diff options
Diffstat (limited to 'src/qml/jsruntime/qv4value_p.h')
| -rw-r--r-- | src/qml/jsruntime/qv4value_p.h | 267 |
1 files changed, 161 insertions, 106 deletions
diff --git a/src/qml/jsruntime/qv4value_p.h b/src/qml/jsruntime/qv4value_p.h index 78cd4de9fb..4428c48d80 100644 --- a/src/qml/jsruntime/qv4value_p.h +++ b/src/qml/jsruntime/qv4value_p.h @@ -76,23 +76,85 @@ private: /* We use two different ways of encoding JS values. One for 32bit and one for 64bit systems. - In both cases, we use 8 bytes for a value and a different variant of NaN boxing. A Double NaN (actually -qNaN) - is indicated by a number that has the top 13 bits set. The other values are usually set to 0 by the - processor, and are thus free for us to store other data. We keep pointers in there for managed objects, - and encode the other types using the free space given to use by the unused bits for NaN values. This also - works for pointers on 64 bit systems, as they all currently only have 48 bits of addressable memory. - - On 32bit, we store doubles as doubles. All other values, have the high 32bits set to a value that - will make the number a NaN. The Masks below are used for encoding the other types. - - On 64 bit, we xor Doubles with (0xffff8000 << 32). That has the effect that no doubles will get encoded - with the 13 highest bits all 0. We are now using special values for bits 14-17 to encode our values. These - can be used, as the highest valid pointer on a 64 bit system is 2^48-1. - - If they are all 0, we have a pointer to a Managed object. If bit 14 is set we have an integer. - This makes testing for pointers and numbers very fast (we have a number if any of the highest 14 bits is set). - - Bit 15-17 is then used to encode other immediates. + In both cases, we use 8 bytes for a value and a different variant of NaN boxing. A Double + NaN (actually -qNaN) is indicated by a number that has the top 13 bits set, and for a + signalling NaN it is the top 14 bits. The other values are usually set to 0 by the + processor, and are thus free for us to store other data. We keep pointers in there for + managed objects, and encode the other types using the free space given to use by the unused + bits for NaN values. This also works for pointers on 64 bit systems, as they all currently + only have 48 bits of addressable memory. (Note: we do leave the lower 49 bits available for + pointers.) + + On 32bit, we store doubles as doubles. All other values, have the high 32bits set to a value + that will make the number a NaN. The Masks below are used for encoding the other types. + + On 64 bit, we xor Doubles with (0xffff8000 << 32). That has the effect that no doubles will + get encoded with bits 63-49 all set to 0. We then use bit 48 to distinguish between + managed/undefined (0), or Null/Int/Bool/Empty (1). So, storing a 49 bit pointer will leave + the top 15 bits 0, which is exactly the 'natural' representation of pointers. If bit 49 is + set, bit 48 indicates Empty (0) or integer-convertible (1). Then the 3 bit below that are + used to encode Null/Int/Bool. + + On both 32bit and 64bit, Undefined is encoded as a managed pointer with value 0. This is + the same as a nullptr. + + Specific bit-sequences: + 0 = always 0 + 1 = always 1 + x = stored value + a,b,c,d = specific bit values, see notes + + 64bit: + + 32109876 54321098 76543210 98765432 10987654 32109876 54321098 76543210 | + 66665555 55555544 44444444 33333333 33222222 22221111 11111100 00000000 | JS Value + ------------------------------------------------------------------------+-------------- + 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 | Undefined + 00000000 0000000x xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx | Managed (heap pointer) + a0000000 0000bc00 00000000 00000000 00000000 00000000 00000000 00000000 | NaN/Inf + dddddddd ddddddxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx | double + 00000000 00000010 00000000 00000000 00000000 00000000 00000000 00000000 | empty (non-sparse array hole) + 00000000 00000011 10000000 00000000 00000000 00000000 00000000 00000000 | Null + 00000000 00000011 01000000 00000000 00000000 00000000 00000000 0000000x | Bool + 00000000 00000011 00100000 00000000 xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx | Int + + Notes: + - a: xor-ed signbit, always 1 for NaN + - bc, xor-ed values: 11 = inf, 10 = sNaN, 01 = qNaN, 00 = boxed value + - d: xor-ed bits, where at least one bit is set, so: (val >> (64-14)) > 0 + - Undefined maps to C++ nullptr, so the "default" initialization is the same for both C++ + and JS + - Managed has the left 15 bits set to 0, so: (val >> (64-15)) == 0 + - empty, Null, Bool, and Int have the left 14 bits set to 0, and bit 49 set to 1, + so: (val >> (64-15)) == 1 + - Null, Bool, and Int have bit 48 set, indicating integer-convertible + - xoring _val with NaNEncodeMask will convert to a double in "natural" representation, where + any non double results in a NaN + + 32bit: + + 32109876 54321098 76543210 98765432 10987654 32109876 54321098 76543210 | + 66665555 55555544 44444444 33333333 33222222 22221111 11111100 00000000 | JS Value + ------------------------------------------------------------------------+-------------- + 01111111 11111100 00000000 00000000 00000000 00000000 00000000 00000000 | Undefined + 01111111 11111100 00000000 00000000 xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx | Managed (heap pointer) + a1111111 1111bc00 00000000 00000000 00000000 00000000 00000000 00000000 | NaN/Inf + xddddddd ddddddxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx | double + 01111111 11111110 00000000 00000000 00000000 00000000 00000000 00000000 | empty (non-sparse array hole) + 01111111 11111111 10000000 00000000 00000000 00000000 00000000 00000000 | Null + 01111111 11111111 01000000 00000000 00000000 00000000 00000000 0000000x | Bool + 01111111 11111111 00100000 00000000 xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx | Int + + Notes: + - the upper 32 bits are the tag, the lower 32 bits the value + - Undefined has a nullptr in the value, Managed has a non-nullptr stored in the value + - a: sign bit, always 0 for NaN + - b,c: 00=inf, 01 = sNaN, 10 = qNaN, 11 = boxed value + - d: stored double value, as long as not *all* of them are 1, because that's a boxed value + (see above) + - empty, Null, Bool, and Int have bit 63 set to 0, bits 62-50 set to 1 (same as undefined + and managed), and bit 49 set to 1 (where undefined and managed have it set to 0) + - Null, Bool, and Int have bit 48 set, indicating integer-convertible */ quint64 _val; @@ -140,7 +202,7 @@ public: { quint32 v; memcpy(&v, &b, 4); - setTagValue(Managed_Type, v); + setTagValue(Managed_Type_Internal, v); } #endif @@ -156,12 +218,43 @@ public: Q_ALWAYS_INLINE void setEmpty() { - setTagValue(Empty_Type, value()); + setTagValue(Empty_Type_Internal, value()); } Q_ALWAYS_INLINE void setEmpty(int i) { - setTagValue(Empty_Type, quint32(i)); + setTagValue(Empty_Type_Internal, quint32(i)); + } + + Q_ALWAYS_INLINE void setEmpty(quint32 i) + { + setTagValue(Empty_Type_Internal, i); + } + + Q_ALWAYS_INLINE quint32 emptyValue() + { + Q_ASSERT(isEmpty()); + return quint32(value()); + } + + enum Type { + Undefined_Type, + Managed_Type, + Empty_Type, + Integer_Type, + Boolean_Type, + Null_Type, + Double_Type + }; + + inline Type type() const { + if (isUndefined()) return Undefined_Type; + if (isManaged()) return Managed_Type; + if (isEmpty()) return Empty_Type; + if (isInteger()) return Integer_Type; + if (isBoolean()) return Boolean_Type; + if (isNull()) return Null_Type; + Q_ASSERT(isDouble()); return Double_Type; } #ifndef QV4_USE_64_BIT_VALUE_ENCODING @@ -169,101 +262,64 @@ public: SilentNaNBit = 0x00040000, NaN_Mask = 0x7ff80000, NotDouble_Mask = 0x7ffa0000, - Type_Mask = 0xffffc000, - Immediate_Mask = NotDouble_Mask | 0x00004000 | SilentNaNBit, - IsNullOrUndefined_Mask = Immediate_Mask | 0x08000, + Immediate_Mask = NotDouble_Mask | 0x00020000u | SilentNaNBit, Tag_Shift = 32 }; - enum ValueType { - Undefined_Type = Immediate_Mask | 0x00000, - Null_Type = Immediate_Mask | 0x10000, - Boolean_Type = Immediate_Mask | 0x08000, - Integer_Type = Immediate_Mask | 0x18000, - Managed_Type = NotDouble_Mask | 0x00000 | SilentNaNBit, - Empty_Type = NotDouble_Mask | 0x18000 | SilentNaNBit - }; - - enum ImmediateFlags { - ConvertibleToInt = Immediate_Mask | 0x1 - }; - - enum ValueTypeInternal { - Null_Type_Internal = Null_Type | ConvertibleToInt, - Boolean_Type_Internal = Boolean_Type | ConvertibleToInt, - Integer_Type_Internal = Integer_Type | ConvertibleToInt, + enum { + Managed_Type_Internal = NotDouble_Mask }; #else - static const quint64 NaNEncodeMask = 0xffff800000000000ll; - static const quint64 IsInt32Mask = 0x0002000000000000ll; - static const quint64 IsDoubleMask = 0xfffc000000000000ll; - static const quint64 IsNumberMask = IsInt32Mask|IsDoubleMask; - static const quint64 IsNullOrUndefinedMask = 0x0000800000000000ll; - static const quint64 IsNullOrBooleanMask = 0x0001000000000000ll; - static const quint64 IsConvertibleToIntMask = IsInt32Mask|IsNullOrBooleanMask; + static const quint64 NaNEncodeMask = 0xfffc000000000000ll; + static const quint64 Immediate_Mask = 0x00020000u; // bit 49 enum Masks { NaN_Mask = 0x7ff80000, - Type_Mask = 0xffff8000, - IsDouble_Mask = 0xfffc0000, - Immediate_Mask = 0x00018000, - IsNullOrUndefined_Mask = 0x00008000, - IsNullOrBoolean_Mask = 0x00010000, - Tag_Shift = 32 - }; - enum ValueType { - Undefined_Type = IsNullOrUndefined_Mask, - Null_Type = IsNullOrUndefined_Mask|IsNullOrBoolean_Mask, - Boolean_Type = IsNullOrBoolean_Mask, - Integer_Type = 0x20000|IsNullOrBoolean_Mask, - Managed_Type = 0, - Empty_Type = Undefined_Type | 0x4000 }; enum { IsDouble_Shift = 64-14, - IsNumber_Shift = 64-15, - IsConvertibleToInt_Shift = 64-16, - IsManaged_Shift = 64-17 + IsManagedOrUndefined_Shift = 64-15, + IsIntegerConvertible_Shift = 64-16, + Tag_Shift = 32, + IsDoubleTag_Shift = IsDouble_Shift - Tag_Shift, + Managed_Type_Internal = 0 }; - - +#endif enum ValueTypeInternal { - Null_Type_Internal = Null_Type, - Boolean_Type_Internal = Boolean_Type, - Integer_Type_Internal = Integer_Type + Empty_Type_Internal = Immediate_Mask | 0, + ConvertibleToInt = Immediate_Mask | 0x10000u, // bit 48 + Null_Type_Internal = ConvertibleToInt | 0x08000u, + Boolean_Type_Internal = ConvertibleToInt | 0x04000u, + Integer_Type_Internal = ConvertibleToInt | 0x02000u }; -#endif - - inline unsigned type() const { - return tag() & Type_Mask; - } // used internally in property - inline bool isEmpty() const { return tag() == Empty_Type; } - - inline bool isUndefined() const { return tag() == Undefined_Type; } + inline bool isEmpty() const { return tag() == Empty_Type_Internal; } inline bool isNull() const { return tag() == Null_Type_Internal; } - inline bool isBoolean() const { return tag ()== Boolean_Type_Internal; } + inline bool isBoolean() const { return tag() == Boolean_Type_Internal; } + inline bool isInteger() const { return tag() == Integer_Type_Internal; } + inline bool isNullOrUndefined() const { return isNull() || isUndefined(); } + inline bool isNumber() const { return isDouble() || isInteger(); } + #ifdef QV4_USE_64_BIT_VALUE_ENCODING - inline bool isInteger() const { return (_val >> IsNumber_Shift) == 1; } + inline bool isUndefined() const { return _val == 0; } inline bool isDouble() const { return (_val >> IsDouble_Shift); } - inline bool isNumber() const { return (_val >> IsNumber_Shift); } - inline bool isManaged() const { return !(_val >> IsManaged_Shift); } - inline bool isNullOrUndefined() const { return ((_val >> IsManaged_Shift) & ~2) == 1; } - inline bool integerCompatible() const { return ((_val >> IsConvertibleToInt_Shift) & ~2) == 1; } + inline bool isManaged() const { return !isUndefined() && ((_val >> IsManagedOrUndefined_Shift) == 0); } + + inline bool integerCompatible() const { + return (_val >> IsIntegerConvertible_Shift) == 3; + } static inline bool integerCompatible(Value a, Value b) { return a.integerCompatible() && b.integerCompatible(); } static inline bool bothDouble(Value a, Value b) { return a.isDouble() && b.isDouble(); } - inline bool isNaN() const { return (tag() & 0x7fff8000) == 0x00078000; } + inline bool isNaN() const { return (tag() & 0x7ffc0000 ) == 0x00040000; } #else - inline bool isInteger() const { return tag() == Integer_Type_Internal; } + inline bool isUndefined() const { return tag() == Managed_Type_Internal && value() == 0; } inline bool isDouble() const { return (tag() & NotDouble_Mask) != NotDouble_Mask; } - inline bool isNumber() const { return tag() == Integer_Type_Internal || (tag() & NotDouble_Mask) != NotDouble_Mask; } - inline bool isManaged() const { return tag() == Managed_Type; } - inline bool isNullOrUndefined() const { return (tag() & IsNullOrUndefined_Mask) == Undefined_Type; } + inline bool isManaged() const { return tag() == Managed_Type_Internal && !isUndefined(); } inline bool integerCompatible() const { return (tag() & ConvertibleToInt) == ConvertibleToInt; } static inline bool integerCompatible(Value a, Value b) { return ((a.tag() & b.tag()) & ConvertibleToInt) == ConvertibleToInt; @@ -428,7 +484,7 @@ public: template<typename T> Value &operator=(const Scoped<T> &t); }; -Q_STATIC_ASSERT(std::is_trivial<Value>::value); +V4_ASSERT_IS_TRIVIAL(Value) inline bool Value::isString() const { @@ -491,6 +547,7 @@ ReturnedValue Heap::Base::asReturnedValue() const struct Q_QML_PRIVATE_EXPORT Primitive : public Value { inline static Primitive emptyValue(); + inline static Primitive emptyValue(uint v); static inline Primitive fromBoolean(bool b); static inline Primitive fromInt32(int i); inline static Primitive undefinedValue(); @@ -509,14 +566,21 @@ struct Q_QML_PRIVATE_EXPORT Primitive : public Value inline Primitive Primitive::undefinedValue() { Primitive v; - v.setTagValue(Undefined_Type, 0); + v.setM(Q_NULLPTR); return v; } inline Primitive Primitive::emptyValue() { Primitive v; - v.setTagValue(Value::Empty_Type, 0); + v.setEmpty(0); + return v; +} + +inline Primitive Primitive::emptyValue(uint e) +{ + Primitive v; + v.setEmpty(e); return v; } @@ -544,7 +608,6 @@ inline Primitive Primitive::fromDouble(double d) inline Primitive Primitive::fromInt32(int i) { Primitive v; - v.setTagValue(Integer_Type_Internal, 0); v.setInt_32(i); return v; } @@ -562,31 +625,23 @@ inline Primitive Primitive::fromUInt32(uint i) struct Encode { static ReturnedValue undefined() { - return quint64(Value::Undefined_Type) << Value::Tag_Shift; + return Primitive::undefinedValue().rawValue(); } static ReturnedValue null() { - return quint64(Value::Null_Type_Internal) << Value::Tag_Shift; + return Primitive::nullValue().rawValue(); } Encode(bool b) { - val = (quint64(Value::Boolean_Type_Internal) << Value::Tag_Shift) | (uint)b; + val = Primitive::fromBoolean(b).rawValue(); } Encode(double d) { - Value v; - v.setDouble(d); - val = v.rawValue(); + val = Primitive::fromDouble(d).rawValue(); } Encode(int i) { - val = (quint64(Value::Integer_Type_Internal) << Value::Tag_Shift) | (uint)i; + val = Primitive::fromInt32(i).rawValue(); } Encode(uint i) { - if (i <= INT_MAX) { - val = (quint64(Value::Integer_Type_Internal) << Value::Tag_Shift) | i; - } else { - Value v; - v.setDouble(i); - val = v.rawValue(); - } + val = Primitive::fromUInt32(i).rawValue(); } Encode(ReturnedValue v) { val = v; |