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From: "olegendo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/59446] New: loop2_doloop creates constant comparison and dead jump Date: Tue, 10 Dec 2013 11:19:00 -0000 [thread overview] Message-ID: <bug-59446-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59446 Bug ID: 59446 Summary: loop2_doloop creates constant comparison and dead jump Product: gcc Version: 4.9.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: rtl-optimization Assignee: unassigned at gcc dot gnu.org Reporter: olegendo at gcc dot gnu.org CC: law at redhat dot com Target: sh*-*-* After the commit that fixed PR 58640 http://gcc.gnu.org/viewcvs?rev=203463&root=gcc&view=rev the SH specific test case gcc.target/sh/pr51244-18.c caught the following sequence: .L15: mov #0,r1 // r1 = 0 tst r1,r1 // T = r1 == 0 bf.s .L7 // if (T == 0) goto .L7 add #-4,r9 The branch above never happens and is dead code. Something causes the loop2_doloop RTL pass to create the following code, which results in the above final code. (code_label 108 107 109 4 2 "" [0 uses]) (note 109 108 110 4 [bb 4] NOTE_INSN_BASIC_BLOCK) . . . (insn 177 176 185 4 (set (reg:SI 304) (plus:SI (reg:SI 305) (const_int 1 [0x1]))) -1 (nil)) (note 185 177 180 16 [bb 16] NOTE_INSN_BASIC_BLOCK) (insn 180 185 182 16 (set (reg:SI 306) (plus:SI (reg/v:SI 278 [ k ]) (const_int -8 [0xfffffffffffffff8]))) -1 (nil)) (insn 182 180 183 16 (set (reg:SI 307) (const_int -8 [0xfffffffffffffff8])) -1 (nil)) (insn 183 182 184 16 (set (reg:SI 147 t) (ge:SI (reg:SI 306) (reg:SI 307))) -1 (nil)) (jump_insn 184 183 181 16 (set (pc) (if_then_else (eq (reg:SI 147 t) (const_int 0 [0])) (label_ref 181) (pc))) -1 (int_list:REG_BR_PROB 0 (nil)) -> 181) (code_label 181 184 178 14 10 "" [1 uses]) (note 178 181 186 14 [bb 14] NOTE_INSN_BASIC_BLOCK) (insn 186 178 179 14 (set (reg:SI 304) (const_int 1 [0x1])) -1 (nil)) (note 179 186 155 15 [bb 15] NOTE_INSN_BASIC_BLOCK) . . . . . . (code_label 149 146 150 9 5 "" [1 uses]) (note 150 149 151 9 [bb 9] NOTE_INSN_BASIC_BLOCK) (insn 151 150 152 9 (set (reg/v:SI 261 [ k ]) (plus:SI (reg/v:SI 261 [ k ]) (const_int -8 [0xfffffffffffffff8]))) pr51244-18.c:48 68 {*addsi3_compact} (nil)) (insn 152 151 175 9 (set (reg:SI 147 t) (ge:SI (reg/v:SI 261 [ k ]) (const_int 0 [0]))) pr51244-18.c:49 20 {cmpgesi_t} (nil)) (jump_insn 175 152 174 9 (parallel [ (set (pc) (if_then_else (ne:SI (reg:SI 304) (const_int 1 [0x1])) (label_ref 174) (pc))) (set (reg:SI 304) (plus (reg:SI 304) (const_int -1 [0xffffffffffffffff]))) (clobber (reg:SI 147 t)) ]) pr51244-18.c:49 -1 (int_list:REG_BR_PROB 9700 (nil)) -> 174) jump_insn 175 is SH's decrement-and-test pattern that is used for loops.
next reply other threads:[~2013-12-10 11:19 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-12-10 11:19 olegendo at gcc dot gnu.org [this message] 2013-12-10 22:00 ` [Bug rtl-optimization/59446] " law at redhat dot com 2013-12-10 22:17 ` olegendo at gcc dot gnu.org 2013-12-11 22:15 ` law at gcc dot gnu.org 2013-12-11 22:16 ` law at redhat dot com 2013-12-11 22:42 ` olegendo at gcc dot gnu.org
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