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

From: Xin Li
Date: Sun Jun 16 2024 - 03:27:53 EST


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