add zero parameter to primitive allocation to improve codegen for calloc etc

Author: daanx

include/mimalloc-internal.h

@@ -106,7 +106,7 @@ void       _mi_abandoned_await_readers(void);
 
 
 // "page.c"
-void*      _mi_malloc_generic(mi_heap_t* heap, size_t size)  mi_attr_noexcept mi_attr_malloc;
+void*      _mi_malloc_generic(mi_heap_t* heap, size_t size, bool zero)  mi_attr_noexcept mi_attr_malloc;
 
 void       _mi_page_retire(mi_page_t* page) mi_attr_noexcept;                  // free the page if there are no other pages with many free blocks
 void       _mi_page_unfull(mi_page_t* page);
@@ -138,12 +138,11 @@ mi_msecs_t  _mi_clock_end(mi_msecs_t start);
 mi_msecs_t  _mi_clock_start(void);
 
 // "alloc.c"
-void*       _mi_page_malloc(mi_heap_t* heap, mi_page_t* page, size_t size) mi_attr_noexcept;  // called from `_mi_malloc_generic`
+void*       _mi_page_malloc(mi_heap_t* heap, mi_page_t* page, size_t size, bool zero) mi_attr_noexcept;  // called from `_mi_malloc_generic`
 void*       _mi_heap_malloc_zero(mi_heap_t* heap, size_t size, bool zero) mi_attr_noexcept;
 void*       _mi_heap_realloc_zero(mi_heap_t* heap, void* p, size_t newsize, bool zero) mi_attr_noexcept;
 mi_block_t* _mi_page_ptr_unalign(const mi_segment_t* segment, const mi_page_t* page, const void* p);
 bool        _mi_free_delayed_block(mi_block_t* block);
-void        _mi_block_zero_init(const mi_page_t* page, void* p, size_t size); 
 
 #if MI_DEBUG>1
 bool        _mi_page_is_valid(mi_page_t* page);
@@ -267,8 +266,8 @@ static inline bool mi_mul_overflow(size_t count, size_t size, size_t* total) {
 static inline bool mi_mul_overflow(size_t count, size_t size, size_t* total) {
   #define MI_MUL_NO_OVERFLOW ((size_t)1 << (4*sizeof(size_t)))  // sqrt(SIZE_MAX)
   *total = count * size;
-  return ((size >= MI_MUL_NO_OVERFLOW || count >= MI_MUL_NO_OVERFLOW)
-    && size > 0 && (SIZE_MAX / size) < count);
+  // note: gcc/clang optimize this to directly check the overflow flag
+  return ((size >= MI_MUL_NO_OVERFLOW || count >= MI_MUL_NO_OVERFLOW) && size > 0 && (SIZE_MAX / size) < count);
 }
 #endif
 
@@ -279,7 +278,7 @@ static inline bool mi_count_size_overflow(size_t count, size_t size, size_t* tot
     return false;
   }
   else if (mi_unlikely(mi_mul_overflow(count, size, total))) {
-    #if !defined(NDEBUG)
+    #if MI_DEBUG > 0
     _mi_error_message(EOVERFLOW, "allocation request is too large (%zu * %zu bytes)\n", count, size);
     #endif
     *total = SIZE_MAX;
@@ -925,14 +924,25 @@ static inline void _mi_memcpy(void* dst, const void* src, size_t n) {
     __movsb((unsigned char*)dst, (const unsigned char*)src, n);
   }
   else {
-    memcpy(dst, src, n); // todo: use noinline?
+    memcpy(dst, src, n);
+  }
+}
+static inline void _mi_memzero(void* dst, size_t n) {
+  if (_mi_cpu_has_fsrm) {
+    __stosb((unsigned char*)dst, 0, n);
+  }
+  else {
+    memset(dst, 0, n);
   }
 }
 #else
 #include <string.h>
 static inline void _mi_memcpy(void* dst, const void* src, size_t n) {
   memcpy(dst, src, n);
 }
+static inline void _mi_memzero(void* dst, size_t n) {
+  memset(dst, 0, n);
+}
 #endif
 
 
@@ -950,12 +960,23 @@ static inline void _mi_memcpy_aligned(void* dst, const void* src, size_t n) {
   const void* asrc = __builtin_assume_aligned(src, MI_INTPTR_SIZE);
   _mi_memcpy(adst, asrc, n);
 }
+
+static inline void _mi_memzero_aligned(void* dst, size_t n) {
+  mi_assert_internal((uintptr_t)dst % MI_INTPTR_SIZE == 0);
+  void* adst = __builtin_assume_aligned(dst, MI_INTPTR_SIZE);
+  _mi_memzero(adst, n);
+}
 #else
 // Default fallback on `_mi_memcpy`
 static inline void _mi_memcpy_aligned(void* dst, const void* src, size_t n) {
   mi_assert_internal(((uintptr_t)dst % MI_INTPTR_SIZE == 0) && ((uintptr_t)src % MI_INTPTR_SIZE == 0));
   _mi_memcpy(dst, src, n);
 }
+
+static inline void _mi_memzero_aligned(void* dst, size_t n) {
+  mi_assert_internal((uintptr_t)dst % MI_INTPTR_SIZE == 0);
+  _mi_memzero(dst, n);
+}
 #endif
 
 

src/alloc-aligned.c

@@ -79,10 +79,9 @@ static void* mi_heap_malloc_zero_aligned_at(mi_heap_t* const heap, const size_t
       #if MI_STAT>1
       mi_heap_stat_increase(heap, malloc, size);
       #endif
-      void* p = _mi_page_malloc(heap, page, padsize); // TODO: inline _mi_page_malloc
+      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);
-      if (zero) { _mi_block_zero_init(page, p, size); }
       return p;
     }
   }

src/alloc.c

@@ -25,22 +25,29 @@ terms of the MIT license. A copy of the license can be found in the file
 
 // Fast allocation in a page: just pop from the free list.
 // Fall back to generic allocation only if the list is empty.
-extern inline void* _mi_page_malloc(mi_heap_t* heap, mi_page_t* page, size_t size) mi_attr_noexcept {
+extern inline void* _mi_page_malloc(mi_heap_t* heap, mi_page_t* page, size_t size, bool zero) mi_attr_noexcept {
   mi_assert_internal(page->xblock_size==0||mi_page_block_size(page) >= size);
   mi_block_t* const block = page->free;
   if (mi_unlikely(block == NULL)) {
-    return _mi_malloc_generic(heap, size); 
+    return _mi_malloc_generic(heap, size, zero); 
   }
   mi_assert_internal(block != NULL && _mi_ptr_page(block) == page);
   // pop from the free list
   page->used++;
   page->free = mi_block_next(page, block);
   mi_assert_internal(page->free == NULL || _mi_ptr_page(page->free) == page);
 
+  // zero the block?
+  if (mi_unlikely(zero)) {
+    mi_assert_internal(page->xblock_size != 0); // do not call with zero'ing for huge blocks
+    const size_t zsize = (mi_unlikely(page->is_zero) ? sizeof(block->next) : page->xblock_size);
+    _mi_memzero_aligned(block, zsize);
+  }
+
 #if (MI_DEBUG>0)
-  if (!page->is_zero) { memset(block, MI_DEBUG_UNINIT, size); }
+  if (!page->is_zero && !zero) { memset(block, MI_DEBUG_UNINIT, size); }
 #elif (MI_SECURE!=0)
-  block->next = 0;  // don't leak internal data
+  if (!zero) { block->next = 0; } // don't leak internal data
 #endif
 
 #if (MI_STAT>0)
@@ -69,41 +76,45 @@ extern inline void* _mi_page_malloc(mi_heap_t* heap, mi_page_t* page, size_t siz
   return block;
 }
 
-// allocate a small block
-mi_decl_nodiscard extern inline mi_decl_restrict void* mi_heap_malloc_small(mi_heap_t* heap, size_t size) mi_attr_noexcept {
-  mi_assert(heap!=NULL);
+static inline mi_decl_restrict void* mi_heap_malloc_small_zero(mi_heap_t* heap, size_t size, bool zero) mi_attr_noexcept {
+  mi_assert(heap != NULL);
   mi_assert(heap->thread_id == 0 || heap->thread_id == _mi_thread_id()); // heaps are thread local
   mi_assert(size <= MI_SMALL_SIZE_MAX);
-  #if (MI_PADDING)
+#if (MI_PADDING)
   if (size == 0) {
     size = sizeof(void*);
   }
-  #endif
-  mi_page_t* page = _mi_heap_get_free_small_page(heap,size + MI_PADDING_SIZE);
-  void* p = _mi_page_malloc(heap, page, size + MI_PADDING_SIZE);
-  mi_assert_internal(p==NULL || mi_usable_size(p) >= size);
-  #if MI_STAT>1
+#endif
+  mi_page_t* page = _mi_heap_get_free_small_page(heap, size + MI_PADDING_SIZE);
+  void* p = _mi_page_malloc(heap, page, size + MI_PADDING_SIZE, zero);
+  mi_assert_internal(p == NULL || mi_usable_size(p) >= size);
+#if MI_STAT>1
   if (p != NULL) {
     if (!mi_heap_is_initialized(heap)) { heap = mi_get_default_heap(); }
     mi_heap_stat_increase(heap, malloc, mi_usable_size(p));
   }
-  #endif
+#endif
   return p;
 }
 
+// allocate a small block
+mi_decl_nodiscard extern inline mi_decl_restrict void* mi_heap_malloc_small(mi_heap_t* heap, size_t size) mi_attr_noexcept {
+  return mi_heap_malloc_small_zero(heap, size, false);
+}
+
 mi_decl_nodiscard extern inline mi_decl_restrict void* mi_malloc_small(size_t size) mi_attr_noexcept {
   return mi_heap_malloc_small(mi_get_default_heap(), size);
 }
 
 // The main allocation function
-mi_decl_nodiscard extern inline mi_decl_restrict void* mi_heap_malloc(mi_heap_t* heap, size_t size) mi_attr_noexcept {
+mi_decl_nodiscard extern inline void* _mi_heap_malloc_zero(mi_heap_t* heap, size_t size, bool zero) mi_attr_noexcept {
   if (mi_likely(size <= MI_SMALL_SIZE_MAX)) {
-    return mi_heap_malloc_small(heap, size);
+    return mi_heap_malloc_small_zero(heap, size, zero);
   }
   else {
     mi_assert(heap!=NULL);
-    mi_assert(heap->thread_id == 0 || heap->thread_id == _mi_thread_id()); // heaps are thread local
-    void* const p = _mi_malloc_generic(heap, size + MI_PADDING_SIZE);      // note: size can overflow but it is detected in malloc_generic
+    mi_assert(heap->thread_id == 0 || heap->thread_id == _mi_thread_id());   // heaps are thread local
+    void* const p = _mi_malloc_generic(heap, size + MI_PADDING_SIZE, zero);  // note: size can overflow but it is detected in malloc_generic
     mi_assert_internal(p == NULL || mi_usable_size(p) >= size);
     #if MI_STAT>1
     if (p != NULL) {
@@ -115,44 +126,17 @@ mi_decl_nodiscard extern inline mi_decl_restrict void* mi_heap_malloc(mi_heap_t*
   }
 }
 
-mi_decl_nodiscard extern inline mi_decl_restrict void* mi_malloc(size_t size) mi_attr_noexcept {
-  return mi_heap_malloc(mi_get_default_heap(), size);
+mi_decl_nodiscard extern inline mi_decl_restrict void* mi_heap_malloc(mi_heap_t* heap, size_t size) mi_attr_noexcept {
+  return _mi_heap_malloc_zero(heap, size, false);
 }
 
-
-void _mi_block_zero_init(const mi_page_t* page, void* p, size_t size) {
-  // note: we need to initialize the whole usable block size to zero, not just the requested size,
-  // or the recalloc/rezalloc functions cannot safely expand in place (see issue #63)
-  MI_UNUSED(size);
-  mi_assert_internal(p != NULL);
-  mi_assert_internal(mi_usable_size(p) >= size); // size can be zero
-  mi_assert_internal(_mi_ptr_page(p)==page);
-  if (page->is_zero && size > sizeof(mi_block_t)) {
-    // already zero initialized memory
-    ((mi_block_t*)p)->next = 0;  // clear the free list pointer
-    mi_assert_expensive(mi_mem_is_zero(p, mi_usable_size(p)));
-  }
-  else {
-    // otherwise memset
-    memset(p, 0, mi_usable_size(p));
-  }
+mi_decl_nodiscard extern inline mi_decl_restrict void* mi_malloc(size_t size) mi_attr_noexcept {
+  return mi_heap_malloc(mi_get_default_heap(), size);
 }
 
 // zero initialized small block
 mi_decl_nodiscard mi_decl_restrict void* mi_zalloc_small(size_t size) mi_attr_noexcept {
-  void* p = mi_malloc_small(size);
-  if (p != NULL) {
-    _mi_block_zero_init(_mi_ptr_page(p), p, size);  // todo: can we avoid getting the page again?
-  }
-  return p;
-}
-
-void* _mi_heap_malloc_zero(mi_heap_t* heap, size_t size, bool zero) mi_attr_noexcept {
-  void* p = mi_heap_malloc(heap,size);
-  if (zero && p != NULL) {
-    _mi_block_zero_init(_mi_ptr_page(p),p,size);  // todo: can we avoid getting the page again?
-  }
-  return p;
+  return mi_heap_malloc_small_zero(mi_get_default_heap(), size, true);
 }
 
 mi_decl_nodiscard extern inline mi_decl_restrict void* mi_heap_zalloc(mi_heap_t* heap, size_t size) mi_attr_noexcept {
@@ -564,6 +548,7 @@ mi_decl_nodiscard size_t mi_usable_size(const void* p) mi_attr_noexcept {
 #ifdef __cplusplus
 void* _mi_externs[] = {
   (void*)&_mi_page_malloc,
+  (void*)&_mi_heap_malloc_zero,
   (void*)&mi_malloc,
   (void*)&mi_malloc_small,
   (void*)&mi_zalloc_small,

src/page.c

@@ -815,7 +815,7 @@ static mi_page_t* mi_find_page(mi_heap_t* heap, size_t size) mi_attr_noexcept {
 
 // Generic allocation routine if the fast path (`alloc.c:mi_page_malloc`) does not succeed.
 // Note: in debug mode the size includes MI_PADDING_SIZE and might have overflowed.
-void* _mi_malloc_generic(mi_heap_t* heap, size_t size) mi_attr_noexcept
+void* _mi_malloc_generic(mi_heap_t* heap, size_t size, bool zero) mi_attr_noexcept
 {
   mi_assert_internal(heap != NULL);
 
@@ -849,6 +849,15 @@ void* _mi_malloc_generic(mi_heap_t* heap, size_t size) mi_attr_noexcept
   mi_assert_internal(mi_page_immediate_available(page));
   mi_assert_internal(mi_page_block_size(page) >= size);
 
-  // and try again, this time succeeding! (i.e. this should never recurse)
-  return _mi_page_malloc(heap, page, size);
+  // and try again, this time succeeding! (i.e. this should never recurse through _mi_page_malloc)
+  if (mi_unlikely(zero && page->xblock_size == 0)) {
+    // note: we cannot call _mi_page_malloc with zeroing for huge blocks; we zero it afterwards in that case.
+    void* p = _mi_page_malloc(heap, page, size, false);
+    mi_assert_internal(p != NULL);
+    _mi_memzero_aligned(p, mi_page_usable_block_size(page));
+    return p;
+  }
+  else {
+    return _mi_page_malloc(heap, page, size, zero);
+  }
 }

test/test-stress.c

@@ -256,7 +256,7 @@ int main(int argc, char** argv) {
   mi_collect(true);
   #endif
   mi_stats_print(NULL);
-#endif
+#endif  
   //bench_end_program();
   return 0;
 }