[clang] [compiler-rt] [llvm] [X86] Sync multiversion features with libgcc and refactor internal feature tables (PR #168750)

[Phoebe Wang via llvm-commits]

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@@ -556,6 +550,10 @@ constexpr FeatureBitset ImpliedFeaturesRETPOLINE_INDIRECT_BRANCHES = {};
 constexpr FeatureBitset ImpliedFeaturesRETPOLINE_INDIRECT_CALLS = {};
 constexpr FeatureBitset ImpliedFeaturesLVI_CFI = {};
 constexpr FeatureBitset ImpliedFeaturesLVI_LOAD_HARDENING = {};
+constexpr FeatureBitset ImpliedFeaturesX86_64_BASELINE = {};
+constexpr FeatureBitset ImpliedFeaturesX86_64_V2 = {};
+constexpr FeatureBitset ImpliedFeaturesX86_64_V3 = {};
+constexpr FeatureBitset ImpliedFeaturesX86_64_V4 = {};
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phoebewang wrote:

Why we need to define these? They are not single features. See X86_64VXFeatures in X86.td.

https://github.com/llvm/llvm-project/pull/168750