src/v8/src/elements-kind.cc

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  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 const char* ElementsKindToString(ElementsKind kind) {
  39   ElementsAccessor* accessor = ElementsAccessor::ForKind(kind);
  40   return accessor->name();
  41 }
  42
  43
  44 void PrintElementsKind(FILE* out, ElementsKind kind) {
  45   PrintF(out, "%s", ElementsKindToString(kind));
  46 }
  47
  48
  49 ElementsKind GetInitialFastElementsKind() {
  50   if (FLAG_packed_arrays) {
  51     return FAST_SMI_ELEMENTS;
  52   } else {
  53     return FAST_HOLEY_SMI_ELEMENTS;
  54   }
  55 }
  56
  57
  58 struct InitializeFastElementsKindSequence {
  59   static void Construct(
  60       ElementsKind** fast_elements_kind_sequence_ptr) {
  61     ElementsKind* fast_elements_kind_sequence =
  62         new ElementsKind[kFastElementsKindCount];
  63     *fast_elements_kind_sequence_ptr = fast_elements_kind_sequence;
  64     STATIC_ASSERT(FAST_SMI_ELEMENTS == FIRST_FAST_ELEMENTS_KIND);
  65     fast_elements_kind_sequence[0] = FAST_SMI_ELEMENTS;
  66     fast_elements_kind_sequence[1] = FAST_HOLEY_SMI_ELEMENTS;
  67     fast_elements_kind_sequence[2] = FAST_DOUBLE_ELEMENTS;
  68     fast_elements_kind_sequence[3] = FAST_HOLEY_DOUBLE_ELEMENTS;
  69     fast_elements_kind_sequence[4] = FAST_ELEMENTS;
  70     fast_elements_kind_sequence[5] = FAST_HOLEY_ELEMENTS;
  71   }
  72 };
  73
  74
  75 static LazyInstance<ElementsKind*,
  76                     InitializeFastElementsKindSequence>::type
  77     fast_elements_kind_sequence = LAZY_INSTANCE_INITIALIZER;
  78
  79
  80 ElementsKind GetFastElementsKindFromSequenceIndex(int sequence_number) {
  81   ASSERT(sequence_number >= 0 &&
  82          sequence_number < kFastElementsKindCount);
  83   return fast_elements_kind_sequence.Get()[sequence_number];
  84 }
  85
  86
  87 int GetSequenceIndexFromFastElementsKind(ElementsKind elements_kind) {
  88   for (int i = 0; i < kFastElementsKindCount; ++i) {
  89     if (fast_elements_kind_sequence.Get()[i] == elements_kind) {
  90       return i;
  91     }
  92   }
  93   UNREACHABLE();
  94   return 0;
  95 }
  96
  97
  98 ElementsKind GetNextMoreGeneralFastElementsKind(ElementsKind elements_kind,
  99                                                 bool allow_only_packed) {
 100   ASSERT(IsFastElementsKind(elements_kind));
 101   ASSERT(elements_kind != TERMINAL_FAST_ELEMENTS_KIND);
 102   while (true) {
 103     int index =
 104         GetSequenceIndexFromFastElementsKind(elements_kind) + 1;
 105     elements_kind = GetFastElementsKindFromSequenceIndex(index);
 106     if (!IsFastHoleyElementsKind(elements_kind) || !allow_only_packed) {
 107       return elements_kind;
 108     }
 109   }
 110   UNREACHABLE();
 111   return TERMINAL_FAST_ELEMENTS_KIND;
 112 }
 113
 114
 115 bool IsMoreGeneralElementsKindTransition(ElementsKind from_kind,
 116                                          ElementsKind to_kind) {
 117   switch (from_kind) {
 118     case FAST_SMI_ELEMENTS:
 119       return to_kind != FAST_SMI_ELEMENTS;
 120     case FAST_HOLEY_SMI_ELEMENTS:
 121       return to_kind != FAST_SMI_ELEMENTS &&
 122           to_kind != FAST_HOLEY_SMI_ELEMENTS;
 123     case FAST_DOUBLE_ELEMENTS:
 124       return to_kind != FAST_SMI_ELEMENTS &&
 125           to_kind != FAST_HOLEY_SMI_ELEMENTS &&
 126           to_kind != FAST_DOUBLE_ELEMENTS;
 127     case FAST_HOLEY_DOUBLE_ELEMENTS:
 128       return to_kind == FAST_ELEMENTS ||
 129           to_kind == FAST_HOLEY_ELEMENTS;
 130     case FAST_ELEMENTS:
 131       return to_kind == FAST_HOLEY_ELEMENTS;
 132     case FAST_HOLEY_ELEMENTS:
 133       return false;
 134     default:
 135       return false;
 136   }
 137 }
 138
 139
 140 } }  // namespace v8::internal