[Bug middle-end/66867] Suboptimal code generation for atomic_compare_exchange
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66867 --- Comment #11 from dhowells at redhat dot com --- I applied the patch to the Fedora cross-gcc-6.1.1 rpm with one minor fixup. Using the example code I added in bug 70825 I now see: : 0: ba 2a 00 00 00 mov$0x2a,%edx 5: b8 17 00 00 00 mov$0x17,%eax a: f0 0f b1 17 lock cmpxchg %edx,(%rdi) e: c3 retq there's now no extraneous store before the locked instruction. And: 000f : f: ba 2a 00 00 00 mov$0x2a,%edx 14: b8 17 00 00 00 mov$0x17,%eax 19: f0 0f b1 17 lock cmpxchg %edx,(%rdi) 1d: c3 retq it now just passes the return value of cmpxchg back directly without potentially putting on and off the stack and maybe jumping round that bit. And: 0043 : 43: ba 2a 00 00 00 mov$0x2a,%edx 48: b8 17 00 00 00 mov$0x17,%eax 4d: f0 0f b1 17 lock cmpxchg %edx,(%rdi) 51: c3 retq where it makes no difference changing how the the return-statements are contructed in C. I've also booted a kernel built with the patched compiler.
[Bug middle-end/66867] Suboptimal code generation for atomic_compare_exchange
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66867 Jakub Jelinek changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution|--- |FIXED --- Comment #10 from Jakub Jelinek --- Hopefully fixed for 7+.
[Bug middle-end/66867] Suboptimal code generation for atomic_compare_exchange
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66867 --- Comment #9 from Jakub Jelinek --- Author: jakub Date: Tue Jun 28 08:27:18 2016 New Revision: 237814 URL: https://gcc.gnu.org/viewcvs?rev=237814&root=gcc&view=rev Log: PR middle-end/66867 * builtins.c (expand_ifn_atomic_compare_exchange_into_call, expand_ifn_atomic_compare_exchange): New functions. * internal-fn.c (expand_ATOMIC_COMPARE_EXCHANGE): New function. * tree.h (build_call_expr_internal_loc): Rename to ... (build_call_expr_internal_loc_array): ... this. Fix up type of last argument. * internal-fn.def (ATOMIC_COMPARE_EXCHANGE): New internal fn. * predict.c (expr_expected_value_1): Handle IMAGPART_EXPR of ATOMIC_COMPARE_EXCHANGE result. * builtins.h (expand_ifn_atomic_compare_exchange): New prototype. * gimple-fold.h (optimize_atomic_compare_exchange_p, fold_builtin_atomic_compare_exchange): New prototypes. * gimple-fold.c (optimize_atomic_compare_exchange_p, fold_builtin_atomic_compare_exchange): New functions.. * tree-ssa.c (execute_update_addresses_taken): If optimize_atomic_compare_exchange_p, ignore &var in 2nd argument of call when finding addressable vars, and if such var becomes non-addressable, call fold_builtin_atomic_compare_exchange. Modified: trunk/gcc/ChangeLog trunk/gcc/builtins.c trunk/gcc/builtins.h trunk/gcc/gimple-fold.c trunk/gcc/gimple-fold.h trunk/gcc/internal-fn.c trunk/gcc/internal-fn.def trunk/gcc/predict.c trunk/gcc/tree-ssa.c trunk/gcc/tree.h
[Bug middle-end/66867] Suboptimal code generation for atomic_compare_exchange
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66867 Jakub Jelinek changed: What|Removed |Added Attachment #38740|0 |1 is obsolete|| Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org --- Comment #8 from Jakub Jelinek --- Created attachment 38749 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38749&action=edit gcc7-pr66867.patch Patch I'm going to bootstrap/regtest.
[Bug middle-end/66867] Suboptimal code generation for atomic_compare_exchange
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66867 Jakub Jelinek changed: What|Removed |Added CC||jakub at gcc dot gnu.org --- Comment #7 from Jakub Jelinek --- Created attachment 38740 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38740&action=edit gcc7-pr66867-wip.patch WIP untested patch using the same technique as we use for __builtin_*_overflow* builtins. I'll need to still finish writing the expansion for the case when we should expand it to external calls, once that is tested disable the ifn folding for !flag_inline_atomics, fix up -fsanitize=threads, use for other spots that look at atomic builtins. And, we need some optimization that would optimize the case where REALPART_EXPR is conditionally stored into a non-addressable var - we can store the oldval there unconditionally then, because it can't create a race.
[Bug middle-end/66867] Suboptimal code generation for atomic_compare_exchange
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66867 Andrew Pinski changed: What|Removed |Added CC||tkoeppe at google dot com --- Comment #5 from Andrew Pinski --- *** Bug 66713 has been marked as a duplicate of this bug. ***
[Bug middle-end/66867] Suboptimal code generation for atomic_compare_exchange
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66867 Andrew Pinski changed: What|Removed |Added CC||dhowells at redhat dot com --- Comment #4 from Andrew Pinski --- *** Bug 70825 has been marked as a duplicate of this bug. ***
[Bug middle-end/66867] Suboptimal code generation for atomic_compare_exchange
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66867 Andrew Pinski changed: What|Removed |Added CC||jianjin2016 at fb dot com --- Comment #6 from Andrew Pinski --- *** Bug 71599 has been marked as a duplicate of this bug. ***
