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From: "jakub at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/37102] [4.3/4.4 Regression] possible integer codegen bug Date: Thu, 14 Aug 2008 10:04:00 -0000 [thread overview] Message-ID: <20080814100243.16104.qmail@sourceware.org> (raw) In-Reply-To: <bug-37102-12544@http.gcc.gnu.org/bugzilla/> ------- Comment #3 from jakub at gcc dot gnu dot org 2008-08-14 10:02 ------- Somewhat shorter: extern void abort (void); unsigned int a, b = 1, c; void __attribute__ ((noinline)) foo (int x) { if (x != 5) abort (); } int main () { unsigned int d, e; for (d = 1; d < 5; d++) if (c) a = b; a = b; e = a << 1; if (e) e = (e << 1) ^ 1; foo (e); return 0; } At *.tailc looks sane to me. <bb 2>: pretmp.35_15 = c; b.1_5 = b; a_lsm.48_4 = a; if (pretmp.35_15 != 0) goto <bb 3>; else goto <bb 4>; <bb 3>: <bb 4>: # a_lsm.48_28 = PHI <b.1_5(3), a_lsm.48_4(2)> a = b.1_5; e_9 = b.1_5 << 1; if (e_9 != 0) goto <bb 5>; else goto <bb 6>; so a_lsm.48_28 is either b or a, depending on whether c != 0 or not, and a = b. Then copyrename4 decides to replace a = b.1_5; with a = a_lsm_48_5; and at *.uncprop we have: <bb 2>: pretmp.35_15 = c; a_lsm.48_5 = b; a_lsm.48_4 = a; if (pretmp.35_15 != 0) goto <bb 3>; else goto <bb 4>; <bb 3>: <bb 4>: # a_lsm.48_28 = PHI <a_lsm.48_5(3), a_lsm.48_4(2)> a = a_lsm.48_5; e_9 = a_lsm.48_5 << 1; if (e_9 != 0) goto <bb 5>; else goto <bb 6>; which looks correct too. But *.optimized is already wrong: <bb 2>: a_lsm.49 = b; a_lsm.48 = a; if (c != 0) goto <bb 3>; else goto <bb 7>; <bb 7>: a_lsm.49 = a_lsm.48; goto <bb 4>; <bb 3>: <bb 4>: a = a_lsm.49; e = a_lsm.49 << 1; if (e != 0) goto <bb 5>; else goto <bb 8>; While in *.uncprop a was set unconditionally to b, now it is sometimes b and sometimes a. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37102
next prev parent reply other threads:[~2008-08-14 10:04 UTC|newest] Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top 2008-08-13 3:46 [Bug c/37102] New: " regehr at cs dot utah dot edu 2008-08-13 9:54 ` [Bug tree-optimization/37102] [4.3/4.4 Regression] " rguenth at gcc dot gnu dot org 2008-08-13 9:55 ` rguenth at gcc dot gnu dot org 2008-08-14 10:04 ` jakub at gcc dot gnu dot org [this message] 2008-08-18 13:58 ` jsm28 at gcc dot gnu dot org 2008-08-26 13:39 ` cnstar9988 at gmail dot com 2008-08-27 22:13 ` jsm28 at gcc dot gnu dot org 2008-08-28 14:49 ` rguenth at gcc dot gnu dot org 2008-09-04 14:54 ` [Bug tree-optimization/37102] [4.3/4.4 Regression] out-of-SSA is broken rguenth at gcc dot gnu dot org 2008-09-04 16:10 ` amacleod at redhat dot com 2008-09-04 16:19 ` rguenth at gcc dot gnu dot org 2008-09-04 16:53 ` amacleod at redhat dot com 2008-09-15 1:04 ` lthode at mail dot unomaha dot edu 2008-09-17 14:26 ` rguenth at gcc dot gnu dot org 2008-09-17 14:35 ` amacleod at redhat dot com 2008-09-17 14:39 ` rguenth at gcc dot gnu dot org 2008-09-17 14:40 ` amacleod at redhat dot com 2008-09-17 14:49 ` amacleod at redhat dot com 2008-09-17 21:57 ` amacleod at redhat dot com 2008-09-18 14:01 ` amacleod at gcc dot gnu dot org 2008-09-18 20:06 ` [Bug tree-optimization/37102] [4.3 " amacleod at redhat dot com 2008-09-27 11:33 ` cnstar9988 at gmail dot com 2008-10-10 0:57 ` cnstar9988 at gmail dot com 2008-10-12 19:59 ` lthode at mail dot unomaha dot edu 2008-10-17 17:38 ` amacleod at gcc dot gnu dot org 2008-10-18 11:19 ` rguenth at gcc dot gnu dot org
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