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Cache the default malloc zone #29978

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Merged
merged 1 commit into from
Feb 21, 2020
Merged

Cache the default malloc zone #29978

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19 changes: 19 additions & 0 deletions stdlib/public/runtime/Heap.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,10 @@
#include "../SwiftShims/RuntimeShims.h"
#include <algorithm>
#include <stdlib.h>
#if defined(__APPLE__)
#include "swift/Basic/Lazy.h"
#include <malloc/malloc.h>
#endif

using namespace swift;

Expand Down Expand Up @@ -57,6 +61,13 @@ using namespace swift;
static_assert(_swift_MinAllocationAlignment > MALLOC_ALIGN_MASK,
"Swift's default alignment must exceed platform malloc mask.");

#if defined(__APPLE__)
static inline malloc_zone_t *DEFAULT_ZONE() {
static malloc_zone_t *z = SWIFT_LAZY_CONSTANT(malloc_default_zone());
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The static and SWIFT_LAZY_CONSTANT create two levels of lazy initialization; we only need one of them IIUC.

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Good catch! This shouldn't have the static.

return z;
}
#endif

// When alignMask == ~(size_t(0)), allocation uses the "default"
// _swift_MinAllocationAlignment. This is different than calling swift_slowAlloc
// with `alignMask == _swift_MinAllocationAlignment - 1` because it forces
Expand All @@ -77,7 +88,11 @@ void *swift::swift_slowAlloc(size_t size, size_t alignMask) {
void *p;
// This check also forces "default" alignment to use AlignedAlloc.
if (alignMask <= MALLOC_ALIGN_MASK) {
#if defined(__APPLE__)
p = malloc_zone_malloc(DEFAULT_ZONE(), size);
#else
p = malloc(size);
#endif
} else {
size_t alignment = (alignMask == ~(size_t(0)))
? _swift_MinAllocationAlignment
Expand Down Expand Up @@ -106,7 +121,11 @@ void *swift::swift_slowAlloc(size_t size, size_t alignMask) {
// consistent with allocation with the same alignment.
void swift::swift_slowDealloc(void *ptr, size_t bytes, size_t alignMask) {
if (alignMask <= MALLOC_ALIGN_MASK) {
#if defined(__APPLE__)
malloc_zone_free(DEFAULT_ZONE(), ptr);
#else
free(ptr);
#endif
} else {
AlignedFree(ptr);
}
Expand Down