1 //===-- SystemZSelectionDAGInfo.cpp - SystemZ SelectionDAG Info -----------===// 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 implements the SystemZSelectionDAGInfo class. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "SystemZTargetMachine.h" 14 #include "llvm/CodeGen/SelectionDAG.h" 15 16 using namespace llvm; 17 18 #define DEBUG_TYPE "systemz-selectiondag-info" 19 20 // Decide whether it is best to use a loop or straight-line code for 21 // a block operation of Size bytes with source address Src and destination 22 // address Dest. Sequence is the opcode to use for straight-line code 23 // (such as MVC) and Loop is the opcode to use for loops (such as MVC_LOOP). 24 // Return the chain for the completed operation. 25 static SDValue emitMemMem(SelectionDAG &DAG, const SDLoc &DL, unsigned Sequence, 26 unsigned Loop, SDValue Chain, SDValue Dst, 27 SDValue Src, uint64_t Size) { 28 EVT PtrVT = Src.getValueType(); 29 // The heuristic we use is to prefer loops for anything that would 30 // require 7 or more MVCs. With these kinds of sizes there isn't 31 // much to choose between straight-line code and looping code, 32 // since the time will be dominated by the MVCs themselves. 33 // However, the loop has 4 or 5 instructions (depending on whether 34 // the base addresses can be proved equal), so there doesn't seem 35 // much point using a loop for 5 * 256 bytes or fewer. Anything in 36 // the range (5 * 256, 6 * 256) will need another instruction after 37 // the loop, so it doesn't seem worth using a loop then either. 38 // The next value up, 6 * 256, can be implemented in the same 39 // number of straight-line MVCs as 6 * 256 - 1. 40 if (Size > 6 * 256) 41 return DAG.getNode(Loop, DL, MVT::Other, Chain, Dst, Src, 42 DAG.getConstant(Size, DL, PtrVT), 43 DAG.getConstant(Size / 256, DL, PtrVT)); 44 return DAG.getNode(Sequence, DL, MVT::Other, Chain, Dst, Src, 45 DAG.getConstant(Size, DL, PtrVT)); 46 } 47 48 SDValue SystemZSelectionDAGInfo::EmitTargetCodeForMemcpy( 49 SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Dst, SDValue Src, 50 SDValue Size, unsigned Align, bool IsVolatile, bool AlwaysInline, 51 MachinePointerInfo DstPtrInfo, MachinePointerInfo SrcPtrInfo) const { 52 if (IsVolatile) 53 return SDValue(); 54 55 if (auto *CSize = dyn_cast<ConstantSDNode>(Size)) 56 return emitMemMem(DAG, DL, SystemZISD::MVC, SystemZISD::MVC_LOOP, 57 Chain, Dst, Src, CSize->getZExtValue()); 58 return SDValue(); 59 } 60 61 // Handle a memset of 1, 2, 4 or 8 bytes with the operands given by 62 // Chain, Dst, ByteVal and Size. These cases are expected to use 63 // MVI, MVHHI, MVHI and MVGHI respectively. 64 static SDValue memsetStore(SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, 65 SDValue Dst, uint64_t ByteVal, uint64_t Size, 66 unsigned Align, MachinePointerInfo DstPtrInfo) { 67 uint64_t StoreVal = ByteVal; 68 for (unsigned I = 1; I < Size; ++I) 69 StoreVal |= ByteVal << (I * 8); 70 return DAG.getStore( 71 Chain, DL, DAG.getConstant(StoreVal, DL, MVT::getIntegerVT(Size * 8)), 72 Dst, DstPtrInfo, Align); 73 } 74 75 SDValue SystemZSelectionDAGInfo::EmitTargetCodeForMemset( 76 SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Dst, 77 SDValue Byte, SDValue Size, unsigned Align, bool IsVolatile, 78 MachinePointerInfo DstPtrInfo) const { 79 EVT PtrVT = Dst.getValueType(); 80 81 if (IsVolatile) 82 return SDValue(); 83 84 if (auto *CSize = dyn_cast<ConstantSDNode>(Size)) { 85 uint64_t Bytes = CSize->getZExtValue(); 86 if (Bytes == 0) 87 return SDValue(); 88 if (auto *CByte = dyn_cast<ConstantSDNode>(Byte)) { 89 // Handle cases that can be done using at most two of 90 // MVI, MVHI, MVHHI and MVGHI. The latter two can only be 91 // used if ByteVal is all zeros or all ones; in other casees, 92 // we can move at most 2 halfwords. 93 uint64_t ByteVal = CByte->getZExtValue(); 94 if (ByteVal == 0 || ByteVal == 255 ? 95 Bytes <= 16 && countPopulation(Bytes) <= 2 : 96 Bytes <= 4) { 97 unsigned Size1 = Bytes == 16 ? 8 : 1 << findLastSet(Bytes); 98 unsigned Size2 = Bytes - Size1; 99 SDValue Chain1 = memsetStore(DAG, DL, Chain, Dst, ByteVal, Size1, 100 Align, DstPtrInfo); 101 if (Size2 == 0) 102 return Chain1; 103 Dst = DAG.getNode(ISD::ADD, DL, PtrVT, Dst, 104 DAG.getConstant(Size1, DL, PtrVT)); 105 DstPtrInfo = DstPtrInfo.getWithOffset(Size1); 106 SDValue Chain2 = memsetStore(DAG, DL, Chain, Dst, ByteVal, Size2, 107 std::min(Align, Size1), DstPtrInfo); 108 return DAG.getNode(ISD::TokenFactor, DL, MVT::Other, Chain1, Chain2); 109 } 110 } else { 111 // Handle one and two bytes using STC. 112 if (Bytes <= 2) { 113 SDValue Chain1 = DAG.getStore(Chain, DL, Byte, Dst, DstPtrInfo, Align); 114 if (Bytes == 1) 115 return Chain1; 116 SDValue Dst2 = DAG.getNode(ISD::ADD, DL, PtrVT, Dst, 117 DAG.getConstant(1, DL, PtrVT)); 118 SDValue Chain2 = 119 DAG.getStore(Chain, DL, Byte, Dst2, DstPtrInfo.getWithOffset(1), 120 /* Alignment = */ 1); 121 return DAG.getNode(ISD::TokenFactor, DL, MVT::Other, Chain1, Chain2); 122 } 123 } 124 assert(Bytes >= 2 && "Should have dealt with 0- and 1-byte cases already"); 125 126 // Handle the special case of a memset of 0, which can use XC. 127 auto *CByte = dyn_cast<ConstantSDNode>(Byte); 128 if (CByte && CByte->getZExtValue() == 0) 129 return emitMemMem(DAG, DL, SystemZISD::XC, SystemZISD::XC_LOOP, 130 Chain, Dst, Dst, Bytes); 131 132 // Copy the byte to the first location and then use MVC to copy 133 // it to the rest. 134 Chain = DAG.getStore(Chain, DL, Byte, Dst, DstPtrInfo, Align); 135 SDValue DstPlus1 = DAG.getNode(ISD::ADD, DL, PtrVT, Dst, 136 DAG.getConstant(1, DL, PtrVT)); 137 return emitMemMem(DAG, DL, SystemZISD::MVC, SystemZISD::MVC_LOOP, 138 Chain, DstPlus1, Dst, Bytes - 1); 139 } 140 return SDValue(); 141 } 142 143 // Use CLC to compare [Src1, Src1 + Size) with [Src2, Src2 + Size), 144 // deciding whether to use a loop or straight-line code. 145 static SDValue emitCLC(SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, 146 SDValue Src1, SDValue Src2, uint64_t Size) { 147 SDVTList VTs = DAG.getVTList(MVT::i32, MVT::Other); 148 EVT PtrVT = Src1.getValueType(); 149 // A two-CLC sequence is a clear win over a loop, not least because it 150 // needs only one branch. A three-CLC sequence needs the same number 151 // of branches as a loop (i.e. 2), but is shorter. That brings us to 152 // lengths greater than 768 bytes. It seems relatively likely that 153 // a difference will be found within the first 768 bytes, so we just 154 // optimize for the smallest number of branch instructions, in order 155 // to avoid polluting the prediction buffer too much. A loop only ever 156 // needs 2 branches, whereas a straight-line sequence would need 3 or more. 157 if (Size > 3 * 256) 158 return DAG.getNode(SystemZISD::CLC_LOOP, DL, VTs, Chain, Src1, Src2, 159 DAG.getConstant(Size, DL, PtrVT), 160 DAG.getConstant(Size / 256, DL, PtrVT)); 161 return DAG.getNode(SystemZISD::CLC, DL, VTs, Chain, Src1, Src2, 162 DAG.getConstant(Size, DL, PtrVT)); 163 } 164 165 // Convert the current CC value into an integer that is 0 if CC == 0, 166 // greater than zero if CC == 1 and less than zero if CC >= 2. 167 // The sequence starts with IPM, which puts CC into bits 29 and 28 168 // of an integer and clears bits 30 and 31. 169 static SDValue addIPMSequence(const SDLoc &DL, SDValue CCReg, 170 SelectionDAG &DAG) { 171 SDValue IPM = DAG.getNode(SystemZISD::IPM, DL, MVT::i32, CCReg); 172 SDValue SHL = DAG.getNode(ISD::SHL, DL, MVT::i32, IPM, 173 DAG.getConstant(30 - SystemZ::IPM_CC, DL, MVT::i32)); 174 SDValue SRA = DAG.getNode(ISD::SRA, DL, MVT::i32, SHL, 175 DAG.getConstant(30, DL, MVT::i32)); 176 return SRA; 177 } 178 179 std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::EmitTargetCodeForMemcmp( 180 SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Src1, 181 SDValue Src2, SDValue Size, MachinePointerInfo Op1PtrInfo, 182 MachinePointerInfo Op2PtrInfo) const { 183 if (auto *CSize = dyn_cast<ConstantSDNode>(Size)) { 184 uint64_t Bytes = CSize->getZExtValue(); 185 assert(Bytes > 0 && "Caller should have handled 0-size case"); 186 // Swap operands to invert CC == 1 vs. CC == 2 cases. 187 SDValue CCReg = emitCLC(DAG, DL, Chain, Src2, Src1, Bytes); 188 Chain = CCReg.getValue(1); 189 return std::make_pair(addIPMSequence(DL, CCReg, DAG), Chain); 190 } 191 return std::make_pair(SDValue(), SDValue()); 192 } 193 194 std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::EmitTargetCodeForMemchr( 195 SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Src, 196 SDValue Char, SDValue Length, MachinePointerInfo SrcPtrInfo) const { 197 // Use SRST to find the character. End is its address on success. 198 EVT PtrVT = Src.getValueType(); 199 SDVTList VTs = DAG.getVTList(PtrVT, MVT::i32, MVT::Other); 200 Length = DAG.getZExtOrTrunc(Length, DL, PtrVT); 201 Char = DAG.getZExtOrTrunc(Char, DL, MVT::i32); 202 Char = DAG.getNode(ISD::AND, DL, MVT::i32, Char, 203 DAG.getConstant(255, DL, MVT::i32)); 204 SDValue Limit = DAG.getNode(ISD::ADD, DL, PtrVT, Src, Length); 205 SDValue End = DAG.getNode(SystemZISD::SEARCH_STRING, DL, VTs, Chain, 206 Limit, Src, Char); 207 SDValue CCReg = End.getValue(1); 208 Chain = End.getValue(2); 209 210 // Now select between End and null, depending on whether the character 211 // was found. 212 SDValue Ops[] = { 213 End, DAG.getConstant(0, DL, PtrVT), 214 DAG.getTargetConstant(SystemZ::CCMASK_SRST, DL, MVT::i32), 215 DAG.getTargetConstant(SystemZ::CCMASK_SRST_FOUND, DL, MVT::i32), CCReg}; 216 End = DAG.getNode(SystemZISD::SELECT_CCMASK, DL, PtrVT, Ops); 217 return std::make_pair(End, Chain); 218 } 219 220 std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::EmitTargetCodeForStrcpy( 221 SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Dest, 222 SDValue Src, MachinePointerInfo DestPtrInfo, MachinePointerInfo SrcPtrInfo, 223 bool isStpcpy) const { 224 SDVTList VTs = DAG.getVTList(Dest.getValueType(), MVT::Other); 225 SDValue EndDest = DAG.getNode(SystemZISD::STPCPY, DL, VTs, Chain, Dest, Src, 226 DAG.getConstant(0, DL, MVT::i32)); 227 return std::make_pair(isStpcpy ? EndDest : Dest, EndDest.getValue(1)); 228 } 229 230 std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::EmitTargetCodeForStrcmp( 231 SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Src1, 232 SDValue Src2, MachinePointerInfo Op1PtrInfo, 233 MachinePointerInfo Op2PtrInfo) const { 234 SDVTList VTs = DAG.getVTList(Src1.getValueType(), MVT::i32, MVT::Other); 235 // Swap operands to invert CC == 1 vs. CC == 2 cases. 236 SDValue Unused = DAG.getNode(SystemZISD::STRCMP, DL, VTs, Chain, Src2, Src1, 237 DAG.getConstant(0, DL, MVT::i32)); 238 SDValue CCReg = Unused.getValue(1); 239 Chain = Unused.getValue(2); 240 return std::make_pair(addIPMSequence(DL, CCReg, DAG), Chain); 241 } 242 243 // Search from Src for a null character, stopping once Src reaches Limit. 244 // Return a pair of values, the first being the number of nonnull characters 245 // and the second being the out chain. 246 // 247 // This can be used for strlen by setting Limit to 0. 248 static std::pair<SDValue, SDValue> getBoundedStrlen(SelectionDAG &DAG, 249 const SDLoc &DL, 250 SDValue Chain, SDValue Src, 251 SDValue Limit) { 252 EVT PtrVT = Src.getValueType(); 253 SDVTList VTs = DAG.getVTList(PtrVT, MVT::i32, MVT::Other); 254 SDValue End = DAG.getNode(SystemZISD::SEARCH_STRING, DL, VTs, Chain, 255 Limit, Src, DAG.getConstant(0, DL, MVT::i32)); 256 Chain = End.getValue(2); 257 SDValue Len = DAG.getNode(ISD::SUB, DL, PtrVT, End, Src); 258 return std::make_pair(Len, Chain); 259 } 260 261 std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::EmitTargetCodeForStrlen( 262 SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Src, 263 MachinePointerInfo SrcPtrInfo) const { 264 EVT PtrVT = Src.getValueType(); 265 return getBoundedStrlen(DAG, DL, Chain, Src, DAG.getConstant(0, DL, PtrVT)); 266 } 267 268 std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::EmitTargetCodeForStrnlen( 269 SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Src, 270 SDValue MaxLength, MachinePointerInfo SrcPtrInfo) const { 271 EVT PtrVT = Src.getValueType(); 272 MaxLength = DAG.getZExtOrTrunc(MaxLength, DL, PtrVT); 273 SDValue Limit = DAG.getNode(ISD::ADD, DL, PtrVT, Src, MaxLength); 274 return getBoundedStrlen(DAG, DL, Chain, Src, Limit); 275 } 276