[llvm] [AArch64] Initial sched model for Neoverse N3 (PR #106371)

[via llvm-commits]

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+//=- AArch64SchedNeoverseN3.td - NeoverseN3 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the scheduling model for the Arm Neoverse N3 processors.
+//
+//===----------------------------------------------------------------------===//
+
+def NeoverseN3Model : SchedMachineModel {
+    let IssueWidth            =  10; // Micro-ops dispatched at a time.
+    let MicroOpBufferSize     = 160; // Entries in micro-op re-order buffer. NOTE: Copied from N2.
+    let LoadLatency           =   4; // Optimistic load latency.
+    let MispredictPenalty     =  10; // Extra cycles for mispredicted branch. NOTE: Copied from N2.
+    let LoopMicroOpBufferSize =  16; // NOTE: Copied from Cortex-A57.
+    let CompleteModel         =   1;
+
+    list<Predicate> UnsupportedFeatures = !listconcat(SMEUnsupported.F,
+        [HasSVE2p1, HasPAuthLR, HasCPA, HasCSSC]);
+}
+
+//===----------------------------------------------------------------------===//
+// Define each kind of processor resource and number available on Neoverse N3.
+// Instructions are first fetched and then decoded into internal Macro-OPerations
+// (MOPs). From there, the MOPs proceed through register renaming and dispatch stages.
+// A MOP can be split into two Micro-OPerations (µOPs) further down the pipeline
+// after the decode stage. Once dispatched, µOPs wait for their operands and issue
+// out-of-order to one of thirteen issue pipelines. Each issue pipeline can accept
+// one µOP per cycle.
+
+let SchedModel = NeoverseN3Model in {
+
+// Define the (13) issue ports.
+def N3UnitB   : ProcResource<2>;  // Branch 0/1
+def N3UnitS   : ProcResource<2>;  // Integer Single-Cycle 0/1
+def N3UnitM0  : ProcResource<1>;  // Integer Single/Multi-Cycle 0
+def N3UnitM1  : ProcResource<1>;  // Integer Single/Multi-Cycle 1
+def N3UnitV0  : ProcResource<1>;  // FP/ASIMD 0
+def N3UnitV1  : ProcResource<1>;  // FP/ASIMD 1
+def N3UnitD   : ProcResource<2>;  // Integer Store data 0/1
+def N3UnitL01 : ProcResource<2>;  // Load/Store 0/1
+def N3UnitL2  : ProcResource<1>;  // Load 2
+
+def N3UnitI : ProcResGroup<[N3UnitS, N3UnitM0, N3UnitM1]>;
+def N3UnitM : ProcResGroup<[N3UnitM0, N3UnitM1]>;
+def N3UnitL : ProcResGroup<[N3UnitL01, N3UnitL2]>;
+def N3UnitV : ProcResGroup<[N3UnitV0, N3UnitV1]>;
+
+//===----------------------------------------------------------------------===//
+
+def : ReadAdvance<ReadI,       0>;
+def : ReadAdvance<ReadISReg,   0>;
+def : ReadAdvance<ReadIEReg,   0>;
+def : ReadAdvance<ReadIM,      0>;
+def : ReadAdvance<ReadIMA,     1, [WriteIM32, WriteIM64]>;
+def : ReadAdvance<ReadID,      0>;
+def : ReadAdvance<ReadExtrHi,  0>;
+def : ReadAdvance<ReadAdrBase, 0>;
+def : ReadAdvance<ReadST,      0>;
+def : ReadAdvance<ReadVLD,     0>;
+
+def : WriteRes<WriteAtomic,  []> { let Unsupported = 1; }
+def : WriteRes<WriteFDiv,    []> { let Unsupported = 1; }
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FLZ101 wrote:

Since they are not used by the sched model. Is it better to set them even they are not used? 

https://github.com/llvm/llvm-project/pull/106371