[llvm] [RISCV] Add sched model for XiangShan-NanHu (PR #70232)

[Wang Pengcheng via llvm-commits]

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+//==- RISCVSchedXiangShanNanHu.td - XiangShan-NanHu Scheduling Definitions --*- 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
+//
+//===-------------------------------------------------------------------------------------===//
+
+//===-------------------------------------------------------------------------------------===//
+
+// XiangShan is a high-performance open-source RISC-V processor developed by
+// the Institute of Computing Technology (ICT), Chinese Academy of Sciences.
+// Source: https://github.com/OpenXiangShan/XiangShan
+// Documentation: https://github.com/OpenXiangShan/XiangShan-doc
+
+// XiangShan-NanHu is the second generation of XiangShan processor series.
+// Overview: https://xiangshan-doc.readthedocs.io/zh-cn/latest/integration/overview/
+
+def XiangShanNanHuModel : SchedMachineModel {
+  let MicroOpBufferSize = 256;
+  let LoopMicroOpBufferSize = 48;  // Instruction queue size
+  let IssueWidth = 6;  // 6-way decode and dispatch
+  let LoadLatency = 4;
+  let MispredictPenalty = 11; // Based on estimate of pipeline depth.
+  let CompleteModel = 0;
+  let PostRAScheduler = 1; // Enable Post RegAlloc Scheduler pass.
+  let UnsupportedFeatures = [];
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wangpc-pp wrote:

Add `UnsupportedFeatures`? I don't think XiangShan has implement all extensions.

https://github.com/llvm/llvm-project/pull/70232