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From: "unlvsur at live dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/99548] Help me! Lost the fight against the compiler.
Date: Thu, 11 Mar 2021 23:35:52 +0000 [thread overview]
Message-ID: <bug-99548-4-MrIIs992iR@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-99548-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99548
--- Comment #2 from cqwrteur <unlvsur at live dot com> ---
(In reply to Andrew Pinski from comment #1)
> For aarch64 we get:
> ldp x4, x3, [x1]
> mov x7, 38
> ldp x6, x5, [x2]
> ldr x8, [x1, 16]
> add x6, x4, x6
> cmp x4, x6
> adc x5, x3, x5
> cmp x3, x5
> ldr x3, [x1, 24]
> ldp x4, x1, [x2, 16]
> adc x4, x8, x4
> cmp x8, x4
> adc x1, x3, x1
> cmp x3, x1
> csetm x2, cs
> and x2, x2, x7
> add x2, x2, x6
> cmp x2, x6
> cinc x6, x5, ls
> cmp x6, x5
> cinc x5, x4, ls
> cmp x5, x4
> cinc x3, x1, ls
> cmp x3, x1
> csetm x1, ls
> and x1, x1, x7
> add x1, x1, x2
> str x1, [x0]
> cmp x1, x2
> cinc x1, x6, ls
> str x1, [x0, 8]
> cmp x1, x6
> cinc x1, x5, ls
> cmp x1, x5
> cinc x3, x3, ls
> stp x1, x3, [x0, 16]
> ret
> There is only one missing optimization there really:
> csetm x1, ls
> and x1, x1, x7
> Should be turned into:
> csel x1, x7, xzw, ls
> Which is repeated a few times.
>
> It looks like x86_64 has other issues.
my add carry implementation for none-x86_64 platforms is wrong on godbolt.
next prev parent reply other threads:[~2021-03-11 23:35 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-11 11:00 [Bug rtl-optimization/99548] New: " unlvsur at live dot com
2021-03-11 20:10 ` [Bug target/99548] " pinskia at gcc dot gnu.org
2021-03-11 23:35 ` unlvsur at live dot com [this message]
2021-12-23 21:45 ` pinskia at gcc dot gnu.org
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