1 //===- GCNCreateVOPD.cpp - Create VOPD Instructions ----------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 /// \file
10 /// Combine VALU pairs into VOPD instructions
11 /// Only works on wave32
12 /// Has register requirements, we reject creating VOPD if the requirements are
13 /// not met.
14 /// shouldCombineVOPD mutator in postRA machine scheduler puts candidate
15 /// instructions for VOPD back-to-back
16 ///
17 //
18 //===----------------------------------------------------------------------===//
19 
20 #include "AMDGPU.h"
21 #include "GCNSubtarget.h"
22 #include "GCNVOPDUtils.h"
23 #include "MCTargetDesc/AMDGPUMCTargetDesc.h"
24 #include "SIInstrInfo.h"
25 #include "Utils/AMDGPUBaseInfo.h"
26 #include "llvm/ADT/SmallVector.h"
27 #include "llvm/ADT/Statistic.h"
28 #include "llvm/ADT/StringMap.h"
29 #include "llvm/CodeGen/MachineBasicBlock.h"
30 #include "llvm/CodeGen/MachineInstr.h"
31 #include "llvm/CodeGen/MachineOperand.h"
32 #include "llvm/Support/Casting.h"
33 #include "llvm/Support/Debug.h"
34 #include <utility>
35 
36 #define DEBUG_TYPE "gcn-create-vopd"
37 STATISTIC(NumVOPDCreated, "Number of VOPD Insts Created.");
38 
39 using namespace llvm;
40 
41 namespace {
42 
43 class GCNCreateVOPD : public MachineFunctionPass {
44 private:
45 public:
46   static char ID;
47   const GCNSubtarget *ST = nullptr;
48 
49   GCNCreateVOPD() : MachineFunctionPass(ID) {}
50 
51   void getAnalysisUsage(AnalysisUsage &AU) const override {
52     AU.setPreservesCFG();
53     MachineFunctionPass::getAnalysisUsage(AU);
54   }
55 
56   StringRef getPassName() const override {
57     return "GCN Create VOPD Instructions";
58   }
59 
60   bool doReplace(const SIInstrInfo *SII,
61                  std::pair<MachineInstr *, MachineInstr *> &Pair) {
62     auto *FirstMI = Pair.first;
63     auto *SecondMI = Pair.second;
64     unsigned Opc1 = FirstMI->getOpcode();
65     unsigned Opc2 = SecondMI->getOpcode();
66     int NewOpcode = AMDGPU::getVOPDFull(AMDGPU::getVOPDOpcode(Opc1),
67                                         AMDGPU::getVOPDOpcode(Opc2));
68     assert(NewOpcode != -1 &&
69            "Should have previously determined this as a possible VOPD\n");
70 
71     auto VOPDInst = BuildMI(*FirstMI->getParent(), FirstMI,
72                             FirstMI->getDebugLoc(), SII->get(NewOpcode))
73                         .setMIFlags(FirstMI->getFlags() | SecondMI->getFlags());
74 
75     namespace VOPD = AMDGPU::VOPD;
76     MachineInstr *MI[] = {FirstMI, SecondMI};
77     auto InstInfo =
78         AMDGPU::getVOPDInstInfo(FirstMI->getDesc(), SecondMI->getDesc());
79 
80     for (auto CompIdx : VOPD::COMPONENTS) {
81       auto MCOprIdx = InstInfo[CompIdx].getIndexOfDstInMCOperands();
82       VOPDInst.add(MI[CompIdx]->getOperand(MCOprIdx));
83     }
84 
85     for (auto CompIdx : VOPD::COMPONENTS) {
86       auto CompSrcOprNum = InstInfo[CompIdx].getCompSrcOperandsNum();
87       for (unsigned CompSrcIdx = 0; CompSrcIdx < CompSrcOprNum; ++CompSrcIdx) {
88         auto MCOprIdx = InstInfo[CompIdx].getIndexOfSrcInMCOperands(CompSrcIdx);
89         VOPDInst.add(MI[CompIdx]->getOperand(MCOprIdx));
90       }
91     }
92 
93     for (auto CompIdx : VOPD::COMPONENTS)
94       VOPDInst.copyImplicitOps(*MI[CompIdx]);
95 
96     LLVM_DEBUG(dbgs() << "VOPD Fused: " << *VOPDInst << " from\tX: "
97                       << *Pair.first << "\tY: " << *Pair.second << "\n");
98 
99     for (auto CompIdx : VOPD::COMPONENTS)
100       MI[CompIdx]->eraseFromParent();
101 
102     ++NumVOPDCreated;
103     return true;
104   }
105 
106   bool runOnMachineFunction(MachineFunction &MF) override {
107     if (skipFunction(MF.getFunction()))
108       return false;
109     ST = &MF.getSubtarget<GCNSubtarget>();
110     if (!AMDGPU::hasVOPD(*ST) || !ST->isWave32())
111       return false;
112     LLVM_DEBUG(dbgs() << "CreateVOPD Pass:\n");
113 
114     const SIInstrInfo *SII = ST->getInstrInfo();
115     bool Changed = false;
116 
117     SmallVector<std::pair<MachineInstr *, MachineInstr *>> ReplaceCandidates;
118 
119     for (auto &MBB : MF) {
120       auto MII = MBB.begin(), E = MBB.end();
121       while (MII != E) {
122         auto *FirstMI = &*MII;
123         MII = next_nodbg(MII, MBB.end());
124         if (MII == MBB.end())
125           break;
126         if (FirstMI->isDebugInstr())
127           continue;
128         auto *SecondMI = &*MII;
129         unsigned Opc = FirstMI->getOpcode();
130         unsigned Opc2 = SecondMI->getOpcode();
131         llvm::AMDGPU::CanBeVOPD FirstCanBeVOPD = AMDGPU::getCanBeVOPD(Opc);
132         llvm::AMDGPU::CanBeVOPD SecondCanBeVOPD = AMDGPU::getCanBeVOPD(Opc2);
133         std::pair<MachineInstr *, MachineInstr *> Pair;
134 
135         if (FirstCanBeVOPD.X && SecondCanBeVOPD.Y)
136           Pair = {FirstMI, SecondMI};
137         else if (FirstCanBeVOPD.Y && SecondCanBeVOPD.X)
138           Pair = {SecondMI, FirstMI};
139         else
140           continue;
141         // checkVOPDRegConstraints cares about program order, but doReplace
142         // cares about X-Y order in the constituted VOPD
143         if (llvm::checkVOPDRegConstraints(*SII, *FirstMI, *SecondMI)) {
144           ReplaceCandidates.push_back(Pair);
145           ++MII;
146         }
147       }
148     }
149     for (auto &Pair : ReplaceCandidates) {
150       Changed |= doReplace(SII, Pair);
151     }
152 
153     return Changed;
154   }
155 };
156 
157 } // namespace
158 
159 char GCNCreateVOPD::ID = 0;
160 
161 char &llvm::GCNCreateVOPDID = GCNCreateVOPD::ID;
162 
163 INITIALIZE_PASS(GCNCreateVOPD, DEBUG_TYPE, "GCN Create VOPD Instructions",
164                 false, false)
165