[llvm] [RISCV] Add SiFiveP600Model SchedModel that is used by sifive-p670 (PR #84962)

[Philip Reames via llvm-commits]

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+//==- RISCVSchedSiFiveP600.td - SiFiveP600 Scheduling Defs ---*- tablegen -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+//===----------------------------------------------------------------------===//
+
+/// c is true if mx has the worst case behavior compared to LMULs in MxList.
+/// On the SiFiveP600, the worst case LMUL is the Largest LMUL
+/// and the worst case sew is the smallest SEW for that LMUL.
+class SiFiveP600IsWorstCaseMX<string mx, list<string> MxList> {
+  string LLMUL = LargestLMUL<MxList>.r;
+  bit c = !eq(mx, LLMUL);
+}
+
+class SiFiveP600IsWorstCaseMXSEW<string mx, int sew, list<string> MxList, bit isF = 0> {
+  string LLMUL = LargestLMUL<MxList>.r;
+  int SSEW = SmallestSEW<mx, isF>.r;
+  bit c = !and(!eq(mx, LLMUL), !eq(sew, SSEW));
+}
+
+// 1 Micro-Op per cycle.
+class SiFiveP600GetLMulCycles<string mx> {
+  int c = !cond(
+    !eq(mx, "M1") : 1,
+    !eq(mx, "M2") : 2,
+    !eq(mx, "M4") : 4,
+    !eq(mx, "M8") : 8,
+    !eq(mx, "MF2") : 1,
+    !eq(mx, "MF4") : 1,
+    !eq(mx, "MF8") : 1
+  );
+}
+
+// Latency for segmented loads and stores are calculated as vl * nf.
+class SiFiveP600GetCyclesSegmented<string mx, int sew, int nf> {
+  defvar VLEN = 128;
+  defvar VLUpperBound = !cond(
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preames wrote:

This looks to simply be computing VLMAX.  If we don't already have a shared utility for that, we should extract one.  

https://github.com/llvm/llvm-project/pull/84962