1 //===-- X86LowerTileCopy.cpp - Expand Tile Copy 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 // This file defines the pass which lower AMX tile copy instructions. Since
10 // there is no tile copy instruction, we need store tile register to stack
11 // and load from stack to another tile register. We need extra GR to hold
12 // the stride, and we need stack slot to hold the tile data register.
13 // We would run this pass after copy propagation, so that we don't miss copy
14 // optimization. And we would run this pass before prolog/epilog insertion,
15 // so that we can allocate stack slot.
16 //
17 //===----------------------------------------------------------------------===//
18 
19 #include "X86.h"
20 #include "X86InstrBuilder.h"
21 #include "X86InstrInfo.h"
22 #include "X86Subtarget.h"
23 #include "llvm/CodeGen/MachineBasicBlock.h"
24 #include "llvm/CodeGen/MachineFrameInfo.h"
25 #include "llvm/CodeGen/MachineFunction.h"
26 #include "llvm/CodeGen/MachineFunctionPass.h"
27 #include "llvm/CodeGen/MachineInstr.h"
28 #include "llvm/CodeGen/MachineInstrBuilder.h"
29 #include "llvm/CodeGen/MachineOperand.h"
30 #include "llvm/CodeGen/Passes.h"
31 #include "llvm/IR/DebugLoc.h"
32 #include "llvm/InitializePasses.h"
33 #include "llvm/Support/Debug.h"
34 
35 using namespace llvm;
36 
37 #define DEBUG_TYPE "x86-lower-tile-copy"
38 
39 namespace {
40 
41 class X86LowerTileCopy : public MachineFunctionPass {
42 public:
43   static char ID;
44 
45   X86LowerTileCopy() : MachineFunctionPass(ID) {}
46 
47   void getAnalysisUsage(AnalysisUsage &AU) const override;
48 
49   bool runOnMachineFunction(MachineFunction &MF) override;
50 
51   StringRef getPassName() const override { return "X86 Lower Tile Copy"; }
52 };
53 
54 } // namespace
55 
56 char X86LowerTileCopy::ID = 0;
57 
58 INITIALIZE_PASS_BEGIN(X86LowerTileCopy, "lowertilecopy", "Tile Copy Lowering",
59                       false, false)
60 INITIALIZE_PASS_END(X86LowerTileCopy, "lowertilecopy", "Tile Copy Lowering",
61                     false, false)
62 
63 void X86LowerTileCopy::getAnalysisUsage(AnalysisUsage &AU) const {
64   AU.setPreservesAll();
65   MachineFunctionPass::getAnalysisUsage(AU);
66 }
67 
68 FunctionPass *llvm::createX86LowerTileCopyPass() {
69   return new X86LowerTileCopy();
70 }
71 
72 bool X86LowerTileCopy::runOnMachineFunction(MachineFunction &MF) {
73   const X86Subtarget &ST = MF.getSubtarget<X86Subtarget>();
74   const X86InstrInfo *TII = ST.getInstrInfo();
75   bool Changed = false;
76 
77   for (MachineBasicBlock &MBB : MF) {
78     for (MachineBasicBlock::iterator MII = MBB.begin(), MIE = MBB.end();
79          MII != MIE;) {
80       MachineInstr &MI = *MII++;
81       if (!MI.isCopy())
82         continue;
83       MachineOperand &DstMO = MI.getOperand(0);
84       MachineOperand &SrcMO = MI.getOperand(1);
85       Register SrcReg = SrcMO.getReg();
86       Register DstReg = DstMO.getReg();
87       if (!X86::TILERegClass.contains(DstReg, SrcReg))
88         continue;
89 
90       const TargetRegisterInfo *TRI = ST.getRegisterInfo();
91       // Allocate stack slot for tile register
92       unsigned Size = TRI->getSpillSize(X86::TILERegClass);
93       Align Alignment = TRI->getSpillAlign(X86::TILERegClass);
94       int TileSS = MF.getFrameInfo().CreateSpillStackObject(Size, Alignment);
95       // Allocate stack slot for stride register
96       Size = TRI->getSpillSize(X86::GR64RegClass);
97       Alignment = TRI->getSpillAlign(X86::GR64RegClass);
98       int StrideSS = MF.getFrameInfo().CreateSpillStackObject(Size, Alignment);
99 
100       // TODO: Pick a killed regiter to avoid save/reload. There is problem
101       // to get live interval in this stage.
102       Register GR64Cand = X86::RAX;
103 
104       const DebugLoc &DL = MI.getDebugLoc();
105       // mov %rax (%sp)
106       BuildMI(MBB, MI, DL, TII->get(X86::IMPLICIT_DEF), GR64Cand);
107       addFrameReference(BuildMI(MBB, MI, DL, TII->get(X86::MOV64mr)), StrideSS)
108           .addReg(GR64Cand);
109       // mov 64 %rax
110       BuildMI(MBB, MI, DL, TII->get(X86::MOV64ri), GR64Cand).addImm(64);
111       // tilestored %tmm, (%sp, %idx)
112       unsigned Opc = X86::TILESTORED;
113       MachineInstr *NewMI =
114           addFrameReference(BuildMI(MBB, MI, DL, TII->get(Opc)), TileSS)
115               .addReg(SrcReg, getKillRegState(SrcMO.isKill()));
116       MachineOperand &MO = NewMI->getOperand(2);
117       MO.setReg(GR64Cand);
118       MO.setIsKill(true);
119       // tileloadd (%sp, %idx), %tmm
120       Opc = X86::TILELOADD;
121       NewMI = addFrameReference(BuildMI(MBB, MI, DL, TII->get(Opc), DstReg),
122                                 TileSS);
123       // restore %rax
124       // mov (%sp) %rax
125       addFrameReference(BuildMI(MBB, MI, DL, TII->get(X86::MOV64rm), GR64Cand),
126                         StrideSS);
127       MI.eraseFromParent();
128       Changed = true;
129     }
130   }
131   return Changed;
132 }
133