Hello, if you build postgresql (tested all releases from 8.4 up to trunk) for ARM with the -mthumb instruction set (much better performance), it fails with
gcc -g -O2 -g -Wall -O2 -fPIC -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -fno-strict-aliasing -fwrapv -g -I../../../../src/include -D_GNU_SOURCE -I/usr/include/libxml2 -I/usr/include/tcl8.5 -c -o xlog.o xlog.c /tmp/cc8Wkglp.s: Assembler messages: /tmp/cc8Wkglp.s:1456: Error: selected processor does not support `swpb r3,r3,[r0]' /tmp/cc8Wkglp.s:1587: Error: selected processor does not support `swpb r2,r2,[r0]' A fair while ago, Alexander Sack from Linaro applied a patch to our packages to drop the Assembler bits and instead use gcc's atomic builtins [1], which provide a proper implementation for thumb, too. The original patch spectacularly failed on our slightly newer Panda boards (our old builders were Freescale Babbage boards), but I got that to work yesterday. Now it's working on Babbage, Panda, both with and without hard float (armhf) enabled. I'm not sure how appropriate it is for upstream to have GCC-isms in the code, but even if it can't land upstream, perhaps it is useful for other porters/packagers. Thanks, Martin [1] http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Atomic-Builtins.html -- Martin Pitt | http://www.piware.de Ubuntu Developer (www.ubuntu.com) | Debian Developer (www.debian.org)
Description: use gcc intrinsics rather than assembler to implement tas Author: Alexander Sack <a...@ubuntu.com> Author: Martin Pitt <martin.p...@ubuntu.com> Bug-Ubuntu: https://launchpad.net/bugs/497331 Bug-Ubuntu: https://launchpad.net/bugs/904828 Index: postgresql-9.1-9.1.2/src/include/storage/s_lock.h =================================================================== --- postgresql-9.1-9.1.2.orig/src/include/storage/s_lock.h 2011-12-01 22:47:20.000000000 +0100 +++ postgresql-9.1-9.1.2/src/include/storage/s_lock.h 2011-12-15 21:17:32.965569760 +0100 @@ -255,21 +255,15 @@ #if defined(__arm__) || defined(__arm) #define HAS_TEST_AND_SET -typedef unsigned char slock_t; +typedef unsigned int slock_t; #define TAS(lock) tas(lock) +#define S_UNLOCK(lock) __sync_lock_release(lock) static __inline__ int tas(volatile slock_t *lock) { - register slock_t _res = 1; - - __asm__ __volatile__( - " swpb %0, %0, [%2] \n" -: "+r"(_res), "+m"(*lock) -: "r"(lock) -: "memory"); - return (int) _res; + return __sync_lock_test_and_set (lock, 1); } #endif /* __arm__ */
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