Date: Wed, 25 Sep 2019 01:39:58 +0000 (UTC) From: Justin Hibbits <jhibbits@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r352667 - head/sys/powerpc/include Message-ID: <201909250139.x8P1dw15098431@repo.freebsd.org>
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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 */
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