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From: "zhenqiang.chen at arm dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/64015] [5.0 Regression] AArch64 ICE due to conditional compare
Date: Mon, 24 Nov 2014 05:29:00 -0000	[thread overview]
Message-ID: <bug-64015-4-yLPidBxNfV@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-64015-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64015

--- Comment #2 from Zhenqiang Chen <zhenqiang.chen at arm dot com> ---
You force it to register? In fact, I tend to not force it to register in
gen_ccmp_next, since it will introduce more overhead for ccmp, which
performance maybe worse.

My patch to fix the issue is at:
https://gcc.gnu.org/ml/gcc-patches/2014-11/msg02966.html

For CCMP, we still miss two optimizations for it:
1) Change the order of compares. In the case, if you change it to

  b > 252 && a > 10

You don't need "mov w0, 252"

        uxtb    w1, w1
    uxtb    w0, w0
    cmp    w1, 252
    ccmp    w0, 10, 0, hi
    cset    w0, hi
    ret

2) How to justify it is valueable (the overhead of ccmp is OK) when generating
ccmp?


  parent reply	other threads:[~2014-11-24  5:29 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-21  9:46 [Bug target/64015] New: " ktkachov at gcc dot gnu.org
2014-11-21  9:46 ` [Bug target/64015] " ktkachov at gcc dot gnu.org
2014-11-21 12:38 ` rguenth at gcc dot gnu.org
2014-11-21 18:24 ` pinskia at gcc dot gnu.org
2014-11-24  5:29 ` zhenqiang.chen at arm dot com [this message]
2014-11-24  5:39 ` pinskia at gcc dot gnu.org
2014-11-24  5:40 ` pinskia at gcc dot gnu.org
2014-11-24  6:16 ` zhenqiang.chen at arm dot com
2014-11-24 11:24 ` ktkachov at gcc dot gnu.org
2014-11-27  7:36 ` zhenqiang.chen at arm dot com
2015-01-13 14:28 ` StaffLeavers at arm dot com
2015-01-13 14:29 ` StaffLeavers at arm dot com
2015-01-13 14:29 ` StaffLeavers at arm dot com
2015-01-13 14:30 ` StaffLeavers at arm dot com
2015-01-13 14:31 ` StaffLeavers at arm dot com
2015-01-13 14:32 ` StaffLeavers at arm dot com
2015-01-13 14:32 ` StaffLeavers at arm dot com
2015-01-13 14:33 ` StaffLeavers at arm dot com
2015-01-16 11:48 ` jiwang at gcc dot gnu.org
2015-01-16 11:50 ` jiwang at gcc dot gnu.org

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