[PATCH] arm: ignore inapplicable .arch=no...

[Jan Beulich]

On 30.04.2025 16:10, Richard Earnshaw (lists) wrote:
> On 30/04/2025 14:34, Jan Beulich wrote:
>> Unlike for command line options, where a base architecture needs to be
>> provided explicitly, the .arch directive doesn't have such a
>> requirement. Therefore it is odd that disabling of an inapplicable
>> extension isn't silently ignored; claiming "not allowed for the current
>> base architecture" is at best misleading. Simply skip the error path,
>> leveraging that in such a case ARM_CLEAR_FEATURE() is (supposed to be)
>> a no-op.
>>
>> --- a/gas/config/tc-arm.c
>> +++ b/gas/config/tc-arm.c
>> @@ -32792,7 +32792,7 @@ s_arm_arch_extension (int ignored ATTRIB
>>  	      break;
>>  	  }
>>  
>> -	if (i == nb_allowed_archs)
>> +	if (i == nb_allowed_archs && adding_value)
>>  	  {
>>  	    as_bad (_("architectural extension `%s' is not allowed for the "
>>  		      "current base architecture"), name);
> 
> 
> Sorry, I don't follow the logic you have in mind.  Trying to enable, for example, MVE on an a-profile architecture is completely meaningless and should be diagnosed as an error in the source file.

Of course; the change here is about disabling of extensions.

> Can you give an example of what you're trying to permit here?

The example I noticed this was with ".arch nocrypto" under -march=all. I
simply don't think this needs diagnosing. And if there was a diagnostic,
I think it shouldn't say "crypto", kind of suggesting that's being turned
on, not off.

Jan