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simplified aligned allocation; improved codegen; fix mi_good_size with padding included; add MI_MAX_ALIGN_GUARANTEE

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Daan
2024-05-11 06:43:52 -07:00
parent c70c1df16a
commit 7128db7bba
7 changed files with 69 additions and 55 deletions
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75
src/alloc-aligned.c
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@@ -15,15 +15,15 @@ terms of the MIT license. A copy of the license can be found in the file
// Aligned Allocation
// ------------------------------------------------------
static inline bool mi_is_naturally_aligned( size_t size, size_t alignment ) {
// objects up to `MI_MEDIUM_OBJ_SIZE_MAX` are allocated aligned to their size (see `segment.c:_mi_segment_page_start`).
// note: the size may not be not an actual bin-size but it turns out the test below is still correct for our
// powers of two bin spacing (see test-api.c:test-aligned13).
static bool mi_malloc_is_naturally_aligned( size_t size, size_t alignment ) {
// objects up to `MI_MAX_ALIGN_GUARANTEE` are allocated aligned to their size (see `segment.c:_mi_segment_page_start`).
mi_assert_internal(_mi_is_power_of_two(alignment) && (alignment > 0));
return (size <= MI_MEDIUM_OBJ_SIZE_MAX && alignment <= size && ((size + MI_PADDING_SIZE) & (alignment-1)) == 0);
if (alignment > size) return false;
if (alignment <= MI_MAX_ALIGN_SIZE) return true;
const size_t bsize = mi_good_size(size);
return (bsize <= MI_MAX_ALIGN_GUARANTEE && (bsize & (alignment-1)) == 0);
}
// Fallback primitive aligned allocation -- split out for better codegen
static mi_decl_noinline void* mi_heap_malloc_zero_aligned_at_fallback(mi_heap_t* const heap, const size_t size, const size_t alignment, const size_t offset, const bool zero) mi_attr_noexcept
{
@@ -31,10 +31,18 @@ static mi_decl_noinline void* mi_heap_malloc_zero_aligned_at_fallback(mi_heap_t*
mi_assert_internal(alignment != 0 && _mi_is_power_of_two(alignment));
// use regular allocation if it is guaranteed to fit the alignment constraints.
if (offset == 0 && mi_is_naturally_aligned(size,alignment)) {
if (offset == 0 && mi_malloc_is_naturally_aligned(size,alignment)) {
void* p = _mi_heap_malloc_zero(heap, size, zero);
mi_assert_internal(p == NULL || ((uintptr_t)p % alignment) == 0);
return p;
const bool is_aligned_or_null = (((uintptr_t)p) & (alignment-1))==0;
if mi_likely(is_aligned_or_null) {
return p;
}
else {
// this should never happen if the `mi_malloc_is_naturally_aligned` check is correct..
mi_assert(false);
mi_free(p);
}
}
void* p;
@@ -106,33 +114,35 @@ static void* mi_heap_malloc_zero_aligned_at(mi_heap_t* const heap, const size_t
#endif
return NULL;
}
// try first if there happens to be a small block available with just the right alignment
if mi_likely(size <= MI_SMALL_SIZE_MAX && alignment <= size) {
const uintptr_t align_mask = alignment-1; // for any x, `(x & align_mask) == (x % alignment)`
const size_t padsize = size + MI_PADDING_SIZE;
mi_page_t* page = _mi_heap_get_free_small_page(heap, padsize);
if mi_likely(page->free != NULL) {
const bool is_aligned = (((uintptr_t)page->free + offset) & align_mask)==0;
if mi_likely(is_aligned)
{
#if MI_STAT>1
mi_heap_stat_increase(heap, malloc, size);
#endif
void* p = (zero ? _mi_page_malloc_zeroed(heap,page,padsize) : _mi_page_malloc(heap,page,padsize)); // call specific page malloc for better codegen
mi_assert_internal(p != NULL);
mi_assert_internal(((uintptr_t)p + offset) % alignment == 0);
mi_track_malloc(p,size,zero);
return p;
}
}
}
// fallback
if mi_unlikely(size > (MI_MAX_ALLOC_SIZE - MI_PADDING_SIZE)) { // we don't allocate more than MI_MAX_ALLOC_SIZE (see <https://sourceware.org/ml/libc-announce/2019/msg00001.html>)
#if MI_DEBUG > 0
_mi_error_message(EOVERFLOW, "aligned allocation request is too large (size %zu, alignment %zu)\n", size, alignment);
#endif
return NULL;
}
const uintptr_t align_mask = alignment-1; // for any x, `(x & align_mask) == (x % alignment)`
const size_t padsize = size + MI_PADDING_SIZE; // note: cannot overflow due to earlier size check
// try first if there happens to be a small block available with just the right alignment
if mi_likely(padsize <= MI_SMALL_SIZE_MAX && alignment <= padsize) {
mi_page_t* page = _mi_heap_get_free_small_page(heap, padsize);
const bool is_aligned = (((uintptr_t)page->free+offset) & align_mask)==0;
if mi_likely(page->free != NULL && is_aligned)
{
#if MI_STAT>1
mi_heap_stat_increase(heap, malloc, size);
#endif
void* p = _mi_page_malloc(heap, page, padsize, zero); // TODO: inline _mi_page_malloc
mi_assert_internal(p != NULL);
mi_assert_internal(((uintptr_t)p + offset) % alignment == 0);
mi_track_malloc(p,size,zero);
return p;
}
}
// fallback
return mi_heap_malloc_zero_aligned_at_fallback(heap, size, alignment, offset, zero);
}
@@ -146,14 +156,7 @@ mi_decl_nodiscard mi_decl_restrict void* mi_heap_malloc_aligned_at(mi_heap_t* he
}
mi_decl_nodiscard mi_decl_restrict void* mi_heap_malloc_aligned(mi_heap_t* heap, size_t size, size_t alignment) mi_attr_noexcept {
if (alignment == 0 || !_mi_is_power_of_two(alignment)) return NULL;
if (size <= MI_SMALL_SIZE_MAX && mi_is_naturally_aligned(size,alignment)) {
// fast path for common alignment and size
return mi_heap_malloc_small(heap, size);
}
else {
return mi_heap_malloc_aligned_at(heap, size, alignment, 0);
}
return mi_heap_malloc_aligned_at(heap, size, alignment, 0);
}
// ------------------------------------------------------