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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/101179] New: y % (x ? 16 : 4) and y % (4 << (2 * (bool)x)) produce different code
Date: Wed, 23 Jun 2021 11:05:32 +0000 [thread overview]
Message-ID: <bug-101179-4@http.gcc.gnu.org/bugzilla/> (raw)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101179
Bug ID: 101179
Summary: y % (x ? 16 : 4) and y % (4 << (2 * (bool)x)) produce
different code
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
These produces different assembly:
int f1(int y)
{
const bool x = y % 100 == 0;
return y % (x ? 16 : 4) == 0;
}
int f2(int y)
{
const bool x = y % 100 == 0;
return y % (4 << (x * 2)) == 0;
}
Since they do the same calculation, I would expect them to produce the same
code.
Currently f1 produces slightly smaller code for aarch64 and x86_64.
With Clang they produce the same code (but using cmov which might not be
optimal).
next reply other threads:[~2021-06-23 11:05 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-23 11:05 redi at gcc dot gnu.org [this message]
2021-06-23 13:58 ` [Bug tree-optimization/101179] " redi at gcc dot gnu.org
2021-06-23 17:51 ` pinskia at gcc dot gnu.org
2021-06-23 17:55 ` redi at gcc dot gnu.org
2021-06-23 18:05 ` pinskia at gcc dot gnu.org
2021-06-23 20:10 ` pinskia at gcc dot gnu.org
2021-06-24 6:40 ` rguenth at gcc dot gnu.org
2021-07-01 20:43 ` pinskia at gcc dot gnu.org
2021-07-01 20:43 ` pinskia at gcc dot gnu.org
2021-07-01 20:49 ` pinskia at gcc dot gnu.org
2023-01-18 16:51 ` pinskia at gcc dot gnu.org
2023-05-06 21:52 ` pinskia at gcc dot gnu.org
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