aboutsummaryrefslogtreecommitdiffstats
path: root/lib/Target/SystemZ/SystemZSelectionDAGInfo.cpp
blob: 3b43cbdb3e723395582007a9823b2bf768227f52 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
//===-- SystemZSelectionDAGInfo.cpp - SystemZ SelectionDAG Info -----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the SystemZSelectionDAGInfo class.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "systemz-selectiondag-info"
#include "SystemZTargetMachine.h"
#include "llvm/CodeGen/SelectionDAG.h"

using namespace llvm;

SystemZSelectionDAGInfo::
SystemZSelectionDAGInfo(const SystemZTargetMachine &TM)
  : TargetSelectionDAGInfo(TM) {
}

SystemZSelectionDAGInfo::~SystemZSelectionDAGInfo() {
}

// Decide whether it is best to use a loop or straight-line code for
// a block operation of Size bytes with source address Src and destination
// address Dest.  Sequence is the opcode to use for straight-line code
// (such as MVC) and Loop is the opcode to use for loops (such as MVC_LOOP).
// Return the chain for the completed operation.
static SDValue emitMemMem(SelectionDAG &DAG, SDLoc DL, unsigned Sequence,
                          unsigned Loop, SDValue Chain, SDValue Dst,
                          SDValue Src, uint64_t Size) {
  EVT PtrVT = Src.getValueType();
  // The heuristic we use is to prefer loops for anything that would
  // require 7 or more MVCs.  With these kinds of sizes there isn't
  // much to choose between straight-line code and looping code,
  // since the time will be dominated by the MVCs themselves.
  // However, the loop has 4 or 5 instructions (depending on whether
  // the base addresses can be proved equal), so there doesn't seem
  // much point using a loop for 5 * 256 bytes or fewer.  Anything in
  // the range (5 * 256, 6 * 256) will need another instruction after
  // the loop, so it doesn't seem worth using a loop then either.
  // The next value up, 6 * 256, can be implemented in the same
  // number of straight-line MVCs as 6 * 256 - 1.
  if (Size > 6 * 256)
    return DAG.getNode(Loop, DL, MVT::Other, Chain, Dst, Src,
                       DAG.getConstant(Size, PtrVT),
                       DAG.getConstant(Size / 256, PtrVT));
  return DAG.getNode(Sequence, DL, MVT::Other, Chain, Dst, Src,
                     DAG.getConstant(Size, PtrVT));
}

SDValue SystemZSelectionDAGInfo::
EmitTargetCodeForMemcpy(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
                        SDValue Dst, SDValue Src, SDValue Size, unsigned Align,
                        bool IsVolatile, bool AlwaysInline,
                        MachinePointerInfo DstPtrInfo,
                        MachinePointerInfo SrcPtrInfo) const {
  if (IsVolatile)
    return SDValue();

  if (ConstantSDNode *CSize = dyn_cast<ConstantSDNode>(Size))
    return emitMemMem(DAG, DL, SystemZISD::MVC, SystemZISD::MVC_LOOP,
                      Chain, Dst, Src, CSize->getZExtValue());
  return SDValue();
}

// Handle a memset of 1, 2, 4 or 8 bytes with the operands given by
// Chain, Dst, ByteVal and Size.  These cases are expected to use
// MVI, MVHHI, MVHI and MVGHI respectively.
static SDValue memsetStore(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
                           SDValue Dst, uint64_t ByteVal, uint64_t Size,
                           unsigned Align,
                           MachinePointerInfo DstPtrInfo) {
  uint64_t StoreVal = ByteVal;
  for (unsigned I = 1; I < Size; ++I)
    StoreVal |= ByteVal << (I * 8);
  return DAG.getStore(Chain, DL,
                      DAG.getConstant(StoreVal, MVT::getIntegerVT(Size * 8)),
                      Dst, DstPtrInfo, false, false, Align);
}

SDValue SystemZSelectionDAGInfo::
EmitTargetCodeForMemset(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
                        SDValue Dst, SDValue Byte, SDValue Size,
                        unsigned Align, bool IsVolatile,
                        MachinePointerInfo DstPtrInfo) const {
  EVT PtrVT = Dst.getValueType();

  if (IsVolatile)
    return SDValue();

  if (ConstantSDNode *CSize = dyn_cast<ConstantSDNode>(Size)) {
    uint64_t Bytes = CSize->getZExtValue();
    if (Bytes == 0)
      return SDValue();
    if (ConstantSDNode *CByte = dyn_cast<ConstantSDNode>(Byte)) {
      // Handle cases that can be done using at most two of
      // MVI, MVHI, MVHHI and MVGHI.  The latter two can only be
      // used if ByteVal is all zeros or all ones; in other casees,
      // we can move at most 2 halfwords.
      uint64_t ByteVal = CByte->getZExtValue();
      if (ByteVal == 0 || ByteVal == 255 ?
          Bytes <= 16 && CountPopulation_64(Bytes) <= 2 :
          Bytes <= 4) {
        unsigned Size1 = Bytes == 16 ? 8 : 1 << findLastSet(Bytes);
        unsigned Size2 = Bytes - Size1;
        SDValue Chain1 = memsetStore(DAG, DL, Chain, Dst, ByteVal, Size1,
                                     Align, DstPtrInfo);
        if (Size2 == 0)
          return Chain1;
        Dst = DAG.getNode(ISD::ADD, DL, PtrVT, Dst,
                          DAG.getConstant(Size1, PtrVT));
        DstPtrInfo = DstPtrInfo.getWithOffset(Size1);
        SDValue Chain2 = memsetStore(DAG, DL, Chain, Dst, ByteVal, Size2,
                                     std::min(Align, Size1), DstPtrInfo);
        return DAG.getNode(ISD::TokenFactor, DL, MVT::Other, Chain1, Chain2);
      }
    } else {
      // Handle one and two bytes using STC.
      if (Bytes <= 2) {
        SDValue Chain1 = DAG.getStore(Chain, DL, Byte, Dst, DstPtrInfo,
                                      false, false, Align);
        if (Bytes == 1)
          return Chain1;
        SDValue Dst2 = DAG.getNode(ISD::ADD, DL, PtrVT, Dst,
                                   DAG.getConstant(1, PtrVT));
        SDValue Chain2 = DAG.getStore(Chain, DL, Byte, Dst2,
                                      DstPtrInfo.getWithOffset(1),
                                      false, false, 1);
        return DAG.getNode(ISD::TokenFactor, DL, MVT::Other, Chain1, Chain2);
      }
    }
    assert(Bytes >= 2 && "Should have dealt with 0- and 1-byte cases already");

    // Handle the special case of a memset of 0, which can use XC.
    ConstantSDNode *CByte = dyn_cast<ConstantSDNode>(Byte);
    if (CByte && CByte->getZExtValue() == 0)
      return emitMemMem(DAG, DL, SystemZISD::XC, SystemZISD::XC_LOOP,
                        Chain, Dst, Dst, Bytes);

    // Copy the byte to the first location and then use MVC to copy
    // it to the rest.
    Chain = DAG.getStore(Chain, DL, Byte, Dst, DstPtrInfo,
                         false, false, Align);
    SDValue DstPlus1 = DAG.getNode(ISD::ADD, DL, PtrVT, Dst,
                                   DAG.getConstant(1, PtrVT));
    return emitMemMem(DAG, DL, SystemZISD::MVC, SystemZISD::MVC_LOOP,
                      Chain, DstPlus1, Dst, Bytes - 1);
  }
  return SDValue();
}

// Use CLC to compare [Src1, Src1 + Size) with [Src2, Src2 + Size),
// deciding whether to use a loop or straight-line code.
static SDValue emitCLC(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
                       SDValue Src1, SDValue Src2, uint64_t Size) {
  SDVTList VTs = DAG.getVTList(MVT::Other, MVT::Glue);
  EVT PtrVT = Src1.getValueType();
  // A two-CLC sequence is a clear win over a loop, not least because it
  // needs only one branch.  A three-CLC sequence needs the same number
  // of branches as a loop (i.e. 2), but is shorter.  That brings us to
  // lengths greater than 768 bytes.  It seems relatively likely that
  // a difference will be found within the first 768 bytes, so we just
  // optimize for the smallest number of branch instructions, in order
  // to avoid polluting the prediction buffer too much.  A loop only ever
  // needs 2 branches, whereas a straight-line sequence would need 3 or more.
  if (Size > 3 * 256)
    return DAG.getNode(SystemZISD::CLC_LOOP, DL, VTs, Chain, Src1, Src2,
                       DAG.getConstant(Size, PtrVT),
                       DAG.getConstant(Size / 256, PtrVT));
  return DAG.getNode(SystemZISD::CLC, DL, VTs, Chain, Src1, Src2,
                     DAG.getConstant(Size, PtrVT));
}

// Convert the current CC value into an integer that is 0 if CC == 0,
// less than zero if CC == 1 and greater than zero if CC >= 2.
// The sequence starts with IPM, which puts CC into bits 29 and 28
// of an integer and clears bits 30 and 31.
static SDValue addIPMSequence(SDLoc DL, SDValue Glue, SelectionDAG &DAG) {
  SDValue IPM = DAG.getNode(SystemZISD::IPM, DL, MVT::i32, Glue);
  SDValue SRL = DAG.getNode(ISD::SRL, DL, MVT::i32, IPM,
                            DAG.getConstant(28, MVT::i32));
  SDValue ROTL = DAG.getNode(ISD::ROTL, DL, MVT::i32, SRL,
                             DAG.getConstant(31, MVT::i32));
  return ROTL;
}

std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::
EmitTargetCodeForMemcmp(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
                        SDValue Src1, SDValue Src2, SDValue Size,
                        MachinePointerInfo Op1PtrInfo,
                        MachinePointerInfo Op2PtrInfo) const {
  if (ConstantSDNode *CSize = dyn_cast<ConstantSDNode>(Size)) {
    uint64_t Bytes = CSize->getZExtValue();
    assert(Bytes > 0 && "Caller should have handled 0-size case");
    Chain = emitCLC(DAG, DL, Chain, Src1, Src2, Bytes);
    SDValue Glue = Chain.getValue(1);
    return std::make_pair(addIPMSequence(DL, Glue, DAG), Chain);
  }
  return std::make_pair(SDValue(), SDValue());
}

std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::
EmitTargetCodeForMemchr(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
                        SDValue Src, SDValue Char, SDValue Length,
                        MachinePointerInfo SrcPtrInfo) const {
  // Use SRST to find the character.  End is its address on success.
  EVT PtrVT = Src.getValueType();
  SDVTList VTs = DAG.getVTList(PtrVT, MVT::Other, MVT::Glue);
  Length = DAG.getZExtOrTrunc(Length, DL, PtrVT);
  Char = DAG.getZExtOrTrunc(Char, DL, MVT::i32);
  Char = DAG.getNode(ISD::AND, DL, MVT::i32, Char,
                     DAG.getConstant(255, MVT::i32));
  SDValue Limit = DAG.getNode(ISD::ADD, DL, PtrVT, Src, Length);
  SDValue End = DAG.getNode(SystemZISD::SEARCH_STRING, DL, VTs, Chain,
                            Limit, Src, Char);
  Chain = End.getValue(1);
  SDValue Glue = End.getValue(2);

  // Now select between End and null, depending on whether the character
  // was found.
  SmallVector<SDValue, 5> Ops;
  Ops.push_back(End);
  Ops.push_back(DAG.getConstant(0, PtrVT));
  Ops.push_back(DAG.getConstant(SystemZ::CCMASK_SRST, MVT::i32));
  Ops.push_back(DAG.getConstant(SystemZ::CCMASK_SRST_FOUND, MVT::i32));
  Ops.push_back(Glue);
  VTs = DAG.getVTList(PtrVT, MVT::Glue);
  End = DAG.getNode(SystemZISD::SELECT_CCMASK, DL, VTs, &Ops[0], Ops.size());
  return std::make_pair(End, Chain);
}

std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::
EmitTargetCodeForStrcpy(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
                        SDValue Dest, SDValue Src,
                        MachinePointerInfo DestPtrInfo,
                        MachinePointerInfo SrcPtrInfo, bool isStpcpy) const {
  SDVTList VTs = DAG.getVTList(Dest.getValueType(), MVT::Other);
  SDValue EndDest = DAG.getNode(SystemZISD::STPCPY, DL, VTs, Chain, Dest, Src,
                                DAG.getConstant(0, MVT::i32));
  return std::make_pair(isStpcpy ? EndDest : Dest, EndDest.getValue(1));
}

std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::
EmitTargetCodeForStrcmp(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
                        SDValue Src1, SDValue Src2,
                        MachinePointerInfo Op1PtrInfo,
                        MachinePointerInfo Op2PtrInfo) const {
  SDVTList VTs = DAG.getVTList(Src1.getValueType(), MVT::Other, MVT::Glue);
  SDValue Unused = DAG.getNode(SystemZISD::STRCMP, DL, VTs, Chain, Src1, Src2,
                               DAG.getConstant(0, MVT::i32));
  Chain = Unused.getValue(1);
  SDValue Glue = Chain.getValue(2);
  return std::make_pair(addIPMSequence(DL, Glue, DAG), Chain);
}

// Search from Src for a null character, stopping once Src reaches Limit.
// Return a pair of values, the first being the number of nonnull characters
// and the second being the out chain.
//
// This can be used for strlen by setting Limit to 0.
static std::pair<SDValue, SDValue> getBoundedStrlen(SelectionDAG &DAG, SDLoc DL,
                                                    SDValue Chain, SDValue Src,
                                                    SDValue Limit) {
  EVT PtrVT = Src.getValueType();
  SDVTList VTs = DAG.getVTList(PtrVT, MVT::Other, MVT::Glue);
  SDValue End = DAG.getNode(SystemZISD::SEARCH_STRING, DL, VTs, Chain,
                            Limit, Src, DAG.getConstant(0, MVT::i32));
  Chain = End.getValue(1);
  SDValue Len = DAG.getNode(ISD::SUB, DL, PtrVT, End, Src);
  return std::make_pair(Len, Chain);
}    

std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::
EmitTargetCodeForStrlen(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
                        SDValue Src, MachinePointerInfo SrcPtrInfo) const {
  EVT PtrVT = Src.getValueType();
  return getBoundedStrlen(DAG, DL, Chain, Src, DAG.getConstant(0, PtrVT));
}

std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::
EmitTargetCodeForStrnlen(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
                         SDValue Src, SDValue MaxLength,
                         MachinePointerInfo SrcPtrInfo) const {
  EVT PtrVT = Src.getValueType();
  MaxLength = DAG.getZExtOrTrunc(MaxLength, DL, PtrVT);
  SDValue Limit = DAG.getNode(ISD::ADD, DL, PtrVT, Src, MaxLength);
  return getBoundedStrlen(DAG, DL, Chain, Src, Limit);
}