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From: "joey.ye at arm dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/54742] Switch elimination in FSM loop Date: Mon, 17 Feb 2014 10:07:00 -0000 [thread overview] Message-ID: <bug-54742-4-dOrN4GhooS@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-54742-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54742 --- Comment #35 from Joey Ye <joey.ye at arm dot com> --- Here is good expansion: ;; _41 = _42 * 4; (insn 20 19 0 (set (reg:SI 126 [ D.5038 ]) (ashift:SI (reg/v:SI 131 [ Int_1_Par_Val ]) (const_int 2 [0x2]))) -1 (nil)) ;; _40 = _2 + _41; (insn 21 20 22 (set (reg:SI 136 [ D.5035 ]) (plus:SI (reg/v/f:SI 130 [ Arr_2_Par_Ref ]) (reg:SI 119 [ D.5036 ]))) -1 (nil)) (insn 22 21 0 (set (reg/f:SI 125 [ D.5035 ]) (plus:SI (reg:SI 136 [ D.5035 ]) (reg:SI 126 [ D.5038 ]))) -1 (nil)) ;; MEM[(int[25] *)_51 + 20B] = _34; (insn 29 28 30 (set (reg:SI 139) (plus:SI (reg/v/f:SI 130 [ Arr_2_Par_Ref ]) (reg:SI 119 [ D.5036 ]))) Proc_8.c:23 -1 (nil)) (insn 30 29 31 (set (reg:SI 140) (plus:SI (reg:SI 139) (reg:SI 126 [ D.5038 ]))) Proc_8.c:23 -1 (nil)) (insn 31 30 32 (set (reg/f:SI 141) (plus:SI (reg:SI 140) (const_int 1000 [0x3e8]))) Proc_8.c:23 -1 (nil)) (insn 32 31 0 (set (mem:SI (plus:SI (reg/f:SI 141) (const_int 20 [0x14])) [2 MEM[(int[25] *)_51 + 20B]+0 S4 A32]) (reg:SI 124 [ D.5039 ])) Proc_8.c:23 -1 (nil)) After cse1 140 can be replaced by 125, thus lead a series of transformation make it much more efficient. Here is bad expansion: ;; _40 = Arr_2_Par_Ref_22(D) + _12; (insn 22 21 23 (set (reg:SI 138 [ D.5038 ]) (plus:SI (reg:SI 128 [ D.5038 ]) (reg:SI 121 [ D.5036 ]))) -1 (nil)) (insn 23 22 0 (set (reg/f:SI 127 [ D.5035 ]) (plus:SI (reg/v/f:SI 132 [ Arr_2_Par_Ref ]) (reg:SI 138 [ D.5038 ]))) -1 (nil)) ;; _32 = _20 + 1000; (insn 29 28 0 (set (reg:SI 124 [ D.5038 ]) (plus:SI (reg:SI 121 [ D.5036 ]) (const_int 1000 [0x3e8]))) Proc_8.c:23 -1 (nil)) ;; MEM[(int[25] *)_51 + 20B] = _34; (insn 32 31 33 (set (reg:SI 141) (plus:SI (reg/v/f:SI 132 [ Arr_2_Par_Ref ]) (reg:SI 124 [ D.5038 ]))) Proc_8.c:23 -1 (nil)) (insn 33 32 34 (set (reg/f:SI 142) (plus:SI (reg:SI 141) (reg:SI 128 [ D.5038 ]))) Proc_8.c:23 -1 (nil)) (insn 34 33 0 (set (mem:SI (plus:SI (reg/f:SI 142) (const_int 20 [0x14])) [2 MEM[(int[25] *)_51 + 20B]+0 S4 A32]) (reg:SI 126 [ D.5039 ])) Proc_8.c:23 -1 (nil)) Here cse doesn't happen, resulting in less optimal insns. Reason why cse doesn't happen is unclear yet.
next prev parent reply other threads:[~2014-02-17 10:07 UTC|newest] Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-09-29 3:16 [Bug tree-optimization/54742] New: " joey.ye at arm dot com 2012-09-29 3:21 ` [Bug tree-optimization/54742] " pinskia at gcc dot gnu.org 2012-10-01 10:19 ` rguenth at gcc dot gnu.org 2012-10-10 7:37 ` joey.ye at arm dot com 2013-02-19 10:27 ` rguenth at gcc dot gnu.org 2013-03-04 8:27 ` venkataramanan.kumar at amd dot com 2013-03-04 8:34 ` venkataramanan.kumar at amd dot com 2013-03-04 16:56 ` law at redhat dot com 2013-03-08 3:56 ` joey.ye at arm dot com 2013-05-02 0:11 ` sje at gcc dot gnu.org 2013-11-20 7:23 ` law at redhat dot com 2013-11-20 7:23 ` StaffLeavers at arm dot com 2013-11-20 7:24 ` StaffLeavers at arm dot com 2013-11-20 7:25 ` StaffLeavers at arm dot com 2013-11-20 7:26 ` StaffLeavers at arm dot com 2013-11-20 7:26 ` StaffLeavers at arm dot com 2013-11-20 7:26 ` StaffLeavers at arm dot com 2013-11-20 7:26 ` StaffLeavers at arm dot com 2013-11-20 7:27 ` StaffLeavers at arm dot com 2013-11-20 7:27 ` StaffLeavers at arm dot com 2013-11-20 7:28 ` StaffLeavers at arm dot com 2013-11-20 7:28 ` StaffLeavers at arm dot com 2013-11-20 7:28 ` StaffLeavers at arm dot com 2013-11-20 7:29 ` StaffLeavers at arm dot com 2013-11-20 7:31 ` StaffLeavers at arm dot com 2013-11-22 19:30 ` law at redhat dot com 2013-11-27 12:11 ` jgreenhalgh at gcc dot gnu.org 2013-11-27 12:15 ` jgreenhalgh at gcc dot gnu.org 2013-12-11 18:43 ` izamyatin at gmail dot com 2013-12-11 18:48 ` law at redhat dot com 2013-12-12 11:22 ` izamyatin at gmail dot com 2013-12-13 11:05 ` rguenth at gcc dot gnu.org 2013-12-25 13:48 ` izamyatin at gmail dot com 2014-02-17 10:07 ` joey.ye at arm dot com [this message] 2014-02-19 11:22 ` joey.ye at arm dot com 2014-06-28 15:45 ` spop at gcc dot gnu.org 2014-08-12 22:49 ` sje at gcc dot gnu.org 2014-12-06 19:20 ` spop at gcc dot gnu.org 2014-12-06 19:23 ` spop at gcc dot gnu.org 2015-01-14 10:23 ` yroux at gcc dot gnu.org 2023-12-15 18:21 ` pinskia at gcc dot gnu.org
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