src/llvm/lib/Target/SystemZ/SystemZSelectionDAGInfo.cpp

   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 }