[Lldb-commits] [lldb] [llvm] [AArch64] move extension information into tablgen (PR #90987)

[Tomas Matheson via lldb-commits]

================
@@ -11,42 +11,123 @@
 
 // A SubtargetFeature that can be toggled from the command line, and therefore
 // has an AEK_* entry in ArmExtKind.
+//
+// If Function MultiVersioning (FMV) properties are left at their defaults
+// (FEAT_INIT, no dependencies, priority 0) it indiates that this extension is
+// not an FMV feature, but can be enabled via the command line (-march, -mcpu,
+// etc).
+//
+// Conversely if the ArchExtKindSpelling is set to AEK_NONE, this indicates
+// that a feature is FMV-only, and can not be selected on the command line.
+// Such extensions should be added via FMVOnlyExtension.
 class Extension<
-  string TargetFeatureName,            // String used for -target-feature.
+  string TargetFeatureName,            // String used for -target-feature and -march, unless overridden.
   string Spelling,                     // The XYZ in HasXYZ and AEK_XYZ.
   string Desc,                         // Description.
-  list<SubtargetFeature> Implies = []  // List of dependent features.
+  list<SubtargetFeature> Implies = [], // List of dependent features.
+  // FMV properties
+  string _FMVBit = "FEAT_INIT",        // FEAT_INIT is repurposed to indicate "not an FMV feature"
+  string _FMVDependencies = "",
+  int _FMVPriority = 0
 > : SubtargetFeature<TargetFeatureName, "Has" # Spelling, "true", Desc, Implies>
 {
     string ArchExtKindSpelling = "AEK_" # Spelling; // ArchExtKind enum name.
+
+    // In general, the name written on the command line should match the name
+    // used for -target-feature. However, there are exceptions. Therefore we
+    // add a separate field for this, to allow overriding it. Strongly prefer
+    // not doing so.
+    string MArchName = TargetFeatureName;
+
+    // Function MultiVersioning (FMV) properties
+
+    // A C++ expression giving the number of the bit in the FMV ABI.
+    // Currently this is given as a value from the enum "CPUFeatures".
+    // If this is not set, it indicates that this is not an FMV extension.
+    string FMVBit = _FMVBit;
+
+    // List of features that this feature depends on.
+    // FIXME generate this from Implies.
----------------
tmatheson-arm wrote:

That would require the FMV dependencies being aligned with the existing `SubtargetFeature` dependencies, which I believe is being considered but is a WIP.

https://github.com/llvm/llvm-project/pull/90987