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Bug 1735715 - Handle gMaxSubPageClass == 0 properly r=glandium

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Differential Revision: https://phabricator.services.mozilla.com/D128448
This commit is contained in:
Paul Bone 2021-10-21 06:03:45 +00:00
parent 1af62d829d
commit 1b721fc414
3 changed files with 9 additions and 21 deletions
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14
memory/build/Utils.h
View File

@ -20,20 +20,6 @@ struct Log2 : mozilla::tl::CeilingLog2<N> {
};
#define LOG2(N) Log2<N>::value
// Like Log2, but ignores 0.
template <size_t N>
struct Log2Or0 : mozilla::tl::CeilingLog2<N> {
using mozilla::tl::CeilingLog2<N>::value;
static_assert(1ULL << value == N, "Number is not a power of 2");
};
template <>
struct Log2Or0<0> {
// This makes no sense but neither does any other value. It's just enough
// that this can be used on the unused side of a conditional expression.
static const size_t value = 0;
};
#define LOG2_OR_0(N) Log2Or0<N>::value
enum class Order {
eLess = -1,
eEqual = 0,

14
memory/build/mozjemalloc.cpp
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@ -483,21 +483,21 @@ static size_t gPageSize;
# define END_GLOBALS
# define DEFINE_GLOBAL(type) static const type
# define GLOBAL_LOG2 LOG2
# define GLOBAL_LOG2_OR_0 LOG2_OR_0
# define GLOBAL_ASSERT_HELPER1(x) static_assert(x, # x)
# define GLOBAL_ASSERT_HELPER2(x, y) static_assert(x, y)
# define GLOBAL_ASSERT(...) \
MACRO_CALL( \
MOZ_PASTE_PREFIX_AND_ARG_COUNT(GLOBAL_ASSERT_HELPER, __VA_ARGS__), \
(__VA_ARGS__))
# define GLOBAL_CONSTEXPR constexpr
#else
# define DECLARE_GLOBAL(type, name) static type name;
# define DEFINE_GLOBALS static void DefineGlobals() {
# define END_GLOBALS }
# define DEFINE_GLOBAL(type)
# define GLOBAL_LOG2 FloorLog2
# define GLOBAL_LOG2_OR_0 FloorLog2
# define GLOBAL_ASSERT MOZ_RELEASE_ASSERT
# define GLOBAL_CONSTEXPR
#endif
DECLARE_GLOBAL(size_t, gMaxSubPageClass)
@ -520,10 +520,12 @@ gMaxSubPageClass = gPageSize / 2 >= kMinSubPageClass ? gPageSize / 2 : 0;
// Number of sub-page bins.
DEFINE_GLOBAL(uint8_t)
gNumSubPageClasses =
static_cast<uint8_t>(gMaxSubPageClass ? GLOBAL_LOG2_OR_0(gMaxSubPageClass) -
LOG2(kMinSubPageClass) + 1
: 0);
gNumSubPageClasses = []() GLOBAL_CONSTEXPR -> uint8_t {
if GLOBAL_CONSTEXPR (gMaxSubPageClass != 0) {
return FloorLog2(gMaxSubPageClass) - LOG2(kMinSubPageClass) + 1;
}
return 0;
}();
DEFINE_GLOBAL(uint8_t) gPageSize2Pow = GLOBAL_LOG2(gPageSize);
DEFINE_GLOBAL(size_t) gPageSizeMask = gPageSize - 1;

2
mfbt/MathAlgorithms.h
View File

@ -375,7 +375,7 @@ class FloorLog2<T, 8> {
* FloorLog2(8..15) is 3; and so on.
*/
template <typename T>
inline uint_fast8_t FloorLog2(const T aValue) {
inline constexpr uint_fast8_t FloorLog2(const T aValue) {
return detail::FloorLog2<T>::compute(aValue);
}