1 //===-- llvm/CodeGen/GlobalISel/CSEMIRBuilder.cpp - MIBuilder--*- C++ -*-==// 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 /// \file 9 /// This file implements the CSEMIRBuilder class which CSEs as it builds 10 /// instructions. 11 //===----------------------------------------------------------------------===// 12 // 13 14 #include "llvm/CodeGen/GlobalISel/CSEMIRBuilder.h" 15 #include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h" 16 17 using namespace llvm; 18 19 bool CSEMIRBuilder::dominates(MachineBasicBlock::const_iterator A, 20 MachineBasicBlock::const_iterator B) const { 21 auto MBBEnd = getMBB().end(); 22 if (B == MBBEnd) 23 return true; 24 assert(A->getParent() == B->getParent() && 25 "Iterators should be in same block"); 26 const MachineBasicBlock *BBA = A->getParent(); 27 MachineBasicBlock::const_iterator I = BBA->begin(); 28 for (; &*I != A && &*I != B; ++I) 29 ; 30 return &*I == A; 31 } 32 33 MachineInstrBuilder 34 CSEMIRBuilder::getDominatingInstrForID(FoldingSetNodeID &ID, 35 void *&NodeInsertPos) { 36 GISelCSEInfo *CSEInfo = getCSEInfo(); 37 assert(CSEInfo && "Can't get here without setting CSEInfo"); 38 MachineBasicBlock *CurMBB = &getMBB(); 39 MachineInstr *MI = 40 CSEInfo->getMachineInstrIfExists(ID, CurMBB, NodeInsertPos); 41 if (MI) { 42 CSEInfo->countOpcodeHit(MI->getOpcode()); 43 auto CurrPos = getInsertPt(); 44 if (!dominates(MI, CurrPos)) 45 CurMBB->splice(CurrPos, CurMBB, MI); 46 return MachineInstrBuilder(getMF(), MI); 47 } 48 return MachineInstrBuilder(); 49 } 50 51 bool CSEMIRBuilder::canPerformCSEForOpc(unsigned Opc) const { 52 const GISelCSEInfo *CSEInfo = getCSEInfo(); 53 if (!CSEInfo || !CSEInfo->shouldCSE(Opc)) 54 return false; 55 return true; 56 } 57 58 void CSEMIRBuilder::profileDstOp(const DstOp &Op, 59 GISelInstProfileBuilder &B) const { 60 switch (Op.getDstOpKind()) { 61 case DstOp::DstType::Ty_RC: 62 B.addNodeIDRegType(Op.getRegClass()); 63 break; 64 default: 65 B.addNodeIDRegType(Op.getLLTTy(*getMRI())); 66 break; 67 } 68 } 69 70 void CSEMIRBuilder::profileSrcOp(const SrcOp &Op, 71 GISelInstProfileBuilder &B) const { 72 switch (Op.getSrcOpKind()) { 73 case SrcOp::SrcType::Ty_Predicate: 74 B.addNodeIDImmediate(static_cast<int64_t>(Op.getPredicate())); 75 break; 76 default: 77 B.addNodeIDRegType(Op.getReg()); 78 break; 79 } 80 } 81 82 void CSEMIRBuilder::profileMBBOpcode(GISelInstProfileBuilder &B, 83 unsigned Opc) const { 84 // First add the MBB (Local CSE). 85 B.addNodeIDMBB(&getMBB()); 86 // Then add the opcode. 87 B.addNodeIDOpcode(Opc); 88 } 89 90 void CSEMIRBuilder::profileEverything(unsigned Opc, ArrayRef<DstOp> DstOps, 91 ArrayRef<SrcOp> SrcOps, 92 Optional<unsigned> Flags, 93 GISelInstProfileBuilder &B) const { 94 95 profileMBBOpcode(B, Opc); 96 // Then add the DstOps. 97 profileDstOps(DstOps, B); 98 // Then add the SrcOps. 99 profileSrcOps(SrcOps, B); 100 // Add Flags if passed in. 101 if (Flags) 102 B.addNodeIDFlag(*Flags); 103 } 104 105 MachineInstrBuilder CSEMIRBuilder::memoizeMI(MachineInstrBuilder MIB, 106 void *NodeInsertPos) { 107 assert(canPerformCSEForOpc(MIB->getOpcode()) && 108 "Attempting to CSE illegal op"); 109 MachineInstr *MIBInstr = MIB; 110 getCSEInfo()->insertInstr(MIBInstr, NodeInsertPos); 111 return MIB; 112 } 113 114 bool CSEMIRBuilder::checkCopyToDefsPossible(ArrayRef<DstOp> DstOps) { 115 if (DstOps.size() == 1) 116 return true; // always possible to emit copy to just 1 vreg. 117 118 return std::all_of(DstOps.begin(), DstOps.end(), [](const DstOp &Op) { 119 DstOp::DstType DT = Op.getDstOpKind(); 120 return DT == DstOp::DstType::Ty_LLT || DT == DstOp::DstType::Ty_RC; 121 }); 122 } 123 124 MachineInstrBuilder 125 CSEMIRBuilder::generateCopiesIfRequired(ArrayRef<DstOp> DstOps, 126 MachineInstrBuilder &MIB) { 127 assert(checkCopyToDefsPossible(DstOps) && 128 "Impossible return a single MIB with copies to multiple defs"); 129 if (DstOps.size() == 1) { 130 const DstOp &Op = DstOps[0]; 131 if (Op.getDstOpKind() == DstOp::DstType::Ty_Reg) 132 return buildCopy(Op.getReg(), MIB->getOperand(0).getReg()); 133 } 134 return MIB; 135 } 136 137 MachineInstrBuilder CSEMIRBuilder::buildInstr(unsigned Opc, 138 ArrayRef<DstOp> DstOps, 139 ArrayRef<SrcOp> SrcOps, 140 Optional<unsigned> Flag) { 141 switch (Opc) { 142 default: 143 break; 144 case TargetOpcode::G_ADD: 145 case TargetOpcode::G_AND: 146 case TargetOpcode::G_ASHR: 147 case TargetOpcode::G_LSHR: 148 case TargetOpcode::G_MUL: 149 case TargetOpcode::G_OR: 150 case TargetOpcode::G_SHL: 151 case TargetOpcode::G_SUB: 152 case TargetOpcode::G_XOR: 153 case TargetOpcode::G_UDIV: 154 case TargetOpcode::G_SDIV: 155 case TargetOpcode::G_UREM: 156 case TargetOpcode::G_SREM: { 157 // Try to constant fold these. 158 assert(SrcOps.size() == 2 && "Invalid sources"); 159 assert(DstOps.size() == 1 && "Invalid dsts"); 160 if (Optional<APInt> Cst = ConstantFoldBinOp(Opc, SrcOps[0].getReg(), 161 SrcOps[1].getReg(), *getMRI())) 162 return buildConstant(DstOps[0], Cst->getSExtValue()); 163 break; 164 } 165 case TargetOpcode::G_SEXT_INREG: { 166 assert(DstOps.size() == 1 && "Invalid dst ops"); 167 assert(SrcOps.size() == 2 && "Invalid src ops"); 168 const DstOp &Dst = DstOps[0]; 169 const SrcOp &Src0 = SrcOps[0]; 170 const SrcOp &Src1 = SrcOps[1]; 171 if (auto MaybeCst = 172 ConstantFoldExtOp(Opc, Src0.getReg(), Src1.getImm(), *getMRI())) 173 return buildConstant(Dst, MaybeCst->getSExtValue()); 174 break; 175 } 176 } 177 bool CanCopy = checkCopyToDefsPossible(DstOps); 178 if (!canPerformCSEForOpc(Opc)) 179 return MachineIRBuilder::buildInstr(Opc, DstOps, SrcOps, Flag); 180 // If we can CSE this instruction, but involves generating copies to multiple 181 // regs, give up. This frequently happens to UNMERGEs. 182 if (!CanCopy) { 183 auto MIB = MachineIRBuilder::buildInstr(Opc, DstOps, SrcOps, Flag); 184 // CSEInfo would have tracked this instruction. Remove it from the temporary 185 // insts. 186 getCSEInfo()->handleRemoveInst(&*MIB); 187 return MIB; 188 } 189 FoldingSetNodeID ID; 190 GISelInstProfileBuilder ProfBuilder(ID, *getMRI()); 191 void *InsertPos = nullptr; 192 profileEverything(Opc, DstOps, SrcOps, Flag, ProfBuilder); 193 MachineInstrBuilder MIB = getDominatingInstrForID(ID, InsertPos); 194 if (MIB) { 195 // Handle generating copies here. 196 return generateCopiesIfRequired(DstOps, MIB); 197 } 198 // This instruction does not exist in the CSEInfo. Build it and CSE it. 199 MachineInstrBuilder NewMIB = 200 MachineIRBuilder::buildInstr(Opc, DstOps, SrcOps, Flag); 201 return memoizeMI(NewMIB, InsertPos); 202 } 203 204 MachineInstrBuilder CSEMIRBuilder::buildConstant(const DstOp &Res, 205 const ConstantInt &Val) { 206 constexpr unsigned Opc = TargetOpcode::G_CONSTANT; 207 if (!canPerformCSEForOpc(Opc)) 208 return MachineIRBuilder::buildConstant(Res, Val); 209 210 // For vectors, CSE the element only for now. 211 LLT Ty = Res.getLLTTy(*getMRI()); 212 if (Ty.isVector()) 213 return buildSplatVector(Res, buildConstant(Ty.getElementType(), Val)); 214 215 FoldingSetNodeID ID; 216 GISelInstProfileBuilder ProfBuilder(ID, *getMRI()); 217 void *InsertPos = nullptr; 218 profileMBBOpcode(ProfBuilder, Opc); 219 profileDstOp(Res, ProfBuilder); 220 ProfBuilder.addNodeIDMachineOperand(MachineOperand::CreateCImm(&Val)); 221 MachineInstrBuilder MIB = getDominatingInstrForID(ID, InsertPos); 222 if (MIB) { 223 // Handle generating copies here. 224 return generateCopiesIfRequired({Res}, MIB); 225 } 226 227 MachineInstrBuilder NewMIB = MachineIRBuilder::buildConstant(Res, Val); 228 return memoizeMI(NewMIB, InsertPos); 229 } 230 231 MachineInstrBuilder CSEMIRBuilder::buildFConstant(const DstOp &Res, 232 const ConstantFP &Val) { 233 constexpr unsigned Opc = TargetOpcode::G_FCONSTANT; 234 if (!canPerformCSEForOpc(Opc)) 235 return MachineIRBuilder::buildFConstant(Res, Val); 236 237 // For vectors, CSE the element only for now. 238 LLT Ty = Res.getLLTTy(*getMRI()); 239 if (Ty.isVector()) 240 return buildSplatVector(Res, buildFConstant(Ty.getElementType(), Val)); 241 242 FoldingSetNodeID ID; 243 GISelInstProfileBuilder ProfBuilder(ID, *getMRI()); 244 void *InsertPos = nullptr; 245 profileMBBOpcode(ProfBuilder, Opc); 246 profileDstOp(Res, ProfBuilder); 247 ProfBuilder.addNodeIDMachineOperand(MachineOperand::CreateFPImm(&Val)); 248 MachineInstrBuilder MIB = getDominatingInstrForID(ID, InsertPos); 249 if (MIB) { 250 // Handle generating copies here. 251 return generateCopiesIfRequired({Res}, MIB); 252 } 253 MachineInstrBuilder NewMIB = MachineIRBuilder::buildFConstant(Res, Val); 254 return memoizeMI(NewMIB, InsertPos); 255 } 256