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From: Yujie Yang <yangyujie@loongson.cn>
To: Xi Ruoyao <xry111@xry111.site>
Cc: Yang Yujie <yangyujie@loongson.cn>,
	gcc-patches@gcc.gnu.org,  xuchenghua@loongson.cn,
	chenglulu@loongson.cn, panchenghui@loongson.cn
Subject: Re: [PATCH v2 3/4] LoongArch: add new configure option --with-strict-align-lib
Date: Wed, 30 Aug 2023 14:51:49 +0800	[thread overview]
Message-ID: <syjoyv5ahjrezu5q6nis3vrr3pjbfohh4ztqhzpgoy5pzesxpl@jsbmnj2qimer> (raw)
In-Reply-To: <ea025465147832e9d99745231eb50eed1f1a95a0.camel@xry111.site>

> > LoongArch processors may not support memory accesses without natural
> > alignments.  Building libraries with -mstrict-align may help with
> > toolchain binary compatiblity and performance on these implementations
> > (e.g. Loongson 2K1000LA).
> > 
> > No significant performance degredation is observed on current mainstream
> > LoongArch processors when the option is enabled.
> > 
> > gcc/ChangeLog:
> > 
> >         * config.gcc: use -mstrict-align for building libraries
> >         if --with-strict-align-lib is given.
> 
> Isn't this equivalent to --with-default-multilib=mno-strict-align now?
> 
> And I still believe the easiest way for 2K1000LA is adding -march=la264
> support so the user can simply configure with --with-arch=la264.

Not exactly -- Options given in --with-multilib-default= will not be applied
to multilib variants that have build options specified in --with-multilib-list,
but --with-strict-align-lib is always effective.

e.g. for the following configuration:

  --with-multilib-default=mstrict-align
  --with-multilib-list=lp64d/la464,lp64s

The library build options would be:

  base/lp64d variant: -mabi=lp64d -march=la464 (no -mstrict-align appended)
  base/lp64s variant: -mabi=lp64s -march=abi-default -mstrict-align

Sure, you can do it with --with-arch=la264. It's just a convenient
switch that we can use for building generic toolchains.


  reply	other threads:[~2023-08-30  6:52 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-30  1:58 [PATCH 0/4] LoongArch: target configuration interface update Yang Yujie
2023-08-30  1:58 ` [PATCH v2 1/4] LoongArch: improved target configuration interface Yang Yujie
2023-08-30 21:36   ` Joseph Myers
2023-08-31  3:14     ` Yujie Yang
2023-08-31  7:36       ` Yujie Yang
2023-08-31 17:56       ` Joseph Myers
2023-09-01  1:19         ` Yujie Yang
2023-08-30  1:58 ` [PATCH v2 2/4] LoongArch: define preprocessing macros "__loongarch_{arch,tune}" Yang Yujie
2023-08-30  1:58 ` [PATCH v2 3/4] LoongArch: add new configure option --with-strict-align-lib Yang Yujie
2023-08-30  5:25   ` Xi Ruoyao
2023-08-30  6:51     ` Yujie Yang [this message]
2023-08-30  8:22       ` Xi Ruoyao
2023-08-30 10:01         ` Yujie Yang
2023-08-30  1:58 ` [PATCH v2 4/4] LoongArch: support loongarch*-elf target Yang Yujie

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