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      1 // Copyright 2012 the V8 project authors. All rights reserved.
      2 // Redistribution and use in source and binary forms, with or without
      3 // modification, are permitted provided that the following conditions are
      4 // met:
      5 //
      6 //     * Redistributions of source code must retain the above copyright
      7 //       notice, this list of conditions and the following disclaimer.
      8 //     * Redistributions in binary form must reproduce the above
      9 //       copyright notice, this list of conditions and the following
     10 //       disclaimer in the documentation and/or other materials provided
     11 //       with the distribution.
     12 //     * Neither the name of Google Inc. nor the names of its
     13 //       contributors may be used to endorse or promote products derived
     14 //       from this software without specific prior written permission.
     15 //
     16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27 
     28 #include "elements-kind.h"
     29 
     30 #include "api.h"
     31 #include "elements.h"
     32 #include "objects.h"
     33 
     34 namespace v8 {
     35 namespace internal {
     36 
     37 
     38 int ElementsKindToShiftSize(ElementsKind elements_kind) {
     39   switch (elements_kind) {
     40     case EXTERNAL_BYTE_ELEMENTS:
     41     case EXTERNAL_PIXEL_ELEMENTS:
     42     case EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
     43       return 0;
     44     case EXTERNAL_SHORT_ELEMENTS:
     45     case EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
     46       return 1;
     47     case EXTERNAL_INT_ELEMENTS:
     48     case EXTERNAL_UNSIGNED_INT_ELEMENTS:
     49     case EXTERNAL_FLOAT_ELEMENTS:
     50       return 2;
     51     case EXTERNAL_DOUBLE_ELEMENTS:
     52     case FAST_DOUBLE_ELEMENTS:
     53     case FAST_HOLEY_DOUBLE_ELEMENTS:
     54       return 3;
     55     case FAST_SMI_ELEMENTS:
     56     case FAST_ELEMENTS:
     57     case FAST_HOLEY_SMI_ELEMENTS:
     58     case FAST_HOLEY_ELEMENTS:
     59     case DICTIONARY_ELEMENTS:
     60     case NON_STRICT_ARGUMENTS_ELEMENTS:
     61       return kPointerSizeLog2;
     62   }
     63   UNREACHABLE();
     64   return 0;
     65 }
     66 
     67 
     68 const char* ElementsKindToString(ElementsKind kind) {
     69   ElementsAccessor* accessor = ElementsAccessor::ForKind(kind);
     70   return accessor->name();
     71 }
     72 
     73 
     74 void PrintElementsKind(FILE* out, ElementsKind kind) {
     75   PrintF(out, "%s", ElementsKindToString(kind));
     76 }
     77 
     78 
     79 ElementsKind GetInitialFastElementsKind() {
     80   if (FLAG_packed_arrays) {
     81     return FAST_SMI_ELEMENTS;
     82   } else {
     83     return FAST_HOLEY_SMI_ELEMENTS;
     84   }
     85 }
     86 
     87 
     88 struct InitializeFastElementsKindSequence {
     89   static void Construct(
     90       ElementsKind** fast_elements_kind_sequence_ptr) {
     91     ElementsKind* fast_elements_kind_sequence =
     92         new ElementsKind[kFastElementsKindCount];
     93     *fast_elements_kind_sequence_ptr = fast_elements_kind_sequence;
     94     STATIC_ASSERT(FAST_SMI_ELEMENTS == FIRST_FAST_ELEMENTS_KIND);
     95     fast_elements_kind_sequence[0] = FAST_SMI_ELEMENTS;
     96     fast_elements_kind_sequence[1] = FAST_HOLEY_SMI_ELEMENTS;
     97     fast_elements_kind_sequence[2] = FAST_DOUBLE_ELEMENTS;
     98     fast_elements_kind_sequence[3] = FAST_HOLEY_DOUBLE_ELEMENTS;
     99     fast_elements_kind_sequence[4] = FAST_ELEMENTS;
    100     fast_elements_kind_sequence[5] = FAST_HOLEY_ELEMENTS;
    101 
    102     // Verify that kFastElementsKindPackedToHoley is correct.
    103     STATIC_ASSERT(FAST_SMI_ELEMENTS + kFastElementsKindPackedToHoley ==
    104                   FAST_HOLEY_SMI_ELEMENTS);
    105     STATIC_ASSERT(FAST_DOUBLE_ELEMENTS + kFastElementsKindPackedToHoley ==
    106                   FAST_HOLEY_DOUBLE_ELEMENTS);
    107     STATIC_ASSERT(FAST_ELEMENTS + kFastElementsKindPackedToHoley ==
    108                   FAST_HOLEY_ELEMENTS);
    109   }
    110 };
    111 
    112 
    113 static LazyInstance<ElementsKind*,
    114                     InitializeFastElementsKindSequence>::type
    115     fast_elements_kind_sequence = LAZY_INSTANCE_INITIALIZER;
    116 
    117 
    118 ElementsKind GetFastElementsKindFromSequenceIndex(int sequence_number) {
    119   ASSERT(sequence_number >= 0 &&
    120          sequence_number < kFastElementsKindCount);
    121   return fast_elements_kind_sequence.Get()[sequence_number];
    122 }
    123 
    124 
    125 int GetSequenceIndexFromFastElementsKind(ElementsKind elements_kind) {
    126   for (int i = 0; i < kFastElementsKindCount; ++i) {
    127     if (fast_elements_kind_sequence.Get()[i] == elements_kind) {
    128       return i;
    129     }
    130   }
    131   UNREACHABLE();
    132   return 0;
    133 }
    134 
    135 
    136 ElementsKind GetNextMoreGeneralFastElementsKind(ElementsKind elements_kind,
    137                                                 bool allow_only_packed) {
    138   ASSERT(IsFastElementsKind(elements_kind));
    139   ASSERT(elements_kind != TERMINAL_FAST_ELEMENTS_KIND);
    140   while (true) {
    141     int index =
    142         GetSequenceIndexFromFastElementsKind(elements_kind) + 1;
    143     elements_kind = GetFastElementsKindFromSequenceIndex(index);
    144     if (!IsFastHoleyElementsKind(elements_kind) || !allow_only_packed) {
    145       return elements_kind;
    146     }
    147   }
    148   UNREACHABLE();
    149   return TERMINAL_FAST_ELEMENTS_KIND;
    150 }
    151 
    152 
    153 bool IsMoreGeneralElementsKindTransition(ElementsKind from_kind,
    154                                          ElementsKind to_kind) {
    155   switch (from_kind) {
    156     case FAST_SMI_ELEMENTS:
    157       return to_kind != FAST_SMI_ELEMENTS;
    158     case FAST_HOLEY_SMI_ELEMENTS:
    159       return to_kind != FAST_SMI_ELEMENTS &&
    160           to_kind != FAST_HOLEY_SMI_ELEMENTS;
    161     case FAST_DOUBLE_ELEMENTS:
    162       return to_kind != FAST_SMI_ELEMENTS &&
    163           to_kind != FAST_HOLEY_SMI_ELEMENTS &&
    164           to_kind != FAST_DOUBLE_ELEMENTS;
    165     case FAST_HOLEY_DOUBLE_ELEMENTS:
    166       return to_kind == FAST_ELEMENTS ||
    167           to_kind == FAST_HOLEY_ELEMENTS;
    168     case FAST_ELEMENTS:
    169       return to_kind == FAST_HOLEY_ELEMENTS;
    170     case FAST_HOLEY_ELEMENTS:
    171       return false;
    172     default:
    173       return false;
    174   }
    175 }
    176 
    177 
    178 } }  // namespace v8::internal
    179