From: Lulu Cheng <chenglulu@loongson.cn>
To: Xi Ruoyao <xry111@xry111.site>,
"gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>
Cc: Youling Tang <tangyouling@loongson.cn>,
Chenghua Xu <xuchenghua@loongson.cn>,
Huacai Chen <chenhuacai@kernel.org>,
Jinyang He <hejinyang@loongson.cn>, Wang Xuerui <i@xen0n.name>
Subject: Re: 回复：[PATCH v5] LoongArch: add movable attribute
Date: Fri, 5 Aug 2022 12:01:03 +0800 [thread overview]
Message-ID: <d5305fc0-b046-76fb-3864-a0c3be03cb82@loongson.cn> (raw)
In-Reply-To: <ff1b5ccc96a8c7bd961cb125e40cb19d47401ba2.camel@xry111.site>
在 2022/8/5 上午11:45, Xi Ruoyao 写道:
> On Fri, 2022-08-05 at 11:34 +0800, Xi Ruoyao via Gcc-patches wrote:
>
>> Or maybe we should just use a PC-relative addressing with 4 instructions
>> instead of GOT for -fno-PIC?
> Not possible, Glibc does not support R_LARCH_PCALA* relocations in
> ld.so. So we still need a -mno-got (or something) option to disable GOT
> for special cases like the kernel.
>
>> Both way consumes 16 bytes (4 instructions
>> for PC-relative, 2 instructions and a 64-bit GOT entry for GOT) and PC-
>> relative may be more cache friendly. But such a major change cannot be
>> backported for 12.2 IMO.
I'm very sorry, my understanding of the precpu variable is wrong, I just
read the code of the kernel you submitted, this precpu variable not only
has a large offset but also has an uncertain address when compiling, so
no matter whether it is addressed with pcrel Still got addressing needs
dynamic relocation when loading. It seems that accessing through the got
table is a better choice.
The name movable is also very vivid to describe this function in the
kernel, indicating that the address of the variable can be changed at
will. But this name is more difficult to understand in gcc, I have no
opinion on other, can this name be changed?
next prev parent reply other threads:[~2022-08-05 4:01 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-29 14:22 [PATCH] LoongArch: add addr_global attribute Xi Ruoyao
2022-07-29 15:31 ` [PATCH v2] " Xi Ruoyao
2022-07-29 17:17 ` [PATCH v3] " Xi Ruoyao
2022-07-30 3:13 ` Lulu Cheng
2022-07-30 6:03 ` Huacai Chen
2022-07-31 9:05 ` Chenghua Xu
2022-08-01 10:04 ` [PATCH v4] LoongArch: add movable attribute Xi Ruoyao
2022-08-01 10:07 ` [PATCH v5] " Xi Ruoyao
2022-08-03 1:36 ` Xi Ruoyao
2022-08-03 2:59 ` WANG Xuerui
2022-08-03 3:15 ` Xi Ruoyao
[not found] ` <-2muj1c-68saz6jhkcyw3jo1xp-1mgcvnkbqi2wjp6tue-qsso54-emxgu3-k85590-kpgox7-w67u6h3cai1l-5bi887dsgzsu-g4d7i7-wl316qxrucx4kv4on7-mnna36-iremg8-nwc5ot-9041t2-hu8nsl.1659495047941@email.android.com>
2022-08-03 3:10 ` 回复：[PATCH " Xi Ruoyao
2022-08-04 7:47 ` Xi Ruoyao
2022-08-05 1:05 ` Lulu Cheng
2022-08-05 1:28 ` Xi Ruoyao
2022-08-05 2:38 ` Lulu Cheng
2022-08-05 2:51 ` Xi Ruoyao
2022-08-05 3:34 ` Xi Ruoyao
2022-08-05 3:45 ` Xi Ruoyao
2022-08-05 4:01 ` Lulu Cheng [this message]
2022-08-05 6:03 ` Xi Ruoyao
2022-08-05 7:19 ` Lulu Cheng
2022-08-05 7:41 ` WANG Xuerui
2022-08-05 7:58 ` Lulu Cheng
2022-08-05 9:53 ` Xi Ruoyao
2022-08-08 4:53 ` Lulu Cheng
2022-08-09 11:30 ` Xi Ruoyao
2022-08-09 13:03 ` Lulu Cheng
2022-08-09 14:04 ` Xi Ruoyao
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