[clang] [compiler-rt] [llvm] [FMV][AArch64] Unify ls64, ls64_v and ls64_accdata. (PR #108024)

[Tomas Matheson via cfe-commits]

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@@ -73,8 +73,6 @@ enum CPUFeatures {
   FEAT_SSBS,
   FEAT_SSBS2,
   FEAT_BTI,
-  FEAT_LS64,
-  FEAT_LS64_V,
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tmatheson-arm wrote:

@Wilco1 could you explain the scenario you are worried about in more detail? What you posted above appears to be a snippet of a generated resolver, suggesting that the problematic scenario is:
- You have an old object file which contains a resolver.
- The resolver refers to bit 36 and has references to `__init_cpu_features_resolver` (defined in `compiler-rt`)
- You link against a new `compiler-rt`, which has changed the meaning of bit 36.

I don't think step 3 is allowed. The compiler and compiler-rt need to remain in sync, afaik?

There are no references to specific bit numbers outside of the generated resolvers and `__init_cpu_features_resolver`.

https://github.com/llvm/llvm-project/pull/108024