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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
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@@ -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
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@@ -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
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@@ -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;

2
src/mem/address_space.h
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@@ -175,7 +175,7 @@ namespace snmalloc
template<bool committed>
void* reserve(size_t size)
{
SNMALLOC_ASSERT(bits::next_pow2(size) == size);
SNMALLOC_ASSERT(bits::is_pow2(size));
SNMALLOC_ASSERT(size >= sizeof(void*));
if constexpr (pal_supports<AlignedAllocation, PAL>)

2
src/mem/sizeclass.h
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@@ -183,7 +183,7 @@ namespace snmalloc
// Client responsible for checking alignment is not zero
SNMALLOC_ASSERT(alignment != 0);
// Client responsible for checking alignment is a power of two
SNMALLOC_ASSERT(bits::next_pow2(alignment) == alignment);
SNMALLOC_ASSERT(bits::is_pow2(alignment));
return ((alignment - 1) | (size - 1)) + 1;
}

3
src/pal/pal.h
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@@ -76,8 +76,7 @@ namespace snmalloc
static constexpr size_t OS_PAGE_SIZE = Pal::page_size;
static_assert(
bits::next_pow2_const(OS_PAGE_SIZE) == OS_PAGE_SIZE,
"OS_PAGE_SIZE must be a power of two");
bits::is_pow2(OS_PAGE_SIZE), "OS_PAGE_SIZE must be a power of two");
static_assert(
OS_PAGE_SIZE % Aal::smallest_page_size == 0,
"The smallest architectural page size must divide OS_PAGE_SIZE");

2
src/pal/pal_bsd_aligned.h
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@@ -32,7 +32,7 @@ namespace snmalloc
static void* reserve_aligned(size_t size) noexcept
{
// Alignment must be a power of 2.
SNMALLOC_ASSERT(size == bits::next_pow2(size));
SNMALLOC_ASSERT(bits::is_pow2(size));
SNMALLOC_ASSERT(size >= minimum_alloc_size);
size_t log2align = bits::next_pow2_bits(size);

2
src/pal/pal_freebsd_kernel.h
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@@ -62,7 +62,7 @@ namespace snmalloc
template<bool committed>
static void* reserve_aligned(size_t size) noexcept
{
SNMALLOC_ASSERT(size == bits::next_pow2(size));
SNMALLOC_ASSERT(bits::is_pow2(size));
SNMALLOC_ASSERT(size >= minimum_alloc_size);
size_t align = size;

2
src/pal/pal_posix.h
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@@ -212,7 +212,7 @@ namespace snmalloc
*/
static std::pair<void*, size_t> reserve_at_least(size_t size) noexcept
{
SNMALLOC_ASSERT(size == bits::next_pow2(size));
SNMALLOC_ASSERT(bits::is_pow2(size));
// Magic number for over-allocating chosen by the Pal
// These should be further refined based on experiments.

4
src/pal/pal_windows.h
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@@ -185,7 +185,7 @@ namespace snmalloc
template<bool committed>
static void* reserve_aligned(size_t size) noexcept
{
SNMALLOC_ASSERT(size == bits::next_pow2(size));
SNMALLOC_ASSERT(bits::is_pow2(size));
SNMALLOC_ASSERT(size >= minimum_alloc_size);
DWORD flags = MEM_RESERVE;
@@ -215,7 +215,7 @@ namespace snmalloc
# else
static std::pair<void*, size_t> reserve_at_least(size_t size) noexcept
{
SNMALLOC_ASSERT(size == bits::next_pow2(size));
SNMALLOC_ASSERT(bits::is_pow2(size));
// Magic number for over-allocating chosen by the Pal
// These should be further refined based on experiments.