator, long_separator, non_trivial_array,
+      not_size_one_array, loop, empty_separator_loop, one_char_separator_loop,
+      one_char_separator_loop_entry, long_separator_loop;
+  ZoneList<Expression*>* args = expr->arguments();
+  DCHECK(args->length() == 2);
+  VisitForStackValue(args->at(1));
+  VisitForAccumulatorValue(args->at(0));
+
+  // All aliases of the same register have disjoint lifetimes.
+  Register array = r0;
+  Register elements = no_reg;  // Will be r0.
+  Register result = no_reg;  // Will be r0.
+  Register separator = r1;
+  Register array_length = r2;
+  Register result_pos = no_reg;  // Will be r2
+  Register string_length = r3;
+  Register string = r4;
+  Register element = r5;
+  Register elements_end = r6;
+  Register scratch = r9;
+
+  // Separator operand is on the stack.
+  __ pop(separator);
+
+  // Check that the array is a JSArray.
+  __ JumpIfSmi(array, &bailout);
+  __ CompareObjectType(array, scratch, array_length, JS_ARRAY_TYPE);
+  __ b(ne, &bailout);
+
+  // Check that the array has fast elements.
+  __ CheckFastElements(scratch, array_length, &bailout);
+
+  // If the array has length zero, return the empty string.
+  __ ldr(array_length, FieldMemOperand(array, JSArray::kLengthOffset));
+  __ SmiUntag(array_length, SetCC);
+  __ b(ne, &non_trivial_array);
+  __ LoadRoot(r0, Heap::kempty_stringRootIndex);
+  __ b(&done);
+
+  __ bind(&non_trivial_array);
+
+  // Get the FixedArray containing array's elements.
+  elements = array;
+  __ ldr(elements, FieldMemOperand(array, JSArray::kElementsOffset));
+  array = no_reg;  // End of array's live range.
+
+  // Check that all array elements are sequential one-byte strings, and
+  // accumulate the sum of their lengths, as a smi-encoded value.
+  __ mov(string_length, Operand::Zero());
+  __ add(element,
+         elements, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
+  __ add(elements_end, element, Operand(array_length, LSL, kPointerSizeLog2));
+  // Loop condition: while (element < elements_end).
+  // Live values in registers:
+  //   elements: Fixed array of strings.
+  //   array_length: Length of the fixed array of strings (not smi)
+  //   separator: Separator string
+  //   string_length: Accumulated sum of string lengths (smi).
+  //   element: Current array element.
+  //   elements_end: Array end.
+  if (generate_debug_code_) {
+    __ cmp(array_length, Operand::Zero());
+    __ Assert(gt, kNoEmptyArraysHereInEmitFastOneByteArrayJoin);
+  }
+  __ bind(&loop);
+  __ ldr(string, MemOperand(element, kPointerSize, PostIndex));
+  __ JumpIfSmi(string, &bailout);
+  __ ldr(scratch, FieldMemOperand(string, HeapObject::kMapOffset));
+  __ ldrb(scratch, FieldMemOperand(scratch, Map::kInstanceTypeOffset));
+  __ JumpIfInstanceTypeIsNotSequentialOneByte(scratch, scratch, &bailout);
+  __ ldr(scratch, FieldMemOperand(string, SeqOneByteString::kLengthOffset));
+  __ add(string_length, string_length, Operand(scratch), SetCC);
+  __ b(vs, &bailout);
+  __ cmp(element, elements_end);
+  __ b(lt, &loop);
+
+  // If array_length is 1, return elements[0], a string.
+  __ cmp(array_length, Operand(1));
+  __ b(ne, &not_size_one_array);
+  __ ldr(r0, FieldMemOperand(elements, FixedArray::kHeaderSize));
+  __ b(&done);
+
+  __ bind(&not_size_one_array);
+
+  // Live values in registers:
+  //   separator: Separator string
+  //   array_length: Length of the array.
+  //   string_length: Sum of string lengths (smi).
+  //   elements: FixedArray of strings.
+
+  // Check that the separator is a flat one-byte string.
+  __ JumpIfSmi(separator, &bailout);
+  __ ldr(scratch, FieldMemOperand(separator, HeapObject::kMapOffset));
+  __ ldrb(scratch, FieldMemOperand(scratch, Map::kInstanceTypeOffset));
+  __ JumpIfInstanceTypeIsNotSequentialOneByte(scratch, scratch, &bailout);
+
+  // Add (separator length times array_length) - separator length to the
+  // string_length to get the length of the result string. array_length is not
+  // smi but the other values are, so the result is a smi
+  __ ldr(scratch, FieldMemOperand(separator, SeqOneByteString::kLengthOffset));
+  __ sub(string_length, string_length, Operand(scratch));
+  __ smull(scratch, ip, array_length, scratch);
+  // Check for smi overflow. No overflow if higher 33 bits of 64-bit result are
+  // zero.
+  __ cmp(ip, Operand::Zero());
+  __ b(ne, &bailout);
+  __ tst(scratch, Operand(0x80000000));
+  __ b(ne, &bailout);
+  __ add(string_length, string_length, Operand(scratch), SetCC);
+  __ b(vs, &bailout);
+  __ SmiUntag(string_length);
+
+  // Bailout for large object allocations.
+  __ cmp(string_length, Operand(Page::kMaxRegularHeapObjectSize));
+  __ b(gt, &bailout);
+
+  // Get first element in the array to free up the elements register to be used
+  // for the result.
+  __ add(element,
+         elements, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
+  result = elements;  // End of live range for elements.
+  elements = no_reg;
+  // Live values in registers:
+  //   element: First array element
+  //   separator: Separator string
+  //   string_length: Length of result string (not smi)
+  //   array_length: Length of the array.
+  __ AllocateOneByteString(result, string_length, scratch,
+                           string,        // used as scratch
+                           elements_end,  // used as scratch
+                           &bailout);
+  // Prepare for looping. Set up elements_end to end of the array. Set
+  // result_pos to the position of the result where to write the first
+  // character.
+  __ add(elements_end, element, Operand(array_length, LSL, kPointerSizeLog2));
+  result_pos = array_length;  // End of live range for array_length.
+  array_length = no_reg;
+  __ add(result_pos,
+         result,
+         Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
+
+  // Check the length of the separator.
+  __ ldr(scratch, FieldMemOperand(separator, SeqOneByteString::kLengthOffset));
+  __ cmp(scratch, Operand(Smi::FromInt(1)));
+  __ b(eq, &one_char_separator);
+  __ b(gt, &long_separator);
+
+  // Empty separator case
+  __ bind(&empty_separator_loop);
+  // Live values in registers:
+  //   result_pos: the position to which we are currently copying characters.
+  //   element: Current array element.
+  //   elements_end: Array end.
+
+  // Copy next array element to the result.
+  __ ldr(string, MemOperand(element, kPointerSize, PostIndex));
+  __ ldr(string_length, FieldMemOperand(string, String::kLengthOffset));
+  __ SmiUntag(string_length);
+  __ add(string,
+         string,
+         Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
+  __ CopyBytes(string, result_pos, string_length, scratch);
+  __ cmp(element, elements_end);
+  __ b(lt, &empty_separator_loop);  // End while (element < elements_end).
+  DCHECK(result.is(r0));
+  __ b(&done);
+
+  // One-character separator case
+  __ bind(&one_char_separator);
+  // Replace separator with its one-byte character value.
+  __ ldrb(separator, FieldMemOperand(separator, SeqOneByteString::kHeaderSize));
+  // Jump into the loop after the code that copies the separator, so the first
+  // element is not preceded by a separator
+  __ jmp(&one_char_separator_loop_entry);
+
+  __ bind(&one_char_separator_loop);
+  // Live values in registers:
+  //   result_pos: the position to which we are currently copying characters.
+  //   element: Current array element.
+  //   elements_end: Array end.
+  //   separator: Single separator one-byte char (in lower byte).
+
+  // Copy the separator character to the result.
+  __ strb(separator, MemOperand(result_pos, 1, PostIndex));
+
+  // Copy next array element to the result.
+  __ bind(&one_char_separator_loop_entry);
+  __ ldr(string, MemOperand(element, kPointerSize, PostIndex));
+  __ ldr(string_length, FieldMemOperand(string, String::kLengthOffset));
+  __ SmiUntag(string_length);
+  __ add(string,
+         string,
+         Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
+  __ CopyBytes(string, result_pos, string_length, scratch);
+  __ cmp(element, elements_end);
+  __ b(lt, &one_char_separator_loop);  // End while (element < elements_end).
+  DCHECK(result.is(r0));
+  __ b(&done);
+
+  // Long separator case (separator is more than one character). Entry is at the
+  // label long_separator below.
+  __ bind(&long_separator_loop);
+  // Live values in registers:
+  //   result_pos: the position to which we are currently copying characters.
+  //   element: Current array element.
+  //   elements_end: Array end.
+  //   separator: Separator string.
+
+  // Copy the separator to the result.
+  __ ldr(string_length, FieldMemOperand(separator, String::kLengthOffset));
+  __ SmiUntag(string_length);
+  __ add(string,
+         separator,
+         Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
+  __ CopyBytes(string, result_pos, string_length, scratch);
+
+  __ bind(&long_separator);
+  __ ldr(string, MemOperand(element, kPointerSize, PostIndex));
+  __ ldr(string_length, FieldMemOperand(string, String::kLengthOffset));
+  __ SmiUntag(string_length);
+  __ add(string,
+         string,
+         Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
+  __ CopyBytes(string, result_pos, string_length, scratch);
+  __ cmp(element, elements_end);
+  __ b(lt, &long_separator_loop);  // End while (element < elements_end).
+  DCHECK(result.is(r0));
+  __ b(&done);
+
+  __ bind(&bailout);
+  __ LoadRoot(r0, Heap::kUndefinedValueRootIndex);
+  __ bind(&done);
   context()->Plug(r0);
 }