From: Fangrui Song <i@maskray.me>
To: Xi Ruoyao <xry111@xry111.site>
Cc: liuzhensong <liuzhensong@loongson.cn>,
binutils@sourceware.org, chenglulu@loongson.cn
Subject: Re: [PATCH] LoongArch: Use copy relocation for %pc_lo12 against external symbol
Date: Thu, 1 Sep 2022 00:42:28 -0700 [thread overview]
Message-ID: <20220901074228.pofoyuc6346dlumu@gmail.com> (raw)
In-Reply-To: <d1089572e821cf1cdb6f7e69223bb32df2ec2a41.camel@xry111.site>
On 2022-09-01, Xi Ruoyao via Binutils wrote:
>On Thu, 2022-09-01 at 09:27 +0800, liuzhensong wrote:
>
>> The R_LARCH_COPY is supported in older versions, we removed this
>> feature and are not going to support.
>
>Hmm, then for
>
>extern int x;
>int f() { return x; }
>
>it will produce a GOT access. If x is in another TU but not in a shared
>library, such a GOT access and the GOT entry is unneeded.
>
>This will be really a pain for situations like building an OS kernel, or
>with -static or -static-pie. Even for this simple example, there is no
>way to tell "x" is not in a shared library (maybe, expect LTO or linker
>relaxation, but IIRC LTO or relaxation do not *guarantee* to avoid the
>GOT, just "try to" avoid the GOT).
>
>So is there any serious reason forbidding us from using R_LARCH_COPY? Or
>any options for this "unneeded GOT" issue?
>--
>Xi Ruoyao <xry111@xry111.site>
>School of Aerospace Science and Technology, Xidian University
There is a slow trend to eliminate copy relocations for ELF platforms.
If a new port doesn't have copy relocations, leave it.
An architecture can add GOT indirection to PC-relative addressing
optimization if desired.
prev parent reply other threads:[~2022-09-01 7:42 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-31 13:22 Xi Ruoyao
2022-08-31 13:41 ` Xi Ruoyao
2022-09-01 1:38 ` liuzhensong
2022-09-01 1:38 ` liuzhensong
2022-09-01 2:12 ` Xi Ruoyao
2022-09-01 2:31 ` liuzhensong
2022-09-01 2:31 ` liuzhensong
2022-09-01 1:27 ` liuzhensong
2022-09-01 1:27 ` liuzhensong
2022-09-01 1:41 ` Xi Ruoyao
2022-09-01 2:09 ` liuzhensong
2022-09-01 7:42 ` Fangrui Song [this message]
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