Re: [RESEND v1 2/3] x86/cpufeatures: Generate a feature mask header based on build config

[H. Peter Anvin]

On June 16, 2024 12:26:48 AM PDT, Xin Li <xin@xxxxxxxxx> wrote:
>On 5/9/2024 1:53 PM, Xin Li (Intel) wrote:
>> From: "H. Peter Anvin (Intel)" <hpa@xxxxxxxxx>
>> 
>> Introduce an AWK script to auto-generate a header with required and
>> disabled feature masks based on <asm/cpufeatures.h> and current build
>> config. Thus for any CPU feature with a build config, e.g., X86_FRED,
>> simply add
>
>...
>
>> +
>> +		printf "\n#define %s_MASKS ", s;
>> +		pfx = "{";
>> +		for (i = 0; i < ncapints; i++) {
>> +			printf "%s \\\n\t%s_MASK_%d", pfx, s, i;
>> +			pfx = ",";
>> +		}
>> +		printf " \\\n}\n\n";
>> +
>> +		printf "#define %s_FEATURE(x) \\\n", s;
>> +		printf "\t((( ";
>> +		for (i = 0; i < ncapints; i++) {
>> +			if (masks[i]) {
>> +				printf "\\\n\t\t((x) >> 5) == %2d ? %s_MASK%-3d : ", i, s, i;
>> +			}
>> +		}
>> +		printf "0 \\\n";
>> +		printf "\t) >> ((x) & 31)) & 1)\n\n";
>
>This code generates macros {REQUIRED,DISABLED}_FEATURE(x) to tell if a
>CPU feature, e.g., X86_FEATURE_FRED, is a required or disabled feature
>for this particular compile-time configuration.
>
>But they are NOT currently used, so I prefer to remove them for now.
>
>Thanks!
>    Xin

The goal with these is that it can eliminate the handwritten code that tests a long list of masks. Again, automation.