[AArch64] Merge duplicate extension information.

When we moved the extension information into tablegen in llvm#90987, some
features (FEAT_DPB, FEAT_DPB2, FEAT_FLAGM2, FEAT_FRINTTS, FEAT_RCPC2)
were defined as FMVOnlyExtension despite already having an equivalent
SubtargetFeature in place. This patch is fusing these duplications.

llvm/include/llvm/TargetParser/AArch64TargetParser.h

@@ -229,7 +229,10 @@ inline constexpr ExtensionDependency ExtensionDependencies[] = {
   {AEK_LSE, AEK_LSE128},
   {AEK_PREDRES, AEK_SPECRES2},
   {AEK_RAS, AEK_RASV2},
-  {AEK_RCPC, AEK_RCPC3},
+  {AEK_RCPC, AEK_RCPC2},
+  {AEK_RCPC2, AEK_RCPC3},
+  {AEK_FLAGM, AEK_FLAGM2},
+  {AEK_DPB, AEK_DPB2},
 };
 // clang-format on
 

llvm/lib/Target/AArch64/AArch64Features.td

@@ -75,17 +75,12 @@ class FMVOnlyExtension<string FMVBit, string Name, string Deps, int Priority>
 }
 
 def : FMVOnlyExtension<"FEAT_DGH", "dgh", "", 260>;
-def : FMVOnlyExtension<"FEAT_DPB", "dpb", "+ccpp", 190>;
-def : FMVOnlyExtension<"FEAT_DPB2", "dpb2", "+ccpp,+ccdp", 200>;
 def : FMVOnlyExtension<"FEAT_EBF16", "ebf16", "+bf16", 290>;
-def : FMVOnlyExtension<"FEAT_FLAGM2", "flagm2", "+flagm,+altnzcv", 30>;
-def : FMVOnlyExtension<"FEAT_FRINTTS", "frintts", "+fptoint", 250>;
 def : FMVOnlyExtension<"FEAT_LS64_ACCDATA", "ls64_accdata", "+ls64", 540>;
 def : FMVOnlyExtension<"FEAT_LS64_V", "ls64_v", "", 530>;
 def : FMVOnlyExtension<"FEAT_MEMTAG2", "memtag2", "+mte", 450>;
 def : FMVOnlyExtension<"FEAT_MEMTAG3", "memtag3", "+mte", 460>;
 def : FMVOnlyExtension<"FEAT_PMULL", "pmull", "+aes,+fp-armv8,+neon", 160>;
-def : FMVOnlyExtension<"FEAT_RCPC2", "rcpc2", "+rcpc", 240>;
 def : FMVOnlyExtension<"FEAT_RPRES", "rpres", "", 300>;
 def : FMVOnlyExtension<"FEAT_SHA1", "sha1", "+fp-armv8,+neon", 120>;
 def : FMVOnlyExtension<"FEAT_SSBS2", "ssbs2", "+ssbs", 500>;
@@ -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>;
 
 def FeatureSVE : Extension<"sve", "SVE",
   "Enable Scalable Vector Extension (SVE) instructions (FEAT_SVE)", [FeatureFullFP16],
@@ -491,9 +488,10 @@ def FeatureFlagM : Extension<
     "FEAT_FLAGM", "+flagm", 20>;
 
 // 8.4 RCPC enchancements: LDAPR & STLR instructions with Immediate Offset
-def FeatureRCPC_IMMO : SubtargetFeature<"rcpc-immo", "HasRCPC_IMMO", "true",
+let ArchExtKindSpelling = "AEK_RCPC2", MArchName = "rcpc2" in
+def FeatureRCPC_IMMO : Extension<"rcpc-immo", "RCPC_IMMO",
     "Enable v8.4-A RCPC instructions with Immediate Offsets (FEAT_LRCPC2)",
-    [FeatureRCPC]>;
+    [FeatureRCPC], "FEAT_RCPC2", "+rcpc", 240>;
 
 def FeatureNoNegativeImmediates : SubtargetFeature<"no-neg-immediates",
                                         "NegativeImmediates", "false",
@@ -525,12 +523,16 @@ def FeatureAggressiveFMA :
                    "true",
                    "Enable Aggressive FMA for floating-point.">;
 
-def FeatureAltFPCmp : SubtargetFeature<"altnzcv", "HasAlternativeNZCV", "true",
-  "Enable alternative NZCV format for floating point comparisons (FEAT_FlagM2)">;
+let ArchExtKindSpelling = "AEK_FLAGM2", MArchName = "flagm2" in
+def FeatureAltFPCmp : Extension<"altnzcv", "AlternativeNZCV",
+  "Enable alternative NZCV format for floating point comparisons (FEAT_FlagM2)",
+  [FeatureFlagM], "FEAT_FLAGM2", "+flagm,+altnzcv", 30>;
 
-def FeatureFRInt3264 : SubtargetFeature<"fptoint", "HasFRInt3264", "true",
+let ArchExtKindSpelling = "AEK_FRINTTS", MArchName = "frintts" in
+def FeatureFRInt3264 : Extension<"fptoint", "FRInt3264",
   "Enable FRInt[32|64][Z|X] instructions that round a floating-point number to "
-  "an integer (in FP format) forcing it to fit into a 32- or 64-bit int (FEAT_FRINTTS)" >;
+  "an integer (in FP format) forcing it to fit into a 32- or 64-bit int (FEAT_FRINTTS)",
+  [], "FEAT_FRINTTS", "+fptoint", 250>;
 
 def FeatureSpecRestrict : SubtargetFeature<"specrestrict", "HasSpecRestrict",
   "true", "Enable architectural speculation restriction (FEAT_CSV2_2)">;
@@ -547,8 +549,10 @@ def FeaturePredRes : Extension<"predres", "PredRes",
   "Enable v8.5a execution and data prediction invalidation instructions (FEAT_SPECRES)", [],
   "FEAT_PREDRES", "+predres", 480>;
 
-def FeatureCacheDeepPersist : SubtargetFeature<"ccdp", "CCDP", "true",
-    "Enable v8.5 Cache Clean to Point of Deep Persistence (FEAT_DPB2)" >;
+let ArchExtKindSpelling = "AEK_DPB2", MArchName = "dpb2" in
+def FeatureCacheDeepPersist : Extension<"ccdp", "CCDP",
+    "Enable v8.5 Cache Clean to Point of Deep Persistence (FEAT_DPB2)",
+    [FeatureCCPP], "FEAT_DPB2", "+ccpp,+ccdp", 200>;
 
 let ArchExtKindSpelling = "AEK_NONE" in
 def FeatureBranchTargetId : Extension<"bti", "BTI",