[llvm] [AArch64] Merge duplicate extension information. (PR #92319)

[Tomas Matheson via llvm-commits]

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@@ -216,8 +211,10 @@ def FeaturePAN_RWV : SubtargetFeature<
 def FeaturePsUAO : SubtargetFeature< "uaops", "HasPsUAO", "true",
     "Enable v8.2 UAO PState (FEAT_UAO)">;
 
-def FeatureCCPP : SubtargetFeature<"ccpp", "HasCCPP",
-    "true", "Enable v8.2 data Cache Clean to Point of Persistence (FEAT_DPB)" >;
+let ArchExtKindSpelling = "AEK_DPB", MArchName = "dpb" in
+def FeatureCCPP : Extension<"ccpp", "CCPP",
+    "Enable v8.2 data Cache Clean to Point of Persistence (FEAT_DPB)", [],
+    "FEAT_DPB", "+ccpp", 190>;
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tmatheson-arm wrote:

Making each of these into Extensions will cause `-march=` and `__attribute__((target(...)))` to accept them. That might be a good idea, but I think it requires coordination with GCC. And if that's the intention there should be tests for each case.

https://github.com/llvm/llvm-project/pull/92319