about summary refs log tree commit diff
path: root/malloc
diff options
context:
space:
mode:
authorSzabolcs Nagy <szabolcs.nagy@arm.com>2021-02-16 17:02:44 +0000
committerSzabolcs Nagy <szabolcs.nagy@arm.com>2021-03-26 11:03:06 +0000
commit9d61722b599a02a6d3caed1d75417a7f5e661693 (patch)
tree565e05bea7b1b44d556a197525d9ac5a3e43dc63 /malloc
parentc076a0bc698c537f72c33bad2925f4e3da59d23c (diff)
downloadglibc-9d61722b599a02a6d3caed1d75417a7f5e661693.tar.gz
glibc-9d61722b599a02a6d3caed1d75417a7f5e661693.tar.xz
glibc-9d61722b599a02a6d3caed1d75417a7f5e661693.zip
malloc: Change calloc when tagging is disabled
When glibc is built with memory tagging support (USE_MTAG) but it is not
enabled at runtime (mtag_enabled) then unconditional memset was used
even though that can be often avoided.

This is for performance when tagging is supported but not enabled.
The extra check should have no overhead: tag_new_zero_region already
had a runtime check which the compiler can now optimize away.

Reviewed-by: DJ Delorie <dj@redhat.com>
Diffstat (limited to 'malloc')
-rw-r--r--malloc/malloc.c10
1 files changed, 4 insertions, 6 deletions
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 9cfea1f878..69ea04f4a7 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -3591,11 +3591,9 @@ __libc_calloc (size_t n, size_t elem_size)
   mchunkptr oldtop;
   INTERNAL_SIZE_T sz, oldtopsize;
   void *mem;
-#ifndef USE_MTAG
   unsigned long clearsize;
   unsigned long nclears;
   INTERNAL_SIZE_T *d;
-#endif
   ptrdiff_t bytes;
 
   if (__glibc_unlikely (__builtin_mul_overflow (n, elem_size, &bytes)))
@@ -3674,12 +3672,13 @@ __libc_calloc (size_t n, size_t elem_size)
     return 0;
 
   mchunkptr p = mem2chunk (mem);
+
   /* If we are using memory tagging, then we need to set the tags
      regardless of MORECORE_CLEARS, so we zero the whole block while
      doing so.  */
-#ifdef USE_MTAG
-  return tag_new_zero_region (mem, CHUNK_AVAILABLE_SIZE (p) - CHUNK_HDR_SZ);
-#else
+  if (__glibc_unlikely (mtag_enabled))
+    return tag_new_zero_region (mem, CHUNK_AVAILABLE_SIZE (p) - CHUNK_HDR_SZ);
+
   INTERNAL_SIZE_T csz = chunksize (p);
 
   /* Two optional cases in which clearing not necessary */
@@ -3733,7 +3732,6 @@ __libc_calloc (size_t n, size_t elem_size)
     }
 
   return mem;
-#endif
 }
 
 /*