[llvm] [TableGen] Add a backend to generate MacroFusion predicators (PR #72222)

[Joe Nash via llvm-commits]

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@@ -584,3 +584,116 @@ class MemoryQueue<ProcResourceKind PR> {
 
 class LoadQueue<ProcResourceKind LDQueue> : MemoryQueue<LDQueue>;
 class StoreQueue<ProcResourceKind STQueue> : MemoryQueue<STQueue>;
+
+// The target instruction that FusionPredicate will evaluate on.
+class FusionTarget;
+def first : FusionTarget;
+def second : FusionTarget;
+def both : FusionTarget;
+
+// Base class of FusionPredicate, etc. The avaliable variables are:
+// * const TargetInstrInfo &TII
+// * const TargetSubtargetInfo &STI
+// * const MachineRegisterInfo &MRI
+// * const MachineInstr *FirstMI
+// * const MachineInstr &SecondMI
+class FusionPredicate<FusionTarget target> {
+  FusionTarget Target = target;
+}
+class FirstFusionPredicate: FusionPredicate<first>;
+class SecondFusionPredicate: FusionPredicate<second>;
+class BothFusionPredicate: FusionPredicate<both>;
+
+// FusionPredicate with raw code predicate.
+class FusionPredicateWithCode<code pred> : FusionPredicate<both> {
+  code Predicate = pred;
+}
+
+// FusionPredicate with MCInstPredicate.
+class FusionPredicateWithMCInstPredicate<FusionTarget target, MCInstPredicate pred>
+  : FusionPredicate<target> {
+  MCInstPredicate Predicate = pred;
+}
+class FirstFusionPredicateWithMCInstPredicate<MCInstPredicate pred>
+  : FusionPredicateWithMCInstPredicate<first, pred>;
+class SecondFusionPredicateWithMCInstPredicate<MCInstPredicate pred>
+  : FusionPredicateWithMCInstPredicate<second, pred>;
+// The pred will be applied on both firstMI and secondMI.
+class BothFusionPredicateWithMCInstPredicate<MCInstPredicate pred>
+  : FusionPredicateWithMCInstPredicate<second, pred>;
+
+// Tie firstOpIdx and secondOpIdx. The operand of `FirstMI` at position
+// `firstOpIdx` should be the same as the operand of `SenondMI` at position
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Sisyph wrote:

Typo SenondMI -> SecondMI

https://github.com/llvm/llvm-project/pull/72222