зеркало из https://github.com/mozilla/gecko-dev.git
Bug 899309 - modify JS::Value and some helper functions to be constexpr-foldable; r=luke
This commit is contained in:
Nathan Froyd
Родитель
84ba23610c
Коммит
b0ca59e796
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@ -333,6 +333,49 @@ typedef union jsval_layout
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JS_STATIC_ASSERT(sizeof(jsval_layout) == 8);
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/*
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* For codesize purposes on some platforms, it's important that the
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* compiler know that JS::Values constructed from constant values can be
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* folded to constant bit patterns at compile time, rather than
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* constructed at runtime. Doing this requires a fair amount of C++11
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* features, which are not supported on all of our compilers. Set up
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* some defines and helper macros in an attempt to confine the ugliness
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* here, rather than scattering it all about the file. The important
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* features are:
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*
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* - constexpr;
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* - defaulted functions;
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* - C99-style designated initializers.
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*/
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#if defined(__clang__)
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# if __has_feature(cxx_constexpr) && __has_feature(cxx_defaulted_functions)
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# define JS_VALUE_IS_CONSTEXPR
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# endif
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#elif defined(__GNUC__)
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/*
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* We need 4.5 for defaulted functions, 4.6 for constexpr, 4.7 because 4.6
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* doesn't understand |(X) { .field = ... }| syntax, and 4.7.3 because
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* versions prior to that have bugs in the C++ front-end that cause crashes.
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*/
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# if MOZ_GCC_VERSION_AT_LEAST(4, 7, 3)
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# define JS_VALUE_IS_CONSTEXPR
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# endif
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#endif
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#if defined(JS_VALUE_IS_CONSTEXPR)
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# define JS_RETURN_LAYOUT_FROM_BITS(BITS) \
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return (jsval_layout) { .asBits = (BITS) }
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# define JS_VALUE_CONSTEXPR MOZ_CONSTEXPR
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# define JS_VALUE_CONSTEXPR_VAR MOZ_CONSTEXPR_VAR
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#else
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# define JS_RETURN_LAYOUT_FROM_BITS(BITS) \
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jsval_layout l; \
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l.asBits = (BITS); \
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return l;
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# define JS_VALUE_CONSTEXPR
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# define JS_VALUE_CONSTEXPR_VAR const
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#endif
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#if JS_BITS_PER_WORD == 32
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/*
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@ -341,12 +384,10 @@ JS_STATIC_ASSERT(sizeof(jsval_layout) == 8);
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* Thus, all comparisons should explicitly cast operands to uint32_t.
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*/
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static inline jsval_layout
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static inline JS_VALUE_CONSTEXPR jsval_layout
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BUILD_JSVAL(JSValueTag tag, uint32_t payload)
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{
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jsval_layout l;
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l.asBits = (((uint64_t)(uint32_t)tag) << 32) | payload;
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return l;
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JS_RETURN_LAYOUT_FROM_BITS((((uint64_t)(uint32_t)tag) << 32) | payload);
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}
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static inline bool
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@ -376,13 +417,17 @@ JSVAL_TO_INT32_IMPL(jsval_layout l)
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return l.s.payload.i32;
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}
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static inline jsval_layout
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static inline JS_VALUE_CONSTEXPR jsval_layout
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INT32_TO_JSVAL_IMPL(int32_t i)
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{
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#if defined(JS_VALUE_IS_CONSTEXPR)
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return BUILD_JSVAL(JSVAL_TAG_INT32, i);
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#else
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jsval_layout l;
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l.s.tag = JSVAL_TAG_INT32;
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l.s.payload.i32 = i;
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return l;
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#endif
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}
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static inline bool
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@ -569,12 +614,10 @@ JSVAL_EXTRACT_NON_DOUBLE_TYPE_IMPL(jsval_layout l)
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#elif JS_BITS_PER_WORD == 64
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static inline jsval_layout
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static inline JS_VALUE_CONSTEXPR jsval_layout
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BUILD_JSVAL(JSValueTag tag, uint64_t payload)
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{
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jsval_layout l;
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l.asBits = (((uint64_t)(uint32_t)tag) << JSVAL_TAG_SHIFT) | payload;
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return l;
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JS_RETURN_LAYOUT_FROM_BITS((((uint64_t)(uint32_t)tag) << JSVAL_TAG_SHIFT) | payload);
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}
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static inline bool
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@ -604,12 +647,10 @@ JSVAL_TO_INT32_IMPL(jsval_layout l)
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return (int32_t)l.asBits;
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}
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static inline jsval_layout
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static inline JS_VALUE_CONSTEXPR jsval_layout
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INT32_TO_JSVAL_IMPL(int32_t i32)
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{
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jsval_layout l;
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l.asBits = ((uint64_t)(uint32_t)i32) | JSVAL_SHIFTED_TAG_INT32;
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return l;
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JS_RETURN_LAYOUT_FROM_BITS(((uint64_t)(uint32_t)i32) | JSVAL_SHIFTED_TAG_INT32);
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}
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static inline bool
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@ -812,10 +853,12 @@ JS_CANONICALIZE_NAN(double d)
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}
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static inline jsval_layout JSVAL_TO_IMPL(JS::Value v);
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static inline JS::Value IMPL_TO_JSVAL(jsval_layout l);
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static inline JS_VALUE_CONSTEXPR JS::Value IMPL_TO_JSVAL(jsval_layout l);
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namespace JS {
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static inline JS_VALUE_CONSTEXPR JS::Value UndefinedValue();
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/*
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* JS::Value is the interface for a single JavaScript Engine value. A few
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* general notes on JS::Value:
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@ -858,6 +901,10 @@ class Value
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* N.B. the default constructor leaves Value unitialized. Adding a default
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* constructor prevents Value from being stored in a union.
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*/
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#if defined(JS_VALUE_IS_CONSTEXPR)
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Value() = default;
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Value(const Value& v) = default;
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#endif
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/*** Mutators ***/
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@ -1162,6 +1209,10 @@ class Value
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jsval_layout data;
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private:
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#if defined(JS_VALUE_IS_CONSTEXPR)
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JS_VALUE_CONSTEXPR Value(jsval_layout layout) : data(layout) {}
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#endif
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void staticAssertions() {
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JS_STATIC_ASSERT(sizeof(JSValueType) == 1);
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JS_STATIC_ASSERT(sizeof(JSValueTag) == 4);
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@ -1170,7 +1221,8 @@ class Value
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}
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friend jsval_layout (::JSVAL_TO_IMPL)(Value);
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friend Value (::IMPL_TO_JSVAL)(jsval_layout l);
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friend Value JS_VALUE_CONSTEXPR (::IMPL_TO_JSVAL)(jsval_layout l);
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friend Value JS_VALUE_CONSTEXPR (JS::UndefinedValue)();
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};
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inline bool
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@ -1193,12 +1245,16 @@ NullValue()
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return v;
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}
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static inline Value
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static inline JS_VALUE_CONSTEXPR Value
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UndefinedValue()
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{
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Value v;
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#if defined(JS_VALUE_IS_CONSTEXPR)
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return Value(BUILD_JSVAL(JSVAL_TAG_UNDEFINED, 0));
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#else
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JS::Value v;
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v.setUndefined();
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return v;
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#endif
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}
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static inline Value
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@ -1608,12 +1664,16 @@ JSVAL_TO_IMPL(JS::Value v)
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return v.data;
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}
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inline JS::Value
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inline JS_VALUE_CONSTEXPR JS::Value
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IMPL_TO_JSVAL(jsval_layout l)
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{
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#if defined(JS_VALUE_IS_CONSTEXPR)
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return JS::Value(l);
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#else
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JS::Value v;
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v.data = l;
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return v;
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#endif
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}
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namespace JS {
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@ -1691,7 +1751,7 @@ JSVAL_TO_INT(jsval v)
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return JSVAL_TO_INT32_IMPL(JSVAL_TO_IMPL(v));
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}
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static inline jsval
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static inline JS_VALUE_CONSTEXPR jsval
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INT_TO_JSVAL(int32_t i)
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{
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return IMPL_TO_JSVAL(INT32_TO_JSVAL_IMPL(i));
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@ -1712,7 +1772,7 @@ JSVAL_TO_DOUBLE(jsval v)
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return l.asDouble;
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}
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static inline jsval
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static inline JS_VALUE_CONSTEXPR jsval
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DOUBLE_TO_JSVAL(double d)
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{
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/*
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@ -1721,20 +1781,26 @@ DOUBLE_TO_JSVAL(double d)
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* return IMPL_TO_JSVAL(DOUBLE_TO_JSVAL_IMPL(d));
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* because GCC from XCode 3.1.4 miscompiles the above code.
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*/
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#if defined(JS_VALUE_IS_CONSTEXPR)
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return IMPL_TO_JSVAL(MOZ_UNLIKELY(d != d)
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? (jsval_layout) { .asBits = 0x7FF8000000000000LL }
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: (jsval_layout) { .asDouble = d });
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#else
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jsval_layout l;
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if (MOZ_UNLIKELY(d != d))
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l.asBits = 0x7FF8000000000000LL;
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else
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l.asDouble = d;
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return IMPL_TO_JSVAL(l);
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#endif
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}
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static inline jsval
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static inline JS_VALUE_CONSTEXPR jsval
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UINT_TO_JSVAL(uint32_t i)
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{
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if (i <= JSVAL_INT_MAX)
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return INT_TO_JSVAL((int32_t)i);
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return DOUBLE_TO_JSVAL((double)i);
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return (i <= JSVAL_INT_MAX
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? INT_TO_JSVAL((int32_t)i)
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: DOUBLE_TO_JSVAL((double)i));
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}
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static inline bool
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@ -1830,4 +1896,7 @@ JSVAL_TO_PRIVATE(jsval v)
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return JSVAL_TO_PRIVATE_PTR_IMPL(JSVAL_TO_IMPL(v));
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}
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#undef JS_VALUE_IS_CONSTEXPR
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#undef JS_RETURN_LAYOUT_FROM_BITS
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#endif /* js_Value_h */
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