Revert of [stubs] Port SubStringStub to TurboFan

src/x64/code-stubs-x64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/code-stubs.h"
 #include "src/api-arguments.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 1993 matching lines @@
   __ movb(kScratchRegister, Operand(src, 0));
   __ movb(Operand(dest, 0), kScratchRegister);
   __ incp(src);
   __ incp(dest);
   __ decl(count);
   __ j(not_zero, &loop);
 
   __ bind(&done);
 }
 
+
+void SubStringStub::Generate(MacroAssembler* masm) {
+  Label runtime;
+
+  // Stack frame on entry.
+  //  rsp[0]  : return address
+  //  rsp[8]  : to
+  //  rsp[16] : from
+  //  rsp[24] : string
+
+  enum SubStringStubArgumentIndices {
+    STRING_ARGUMENT_INDEX,
+    FROM_ARGUMENT_INDEX,
+    TO_ARGUMENT_INDEX,
+    SUB_STRING_ARGUMENT_COUNT
+  };
+
+  StackArgumentsAccessor args(rsp, SUB_STRING_ARGUMENT_COUNT,
+                              ARGUMENTS_DONT_CONTAIN_RECEIVER);
+
+  // Make sure first argument is a string.
+  __ movp(rax, args.GetArgumentOperand(STRING_ARGUMENT_INDEX));
+  STATIC_ASSERT(kSmiTag == 0);
+  __ testl(rax, Immediate(kSmiTagMask));
+  __ j(zero, &runtime);
+  Condition is_string = masm->IsObjectStringType(rax, rbx, rbx);
+  __ j(NegateCondition(is_string), &runtime);
+
+  // rax: string
+  // rbx: instance type
+  // Calculate length of sub string using the smi values.
+  __ movp(rcx, args.GetArgumentOperand(TO_ARGUMENT_INDEX));
+  __ movp(rdx, args.GetArgumentOperand(FROM_ARGUMENT_INDEX));
+  __ JumpUnlessBothNonNegativeSmi(rcx, rdx, &runtime);
+
+  __ SmiSub(rcx, rcx, rdx);  // Overflow doesn't happen.
+  __ cmpp(rcx, FieldOperand(rax, String::kLengthOffset));
+  Label not_original_string;
+  // Shorter than original string's length: an actual substring.
+  __ j(below, &not_original_string, Label::kNear);
+  // Longer than original string's length or negative: unsafe arguments.
+  __ j(above, &runtime);
+  // Return original string.
+  Counters* counters = isolate()->counters();
+  __ IncrementCounter(counters->sub_string_native(), 1);
+  __ ret(SUB_STRING_ARGUMENT_COUNT * kPointerSize);
+  __ bind(&not_original_string);
+
+  Label single_char;
+  __ SmiCompare(rcx, Smi::FromInt(1));
+  __ j(equal, &single_char);
+
+  __ SmiToInteger32(rcx, rcx);
+
+  // rax: string
+  // rbx: instance type
+  // rcx: sub string length
+  // rdx: from index (smi)
+  // Deal with different string types: update the index if necessary
+  // and put the underlying string into edi.
+  Label underlying_unpacked, sliced_string, seq_or_external_string;
+  // If the string is not indirect, it can only be sequential or external.
+  STATIC_ASSERT(kIsIndirectStringMask == (kSlicedStringTag & kConsStringTag));
+  STATIC_ASSERT(kIsIndirectStringMask != 0);
+  __ testb(rbx, Immediate(kIsIndirectStringMask));
+  __ j(zero, &seq_or_external_string, Label::kNear);
+
+  __ testb(rbx, Immediate(kSlicedNotConsMask));
+  __ j(not_zero, &sliced_string, Label::kNear);
+  // Cons string.  Check whether it is flat, then fetch first part.
+  // Flat cons strings have an empty second part.
+  __ CompareRoot(FieldOperand(rax, ConsString::kSecondOffset),
+                 Heap::kempty_stringRootIndex);
+  __ j(not_equal, &runtime);
+  __ movp(rdi, FieldOperand(rax, ConsString::kFirstOffset));
+  // Update instance type.
+  __ movp(rbx, FieldOperand(rdi, HeapObject::kMapOffset));
+  __ movzxbl(rbx, FieldOperand(rbx, Map::kInstanceTypeOffset));
+  __ jmp(&underlying_unpacked, Label::kNear);
+
+  __ bind(&sliced_string);
+  // Sliced string.  Fetch parent and correct start index by offset.
+  __ addp(rdx, FieldOperand(rax, SlicedString::kOffsetOffset));
+  __ movp(rdi, FieldOperand(rax, SlicedString::kParentOffset));
+  // Update instance type.
+  __ movp(rbx, FieldOperand(rdi, HeapObject::kMapOffset));
+  __ movzxbl(rbx, FieldOperand(rbx, Map::kInstanceTypeOffset));
+  __ jmp(&underlying_unpacked, Label::kNear);
+
+  __ bind(&seq_or_external_string);
+  // Sequential or external string.  Just move string to the correct register.
+  __ movp(rdi, rax);
+
+  __ bind(&underlying_unpacked);
+
+  if (FLAG_string_slices) {
+    Label copy_routine;
+    // rdi: underlying subject string
+    // rbx: instance type of underlying subject string
+    // rdx: adjusted start index (smi)
+    // rcx: length
+    // If coming from the make_two_character_string path, the string
+    // is too short to be sliced anyways.
+    __ cmpp(rcx, Immediate(SlicedString::kMinLength));
+    // Short slice.  Copy instead of slicing.
+    __ j(less, &copy_routine);
+    // Allocate new sliced string.  At this point we do not reload the instance
+    // type including the string encoding because we simply rely on the info
+    // provided by the original string.  It does not matter if the original
+    // string's encoding is wrong because we always have to recheck encoding of
+    // the newly created string's parent anyways due to externalized strings.
+    Label two_byte_slice, set_slice_header;
+    STATIC_ASSERT((kStringEncodingMask & kOneByteStringTag) != 0);
+    STATIC_ASSERT((kStringEncodingMask & kTwoByteStringTag) == 0);
+    __ testb(rbx, Immediate(kStringEncodingMask));
+    __ j(zero, &two_byte_slice, Label::kNear);
+    __ AllocateOneByteSlicedString(rax, rbx, r14, &runtime);
+    __ jmp(&set_slice_header, Label::kNear);
+    __ bind(&two_byte_slice);
+    __ AllocateTwoByteSlicedString(rax, rbx, r14, &runtime);
+    __ bind(&set_slice_header);
+    __ Integer32ToSmi(rcx, rcx);
+    __ movp(FieldOperand(rax, SlicedString::kLengthOffset), rcx);
+    __ movp(FieldOperand(rax, SlicedString::kHashFieldOffset),
+           Immediate(String::kEmptyHashField));
+    __ movp(FieldOperand(rax, SlicedString::kParentOffset), rdi);
+    __ movp(FieldOperand(rax, SlicedString::kOffsetOffset), rdx);
+    __ IncrementCounter(counters->sub_string_native(), 1);
+    __ ret(3 * kPointerSize);
+
+    __ bind(&copy_routine);
+  }
+
+  // rdi: underlying subject string
+  // rbx: instance type of underlying subject string
+  // rdx: adjusted start index (smi)
+  // rcx: length
+  // The subject string can only be external or sequential string of either
+  // encoding at this point.
+  Label two_byte_sequential, sequential_string;
+  STATIC_ASSERT(kExternalStringTag != 0);
+  STATIC_ASSERT(kSeqStringTag == 0);
+  __ testb(rbx, Immediate(kExternalStringTag));
+  __ j(zero, &sequential_string);
+
+  // Handle external string.
+  // Rule out short external strings.
+  STATIC_ASSERT(kShortExternalStringTag != 0);
+  __ testb(rbx, Immediate(kShortExternalStringMask));
+  __ j(not_zero, &runtime);
+  __ movp(rdi, FieldOperand(rdi, ExternalString::kResourceDataOffset));
+  // Move the pointer so that offset-wise, it looks like a sequential string.
+  STATIC_ASSERT(SeqTwoByteString::kHeaderSize == SeqOneByteString::kHeaderSize);
+  __ subp(rdi, Immediate(SeqTwoByteString::kHeaderSize - kHeapObjectTag));
+
+  __ bind(&sequential_string);
+  STATIC_ASSERT((kOneByteStringTag & kStringEncodingMask) != 0);
+  __ testb(rbx, Immediate(kStringEncodingMask));
+  __ j(zero, &two_byte_sequential);
+
+  // Allocate the result.
+  __ AllocateOneByteString(rax, rcx, r11, r14, r15, &runtime);
+
+  // rax: result string
+  // rcx: result string length
+  {  // Locate character of sub string start.
+    SmiIndex smi_as_index = masm->SmiToIndex(rdx, rdx, times_1);
+    __ leap(r14, Operand(rdi, smi_as_index.reg, smi_as_index.scale,
+                        SeqOneByteString::kHeaderSize - kHeapObjectTag));
+  }
+  // Locate first character of result.
+  __ leap(rdi, FieldOperand(rax, SeqOneByteString::kHeaderSize));
+
+  // rax: result string
+  // rcx: result length
+  // r14: first character of result
+  // rsi: character of sub string start
+  StringHelper::GenerateCopyCharacters(
+      masm, rdi, r14, rcx, String::ONE_BYTE_ENCODING);
+  __ IncrementCounter(counters->sub_string_native(), 1);
+  __ ret(SUB_STRING_ARGUMENT_COUNT * kPointerSize);
+
+  __ bind(&two_byte_sequential);
+  // Allocate the result.
+  __ AllocateTwoByteString(rax, rcx, r11, r14, r15, &runtime);
+
+  // rax: result string
+  // rcx: result string length
+  {  // Locate character of sub string start.
+    SmiIndex smi_as_index = masm->SmiToIndex(rdx, rdx, times_2);
+    __ leap(r14, Operand(rdi, smi_as_index.reg, smi_as_index.scale,
+                        SeqOneByteString::kHeaderSize - kHeapObjectTag));
+  }
+  // Locate first character of result.
+  __ leap(rdi, FieldOperand(rax, SeqTwoByteString::kHeaderSize));
+
+  // rax: result string
+  // rcx: result length
+  // rdi: first character of result
+  // r14: character of sub string start
+  StringHelper::GenerateCopyCharacters(
+      masm, rdi, r14, rcx, String::TWO_BYTE_ENCODING);
+  __ IncrementCounter(counters->sub_string_native(), 1);
+  __ ret(SUB_STRING_ARGUMENT_COUNT * kPointerSize);
+
+  // Just jump to runtime to create the sub string.
+  __ bind(&runtime);
+  __ TailCallRuntime(Runtime::kSubString);
+
+  __ bind(&single_char);
+  // rax: string
+  // rbx: instance type
+  // rcx: sub string length (smi)
+  // rdx: from index (smi)
+  StringCharAtGenerator generator(rax, rdx, rcx, rax, &runtime, &runtime,
+                                  &runtime, RECEIVER_IS_STRING);
+  generator.GenerateFast(masm);
+  __ ret(SUB_STRING_ARGUMENT_COUNT * kPointerSize);
+  generator.SkipSlow(masm, &runtime);
+}
+
 void ToStringStub::Generate(MacroAssembler* masm) {
   // The ToString stub takes one argument in rax.
   Label is_number;
   __ JumpIfSmi(rax, &is_number, Label::kNear);
 
   Label not_string;
   __ CmpObjectType(rax, FIRST_NONSTRING_TYPE, rdi);
   // rax: receiver
   // rdi: receiver map
   __ j(above_equal, &not_string, Label::kNear);
@@ skipping 2916 matching lines @@
                            kStackUnwindSpace, nullptr, return_value_operand,
                            NULL);
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64