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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/58143] [4.8/4.9 regression] wrong code at -O3
Date: Tue, 15 Oct 2013 11:03:00 -0000 [thread overview]
Message-ID: <bug-58143-4-LVlZ50KGoi@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-58143-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58143
--- Comment #21 from Richard Biener <rguenth at gcc dot gnu.org> ---
For the testcase in PR58731,
int a, b, c, d, e;
int
main ()
{
for (b = 4; b > -30; b--)
for (; c;)
for (;;)
{
e = a > 2147483647 - b;
if (d)
break;
}
return 0;
}
after rewriting 2147483647 - b to unsigned arithmetic, IVOPTs re-writes it
to signed arithmetic again, making VRP remove the loop exit test. Bah.
--- pr58143-3.c.118t.slp 2013-10-15 12:56:07.040864240 +0200
+++ pr58143-3.c.120t.ivopts 2013-10-15 12:56:07.041864251 +0200
@@ -5,18 +5,14 @@
{
int b_lsm.10;
int e_lsm.9;
- int pretmp_3;
- unsigned int ivtmp_6;
- unsigned int _12;
+ int _13;
int b.5_14;
- unsigned int _15;
int pretmp_16;
int pretmp_17;
int b.0_20;
_Bool pretmp_22;
int pretmp_23;
int pretmp_24;
- unsigned int ivtmp_27;
<bb 2>:
b = 4;
@@ -45,11 +41,8 @@
<bb 8>:
# b.0_20 = PHI <b.5_14(11), 4(2)>
# e_lsm.9_19 = PHI <e_lsm.9_30(11), e_lsm.9_21(2)>
- # ivtmp_6 = PHI <ivtmp_27(11), 34(2)>
- _15 = (unsigned int) b.0_20;
- _12 = 2147483647 - _15;
- pretmp_3 = (int) _12;
- pretmp_22 = pretmp_3 < pretmp_16;
+ _13 = 2147483647 - b.0_20;
+ pretmp_22 = _13 < pretmp_16;
pretmp_23 = (int) pretmp_22;
<bb 9>:
@@ -62,8 +55,7 @@
<bb 10>:
# e_lsm.9_30 = PHI <e_lsm.9_25(9)>
b.5_14 = b.0_20 + -1;
- ivtmp_27 = ivtmp_6 - 1;
- if (ivtmp_27 != 0)
+ if (b.5_14 != -30)
goto <bb 11>;
else
goto <bb 12>;
possibly via some bug in SCEV and/or fold. That said,
int a, b, c, d, e;
int
main ()
{
for (b = 4; b > -30; b--)
{
e = a > (int)((unsigned int) __INT_MAX__ - (unsigned int) b);
for (; c;)
for (;;)
{
if (d)
break;
}
}
return 0;
}
fails the same way, even with -fno-tree-loop-im (but still needs -O3
for some reason).
next prev parent reply other threads:[~2013-10-15 11:03 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-13 0:05 [Bug middle-end/58143] New: wrong code at -O3 on x86_64-linux-gnu su at cs dot ucdavis.edu
2013-08-13 0:08 ` [Bug middle-end/58143] " pinskia at gcc dot gnu.org
2013-08-13 0:24 ` su at cs dot ucdavis.edu
2013-08-14 21:11 ` mikpe at it dot uu.se
2013-08-20 0:21 ` bernd.edlinger at hotmail dot de
2013-08-20 0:59 ` bernd.edlinger at hotmail dot de
2013-08-20 22:25 ` bernd.edlinger at hotmail dot de
2013-08-21 8:53 ` bernd.edlinger at hotmail dot de
2013-08-21 17:41 ` [Bug tree-optimization/58143] [4.8/4.9 regression] wrong code at -O3 ebotcazou at gcc dot gnu.org
2013-08-21 18:02 ` jakub at gcc dot gnu.org
2013-08-21 21:50 ` bernd.edlinger at hotmail dot de
2013-08-23 9:15 ` bernd.edlinger at hotmail dot de
2013-08-23 9:16 ` jakub at gcc dot gnu.org
2013-08-23 12:08 ` bernd.edlinger at hotmail dot de
2013-08-23 12:59 ` jakub at gcc dot gnu.org
2013-08-25 22:08 ` bernd.edlinger at hotmail dot de
2013-08-28 21:30 ` bernd.edlinger at hotmail dot de
2013-10-15 8:15 ` rguenth at gcc dot gnu.org
2013-10-15 8:17 ` rguenth at gcc dot gnu.org
2013-10-15 8:39 ` bernd.edlinger at hotmail dot de
2013-10-15 9:05 ` rguenth at gcc dot gnu.org
2013-10-15 9:41 ` rguenth at gcc dot gnu.org
2013-10-15 11:03 ` rguenth at gcc dot gnu.org [this message]
2013-10-15 11:45 ` bernd.edlinger at hotmail dot de
2013-10-15 11:54 ` rguenth at gcc dot gnu.org
2013-10-15 11:54 ` rguenther at suse dot de
2013-10-15 13:21 ` bernd.edlinger at hotmail dot de
2013-10-15 13:27 ` rguenther at suse dot de
2013-10-15 13:36 ` mikpelinux at gmail dot com
2013-10-15 13:38 ` bernd.edlinger at hotmail dot de
2013-10-15 13:40 ` rguenther at suse dot de
2013-10-16 9:51 ` jakub at gcc dot gnu.org
2013-10-17 9:59 ` rguenth at gcc dot gnu.org
2013-10-17 10:08 ` [Bug tree-optimization/58143] [4.8 " rguenth at gcc dot gnu.org
2013-11-18 15:14 ` rguenth at gcc dot gnu.org
2013-11-18 15:15 ` rguenth at gcc dot gnu.org
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