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/CodeGen/MachineBasicBlock.h"
29 #include "llvm/CodeGen/MachineInstr.h"
30 #include "llvm/CodeGen/MachineOperand.h"
31 #include "llvm/Support/Casting.h"
32 #include "llvm/Support/Debug.h"
33 #include <utility>
34 
35 #define DEBUG_TYPE "gcn-create-vopd"
36 STATISTIC(NumVOPDCreated, "Number of VOPD Insts Created.");
37 
38 using namespace llvm;
39 
40 namespace {
41 
42 class GCNCreateVOPD : public MachineFunctionPass {
43 private:
44     class VOPDCombineInfo {
45     public:
46       VOPDCombineInfo() {}
47       VOPDCombineInfo(MachineInstr *First, MachineInstr *Second)
48           : FirstMI(First), SecondMI(Second) {}
49 
50       MachineInstr *FirstMI;
51       MachineInstr *SecondMI;
52     };
53 
54 public:
55   static char ID;
56   const GCNSubtarget *ST = nullptr;
57 
58   GCNCreateVOPD() : MachineFunctionPass(ID) {}
59 
60   void getAnalysisUsage(AnalysisUsage &AU) const override {
61     AU.setPreservesCFG();
62     MachineFunctionPass::getAnalysisUsage(AU);
63   }
64 
65   StringRef getPassName() const override {
66     return "GCN Create VOPD Instructions";
67   }
68 
69   bool doReplace(const SIInstrInfo *SII, VOPDCombineInfo &CI) {
70     auto *FirstMI = CI.FirstMI;
71     auto *SecondMI = CI.SecondMI;
72     unsigned Opc1 = FirstMI->getOpcode();
73     unsigned Opc2 = SecondMI->getOpcode();
74     unsigned EncodingFamily =
75         AMDGPU::getVOPDEncodingFamily(SII->getSubtarget());
76     int NewOpcode =
77         AMDGPU::getVOPDFull(AMDGPU::getVOPDOpcode(Opc1),
78                             AMDGPU::getVOPDOpcode(Opc2), EncodingFamily);
79     assert(NewOpcode != -1 &&
80            "Should have previously determined this as a possible VOPD\n");
81 
82     auto VOPDInst = BuildMI(*FirstMI->getParent(), FirstMI,
83                             FirstMI->getDebugLoc(), SII->get(NewOpcode))
84                         .setMIFlags(FirstMI->getFlags() | SecondMI->getFlags());
85 
86     namespace VOPD = AMDGPU::VOPD;
87     MachineInstr *MI[] = {FirstMI, SecondMI};
88     auto InstInfo =
89         AMDGPU::getVOPDInstInfo(FirstMI->getDesc(), SecondMI->getDesc());
90 
91     for (auto CompIdx : VOPD::COMPONENTS) {
92       auto MCOprIdx = InstInfo[CompIdx].getIndexOfDstInMCOperands();
93       VOPDInst.add(MI[CompIdx]->getOperand(MCOprIdx));
94     }
95 
96     for (auto CompIdx : VOPD::COMPONENTS) {
97       auto CompSrcOprNum = InstInfo[CompIdx].getCompSrcOperandsNum();
98       for (unsigned CompSrcIdx = 0; CompSrcIdx < CompSrcOprNum; ++CompSrcIdx) {
99         auto MCOprIdx = InstInfo[CompIdx].getIndexOfSrcInMCOperands(CompSrcIdx);
100         VOPDInst.add(MI[CompIdx]->getOperand(MCOprIdx));
101       }
102     }
103 
104     for (auto CompIdx : VOPD::COMPONENTS)
105       VOPDInst.copyImplicitOps(*MI[CompIdx]);
106 
107     LLVM_DEBUG(dbgs() << "VOPD Fused: " << *VOPDInst << " from\tX: "
108                       << *CI.FirstMI << "\tY: " << *CI.SecondMI << "\n");
109 
110     for (auto CompIdx : VOPD::COMPONENTS)
111       MI[CompIdx]->eraseFromParent();
112 
113     ++NumVOPDCreated;
114     return true;
115   }
116 
117   bool runOnMachineFunction(MachineFunction &MF) override {
118     if (skipFunction(MF.getFunction()))
119       return false;
120     ST = &MF.getSubtarget<GCNSubtarget>();
121     if (!AMDGPU::hasVOPD(*ST) || !ST->isWave32())
122       return false;
123     LLVM_DEBUG(dbgs() << "CreateVOPD Pass:\n");
124 
125     const SIInstrInfo *SII = ST->getInstrInfo();
126     bool Changed = false;
127 
128     SmallVector<VOPDCombineInfo> ReplaceCandidates;
129 
130     for (auto &MBB : MF) {
131       auto MII = MBB.begin(), E = MBB.end();
132       while (MII != E) {
133         auto *FirstMI = &*MII;
134         MII = next_nodbg(MII, MBB.end());
135         if (MII == MBB.end())
136           break;
137         if (FirstMI->isDebugInstr())
138           continue;
139         auto *SecondMI = &*MII;
140         unsigned Opc = FirstMI->getOpcode();
141         unsigned Opc2 = SecondMI->getOpcode();
142         llvm::AMDGPU::CanBeVOPD FirstCanBeVOPD = AMDGPU::getCanBeVOPD(Opc);
143         llvm::AMDGPU::CanBeVOPD SecondCanBeVOPD = AMDGPU::getCanBeVOPD(Opc2);
144         VOPDCombineInfo CI;
145 
146         if (FirstCanBeVOPD.X && SecondCanBeVOPD.Y)
147           CI = VOPDCombineInfo(FirstMI, SecondMI);
148         else if (FirstCanBeVOPD.Y && SecondCanBeVOPD.X)
149           CI = VOPDCombineInfo(SecondMI, FirstMI);
150         else
151           continue;
152         // checkVOPDRegConstraints cares about program order, but doReplace
153         // cares about X-Y order in the constituted VOPD
154         if (llvm::checkVOPDRegConstraints(*SII, *FirstMI, *SecondMI)) {
155           ReplaceCandidates.push_back(CI);
156           ++MII;
157         }
158       }
159     }
160     for (auto &CI : ReplaceCandidates) {
161       Changed |= doReplace(SII, CI);
162     }
163 
164     return Changed;
165   }
166 };
167 
168 } // namespace
169 
170 char GCNCreateVOPD::ID = 0;
171 
172 char &llvm::GCNCreateVOPDID = GCNCreateVOPD::ID;
173 
174 INITIALIZE_PASS(GCNCreateVOPD, DEBUG_TYPE, "GCN Create VOPD Instructions",
175                 false, false)
176