[llvm] [RISCV] Use TableGen-based macro fusion (PR #72224)

[Mikhail Gudim via llvm-commits]

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@@ -469,6 +473,67 @@ class SchedAlias<SchedReadWrite match, SchedReadWrite alias> {
   SchedMachineModel SchedModel = ?;
 }
 
+// Base class of MacroFusionPredicate, etc. The avaliable variables are:
+// * const TargetInstrInfo &TII
+// * const TargetSubtargetInfo &STI
+// * const MachineRegisterInfo &MRI
+// * const MachineInstr *FirstMI
+// * const MachineInstr &SecondMI
+class MacroFusionPredicateBase;
+
+// MacroFusionPredicate with raw code predicate.
+class MacroFusionPredicate<code pred> : MacroFusionPredicateBase {
+  code Predicate = pred;
+}
+
+// Binds firstOpIdx and secondOpIdx. The operand of `FirstMI` at position
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mgudim wrote:

In llvm custom terminology is `tied` operand, rather than `bind`.

https://github.com/llvm/llvm-project/pull/72224