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Issue 7477045: Tentative implementation of string slices (hidden under the flag --string-slices). (Closed) Base URL: https://v8.googlecode.com/svn/branches/bleeding_edge
Patch Set: Some more suggested changes. Created 9 years, 3 months ago
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1 // Copyright 2011 the V8 project authors. All rights reserved. 1 // Copyright 2011 the V8 project authors. All rights reserved.
2 // Redistribution and use in source and binary forms, with or without 2 // Redistribution and use in source and binary forms, with or without
3 // modification, are permitted provided that the following conditions are 3 // modification, are permitted provided that the following conditions are
4 // met: 4 // met:
5 // 5 //
6 // * Redistributions of source code must retain the above copyright 6 // * Redistributions of source code must retain the above copyright
7 // notice, this list of conditions and the following disclaimer. 7 // notice, this list of conditions and the following disclaimer.
8 // * Redistributions in binary form must reproduce the above 8 // * Redistributions in binary form must reproduce the above
9 // copyright notice, this list of conditions and the following 9 // copyright notice, this list of conditions and the following
10 // disclaimer in the documentation and/or other materials provided 10 // disclaimer in the documentation and/or other materials provided
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1281 table_.Register(kVisitFixedDoubleArray, &EvacuateFixedDoubleArray); 1281 table_.Register(kVisitFixedDoubleArray, &EvacuateFixedDoubleArray);
1282 1282
1283 table_.Register(kVisitGlobalContext, 1283 table_.Register(kVisitGlobalContext,
1284 &ObjectEvacuationStrategy<POINTER_OBJECT>:: 1284 &ObjectEvacuationStrategy<POINTER_OBJECT>::
1285 template VisitSpecialized<Context::kSize>); 1285 template VisitSpecialized<Context::kSize>);
1286 1286
1287 table_.Register(kVisitConsString, 1287 table_.Register(kVisitConsString,
1288 &ObjectEvacuationStrategy<POINTER_OBJECT>:: 1288 &ObjectEvacuationStrategy<POINTER_OBJECT>::
1289 template VisitSpecialized<ConsString::kSize>); 1289 template VisitSpecialized<ConsString::kSize>);
1290 1290
1291 table_.Register(kVisitSlicedString,
1292 &ObjectEvacuationStrategy<POINTER_OBJECT>::
1293 template VisitSpecialized<SlicedString::kSize>);
1294
1291 table_.Register(kVisitSharedFunctionInfo, 1295 table_.Register(kVisitSharedFunctionInfo,
1292 &ObjectEvacuationStrategy<POINTER_OBJECT>:: 1296 &ObjectEvacuationStrategy<POINTER_OBJECT>::
1293 template VisitSpecialized<SharedFunctionInfo::kSize>); 1297 template VisitSpecialized<SharedFunctionInfo::kSize>);
1294 1298
1295 table_.Register(kVisitJSRegExp, 1299 table_.Register(kVisitJSRegExp,
1296 &ObjectEvacuationStrategy<POINTER_OBJECT>:: 1300 &ObjectEvacuationStrategy<POINTER_OBJECT>::
1297 Visit); 1301 Visit);
1298 1302
1299 table_.Register(kVisitJSFunction, 1303 table_.Register(kVisitJSFunction,
1300 &ObjectEvacuationStrategy<POINTER_OBJECT>:: 1304 &ObjectEvacuationStrategy<POINTER_OBJECT>::
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2538 // we can try to save memory if all chars actually fit in ascii. 2542 // we can try to save memory if all chars actually fit in ascii.
2539 is_ascii_data_in_two_byte_string = 2543 is_ascii_data_in_two_byte_string =
2540 first->HasOnlyAsciiChars() && second->HasOnlyAsciiChars(); 2544 first->HasOnlyAsciiChars() && second->HasOnlyAsciiChars();
2541 if (is_ascii_data_in_two_byte_string) { 2545 if (is_ascii_data_in_two_byte_string) {
2542 isolate_->counters()->string_add_runtime_ext_to_ascii()->Increment(); 2546 isolate_->counters()->string_add_runtime_ext_to_ascii()->Increment();
2543 } 2547 }
2544 } 2548 }
2545 2549
2546 // If the resulting string is small make a flat string. 2550 // If the resulting string is small make a flat string.
2547 if (length < String::kMinNonFlatLength) { 2551 if (length < String::kMinNonFlatLength) {
2552 // Note that neither of the two inputs can be a slice because:
2553 STATIC_ASSERT(String::kMinNonFlatLength <= SlicedString::kMinLength);
2548 ASSERT(first->IsFlat()); 2554 ASSERT(first->IsFlat());
2549 ASSERT(second->IsFlat()); 2555 ASSERT(second->IsFlat());
2550 if (is_ascii) { 2556 if (is_ascii) {
2551 Object* result; 2557 Object* result;
2552 { MaybeObject* maybe_result = AllocateRawAsciiString(length); 2558 { MaybeObject* maybe_result = AllocateRawAsciiString(length);
2553 if (!maybe_result->ToObject(&result)) return maybe_result; 2559 if (!maybe_result->ToObject(&result)) return maybe_result;
2554 } 2560 }
2555 // Copy the characters into the new object. 2561 // Copy the characters into the new object.
2556 char* dest = SeqAsciiString::cast(result)->GetChars(); 2562 char* dest = SeqAsciiString::cast(result)->GetChars();
2557 // Copy first part. 2563 // Copy first part.
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2629 // dictionary. Check whether we already have the string in the symbol 2635 // dictionary. Check whether we already have the string in the symbol
2630 // table to prevent creation of many unneccesary strings. 2636 // table to prevent creation of many unneccesary strings.
2631 unsigned c1 = buffer->Get(start); 2637 unsigned c1 = buffer->Get(start);
2632 unsigned c2 = buffer->Get(start + 1); 2638 unsigned c2 = buffer->Get(start + 1);
2633 return MakeOrFindTwoCharacterString(this, c1, c2); 2639 return MakeOrFindTwoCharacterString(this, c1, c2);
2634 } 2640 }
2635 2641
2636 // Make an attempt to flatten the buffer to reduce access time. 2642 // Make an attempt to flatten the buffer to reduce access time.
2637 buffer = buffer->TryFlattenGetString(); 2643 buffer = buffer->TryFlattenGetString();
2638 2644
2645 // TODO(1626): For now slicing external strings is not supported. However,
2646 // a flat cons string can have an external string as first part in some cases.
2647 // Therefore we have to single out this case as well.
2648 if (!FLAG_string_slices ||
2649 (buffer->IsConsString() &&
2650 (!buffer->IsFlat() ||
2651 !ConsString::cast(buffer)->first()->IsSeqString())) ||
2652 buffer->IsExternalString() ||
2653 length < SlicedString::kMinLength ||
2654 pretenure == TENURED) {
2655 Object* result;
2656 { MaybeObject* maybe_result = buffer->IsAsciiRepresentation()
2657 ? AllocateRawAsciiString(length, pretenure)
2658 : AllocateRawTwoByteString(length, pretenure);
2659 if (!maybe_result->ToObject(&result)) return maybe_result;
2660 }
2661 String* string_result = String::cast(result);
2662 // Copy the characters into the new object.
2663 if (buffer->IsAsciiRepresentation()) {
2664 ASSERT(string_result->IsAsciiRepresentation());
2665 char* dest = SeqAsciiString::cast(string_result)->GetChars();
2666 String::WriteToFlat(buffer, dest, start, end);
2667 } else {
2668 ASSERT(string_result->IsTwoByteRepresentation());
2669 uc16* dest = SeqTwoByteString::cast(string_result)->GetChars();
2670 String::WriteToFlat(buffer, dest, start, end);
2671 }
2672 return result;
2673 }
2674
2675 ASSERT(buffer->IsFlat());
2676 ASSERT(!buffer->IsExternalString());
2677 #if DEBUG
2678 buffer->StringVerify();
2679 #endif
2680
2639 Object* result; 2681 Object* result;
2640 { MaybeObject* maybe_result = buffer->IsAsciiRepresentation() 2682 { Map* map = buffer->IsAsciiRepresentation()
2641 ? AllocateRawAsciiString(length, pretenure ) 2683 ? sliced_ascii_string_map()
2642 : AllocateRawTwoByteString(length, pretenure); 2684 : sliced_string_map();
2685 MaybeObject* maybe_result = Allocate(map, NEW_SPACE);
2643 if (!maybe_result->ToObject(&result)) return maybe_result; 2686 if (!maybe_result->ToObject(&result)) return maybe_result;
2644 } 2687 }
2645 String* string_result = String::cast(result); 2688
2646 // Copy the characters into the new object. 2689 AssertNoAllocation no_gc;
2647 if (buffer->IsAsciiRepresentation()) { 2690 SlicedString* sliced_string = SlicedString::cast(result);
2648 ASSERT(string_result->IsAsciiRepresentation()); 2691 sliced_string->set_length(length);
2649 char* dest = SeqAsciiString::cast(string_result)->GetChars(); 2692 sliced_string->set_hash_field(String::kEmptyHashField);
2650 String::WriteToFlat(buffer, dest, start, end); 2693 if (buffer->IsConsString()) {
2694 ConsString* cons = ConsString::cast(buffer);
2695 ASSERT(cons->second()->length() == 0);
2696 sliced_string->set_parent(cons->first());
2697 sliced_string->set_offset(start);
2698 } else if (buffer->IsSlicedString()) {
2699 // Prevent nesting sliced strings.
2700 SlicedString* parent_slice = SlicedString::cast(buffer);
2701 sliced_string->set_parent(parent_slice->parent());
2702 sliced_string->set_offset(start + parent_slice->offset());
2651 } else { 2703 } else {
2652 ASSERT(string_result->IsTwoByteRepresentation()); 2704 sliced_string->set_parent(buffer);
2653 uc16* dest = SeqTwoByteString::cast(string_result)->GetChars(); 2705 sliced_string->set_offset(start);
2654 String::WriteToFlat(buffer, dest, start, end);
2655 } 2706 }
2656 2707 ASSERT(sliced_string->parent()->IsSeqString());
2657 return result; 2708 return result;
2658 } 2709 }
2659 2710
2660 2711
2661 MaybeObject* Heap::AllocateExternalStringFromAscii( 2712 MaybeObject* Heap::AllocateExternalStringFromAscii(
2662 ExternalAsciiString::Resource* resource) { 2713 ExternalAsciiString::Resource* resource) {
2663 size_t length = resource->length(); 2714 size_t length = resource->length();
2664 if (length > static_cast<size_t>(String::kMaxLength)) { 2715 if (length > static_cast<size_t>(String::kMaxLength)) {
2665 isolate()->context()->mark_out_of_memory(); 2716 isolate()->context()->mark_out_of_memory();
2666 return Failure::OutOfMemoryException(); 2717 return Failure::OutOfMemoryException();
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6024 } 6075 }
6025 6076
6026 6077
6027 void ExternalStringTable::TearDown() { 6078 void ExternalStringTable::TearDown() {
6028 new_space_strings_.Free(); 6079 new_space_strings_.Free();
6029 old_space_strings_.Free(); 6080 old_space_strings_.Free();
6030 } 6081 }
6031 6082
6032 6083
6033 } } // namespace v8::internal 6084 } } // namespace v8::internal
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