Re: x86_64: clang-10: <instantiation>:2:2: error: unknown use of instruction mnemonic without a size suffix

[Naresh Kamboju]

Hi Nathan,

On Mon, 20 Sept 2021 at 09:13, Nathan Chancellor <nathan@xxxxxxxxxx> wrote:
>
> Hi Naresh,
>
> On Mon, Sep 20, 2021 at 08:55:46AM +0530, Naresh Kamboju wrote:
> > [Please ignore this email if it is already reported ]
> >
> > Following build warnings/ errors noticed while building linux mainline
> > master branch
> > with clang-10 for x86_64 architecture.
> > But clang-11, clang-12 and clang-13 build pass.
> >
> > <instantiation>:2:2: error: unknown use of instruction mnemonic
> > without a size suffix
> >  lsl %rax, %rax
> >  ^
> > <instantiation>:1:1: note: while in macro instantiation
> > LOAD_CPU_AND_NODE_SEG_LIMIT %rax
> > ^
> > <instantiation>:2:2: note: while in macro instantiation
> >  GET_PERCPU_BASE %rax
> >  ^
> > /builds/linux/arch/x86/entry/entry_64.S:887:2: note: while in macro
> > instantiation
> >  SAVE_AND_SET_GSBASE scratch_reg=%rax save_reg=%rbx
> >  ^
> > make[3]: *** [/builds/linux/scripts/Makefile.build:379:

> Thanks for the report. This is another case where the implicit switch to
> the integrated assembler exposed a previously fixed issue in LLVM:
>
> https://github.com/ClangBuiltLinux/linux/issues/1079
>
> This cannot be fixed in the LLVM 10 branch as it is no longer updated so
> if you want to keep testing with clang-10 for x86_64 on mainline, please
> add 'LLVM_IAS=0' to your make command like we did in our own CI.

We will update our gitlab pipeline CI configs with 'LLVM_IAS=0'.

>
> As a quick aside, would you mind updating my email address in your
> system for reports to nathan@xxxxxxxxxx? It will ensure it gets sent to
> the correct inbox so that I do not miss things, as I do not use my
> personal address for kernel development anymore.

Noted.

- Naresh