Revert of [stubs] Port SubStringStub to TurboFan

src/mips/code-stubs-mips.cc

Index: src/mips/code-stubs-mips.cc
diff --git a/src/mips/code-stubs-mips.cc b/src/mips/code-stubs-mips.cc
index 7ab85dcec89c81ed4fa136a661aff1a2ea227bc4..68cb356d002b781f73056230ec664c2f887d9c91 100644
--- a/src/mips/code-stubs-mips.cc
+++ b/src/mips/code-stubs-mips.cc
@@ -2268,6 +2268,229 @@
   __ bind(&done);
 }
 
+
+void SubStringStub::Generate(MacroAssembler* masm) {
+  Label runtime;
+  // Stack frame on entry.
+  //  ra: return address
+  //  sp[0]: to
+  //  sp[4]: from
+  //  sp[8]: string
+
+  // This stub is called from the native-call %_SubString(...), so
+  // nothing can be assumed about the arguments. It is tested that:
+  //  "string" is a sequential string,
+  //  both "from" and "to" are smis, and
+  //  0 <= from <= to <= string.length.
+  // If any of these assumptions fail, we call the runtime system.
+
+  const int kToOffset = 0 * kPointerSize;
+  const int kFromOffset = 1 * kPointerSize;
+  const int kStringOffset = 2 * kPointerSize;
+
+  __ lw(a2, MemOperand(sp, kToOffset));
+  __ lw(a3, MemOperand(sp, kFromOffset));
+  STATIC_ASSERT(kFromOffset == kToOffset + 4);
+  STATIC_ASSERT(kSmiTag == 0);
+  STATIC_ASSERT(kSmiTagSize + kSmiShiftSize == 1);
+
+  // Utilize delay slots. SmiUntag doesn't emit a jump, everything else is
+  // safe in this case.
+  __ UntagAndJumpIfNotSmi(a2, a2, &runtime);
+  __ UntagAndJumpIfNotSmi(a3, a3, &runtime);
+  // Both a2 and a3 are untagged integers.
+
+  __ Branch(&runtime, lt, a3, Operand(zero_reg));  // From < 0.
+
+  __ Branch(&runtime, gt, a3, Operand(a2));  // Fail if from > to.
+  __ Subu(a2, a2, a3);
+
+  // Make sure first argument is a string.
+  __ lw(v0, MemOperand(sp, kStringOffset));
+  __ JumpIfSmi(v0, &runtime);
+  __ lw(a1, FieldMemOperand(v0, HeapObject::kMapOffset));
+  __ lbu(a1, FieldMemOperand(a1, Map::kInstanceTypeOffset));
+  __ And(t0, a1, Operand(kIsNotStringMask));
+
+  __ Branch(&runtime, ne, t0, Operand(zero_reg));
+
+  Label single_char;
+  __ Branch(&single_char, eq, a2, Operand(1));
+
+  // Short-cut for the case of trivial substring.
+  Label return_v0;
+  // v0: original string
+  // a2: result string length
+  __ lw(t0, FieldMemOperand(v0, String::kLengthOffset));
+  __ sra(t0, t0, 1);
+  // Return original string.
+  __ Branch(&return_v0, eq, a2, Operand(t0));
+  // Longer than original string's length or negative: unsafe arguments.
+  __ Branch(&runtime, hi, a2, Operand(t0));
+  // Shorter than original string's length: an actual substring.
+
+  // Deal with different string types: update the index if necessary
+  // and put the underlying string into t1.
+  // v0: original string
+  // a1: instance type
+  // a2: length
+  // a3: from index (untagged)
+  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);
+  __ And(t0, a1, Operand(kIsIndirectStringMask));
+  __ Branch(USE_DELAY_SLOT, &seq_or_external_string, eq, t0, Operand(zero_reg));
+  // t0 is used as a scratch register and can be overwritten in either case.
+  __ And(t0, a1, Operand(kSlicedNotConsMask));
+  __ Branch(&sliced_string, ne, t0, Operand(zero_reg));
+  // Cons string.  Check whether it is flat, then fetch first part.
+  __ lw(t1, FieldMemOperand(v0, ConsString::kSecondOffset));
+  __ LoadRoot(t0, Heap::kempty_stringRootIndex);
+  __ Branch(&runtime, ne, t1, Operand(t0));
+  __ lw(t1, FieldMemOperand(v0, ConsString::kFirstOffset));
+  // Update instance type.
+  __ lw(a1, FieldMemOperand(t1, HeapObject::kMapOffset));
+  __ lbu(a1, FieldMemOperand(a1, Map::kInstanceTypeOffset));
+  __ jmp(&underlying_unpacked);
+
+  __ bind(&sliced_string);
+  // Sliced string.  Fetch parent and correct start index by offset.
+  __ lw(t1, FieldMemOperand(v0, SlicedString::kParentOffset));
+  __ lw(t0, FieldMemOperand(v0, SlicedString::kOffsetOffset));
+  __ sra(t0, t0, 1);  // Add offset to index.
+  __ Addu(a3, a3, t0);
+  // Update instance type.
+  __ lw(a1, FieldMemOperand(t1, HeapObject::kMapOffset));
+  __ lbu(a1, FieldMemOperand(a1, Map::kInstanceTypeOffset));
+  __ jmp(&underlying_unpacked);
+
+  __ bind(&seq_or_external_string);
+  // Sequential or external string.  Just move string to the expected register.
+  __ mov(t1, v0);
+
+  __ bind(&underlying_unpacked);
+
+  if (FLAG_string_slices) {
+    Label copy_routine;
+    // t1: underlying subject string
+    // a1: instance type of underlying subject string
+    // a2: length
+    // a3: adjusted start index (untagged)
+    // Short slice.  Copy instead of slicing.
+    __ Branch(&copy_routine, lt, a2, Operand(SlicedString::kMinLength));
+    // 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);
+    __ And(t0, a1, Operand(kStringEncodingMask));
+    __ Branch(&two_byte_slice, eq, t0, Operand(zero_reg));
+    __ AllocateOneByteSlicedString(v0, a2, t2, t3, &runtime);
+    __ jmp(&set_slice_header);
+    __ bind(&two_byte_slice);
+    __ AllocateTwoByteSlicedString(v0, a2, t2, t3, &runtime);
+    __ bind(&set_slice_header);
+    __ sll(a3, a3, 1);
+    __ sw(t1, FieldMemOperand(v0, SlicedString::kParentOffset));
+    __ sw(a3, FieldMemOperand(v0, SlicedString::kOffsetOffset));
+    __ jmp(&return_v0);
+
+    __ bind(&copy_routine);
+  }
+
+  // t1: underlying subject string
+  // a1: instance type of underlying subject string
+  // a2: length
+  // a3: adjusted start index (untagged)
+  Label two_byte_sequential, sequential_string, allocate_result;
+  STATIC_ASSERT(kExternalStringTag != 0);
+  STATIC_ASSERT(kSeqStringTag == 0);
+  __ And(t0, a1, Operand(kExternalStringTag));
+  __ Branch(&sequential_string, eq, t0, Operand(zero_reg));
+
+  // Handle external string.
+  // Rule out short external strings.
+  STATIC_ASSERT(kShortExternalStringTag != 0);
+  __ And(t0, a1, Operand(kShortExternalStringTag));
+  __ Branch(&runtime, ne, t0, Operand(zero_reg));
+  __ lw(t1, FieldMemOperand(t1, ExternalString::kResourceDataOffset));
+  // t1 already points to the first character of underlying string.
+  __ jmp(&allocate_result);
+
+  __ bind(&sequential_string);
+  // Locate first character of underlying subject string.
+  STATIC_ASSERT(SeqTwoByteString::kHeaderSize == SeqOneByteString::kHeaderSize);
+  __ Addu(t1, t1, Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
+
+  __ bind(&allocate_result);
+  // Sequential acii string.  Allocate the result.
+  STATIC_ASSERT((kOneByteStringTag & kStringEncodingMask) != 0);
+  __ And(t0, a1, Operand(kStringEncodingMask));
+  __ Branch(&two_byte_sequential, eq, t0, Operand(zero_reg));
+
+  // Allocate and copy the resulting ASCII string.
+  __ AllocateOneByteString(v0, a2, t0, t2, t3, &runtime);
+
+  // Locate first character of substring to copy.
+  __ Addu(t1, t1, a3);
+
+  // Locate first character of result.
+  __ Addu(a1, v0, Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
+
+  // v0: result string
+  // a1: first character of result string
+  // a2: result string length
+  // t1: first character of substring to copy
+  STATIC_ASSERT((SeqOneByteString::kHeaderSize & kObjectAlignmentMask) == 0);
+  StringHelper::GenerateCopyCharacters(
+      masm, a1, t1, a2, a3, String::ONE_BYTE_ENCODING);
+  __ jmp(&return_v0);
+
+  // Allocate and copy the resulting two-byte string.
+  __ bind(&two_byte_sequential);
+  __ AllocateTwoByteString(v0, a2, t0, t2, t3, &runtime);
+
+  // Locate first character of substring to copy.
+  STATIC_ASSERT(kSmiTagSize == 1 && kSmiTag == 0);
+  __ Lsa(t1, t1, a3, 1);
+  // Locate first character of result.
+  __ Addu(a1, v0, Operand(SeqTwoByteString::kHeaderSize - kHeapObjectTag));
+
+  // v0: result string.
+  // a1: first character of result.
+  // a2: result length.
+  // t1: first character of substring to copy.
+  STATIC_ASSERT((SeqTwoByteString::kHeaderSize & kObjectAlignmentMask) == 0);
+  StringHelper::GenerateCopyCharacters(
+      masm, a1, t1, a2, a3, String::TWO_BYTE_ENCODING);
+
+  __ bind(&return_v0);
+  Counters* counters = isolate()->counters();
+  __ IncrementCounter(counters->sub_string_native(), 1, a3, t0);
+  __ DropAndRet(3);
+
+  // Just jump to runtime to create the sub string.
+  __ bind(&runtime);
+  __ TailCallRuntime(Runtime::kSubString);
+
+  __ bind(&single_char);
+  // v0: original string
+  // a1: instance type
+  // a2: length
+  // a3: from index (untagged)
+  __ SmiTag(a3, a3);
+  StringCharAtGenerator generator(v0, a3, a2, v0, &runtime, &runtime, &runtime,
+                                  RECEIVER_IS_STRING);
+  generator.GenerateFast(masm);
+  __ DropAndRet(3);
+  generator.SkipSlow(masm, &runtime);
+}
+
+
 void ToStringStub::Generate(MacroAssembler* masm) {
   // The ToString stub takes on argument in a0.
   Label is_number;