Author: jhibbits
Date: Wed Sep 25 01:39:58 2019
New Revision: 352667
URL: https://svnweb.freebsd.org/changeset/base/352667
Log:
powerpc/atomic: Follow recommendations on atomic primitive comparisons
Both IBM and Freescale programming examples presume the cmpset operands will
favor equal, and pessimize the non-equal case instead. Do the same for
atomic_cmpset_* and atomic_fcmpset_*. This slightly pessimizes the failure
case, in favor of the success case.
MFC after: 3 weeks
Modified:
head/sys/powerpc/include/atomic.h
Modified: head/sys/powerpc/include/atomic.h
==============================================================================
--- head/sys/powerpc/include/atomic.h Wed Sep 25 01:23:08 2019
(r352666)
+++ head/sys/powerpc/include/atomic.h Wed Sep 25 01:39:58 2019
(r352667)
@@ -568,7 +568,7 @@ atomic_cmpset_int(volatile u_int* p, u_int cmpval, u_i
__asm __volatile (
"1:\tlwarx %0, 0, %2\n\t" /* load old value */
"cmplw %3, %0\n\t" /* compare */
- "bne 2f\n\t" /* exit if not equal */
+ "bne- 2f\n\t" /* exit if not equal */
"stwcx. %4, 0, %2\n\t" /* attempt to store */
"bne- 1b\n\t" /* spin if failed */
"li %0, 1\n\t" /* success - retval = 1 */
@@ -592,12 +592,12 @@ atomic_cmpset_long(volatile u_long* p, u_long cmpval,
#ifdef __powerpc64__
"1:\tldarx %0, 0, %2\n\t" /* load old value */
"cmpld %3, %0\n\t" /* compare */
- "bne 2f\n\t" /* exit if not equal */
+ "bne- 2f\n\t" /* exit if not equal */
"stdcx. %4, 0, %2\n\t" /* attempt to store */
#else
"1:\tlwarx %0, 0, %2\n\t" /* load old value */
"cmplw %3, %0\n\t" /* compare */
- "bne 2f\n\t" /* exit if not equal */
+ "bne- 2f\n\t" /* exit if not equal */
"stwcx. %4, 0, %2\n\t" /* attempt to store */
#endif
"bne- 1b\n\t" /* spin if failed */
@@ -684,7 +684,7 @@ atomic_fcmpset_int(volatile u_int *p, u_int *cmpval, u
__asm __volatile (
"lwarx %0, 0, %3\n\t" /* load old value */
"cmplw %4, %0\n\t" /* compare */
- "bne 1f\n\t" /* exit if not equal */
+ "bne- 1f\n\t" /* exit if not equal */
"stwcx. %5, 0, %3\n\t" /* attempt to store */
"bne- 1f\n\t" /* exit if failed */
"li %0, 1\n\t" /* success - retval = 1 */
@@ -709,12 +709,12 @@ atomic_fcmpset_long(volatile u_long *p, u_long *cmpval
#ifdef __powerpc64__
"ldarx %0, 0, %3\n\t" /* load old value */
"cmpld %4, %0\n\t" /* compare */
- "bne 1f\n\t" /* exit if not equal */
+ "bne- 1f\n\t" /* exit if not equal */
"stdcx. %5, 0, %3\n\t" /* attempt to store */
#else
"lwarx %0, 0, %3\n\t" /* load old value */
"cmplw %4, %0\n\t" /* compare */
- "bne 1f\n\t" /* exit if not equal */
+ "bne- 1f\n\t" /* exit if not equal */
"stwcx. %5, 0, %3\n\t" /* attempt to store */
#endif
"bne- 1f\n\t" /* exit if failed */
_______________________________________________
svn-src-all@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/svn-src-all
To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
