Date: Fri, 19 Jun 2009 04:43:49 +0000 (UTC) From: Oleksandr Tymoshenko <gonzo@FreeBSD.org> To: src-committers@freebsd.org, svn-src-projects@freebsd.org Subject: svn commit: r194469 - projects/mips/sys/mips/include Message-ID: <200906190443.n5J4hnJo031286@svn.freebsd.org>
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Author: gonzo Date: Fri Jun 19 04:43:49 2009 New Revision: 194469 URL: http://svn.freebsd.org/changeset/base/194469 Log: - Mark temp variable as "earlyclobber" in assembler inline in atomic_fetchadd_32. Without it gcc would use it as input register for v and sometimes generate following code for function call like atomic_fetchadd_32(&(fp)->f_count, -1): 801238b4: 2402ffff li v0,-1 801238b8: c2230018 ll v1,24(s1) 801238bc: 00431021 addu v0,v0,v1 801238c0: e2220018 sc v0,24(s1) 801238c4: 1040fffc beqz v0,801238b8 <dupfdopen+0x2e8> 801238c8: 00000000 nop Which is definitly wrong because if sc fails v0 is set to 0 and previous value of -1 is overriden hence whole operation turns to bogus Modified: projects/mips/sys/mips/include/atomic.h Modified: projects/mips/sys/mips/include/atomic.h ============================================================================== --- projects/mips/sys/mips/include/atomic.h Fri Jun 19 04:25:44 2009 (r194468) +++ projects/mips/sys/mips/include/atomic.h Fri Jun 19 04:43:49 2009 (r194469) @@ -294,7 +294,7 @@ atomic_fetchadd_32(__volatile uint32_t * "addu %2, %3, %0\n\t" /* calculate new value */ "sc %2, %1\n\t" /* attempt to store */ "beqz %2, 1b\n\t" /* spin if failed */ - : "=&r" (value), "=m" (*p), "=r" (temp) + : "=&r" (value), "=m" (*p), "=&r" (temp) : "r" (v), "m" (*p)); return (value); }
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