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From: "spam_from_gcc_bugzilla at chezphil dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/33413] New: Please provide __sync_lock_test_and_set builtin for ARM using swap insn Date: Wed, 12 Sep 2007 21:20:00 -0000 [thread overview] Message-ID: <bug-33413-10680@http.gcc.gnu.org/bugzilla/> (raw) For most ARM architecture variants, the only atomic operation is swap. The semantics of the SWP instruction are what gcc calls __sync_lock_test_and_set (a rather odd name since the set is unconditional). Would it be possible to add a __sync_lock_test_and_set builtin for ARM that generates a SWP instruction? It would be useful to also provide a predefined macro that can be tested to determine whether the builtin is implemented. Typically, code that wants to do architecture-independent atomic operations will want to do something like: #if have atomic add etc ... atomic operations using those builtins #elsif have atomic swap ... atomic operations using swap #else ... atomic operations using pthreads, or #error #end I understand that __GCC_HAVE_SYNC_COMPARE_AND_SWAP_n can be tested for the first #if above (on sufficiently new compilers), on the basis that an architecture that provides compare-and-swap can use it to synthesize all of the other builtin atomic operations. However, swap is not sufficient to implement the other builtins without some additional constraints, e.g. a sentinel value, and assumptions about the threading model. For discussions please see: http://thread.gmane.org/gmane.comp.gcc.help/21113 Thanks, Phil. -- Summary: Please provide __sync_lock_test_and_set builtin for ARM using swap insn Product: gcc Version: unknown Status: UNCONFIRMED Severity: enhancement Priority: P3 Component: target AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: spam_from_gcc_bugzilla at chezphil dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33413
next reply other threads:[~2007-09-12 21:20 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2007-09-12 21:20 spam_from_gcc_bugzilla at chezphil dot org [this message] 2010-04-05 13:54 ` [Bug target/33413] " rearnsha at gcc dot gnu dot org 2010-04-05 14:10 ` spam_from_gcc_bugzilla at chezphil dot org
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