1 //===-- HexagonPeephole.cpp - Hexagon Peephole Optimiztions ---------------===// 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 // This peephole pass optimizes in the following cases. 8 // 1. Optimizes redundant sign extends for the following case 9 // Transform the following pattern 10 // %170 = SXTW %166 11 // ... 12 // %176 = COPY %170:isub_lo 13 // 14 // Into 15 // %176 = COPY %166 16 // 17 // 2. Optimizes redundant negation of predicates. 18 // %15 = CMPGTrr %6, %2 19 // ... 20 // %16 = NOT_p killed %15 21 // ... 22 // JMP_c killed %16, <%bb.1>, implicit dead %pc 23 // 24 // Into 25 // %15 = CMPGTrr %6, %2; 26 // ... 27 // JMP_cNot killed %15, <%bb.1>, implicit dead %pc; 28 // 29 // Note: The peephole pass makes the instrucstions like 30 // %170 = SXTW %166 or %16 = NOT_p killed %15 31 // redundant and relies on some form of dead removal instructions, like 32 // DCE or DIE to actually eliminate them. 33 34 //===----------------------------------------------------------------------===// 35 36 #include "Hexagon.h" 37 #include "HexagonTargetMachine.h" 38 #include "llvm/ADT/DenseMap.h" 39 #include "llvm/ADT/Statistic.h" 40 #include "llvm/CodeGen/MachineFunction.h" 41 #include "llvm/CodeGen/MachineFunctionPass.h" 42 #include "llvm/CodeGen/MachineInstrBuilder.h" 43 #include "llvm/CodeGen/MachineRegisterInfo.h" 44 #include "llvm/CodeGen/Passes.h" 45 #include "llvm/CodeGen/TargetInstrInfo.h" 46 #include "llvm/CodeGen/TargetRegisterInfo.h" 47 #include "llvm/IR/Constants.h" 48 #include "llvm/Pass.h" 49 #include "llvm/Support/CommandLine.h" 50 #include "llvm/Support/Debug.h" 51 #include "llvm/Support/raw_ostream.h" 52 #include "llvm/Target/TargetMachine.h" 53 #include <algorithm> 54 55 using namespace llvm; 56 57 #define DEBUG_TYPE "hexagon-peephole" 58 59 static cl::opt<bool> 60 DisableHexagonPeephole("disable-hexagon-peephole", cl::Hidden, 61 cl::desc("Disable Peephole Optimization")); 62 63 static cl::opt<bool> DisablePNotP("disable-hexagon-pnotp", cl::Hidden, 64 cl::desc("Disable Optimization of PNotP")); 65 66 static cl::opt<bool> 67 DisableOptSZExt("disable-hexagon-optszext", cl::Hidden, cl::init(true), 68 cl::desc("Disable Optimization of Sign/Zero Extends")); 69 70 static cl::opt<bool> 71 DisableOptExtTo64("disable-hexagon-opt-ext-to-64", cl::Hidden, 72 cl::init(true), 73 cl::desc("Disable Optimization of extensions to i64.")); 74 75 namespace llvm { 76 FunctionPass *createHexagonPeephole(); 77 void initializeHexagonPeepholePass(PassRegistry&); 78 } 79 80 namespace { 81 struct HexagonPeephole : public MachineFunctionPass { 82 const HexagonInstrInfo *QII; 83 const HexagonRegisterInfo *QRI; 84 const MachineRegisterInfo *MRI; 85 86 public: 87 static char ID; 88 HexagonPeephole() : MachineFunctionPass(ID) { 89 initializeHexagonPeepholePass(*PassRegistry::getPassRegistry()); 90 } 91 92 bool runOnMachineFunction(MachineFunction &MF) override; 93 94 StringRef getPassName() const override { 95 return "Hexagon optimize redundant zero and size extends"; 96 } 97 98 void getAnalysisUsage(AnalysisUsage &AU) const override { 99 MachineFunctionPass::getAnalysisUsage(AU); 100 } 101 }; 102 } 103 104 char HexagonPeephole::ID = 0; 105 106 INITIALIZE_PASS(HexagonPeephole, "hexagon-peephole", "Hexagon Peephole", 107 false, false) 108 109 bool HexagonPeephole::runOnMachineFunction(MachineFunction &MF) { 110 if (skipFunction(MF.getFunction())) 111 return false; 112 113 QII = static_cast<const HexagonInstrInfo *>(MF.getSubtarget().getInstrInfo()); 114 QRI = MF.getSubtarget<HexagonSubtarget>().getRegisterInfo(); 115 MRI = &MF.getRegInfo(); 116 117 DenseMap<unsigned, unsigned> PeepholeMap; 118 DenseMap<unsigned, std::pair<unsigned, unsigned> > PeepholeDoubleRegsMap; 119 120 if (DisableHexagonPeephole) return false; 121 122 // Loop over all of the basic blocks. 123 for (MachineBasicBlock &MBB : MF) { 124 PeepholeMap.clear(); 125 PeepholeDoubleRegsMap.clear(); 126 127 // Traverse the basic block. 128 for (MachineInstr &MI : llvm::make_early_inc_range(MBB)) { 129 // Look for sign extends: 130 // %170 = SXTW %166 131 if (!DisableOptSZExt && MI.getOpcode() == Hexagon::A2_sxtw) { 132 assert(MI.getNumOperands() == 2); 133 MachineOperand &Dst = MI.getOperand(0); 134 MachineOperand &Src = MI.getOperand(1); 135 Register DstReg = Dst.getReg(); 136 Register SrcReg = Src.getReg(); 137 // Just handle virtual registers. 138 if (DstReg.isVirtual() && SrcReg.isVirtual()) { 139 // Map the following: 140 // %170 = SXTW %166 141 // PeepholeMap[170] = %166 142 PeepholeMap[DstReg] = SrcReg; 143 } 144 } 145 146 // Look for %170 = COMBINE_ir_V4 (0, %169) 147 // %170:DoublRegs, %169:IntRegs 148 if (!DisableOptExtTo64 && MI.getOpcode() == Hexagon::A4_combineir) { 149 assert(MI.getNumOperands() == 3); 150 MachineOperand &Dst = MI.getOperand(0); 151 MachineOperand &Src1 = MI.getOperand(1); 152 MachineOperand &Src2 = MI.getOperand(2); 153 if (Src1.getImm() != 0) 154 continue; 155 Register DstReg = Dst.getReg(); 156 Register SrcReg = Src2.getReg(); 157 PeepholeMap[DstReg] = SrcReg; 158 } 159 160 // Look for this sequence below 161 // %DoubleReg1 = LSRd_ri %DoubleReg0, 32 162 // %IntReg = COPY %DoubleReg1:isub_lo. 163 // and convert into 164 // %IntReg = COPY %DoubleReg0:isub_hi. 165 if (MI.getOpcode() == Hexagon::S2_lsr_i_p) { 166 assert(MI.getNumOperands() == 3); 167 MachineOperand &Dst = MI.getOperand(0); 168 MachineOperand &Src1 = MI.getOperand(1); 169 MachineOperand &Src2 = MI.getOperand(2); 170 if (Src2.getImm() != 32) 171 continue; 172 Register DstReg = Dst.getReg(); 173 Register SrcReg = Src1.getReg(); 174 PeepholeDoubleRegsMap[DstReg] = 175 std::make_pair(*&SrcReg, Hexagon::isub_hi); 176 } 177 178 // Look for P=NOT(P). 179 if (!DisablePNotP && MI.getOpcode() == Hexagon::C2_not) { 180 assert(MI.getNumOperands() == 2); 181 MachineOperand &Dst = MI.getOperand(0); 182 MachineOperand &Src = MI.getOperand(1); 183 Register DstReg = Dst.getReg(); 184 Register SrcReg = Src.getReg(); 185 // Just handle virtual registers. 186 if (DstReg.isVirtual() && SrcReg.isVirtual()) { 187 // Map the following: 188 // %170 = NOT_xx %166 189 // PeepholeMap[170] = %166 190 PeepholeMap[DstReg] = SrcReg; 191 } 192 } 193 194 // Look for copy: 195 // %176 = COPY %170:isub_lo 196 if (!DisableOptSZExt && MI.isCopy()) { 197 assert(MI.getNumOperands() == 2); 198 MachineOperand &Dst = MI.getOperand(0); 199 MachineOperand &Src = MI.getOperand(1); 200 201 // Make sure we are copying the lower 32 bits. 202 if (Src.getSubReg() != Hexagon::isub_lo) 203 continue; 204 205 Register DstReg = Dst.getReg(); 206 Register SrcReg = Src.getReg(); 207 if (DstReg.isVirtual() && SrcReg.isVirtual()) { 208 // Try to find in the map. 209 if (unsigned PeepholeSrc = PeepholeMap.lookup(SrcReg)) { 210 // Change the 1st operand. 211 MI.removeOperand(1); 212 MI.addOperand(MachineOperand::CreateReg(PeepholeSrc, false)); 213 } else { 214 DenseMap<unsigned, std::pair<unsigned, unsigned> >::iterator DI = 215 PeepholeDoubleRegsMap.find(SrcReg); 216 if (DI != PeepholeDoubleRegsMap.end()) { 217 std::pair<unsigned,unsigned> PeepholeSrc = DI->second; 218 MI.removeOperand(1); 219 MI.addOperand(MachineOperand::CreateReg( 220 PeepholeSrc.first, false /*isDef*/, false /*isImp*/, 221 false /*isKill*/, false /*isDead*/, false /*isUndef*/, 222 false /*isEarlyClobber*/, PeepholeSrc.second)); 223 } 224 } 225 } 226 } 227 228 // Look for Predicated instructions. 229 if (!DisablePNotP) { 230 bool Done = false; 231 if (QII->isPredicated(MI)) { 232 MachineOperand &Op0 = MI.getOperand(0); 233 Register Reg0 = Op0.getReg(); 234 const TargetRegisterClass *RC0 = MRI->getRegClass(Reg0); 235 if (RC0->getID() == Hexagon::PredRegsRegClassID) { 236 // Handle instructions that have a prediate register in op0 237 // (most cases of predicable instructions). 238 if (Reg0.isVirtual()) { 239 // Try to find in the map. 240 if (unsigned PeepholeSrc = PeepholeMap.lookup(Reg0)) { 241 // Change the 1st operand and, flip the opcode. 242 MI.getOperand(0).setReg(PeepholeSrc); 243 MRI->clearKillFlags(PeepholeSrc); 244 int NewOp = QII->getInvertedPredicatedOpcode(MI.getOpcode()); 245 MI.setDesc(QII->get(NewOp)); 246 Done = true; 247 } 248 } 249 } 250 } 251 252 if (!Done) { 253 // Handle special instructions. 254 unsigned Op = MI.getOpcode(); 255 unsigned NewOp = 0; 256 unsigned PR = 1, S1 = 2, S2 = 3; // Operand indices. 257 258 switch (Op) { 259 case Hexagon::C2_mux: 260 case Hexagon::C2_muxii: 261 NewOp = Op; 262 break; 263 case Hexagon::C2_muxri: 264 NewOp = Hexagon::C2_muxir; 265 break; 266 case Hexagon::C2_muxir: 267 NewOp = Hexagon::C2_muxri; 268 break; 269 } 270 if (NewOp) { 271 Register PSrc = MI.getOperand(PR).getReg(); 272 if (unsigned POrig = PeepholeMap.lookup(PSrc)) { 273 BuildMI(MBB, MI.getIterator(), MI.getDebugLoc(), QII->get(NewOp), 274 MI.getOperand(0).getReg()) 275 .addReg(POrig) 276 .add(MI.getOperand(S2)) 277 .add(MI.getOperand(S1)); 278 MRI->clearKillFlags(POrig); 279 MI.eraseFromParent(); 280 } 281 } // if (NewOp) 282 } // if (!Done) 283 284 } // if (!DisablePNotP) 285 286 } // Instruction 287 } // Basic Block 288 return true; 289 } 290 291 FunctionPass *llvm::createHexagonPeephole() { 292 return new HexagonPeephole(); 293 } 294