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* [Bug target/105773] New: [Aarch64] Failure to optimize and+cmp to tst
@ 2022-05-30 13:29 gabravier at gmail dot com
2022-06-08 12:37 ` [Bug target/105773] " rearnsha at gcc dot gnu.org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: gabravier at gmail dot com @ 2022-05-30 13:29 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105773
Bug ID: 105773
Summary: [Aarch64] Failure to optimize and+cmp to tst
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: gabravier at gmail dot com
Target Milestone: ---
int
baz (unsigned long x, unsigned long y)
{
return (int) (x & y) > 0;
}
With -O3, AArch64 GCC outputs this:
baz(unsigned long, unsigned long):
and w0, w0, w1
cmp w0, 0
cset w0, gt
ret
whereas LLVM outputs this:
baz(unsigned long, unsigned long):
tst w1, w0
cset w0, gt
ret
It seems to me as though using tst should be faster (unless Aarch64 processors
are extremely weird).
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug target/105773] [Aarch64] Failure to optimize and+cmp to tst 2022-05-30 13:29 [Bug target/105773] New: [Aarch64] Failure to optimize and+cmp to tst gabravier at gmail dot com @ 2022-06-08 12:37 ` rearnsha at gcc dot gnu.org 2022-06-08 12:41 ` rearnsha at gcc dot gnu.org ` (3 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: rearnsha at gcc dot gnu.org @ 2022-06-08 12:37 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105773 Richard Earnshaw <rearnsha at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Last reconfirmed| |2022-06-08 Status|UNCONFIRMED |NEW Ever confirmed|0 |1 --- Comment #1 from Richard Earnshaw <rearnsha at gcc dot gnu.org> --- Confirmed. The tricky thing here is the inequality following the logical AND operation. The GT comparison is defined as (Z=0 && N==V), and the logical AND will clear V and set Z & N appropriately. It's important to note that this optimization is not valid in AArch32, because the V flag is not modified by the TST instruction, leaving the flag bit essentially undefined. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug target/105773] [Aarch64] Failure to optimize and+cmp to tst 2022-05-30 13:29 [Bug target/105773] New: [Aarch64] Failure to optimize and+cmp to tst gabravier at gmail dot com 2022-06-08 12:37 ` [Bug target/105773] " rearnsha at gcc dot gnu.org @ 2022-06-08 12:41 ` rearnsha at gcc dot gnu.org 2022-06-22 21:34 ` pinskia at gcc dot gnu.org ` (2 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: rearnsha at gcc dot gnu.org @ 2022-06-08 12:41 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105773 Richard Earnshaw <rearnsha at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Priority|P3 |P4 Severity|normal |minor ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug target/105773] [Aarch64] Failure to optimize and+cmp to tst 2022-05-30 13:29 [Bug target/105773] New: [Aarch64] Failure to optimize and+cmp to tst gabravier at gmail dot com 2022-06-08 12:37 ` [Bug target/105773] " rearnsha at gcc dot gnu.org 2022-06-08 12:41 ` rearnsha at gcc dot gnu.org @ 2022-06-22 21:34 ` pinskia at gcc dot gnu.org 2022-10-13 13:56 ` cvs-commit at gcc dot gnu.org 2022-10-13 13:58 ` wilco at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: pinskia at gcc dot gnu.org @ 2022-06-22 21:34 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105773 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Severity|minor |enhancement ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug target/105773] [Aarch64] Failure to optimize and+cmp to tst 2022-05-30 13:29 [Bug target/105773] New: [Aarch64] Failure to optimize and+cmp to tst gabravier at gmail dot com ` (2 preceding siblings ...) 2022-06-22 21:34 ` pinskia at gcc dot gnu.org @ 2022-10-13 13:56 ` cvs-commit at gcc dot gnu.org 2022-10-13 13:58 ` wilco at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: cvs-commit at gcc dot gnu.org @ 2022-10-13 13:56 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105773 --- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Wilco Dijkstra <wilco@gcc.gnu.org>: https://gcc.gnu.org/g:1cccf644ff92ac1145abdbf255d1862dd787875b commit r13-3274-g1cccf644ff92ac1145abdbf255d1862dd787875b Author: Wilco Dijkstra <wdijkstr@arm.com> Date: Thu Oct 13 14:41:55 2022 +0100 [AArch64] Improve bit tests [PR105773] Since AArch64 sets all flags on logical operations, comparisons with zero can be combined into an AND even if the condition is LE or GT. Add a new CC_NZV mode used by ANDS/BICS/TST instructions. gcc/ PR target/105773 * config/aarch64/aarch64.cc (aarch64_select_cc_mode): Allow GT/LE for merging compare with zero into AND. (aarch64_get_condition_code_1): Add CC_NZVmode support. * config/aarch64/aarch64-modes.def: Add CC_NZV. * config/aarch64/aarch64.md: Use CC_NZV in cmp+and patterns. gcc/testsuite/ PR target/105773 * gcc.target/aarch64/ands_2.c: Test for ANDS. * gcc.target/aarch64/bics_2.c: Test for BICS. * gcc.target/aarch64/tst_2.c: Test for TST. * gcc.target/aarch64/tst_imm_split_1.c: Fix test. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug target/105773] [Aarch64] Failure to optimize and+cmp to tst 2022-05-30 13:29 [Bug target/105773] New: [Aarch64] Failure to optimize and+cmp to tst gabravier at gmail dot com ` (3 preceding siblings ...) 2022-10-13 13:56 ` cvs-commit at gcc dot gnu.org @ 2022-10-13 13:58 ` wilco at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: wilco at gcc dot gnu.org @ 2022-10-13 13:58 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105773 Wilco <wilco at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |FIXED Status|NEW |RESOLVED --- Comment #3 from Wilco <wilco at gcc dot gnu.org> --- Fixed. ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-10-13 13:58 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-05-30 13:29 [Bug target/105773] New: [Aarch64] Failure to optimize and+cmp to tst gabravier at gmail dot com 2022-06-08 12:37 ` [Bug target/105773] " rearnsha at gcc dot gnu.org 2022-06-08 12:41 ` rearnsha at gcc dot gnu.org 2022-06-22 21:34 ` pinskia at gcc dot gnu.org 2022-10-13 13:56 ` cvs-commit at gcc dot gnu.org 2022-10-13 13:58 ` wilco at gcc dot gnu.org
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