1 //===-- SystemZSelectionDAGInfo.cpp - SystemZ SelectionDAG Info -----------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file implements the SystemZSelectionDAGInfo class. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "SystemZTargetMachine.h" 15 #include "llvm/CodeGen/SelectionDAG.h" 16 17 using namespace llvm; 18 19 #define DEBUG_TYPE "systemz-selectiondag-info" 20 21 SystemZSelectionDAGInfo::SystemZSelectionDAGInfo(const DataLayout &DL) 22 : TargetSelectionDAGInfo(&DL) {} 23 24 SystemZSelectionDAGInfo::~SystemZSelectionDAGInfo() { 25 } 26 27 // Decide whether it is best to use a loop or straight-line code for 28 // a block operation of Size bytes with source address Src and destination 29 // address Dest. Sequence is the opcode to use for straight-line code 30 // (such as MVC) and Loop is the opcode to use for loops (such as MVC_LOOP). 31 // Return the chain for the completed operation. 32 static SDValue emitMemMem(SelectionDAG &DAG, SDLoc DL, unsigned Sequence, 33 unsigned Loop, SDValue Chain, SDValue Dst, 34 SDValue Src, uint64_t Size) { 35 EVT PtrVT = Src.getValueType(); 36 // The heuristic we use is to prefer loops for anything that would 37 // require 7 or more MVCs. With these kinds of sizes there isn't 38 // much to choose between straight-line code and looping code, 39 // since the time will be dominated by the MVCs themselves. 40 // However, the loop has 4 or 5 instructions (depending on whether 41 // the base addresses can be proved equal), so there doesn't seem 42 // much point using a loop for 5 * 256 bytes or fewer. Anything in 43 // the range (5 * 256, 6 * 256) will need another instruction after 44 // the loop, so it doesn't seem worth using a loop then either. 45 // The next value up, 6 * 256, can be implemented in the same 46 // number of straight-line MVCs as 6 * 256 - 1. 47 if (Size > 6 * 256) 48 return DAG.getNode(Loop, DL, MVT::Other, Chain, Dst, Src, 49 DAG.getConstant(Size, PtrVT), 50 DAG.getConstant(Size / 256, PtrVT)); 51 return DAG.getNode(Sequence, DL, MVT::Other, Chain, Dst, Src, 52 DAG.getConstant(Size, PtrVT)); 53 } 54 55 SDValue SystemZSelectionDAGInfo:: 56 EmitTargetCodeForMemcpy(SelectionDAG &DAG, SDLoc DL, SDValue Chain, 57 SDValue Dst, SDValue Src, SDValue Size, unsigned Align, 58 bool IsVolatile, bool AlwaysInline, 59 MachinePointerInfo DstPtrInfo, 60 MachinePointerInfo SrcPtrInfo) const { 61 if (IsVolatile) 62 return SDValue(); 63 64 if (auto *CSize = dyn_cast<ConstantSDNode>(Size)) 65 return emitMemMem(DAG, DL, SystemZISD::MVC, SystemZISD::MVC_LOOP, 66 Chain, Dst, Src, CSize->getZExtValue()); 67 return SDValue(); 68 } 69 70 // Handle a memset of 1, 2, 4 or 8 bytes with the operands given by 71 // Chain, Dst, ByteVal and Size. These cases are expected to use 72 // MVI, MVHHI, MVHI and MVGHI respectively. 73 static SDValue memsetStore(SelectionDAG &DAG, SDLoc DL, SDValue Chain, 74 SDValue Dst, uint64_t ByteVal, uint64_t Size, 75 unsigned Align, 76 MachinePointerInfo DstPtrInfo) { 77 uint64_t StoreVal = ByteVal; 78 for (unsigned I = 1; I < Size; ++I) 79 StoreVal |= ByteVal << (I * 8); 80 return DAG.getStore(Chain, DL, 81 DAG.getConstant(StoreVal, MVT::getIntegerVT(Size * 8)), 82 Dst, DstPtrInfo, false, false, Align); 83 } 84 85 SDValue SystemZSelectionDAGInfo:: 86 EmitTargetCodeForMemset(SelectionDAG &DAG, SDLoc DL, SDValue Chain, 87 SDValue Dst, SDValue Byte, SDValue Size, 88 unsigned Align, bool IsVolatile, 89 MachinePointerInfo DstPtrInfo) const { 90 EVT PtrVT = Dst.getValueType(); 91 92 if (IsVolatile) 93 return SDValue(); 94 95 if (auto *CSize = dyn_cast<ConstantSDNode>(Size)) { 96 uint64_t Bytes = CSize->getZExtValue(); 97 if (Bytes == 0) 98 return SDValue(); 99 if (auto *CByte = dyn_cast<ConstantSDNode>(Byte)) { 100 // Handle cases that can be done using at most two of 101 // MVI, MVHI, MVHHI and MVGHI. The latter two can only be 102 // used if ByteVal is all zeros or all ones; in other casees, 103 // we can move at most 2 halfwords. 104 uint64_t ByteVal = CByte->getZExtValue(); 105 if (ByteVal == 0 || ByteVal == 255 ? 106 Bytes <= 16 && CountPopulation_64(Bytes) <= 2 : 107 Bytes <= 4) { 108 unsigned Size1 = Bytes == 16 ? 8 : 1 << findLastSet(Bytes); 109 unsigned Size2 = Bytes - Size1; 110 SDValue Chain1 = memsetStore(DAG, DL, Chain, Dst, ByteVal, Size1, 111 Align, DstPtrInfo); 112 if (Size2 == 0) 113 return Chain1; 114 Dst = DAG.getNode(ISD::ADD, DL, PtrVT, Dst, 115 DAG.getConstant(Size1, PtrVT)); 116 DstPtrInfo = DstPtrInfo.getWithOffset(Size1); 117 SDValue Chain2 = memsetStore(DAG, DL, Chain, Dst, ByteVal, Size2, 118 std::min(Align, Size1), DstPtrInfo); 119 return DAG.getNode(ISD::TokenFactor, DL, MVT::Other, Chain1, Chain2); 120 } 121 } else { 122 // Handle one and two bytes using STC. 123 if (Bytes <= 2) { 124 SDValue Chain1 = DAG.getStore(Chain, DL, Byte, Dst, DstPtrInfo, 125 false, false, Align); 126 if (Bytes == 1) 127 return Chain1; 128 SDValue Dst2 = DAG.getNode(ISD::ADD, DL, PtrVT, Dst, 129 DAG.getConstant(1, PtrVT)); 130 SDValue Chain2 = DAG.getStore(Chain, DL, Byte, Dst2, 131 DstPtrInfo.getWithOffset(1), 132 false, false, 1); 133 return DAG.getNode(ISD::TokenFactor, DL, MVT::Other, Chain1, Chain2); 134 } 135 } 136 assert(Bytes >= 2 && "Should have dealt with 0- and 1-byte cases already"); 137 138 // Handle the special case of a memset of 0, which can use XC. 139 auto *CByte = dyn_cast<ConstantSDNode>(Byte); 140 if (CByte && CByte->getZExtValue() == 0) 141 return emitMemMem(DAG, DL, SystemZISD::XC, SystemZISD::XC_LOOP, 142 Chain, Dst, Dst, Bytes); 143 144 // Copy the byte to the first location and then use MVC to copy 145 // it to the rest. 146 Chain = DAG.getStore(Chain, DL, Byte, Dst, DstPtrInfo, 147 false, false, Align); 148 SDValue DstPlus1 = DAG.getNode(ISD::ADD, DL, PtrVT, Dst, 149 DAG.getConstant(1, PtrVT)); 150 return emitMemMem(DAG, DL, SystemZISD::MVC, SystemZISD::MVC_LOOP, 151 Chain, DstPlus1, Dst, Bytes - 1); 152 } 153 return SDValue(); 154 } 155 156 // Use CLC to compare [Src1, Src1 + Size) with [Src2, Src2 + Size), 157 // deciding whether to use a loop or straight-line code. 158 static SDValue emitCLC(SelectionDAG &DAG, SDLoc DL, SDValue Chain, 159 SDValue Src1, SDValue Src2, uint64_t Size) { 160 SDVTList VTs = DAG.getVTList(MVT::Other, MVT::Glue); 161 EVT PtrVT = Src1.getValueType(); 162 // A two-CLC sequence is a clear win over a loop, not least because it 163 // needs only one branch. A three-CLC sequence needs the same number 164 // of branches as a loop (i.e. 2), but is shorter. That brings us to 165 // lengths greater than 768 bytes. It seems relatively likely that 166 // a difference will be found within the first 768 bytes, so we just 167 // optimize for the smallest number of branch instructions, in order 168 // to avoid polluting the prediction buffer too much. A loop only ever 169 // needs 2 branches, whereas a straight-line sequence would need 3 or more. 170 if (Size > 3 * 256) 171 return DAG.getNode(SystemZISD::CLC_LOOP, DL, VTs, Chain, Src1, Src2, 172 DAG.getConstant(Size, PtrVT), 173 DAG.getConstant(Size / 256, PtrVT)); 174 return DAG.getNode(SystemZISD::CLC, DL, VTs, Chain, Src1, Src2, 175 DAG.getConstant(Size, PtrVT)); 176 } 177 178 // Convert the current CC value into an integer that is 0 if CC == 0, 179 // less than zero if CC == 1 and greater than zero if CC >= 2. 180 // The sequence starts with IPM, which puts CC into bits 29 and 28 181 // of an integer and clears bits 30 and 31. 182 static SDValue addIPMSequence(SDLoc DL, SDValue Glue, SelectionDAG &DAG) { 183 SDValue IPM = DAG.getNode(SystemZISD::IPM, DL, MVT::i32, Glue); 184 SDValue SRL = DAG.getNode(ISD::SRL, DL, MVT::i32, IPM, 185 DAG.getConstant(SystemZ::IPM_CC, MVT::i32)); 186 SDValue ROTL = DAG.getNode(ISD::ROTL, DL, MVT::i32, SRL, 187 DAG.getConstant(31, MVT::i32)); 188 return ROTL; 189 } 190 191 std::pair<SDValue, SDValue> SystemZSelectionDAGInfo:: 192 EmitTargetCodeForMemcmp(SelectionDAG &DAG, SDLoc DL, SDValue Chain, 193 SDValue Src1, SDValue Src2, SDValue Size, 194 MachinePointerInfo Op1PtrInfo, 195 MachinePointerInfo Op2PtrInfo) const { 196 if (auto *CSize = dyn_cast<ConstantSDNode>(Size)) { 197 uint64_t Bytes = CSize->getZExtValue(); 198 assert(Bytes > 0 && "Caller should have handled 0-size case"); 199 Chain = emitCLC(DAG, DL, Chain, Src1, Src2, Bytes); 200 SDValue Glue = Chain.getValue(1); 201 return std::make_pair(addIPMSequence(DL, Glue, DAG), Chain); 202 } 203 return std::make_pair(SDValue(), SDValue()); 204 } 205 206 std::pair<SDValue, SDValue> SystemZSelectionDAGInfo:: 207 EmitTargetCodeForMemchr(SelectionDAG &DAG, SDLoc DL, SDValue Chain, 208 SDValue Src, SDValue Char, SDValue Length, 209 MachinePointerInfo SrcPtrInfo) const { 210 // Use SRST to find the character. End is its address on success. 211 EVT PtrVT = Src.getValueType(); 212 SDVTList VTs = DAG.getVTList(PtrVT, MVT::Other, MVT::Glue); 213 Length = DAG.getZExtOrTrunc(Length, DL, PtrVT); 214 Char = DAG.getZExtOrTrunc(Char, DL, MVT::i32); 215 Char = DAG.getNode(ISD::AND, DL, MVT::i32, Char, 216 DAG.getConstant(255, MVT::i32)); 217 SDValue Limit = DAG.getNode(ISD::ADD, DL, PtrVT, Src, Length); 218 SDValue End = DAG.getNode(SystemZISD::SEARCH_STRING, DL, VTs, Chain, 219 Limit, Src, Char); 220 Chain = End.getValue(1); 221 SDValue Glue = End.getValue(2); 222 223 // Now select between End and null, depending on whether the character 224 // was found. 225 SmallVector<SDValue, 5> Ops; 226 Ops.push_back(End); 227 Ops.push_back(DAG.getConstant(0, PtrVT)); 228 Ops.push_back(DAG.getConstant(SystemZ::CCMASK_SRST, MVT::i32)); 229 Ops.push_back(DAG.getConstant(SystemZ::CCMASK_SRST_FOUND, MVT::i32)); 230 Ops.push_back(Glue); 231 VTs = DAG.getVTList(PtrVT, MVT::Glue); 232 End = DAG.getNode(SystemZISD::SELECT_CCMASK, DL, VTs, Ops); 233 return std::make_pair(End, Chain); 234 } 235 236 std::pair<SDValue, SDValue> SystemZSelectionDAGInfo:: 237 EmitTargetCodeForStrcpy(SelectionDAG &DAG, SDLoc DL, SDValue Chain, 238 SDValue Dest, SDValue Src, 239 MachinePointerInfo DestPtrInfo, 240 MachinePointerInfo SrcPtrInfo, bool isStpcpy) const { 241 SDVTList VTs = DAG.getVTList(Dest.getValueType(), MVT::Other); 242 SDValue EndDest = DAG.getNode(SystemZISD::STPCPY, DL, VTs, Chain, Dest, Src, 243 DAG.getConstant(0, MVT::i32)); 244 return std::make_pair(isStpcpy ? EndDest : Dest, EndDest.getValue(1)); 245 } 246 247 std::pair<SDValue, SDValue> SystemZSelectionDAGInfo:: 248 EmitTargetCodeForStrcmp(SelectionDAG &DAG, SDLoc DL, SDValue Chain, 249 SDValue Src1, SDValue Src2, 250 MachinePointerInfo Op1PtrInfo, 251 MachinePointerInfo Op2PtrInfo) const { 252 SDVTList VTs = DAG.getVTList(Src1.getValueType(), MVT::Other, MVT::Glue); 253 SDValue Unused = DAG.getNode(SystemZISD::STRCMP, DL, VTs, Chain, Src1, Src2, 254 DAG.getConstant(0, MVT::i32)); 255 Chain = Unused.getValue(1); 256 SDValue Glue = Chain.getValue(2); 257 return std::make_pair(addIPMSequence(DL, Glue, DAG), Chain); 258 } 259 260 // Search from Src for a null character, stopping once Src reaches Limit. 261 // Return a pair of values, the first being the number of nonnull characters 262 // and the second being the out chain. 263 // 264 // This can be used for strlen by setting Limit to 0. 265 static std::pair<SDValue, SDValue> getBoundedStrlen(SelectionDAG &DAG, SDLoc DL, 266 SDValue Chain, SDValue Src, 267 SDValue Limit) { 268 EVT PtrVT = Src.getValueType(); 269 SDVTList VTs = DAG.getVTList(PtrVT, MVT::Other, MVT::Glue); 270 SDValue End = DAG.getNode(SystemZISD::SEARCH_STRING, DL, VTs, Chain, 271 Limit, Src, DAG.getConstant(0, MVT::i32)); 272 Chain = End.getValue(1); 273 SDValue Len = DAG.getNode(ISD::SUB, DL, PtrVT, End, Src); 274 return std::make_pair(Len, Chain); 275 } 276 277 std::pair<SDValue, SDValue> SystemZSelectionDAGInfo:: 278 EmitTargetCodeForStrlen(SelectionDAG &DAG, SDLoc DL, SDValue Chain, 279 SDValue Src, MachinePointerInfo SrcPtrInfo) const { 280 EVT PtrVT = Src.getValueType(); 281 return getBoundedStrlen(DAG, DL, Chain, Src, DAG.getConstant(0, PtrVT)); 282 } 283 284 std::pair<SDValue, SDValue> SystemZSelectionDAGInfo:: 285 EmitTargetCodeForStrnlen(SelectionDAG &DAG, SDLoc DL, SDValue Chain, 286 SDValue Src, SDValue MaxLength, 287 MachinePointerInfo SrcPtrInfo) const { 288 EVT PtrVT = Src.getValueType(); 289 MaxLength = DAG.getZExtOrTrunc(MaxLength, DL, PtrVT); 290 SDValue Limit = DAG.getNode(ISD::ADD, DL, PtrVT, Src, MaxLength); 291 return getBoundedStrlen(DAG, DL, Chain, Src, Limit); 292 } 293
