Update mimalloc to v2.2.7 (git-for-windows#6048)

After releasing v2.2.6, they followed up really quickly with a v2.2.7,
which indicates some urgency in taking this update. The diff of this PR
is pretty informative, too.

This closes git-for-windows#6046

Author: dscho

compat/mimalloc/alloc.c

@@ -59,7 +59,6 @@ extern inline void* _mi_page_malloc_zero(mi_heap_t* heap, mi_page_t* page, size_
   // zero the block? note: we need to zero the full block size (issue #63)
   if mi_unlikely(zero) {
     mi_assert_internal(page->block_size != 0); // do not call with zero'ing for huge blocks (see _mi_malloc_generic)
-    mi_assert_internal(!mi_page_is_huge(page));
     #if MI_PADDING
     mi_assert_internal(page->block_size >= MI_PADDING_SIZE);
     #endif
@@ -528,7 +527,7 @@ static std_new_handler_t mi_get_new_handler(void) {
 }
 #else
 // note: on windows we could dynamically link to `?get_new_handler@std@@YAP6AXXZXZ`.
-static std_new_handler_t mi_get_new_handler() {
+static std_new_handler_t mi_get_new_handler(void) {
   return NULL;
 }
 #endif

compat/mimalloc/mimalloc.h

@@ -8,7 +8,7 @@ terms of the MIT license. A copy of the license can be found in the file
 #ifndef MIMALLOC_H
 #define MIMALLOC_H
 
-#define MI_MALLOC_VERSION 226  // major + 2 digits minor
+#define MI_MALLOC_VERSION 227  // major + 2 digits minor
 
 // ------------------------------------------------------
 // Compiler specific attributes

compat/mimalloc/mimalloc/internal.h

@@ -1093,15 +1093,15 @@ static inline size_t mi_popcount(size_t x) {
 extern mi_decl_hidden bool _mi_cpu_has_fsrm;
 extern mi_decl_hidden bool _mi_cpu_has_erms;
 static inline void _mi_memcpy(void* dst, const void* src, size_t n) {
-  if ((_mi_cpu_has_fsrm && n <= 128) || (_mi_cpu_has_erms && n > 128)) {
+  if (_mi_cpu_has_fsrm && n <= 127) { // || (_mi_cpu_has_erms && n > 128)) {
     __movsb((unsigned char*)dst, (const unsigned char*)src, n);
   }
   else {
     memcpy(dst, src, n);
   }
 }
 static inline void _mi_memzero(void* dst, size_t n) {
-  if ((_mi_cpu_has_fsrm && n <= 128) || (_mi_cpu_has_erms && n > 128)) {
+  if (_mi_cpu_has_fsrm && n <= 127) { // || (_mi_cpu_has_erms && n > 128)) {
     __stosb((unsigned char*)dst, 0, n);
   }
   else {

compat/mimalloc/mimalloc/types.h

@@ -480,6 +480,7 @@ typedef struct mi_segment_s {
   struct mi_segment_s* next;            // the list of freed segments in the cache (must be first field, see `segment.c:mi_segment_init`)
   bool              was_reclaimed;      // true if it was reclaimed (used to limit on-free reclamation)
   bool              dont_free;          // can be temporarily true to ensure the segment is not freed
+  bool              free_is_zero;       // if free spans are zero
 
   size_t            abandoned;          // abandoned pages (i.e. the original owning thread stopped) (`abandoned <= used`)
   size_t            abandoned_visits;   // count how often this segment is visited during abondoned reclamation (to force reclaim if it takes too long)

compat/mimalloc/page.c

@@ -1031,17 +1031,9 @@ void* _mi_malloc_generic(mi_heap_t* heap, size_t size, bool zero, size_t huge_al
   mi_assert_internal(mi_page_block_size(page) >= size);
 
   // and try again, this time succeeding! (i.e. this should never recurse through _mi_page_malloc)
-  void* p;
-  if mi_unlikely(zero && mi_page_is_huge(page)) {
-    // note: we cannot call _mi_page_malloc with zeroing for huge blocks; we zero it afterwards in that case.
-    p = _mi_page_malloc_zero(heap, page, size, false, usable);
-    mi_assert_internal(p != NULL);
-    _mi_memzero_aligned(p, mi_page_usable_block_size(page));
-  }
-  else {
-    p = _mi_page_malloc_zero(heap, page, size, zero, usable);
-    mi_assert_internal(p != NULL);
-  }
+  void* const p = _mi_page_malloc_zero(heap, page, size, zero, usable);
+  mi_assert_internal(p != NULL);
+
   // move singleton pages to the full queue
   if (page->reserved == page->used) {
     mi_page_to_full(page, mi_page_queue_of(page));

compat/mimalloc/segment.c

@@ -773,6 +773,7 @@ static mi_page_t* mi_segment_span_allocate(mi_segment_t* segment, size_t slice_i
 
   // and initialize the page
   page->is_committed = true;
+  page->is_zero_init = segment->free_is_zero;
   page->is_huge = (segment->kind == MI_SEGMENT_HUGE);
   segment->used++;
   return page;
@@ -882,6 +883,7 @@ static mi_segment_t* mi_segment_os_alloc( size_t required, size_t page_alignment
   segment->subproc = tld->subproc;
   segment->commit_mask = commit_mask;
   segment->purge_expire = 0;
+  segment->free_is_zero = memid.initially_zero;
   mi_commit_mask_create_empty(&segment->purge_mask);
 
   mi_segments_track_size((long)(segment_size), tld);
@@ -1024,7 +1026,7 @@ static mi_slice_t* mi_segment_page_clear(mi_page_t* page, mi_segments_tld_t* tld
   _mi_stat_decrease(&tld->stats->page_committed, inuse);
   _mi_stat_decrease(&tld->stats->pages, 1);
   _mi_stat_decrease(&tld->stats->page_bins[_mi_page_stats_bin(page)], 1);
-
+  
   // reset the page memory to reduce memory pressure?
   if (segment->allow_decommit && mi_option_is_enabled(mi_option_deprecated_page_reset)) {
     size_t psize;
@@ -1043,6 +1045,8 @@ static mi_slice_t* mi_segment_page_clear(mi_page_t* page, mi_segments_tld_t* tld
   // and free it
   mi_slice_t* slice = mi_segment_span_free_coalesce(mi_page_to_slice(page), tld);
   segment->used--;
+  segment->free_is_zero = false;
+
   // cannot assert segment valid as it is called during reclaim
   // mi_assert_expensive(mi_segment_is_valid(segment, tld));
   return slice;