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

[Nathan Chancellor]

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:
> arch/x86/entry/entry_64.o] Error 1
> arch/x86/entry/entry_64_compat.o: warning: objtool: .entry.text+0x215:
> can't find jump dest instruction at .entry.text+0x21a
> make[3]: Target '__build' not remade because of errors.
> make[2]: *** [/builds/linux/scripts/Makefile.build:540: arch/x86/entry] Error 2
> make[2]: Target '__build' not remade because of errors.
> make[1]: *** [/builds/linux/Makefile:1868: arch/x86] Error 2

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This cannot be fixed in the LLVM 10 branch as it is no longer updated so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.

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.

Cheers,
Nathan