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From: "aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/110233] [12/13/14 Regression] Wrong code at -Os on x86_64-linux-gnu
Date: Wed, 14 Jun 2023 09:03:10 +0000 [thread overview]
Message-ID: <bug-110233-4-eIma5ApmFZ@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-110233-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110233
--- Comment #3 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #2)
> VRP2/DOM3 produces the wrong folding for some reason:
> Folding statement: _27 = b.6_9 * 2;
> Queued stmt for removal. Folds to: 2147483647
>
> I don't uinderstand how it could get that from:
Putting a breakpoint in execute_ranger_vrp() for the VRP2 instance, and dumping
what the ranger knows with debug_ranger() we see:
=========== BB 3 ============
b.6_9 [irange] int [1334323000, +INF] NONZERO 0x7fffffff
<bb 3> [local count: 357878153]:
_28 = b.6_9 * 2;
ivtmp.19_27 = 2147483647;
ivtmp.22_31 = (unsigned long) &f;
goto <bb 5>; [100.00%]
ivtmp.19_27 : [irange] unsigned int [2147483647, 2147483647] NONZERO 0x7fffffff
_28 : [irange] int [+INF, +INF] NONZERO 0x7ffffffe
ivtmp.22_31 : [irange] unsigned long [1, +INF]
So on entry to BB3, b.6_9 is [1334323000, +INF]. This comes from the 2->3
edge, which is the only incoming edge to BB3.
Isn't multiplying any number in that range an overflow, and thus undefined?
Ranger is coming back with:
_28 : [irange] int [+INF, +INF] NONZERO 0x7ffffffe
which sounds reasonable, and the reason you're seeing 2147483647.
next prev parent reply other threads:[~2023-06-14 9:03 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-13 7:18 [Bug c/110233] New: " shaohua.li at inf dot ethz.ch
2023-06-14 0:36 ` [Bug middle-end/110233] [12/13/14 Regression] " pinskia at gcc dot gnu.org
2023-06-14 0:58 ` pinskia at gcc dot gnu.org
2023-06-14 9:03 ` aldyh at gcc dot gnu.org [this message]
2023-06-14 9:09 ` aldyh at gcc dot gnu.org
2023-06-15 4:51 ` pinskia at gcc dot gnu.org
2023-06-15 5:38 ` pinskia at gcc dot gnu.org
2023-06-15 5:39 ` pinskia at gcc dot gnu.org
2023-07-30 14:32 ` shaohua.li at inf dot ethz.ch
2023-07-30 14:47 ` sjames at gcc dot gnu.org
2023-07-30 14:47 ` sjames at gcc dot gnu.org
2023-07-30 15:18 ` shaohua.li at inf dot ethz.ch
2023-10-20 13:57 ` rguenth at gcc dot gnu.org
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