[clang] [compiler-rt] [llvm] [FMV] Remove useless features according the latest ACLE spec. (PR #88965)

[Jon Roelofs via cfe-commits]

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@@ -67,57 +67,42 @@ enum CPUFeatures {
   FEAT_FP,
   FEAT_SIMD,
   FEAT_CRC,
-  FEAT_SHA1,
   FEAT_SHA2,
   FEAT_SHA3,
   FEAT_AES,
-  FEAT_PMULL,
   FEAT_FP16,
-  FEAT_DIT,
   FEAT_DPB,
   FEAT_DPB2,
   FEAT_JSCVT,
   FEAT_FCMA,
   FEAT_RCPC,
   FEAT_RCPC2,
   FEAT_FRINTTS,
-  FEAT_DGH,
   FEAT_I8MM,
   FEAT_BF16,
-  FEAT_EBF16,
   FEAT_RPRES,
   FEAT_SVE,
-  FEAT_SVE_BF16,
-  FEAT_SVE_EBF16,
-  FEAT_SVE_I8MM,
   FEAT_SVE_F32MM,
   FEAT_SVE_F64MM,
   FEAT_SVE2,
   FEAT_SVE_AES,
-  FEAT_SVE_PMULL128,
   FEAT_SVE_BITPERM,
   FEAT_SVE_SHA3,
   FEAT_SVE_SM4,
   FEAT_SME,
   FEAT_MEMTAG,
-  FEAT_MEMTAG2,
-  FEAT_MEMTAG3,
   FEAT_SB,
   FEAT_PREDRES,
   FEAT_SSBS,
-  FEAT_SSBS2,
-  FEAT_BTI,
   FEAT_LS64,
-  FEAT_LS64_V,
-  FEAT_LS64_ACCDATA,
   FEAT_WFXT,
   FEAT_SME_F64,
   FEAT_SME_I64,
   FEAT_SME2,
   FEAT_RCPC3,
   FEAT_MOPS,
   FEAT_MAX,
-  FEAT_EXT = 62, // Reserved to indicate presence of additional features field
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jroelofs wrote:

Did any implementation ship `__aarch64_cpu_features` in a way that would make this an ABI break? We (Apple) talked about putting these in libSystem, and now I am glad we did not. It's okay to change/reorder them if it is a private implementation detail between the compiler and compiler-rt that is shipped with it, but as soon as they're part of an ABI, this list must become append only.

https://github.com/llvm/llvm-project/pull/88965