d/freebsd-dev
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

libc/string/memset.c: Use unsigned long for stores

Browse Source 
While most 64-bit architectures have an assembly implementation of this
file, RISC-V does not. As we now store 8 bytes instead of 4 it should speed
up RISC-V.

Reviewed By:	kib
MFC after:	1 week
Differential Revision: https://reviews.freebsd.org/D29536
This commit is contained in:
Alex Richardson 2021-04-20 00:19:20 +01:00
parent 0b4ad01d91
commit ab147542b7
1 changed files with 11 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
lib/libc/string/memset.c
View File

@ -42,7 +42,7 @@ __FBSDID("$FreeBSD$");
#include <limits.h>
#define wsize sizeof(u_int)
#define wsize sizeof(u_long)
#define wmask (wsize - 1)
#ifdef BZERO
@ -67,7 +67,7 @@ memset(void *dst0, int c0, size_t length)
{
size_t t;
#ifndef BZERO
u_int c;
u_long c;
#endif
u_char *dst;
@ -84,6 +84,9 @@ memset(void *dst0, int c0, size_t length)
*
* but we use a minimum of 3 here since the overhead of the code
* to do word writes is substantial.
*
* TODO: This threshold might not be sensible for 64-bit u_long.
* We should benchmark and revisit this decision.
*/
if (length < 3 * wsize) {
while (length != 0) {
@ -95,12 +98,12 @@ memset(void *dst0, int c0, size_t length)
#ifndef BZERO
if ((c = (u_char)c0) != 0) { /* Fill the word. */
c = (c << 8) | c; /* u_int is 16 bits. */
#if UINT_MAX > 0xffff
c = (c << 16) | c; /* u_int is 32 bits. */
c = (c << 8) | c; /* u_long is 16 bits. */
#if ULONG_MAX > 0xffff
c = (c << 16) | c; /* u_long is 32 bits. */
#endif
#if UINT_MAX > 0xffffffff
c = (c << 32) | c; /* u_int is 64 bits. */
#if ULONG_MAX > 0xffffffff
c = (c << 32) | c; /* u_long is 64 bits. */
#endif
}
#endif
@ -116,7 +119,7 @@ memset(void *dst0, int c0, size_t length)
/* Fill words. Length was >= 2*words so we know t >= 1 here. */
t = length / wsize;
do {
*(u_int *)dst = WIDEVAL;
*(u_long *)(void *)dst = WIDEVAL;
dst += wsize;
} while (--t != 0);