Re: RFC: Formalization of the Intel assembly syntax (PR53929)

[Jan Beulich <jbeulich@suse.com>]

On 20.01.2024 13:40, LIU Hao wrote:
> 在 2024-01-19 17:13, Jan Beulich 写道:
>> But I see a severe issue with your aim at confining strict mode to
>> compiler generated code only: In inline assembly (see your mentioning of
>> APP / NO_APP above) you still potentially reference C symbols. So the
>> ambiguities don't disappear in APP / NO_APP regions.
> 
> My suggestion is that people who write inline assembly should have been aware of the existence of 
> bad names, and should have been careful to avoid them.
> 
> 
>> And an array happening to be indexed by rcx would then result in
>>
>>      mov eax, DWORD PTR rcx[rcx]    # `movl rcx(%rcx), %eax`
>>
>> ? That's going to be confusing at best. 
> 
> This is always confusing, no matter how it is written.
> 
>> I think this whole issue needs
>> taking care of differently, and iirc I did already suggest an alternative
>> in one of the bugzilla entries involved: Potentially ambiguous names
>> (which to a compiler may mean: all symbol names) ought to simply be
>> quoted, and it ought to be specified that quoted symbols are never
>> registers. Iirc this will require gas changes, yes, but it'll address all
>> ambiguities afaict.
> 
> The OP of GCC PR53929 said that 'the problem does _not_ go away even if I quote the symbol name by 
> hand in the assembly output' which was 12 years ago. I tried my local installation and quoting the 
> symbol turned out to avoid the issue:
> 
>     > as --version
>     GNU assembler (GNU Binutils) 2.41.0.20240108
> 
>     > cat test.s
>     .intel_syntax noprefix
>     lea     rax, "bx"[rip]
> 
>     > as test.s -o test.o
> 
>     > objdump -d test.o
>     test.o:     file format pe-x86-64
>     (...)
>        0:   48 8d 05 00 00 00 00    lea    rax,[rip+0x0]        # 7 <.text+0x7>
>        7:   90                      nop

Right, I did some work in that direction a while ago. But iirc there are
still cases left to be addressed.

Jan