[AArch64] Simplify ExactFPImm GenericTable. NFC (#121827)

lookupExactFPImmByRepr is never called. The Name field in the table is
unused. The Name is only used by the GenericEnum.

Author: topperc

llvm/lib/Target/AArch64/AArch64SystemOperands.td

@@ -630,19 +630,14 @@ def ExactFPImmValues : GenericEnum {
 
 def ExactFPImmsList : GenericTable {
   let FilterClass = "ExactFPImm";
-  let Fields = ["Name", "Enum", "Repr"];
+  let Fields = ["Enum", "Repr"];
 }
 
 def lookupExactFPImmByEnum : SearchIndex {
   let Table = ExactFPImmsList;
   let Key = ["Enum"];
 }
 
-def lookupExactFPImmByRepr : SearchIndex {
-  let Table = ExactFPImmsList;
-  let Key = ["Repr"];
-}
-
 def : ExactFPImm<"zero", "0.0", 0x0>;
 def : ExactFPImm<"half", "0.5", 0x1>;
 def : ExactFPImm<"one",  "1.0", 0x2>;

llvm/lib/Target/AArch64/Utils/AArch64BaseInfo.h

@@ -564,11 +564,10 @@ LLVM_DECLARE_ENUM_AS_BITMASK(TailFoldingOpts,
                              /* LargestValue */ (long)TailFoldingOpts::Reverse);
 
 namespace AArch64ExactFPImm {
-  struct ExactFPImm {
-    const char *Name;
-    int Enum;
-    const char *Repr;
-  };
+struct ExactFPImm {
+  int Enum;
+  const char *Repr;
+};
 #define GET_ExactFPImmValues_DECL
 #define GET_ExactFPImmsList_DECL
 #include "AArch64GenSystemOperands.inc"