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Update to use a more efficient power of 2 check. (#274)

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This commit is contained in:
Matthew Parkinson
2021-01-27 11:58:41 +00:00
committed by GitHub
parent db3580a9d8
commit a3660c4069
10 changed files with 21 additions and 18 deletions
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10
src/ds/address.h
View File

@@ -49,7 +49,7 @@ namespace snmalloc
template<size_t alignment>
static inline bool is_aligned_block(void* p, size_t size)
{
static_assert(bits::next_pow2_const(alignment) == alignment);
static_assert(bits::is_pow2(alignment));
return ((address_cast(p) | size) & (alignment - 1)) == 0;
}
@@ -62,7 +62,7 @@ namespace snmalloc
SNMALLOC_FAST_PATH T* pointer_align_down(void* p)
{
static_assert(alignment > 0);
static_assert(bits::next_pow2_const(alignment) == alignment);
static_assert(bits::is_pow2(alignment));
if constexpr (alignment == 1)
return static_cast<T*>(p);
else
@@ -84,7 +84,7 @@ namespace snmalloc
inline T* pointer_align_up(void* p)
{
static_assert(alignment > 0);
static_assert(bits::next_pow2_const(alignment) == alignment);
static_assert(bits::is_pow2(alignment));
if constexpr (alignment == 1)
return static_cast<T*>(p);
else
@@ -106,7 +106,7 @@ namespace snmalloc
SNMALLOC_FAST_PATH T* pointer_align_down(void* p, size_t alignment)
{
SNMALLOC_ASSERT(alignment > 0);
SNMALLOC_ASSERT(bits::next_pow2(alignment) == alignment);
SNMALLOC_ASSERT(bits::is_pow2(alignment));
#if __has_builtin(__builtin_align_down)
return static_cast<T*>(__builtin_align_down(p, alignment));
#else
@@ -123,7 +123,7 @@ namespace snmalloc
inline T* pointer_align_up(void* p, size_t alignment)
{
SNMALLOC_ASSERT(alignment > 0);
SNMALLOC_ASSERT(bits::next_pow2(alignment) == alignment);
SNMALLOC_ASSERT(bits::is_pow2(alignment));
#if __has_builtin(__builtin_align_up)
return static_cast<T*>(__builtin_align_up(p, alignment));
#else

9
src/ds/bits.h
View File

@@ -211,6 +211,11 @@ namespace snmalloc
#endif
}
constexpr SNMALLOC_FAST_PATH bool is_pow2(size_t x)
{
return (x & (x - 1)) == 0;
}
SNMALLOC_FAST_PATH size_t next_pow2(size_t x)
{
// Correct for numbers [0..MAX_SIZE >> 1).
@@ -244,7 +249,7 @@ namespace snmalloc
constexpr SNMALLOC_FAST_PATH size_t
align_down(size_t value, size_t alignment)
{
SNMALLOC_ASSERT(next_pow2_const(alignment) == alignment);
SNMALLOC_ASSERT(is_pow2(alignment));
size_t align_1 = alignment - 1;
value &= ~align_1;
@@ -253,7 +258,7 @@ namespace snmalloc
constexpr SNMALLOC_FAST_PATH size_t align_up(size_t value, size_t alignment)
{
SNMALLOC_ASSERT(next_pow2_const(alignment) == alignment);
SNMALLOC_ASSERT(is_pow2(alignment));
size_t align_1 = alignment - 1;
value += align_1;

3
src/ds/helpers.h
View File

@@ -52,8 +52,7 @@ namespace snmalloc
template<size_t length, typename T>
class Mod
{
static_assert(
length == bits::next_pow2_const(length), "Must be a power of two.");
static_assert(bits::is_pow2(length), "Must be a power of two.");
private:
T value = 0;