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Subject: Re: gcc inline asm unknown mnemonics problems
From: Xi Ruoyao <xry111@xry111.site>
To: mike <gmbgmb@smwireless.net>
Cc: gcc-help@gcc.gnu.org
Date: Tue, 20 Sep 2022 13:39:41 +0800
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On Mon, 2022-09-19 at 21:47 -0700, mike wrote:

/* snip */

> I am having a problem using ldrexb and strexb using inline assembler.=C2=
=A0 The
> code is running on a RPi4 on ubuntu 20.04LTS.
>=20
> I get an error message "Error: unknown mnemonic `ldrexb' -- `ldrexb=20
> x0,[[sp,8]]'"

ldrexb and strexb are Thumb-2 instructions, but RPi4 uses an AArch64
CPU. AArch64 is an extension of the classic ARM instruction set, not an
extension of Thumb-2.  So you can't use them on AArch64.


--=20
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University