[PATCH] x86-64: Support APX NF TLS IE with 2 operands

[Hongyu Wang]

Jan Beulich <jbeulich@suse.com> 于2024年7月3日周三 17:23写道：
>
> On 03.07.2024 09:49, H.J. Lu wrote:
> > Have I missed something? I haven't seen any testcases.
>
> From my description you could have made one yourself, if you really didn't
> believe what I was saying. Here you go:
>
>         .text
> gottpoff:
>         .irp op, add, sub
>         \op     foo@gottpoff(%rip), %rax
>         \op     foo@gottpoff(%rip), %r16
>         \op     foo@gottpoff(%rip), %rax, %rcx
>         \op     %rax, foo@gottpoff(%rip), %rcx
>         {nf} \op foo@gottpoff(%rip), %rax
>         .endr
>
>         popcnt  foo@gottpoff(%rip), %rax
>         popcnt  foo@gottpoff(%rip), %r16
>         {nf} popcnt foo@gottpoff(%rip), %rax
>
>         adox    foo@gottpoff(%rip), %rax
>         adox    foo@gottpoff(%rip), %r16
>

These instructions are actually allowed with the newly added
relocation type R_X86_64_CODE_{5,6}_GOTTPOFF, but there is no chance
for compiler to generate such code in TLS sequence.
I'm not sure how the logic can be simplified, we still need to check
for each operands for the allowed case, while we can add more ops
other than just MN_add.