[llvm] [AMDGPU] New AMDGPUInsertSingleUseVDST pass (PR #72388)

[Jay Foad via llvm-commits]

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+//===- AMDGPUInsertSingleUseVDST.cpp - Insert s_singleuse_vdst instructions ==//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// Insert s_singleuse_vdst instructions on GFX11.5+ to mark regions of VALU
+/// instructions that produce single-use VGPR values. If the value is forwarded
+/// to the consumer instruction prior to VGPR writeback, the hardware can
+/// then skip (kill) the VGPR write.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPU.h"
+#include "GCNSubtarget.h"
+#include "MCTargetDesc/AMDGPUMCTargetDesc.h"
+#include "SIInstrInfo.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineOperand.h"
+#include "llvm/CodeGen/Register.h"
+#include "llvm/CodeGen/TargetSubtargetInfo.h"
+#include "llvm/IR/DebugLoc.h"
+#include "llvm/MC/MCRegister.h"
+#include "llvm/Pass.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "amdgpu-insert-single-use-vdst"
+
+namespace {
+class AMDGPUInsertSingleUseVDST : public MachineFunctionPass {
+private:
+  const SIInstrInfo *SII;
+
+public:
+  static char ID;
+
+  AMDGPUInsertSingleUseVDST() : MachineFunctionPass(ID) {}
+
+  void emitSingleUseVDST(MachineInstr &MI) const {
+    BuildMI(*MI.getParent(), MI, DebugLoc(), SII->get(AMDGPU::S_SINGLEUSE_VDST))
+        .addImm(0x1);
+  }
+
+  bool runOnMachineFunction(MachineFunction &MF) override {
+    const auto &ST = MF.getSubtarget<GCNSubtarget>();
+    if (!ST.hasVGPRSingleUseHintInsts())
+      return false;
+
+    SII = ST.getInstrInfo();
+    const auto *TRI = MF.getSubtarget().getRegisterInfo();
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jayfoad wrote:

Done

https://github.com/llvm/llvm-project/pull/72388