From 15d1d073d1595202b2be48a3788af5b315602ece Mon Sep 17 00:00:00 2001 From: Szabolcs Nagy Date: Tue, 16 Feb 2021 17:02:44 +0000 Subject: 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 --- malloc/malloc.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/malloc/malloc.c b/malloc/malloc.c index 01cf6e9325..0b2aff3768 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 } /* -- cgit 1.4.1