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From: "olegendo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/54236] [SH] Improve addc and subc insn utilization Date: Sun, 19 Jul 2015 05:32:00 -0000 [thread overview] Message-ID: <bug-54236-4-cb4feWk6gV@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-54236-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54236 --- Comment #15 from Oleg Endo <olegendo at gcc dot gnu.org> --- The following shows missed subc cases when there are constants involved. Addc cases can be constructed in the same way. int fun (int x) { return x - 1 - (x > 100); } -O2 -m4: mov #100,r1 mov r4,r0 cmp/gt r1,r4 movt r1 sett rts subc r1,r0 better: mov #100,r1 mov r4,r0 cmp/gt r1,r4 mov #1,r1 rts subc r1,r0 Combine is looking for a pattern like: (parallel [ (set (reg:SI 168 [ D.1659 ]) (plus:SI (not:SI (gt:SI (reg/v:SI 167 [ x ]) (reg:SI 172))) (reg/v:SI 167 [ x ]))) (clobber (reg:SI 147 t)) ]) constants -1 and -2 are represented as not (0) and not (1) in this case. int fun (int x) { return x - 10 - (x > 100); } -O2 -m4: mov #100,r1 mov r4,r0 cmp/gt r1,r4 add #-10,r0 mov #0,r1 rts subc r1,r0 better: mov #100,r1 mov r4,r0 cmp/gt r1,r4 mov #10,r1 rts subc r1,r0 Combine is looking for a pattern like Failed to match this instruction: (parallel [ (set (reg:SI 168 [ D.1659 ]) (plus:SI (minus:SI (reg/v:SI 167 [ x ]) (gt:SI (reg/v:SI 167 [ x ]) (reg:SI 172))) (const_int -10 [0xfffffffffffffff6]))) (clobber (reg:SI 147 t)) ]) there is already a similar pattern *subc_negreg_t
next prev parent reply other threads:[~2015-07-19 5:32 UTC|newest] Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-08-12 22:25 [Bug target/54236] New: " olegendo at gcc dot gnu.org 2012-08-12 22:35 ` [Bug target/54236] " olegendo at gcc dot gnu.org 2012-08-16 23:20 ` olegendo at gcc dot gnu.org 2012-09-19 17:46 ` olegendo at gcc dot gnu.org 2013-09-22 22:22 ` olegendo at gcc dot gnu.org 2013-10-29 20:46 ` olegendo at gcc dot gnu.org 2013-11-02 10:20 ` olegendo at gcc dot gnu.org 2013-11-03 17:50 ` olegendo at gcc dot gnu.org 2013-11-03 20:44 ` olegendo at gcc dot gnu.org 2014-05-21 8:06 ` olegendo at gcc dot gnu.org 2014-09-27 17:42 ` olegendo at gcc dot gnu.org 2015-01-24 13:05 ` olegendo at gcc dot gnu.org 2015-01-25 16:42 ` olegendo at gcc dot gnu.org 2015-05-17 21:02 ` olegendo at gcc dot gnu.org 2015-05-19 8:01 ` olegendo at gcc dot gnu.org 2015-05-21 12:37 ` olegendo at gcc dot gnu.org 2015-07-19 5:32 ` olegendo at gcc dot gnu.org [this message] 2015-07-19 6:47 ` olegendo at gcc dot gnu.org 2015-09-28 14:01 ` olegendo at gcc dot gnu.org
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