[llvm] [RISCV] SiFive7 VLDS Sched should not depend on VL when stride is x0. (PR #70266)

[Wang Pengcheng via llvm-commits]

================
@@ -62,6 +62,45 @@ multiclass LMULSEWWriteResMXSEW<string name, list<ProcResourceKind> resources,
     def : WriteRes<!cast<SchedWrite>(name # "_WorstCase"), resources>;
 }
 
+// Define a SchedAlias for the SchedWrite associated with (name, mx) whose
+// behavior is aliased to a Variant. The Variant has Latency predLad and
+// ReleaseAtCycles predCycles if the SchedPredicate Pred is true, otherwise has
+// Latency noPredLat and ReleaseAtCycles noPredCycles. The WorstCase SchedWrite
+// is created similiarly if IsWorstCase is true. The prefix is used to uniquely
+// define SchedWriteRes and Variant resources.
+multiclass LMULWriteResMXVariant<string name, SchedPredicate Pred,
+                                 list<ProcResourceKind> resources,
+                                 int predLat, list<int> predCycles,
+                                 int noPredLat, list<int> noPredCycles,
+                                 string mx, bit IsWorstCase, string prefix> {
+  defvar nameMX = prefix # name # "_" # mx;
+
+  // Define the different behaviors
+  def nameMX # "_Pred" : SchedWriteRes<resources>
----------------
wangpc-pp wrote:

The name of `SchedAlias` doesn't matter I think, we can just use the form `defm "SiFive7" : LMULWriteResMXVariant`.

https://github.com/llvm/llvm-project/pull/70266