Tweaks to SubStringStub

src/ia32/code-stubs-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 6137 matching lines @@
   __ mov(eax, Operand(esp, 3 * kPointerSize));
   STATIC_ASSERT(kSmiTag == 0);
   __ JumpIfSmi(eax, &runtime);
   Condition is_string = masm->IsObjectStringType(eax, ebx, ebx);
   __ j(NegateCondition(is_string), &runtime);
 
   // eax: string
   // ebx: instance type
 
   // Calculate length of sub string using the smi values.
-  Label result_longer_than_two;
   __ mov(ecx, Operand(esp, 1 * kPointerSize));  // To index.
   __ JumpIfNotSmi(ecx, &runtime);
   __ mov(edx, Operand(esp, 2 * kPointerSize));  // From index.
   __ JumpIfNotSmi(edx, &runtime);
   __ sub(ecx, edx);
   __ cmp(ecx, FieldOperand(eax, String::kLengthOffset));
   Label not_original_string;
   __ j(not_equal, &not_original_string, Label::kNear);
   Counters* counters = masm->isolate()->counters();
   __ IncrementCounter(counters->sub_string_native(), 1);
   __ ret(3 * kPointerSize);
   __ bind(&not_original_string);
-  // Special handling of sub-strings of length 1 and 2. One character strings
-  // are handled in the runtime system (looked up in the single character
-  // cache). Two character strings are looked for in the symbol cache.
-  __ cmp(ecx, Immediate(Smi::FromInt(2)));
-  __ j(greater, &result_longer_than_two);
-  __ j(less, &runtime);
 
-  // Sub string of length 2 requested.
-  // eax: string
-  // ebx: instance type
-  // ecx: sub string length (smi, value is 2)
-  // edx: from index (smi)
-  __ JumpIfInstanceTypeIsNotSequentialAscii(ebx, ebx, &runtime);
-
-  // Get the two characters forming the sub string.
-  __ SmiUntag(edx);  // From index is no longer smi.
-  __ movzx_b(ebx, FieldOperand(eax, edx, times_1, SeqAsciiString::kHeaderSize));
-  __ movzx_b(ecx,
-             FieldOperand(eax, edx, times_1, SeqAsciiString::kHeaderSize + 1));
-
-  // Try to lookup two character string in symbol table.
-  Label combine_two_char, save_two_char;
-  StringHelper::GenerateTwoCharacterSymbolTableProbe(
-      masm, ebx, ecx, eax, edx, edi, &combine_two_char, &save_two_char);
-  __ IncrementCounter(counters->sub_string_native(), 1);
-  __ ret(3 * kPointerSize);
-
-  __ bind(&combine_two_char);
-  __ shl(ecx, kBitsPerByte);
-  __ or_(ebx, ecx);
-  __ bind(&save_two_char);
-  __ AllocateAsciiString(eax, 2, ecx, edx, &runtime);
-  __ mov_w(FieldOperand(eax, SeqAsciiString::kHeaderSize), ebx);
-  __ IncrementCounter(counters->sub_string_native(), 1);
-  __ ret(3 * kPointerSize);
-
-  __ bind(&result_longer_than_two);
   // eax: string
   // ebx: instance type
   // ecx: sub string length (smi)
   // edx: 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);
@@ skipping 46 matching lines @@
     Label two_byte_slice, set_slice_header;
     STATIC_ASSERT((kStringEncodingMask & kAsciiStringTag) != 0);
     STATIC_ASSERT((kStringEncodingMask & kTwoByteStringTag) == 0);
     __ test(ebx, Immediate(kStringEncodingMask));
     __ j(zero, &two_byte_slice, Label::kNear);
     __ AllocateAsciiSlicedString(eax, ebx, no_reg, &runtime);
     __ jmp(&set_slice_header, Label::kNear);
     __ bind(&two_byte_slice);
     __ AllocateTwoByteSlicedString(eax, ebx, no_reg, &runtime);
     __ bind(&set_slice_header);
-    __ mov(FieldOperand(eax, SlicedString::kOffsetOffset), edx);
     __ mov(FieldOperand(eax, SlicedString::kLengthOffset), ecx);
-    __ mov(FieldOperand(eax, SlicedString::kParentOffset), edi);
     __ mov(FieldOperand(eax, SlicedString::kHashFieldOffset),
            Immediate(String::kEmptyHashField));
+    __ mov(FieldOperand(eax, SlicedString::kParentOffset), edi);
+    __ mov(FieldOperand(eax, SlicedString::kOffsetOffset), edx);
     __ IncrementCounter(counters->sub_string_native(), 1);
     __ ret(3 * kPointerSize);
 
     __ bind(&copy_routine);
   }
 
   // edi: underlying subject string
   // ebx: instance type of underlying subject string
   // edx: adjusted start index (smi)
   // ecx: length (smi)
@@ skipping 1111 matching lines @@
                                  false);
   __ pop(edx);
   __ ret(0);
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32