1//===-- X86SelectionDAGInfo.cpp - X86 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 X86SelectionDAGInfo class.
11//
12//===----------------------------------------------------------------------===//
13
14#define DEBUG_TYPE "x86-selectiondag-info"
15#include "X86TargetMachine.h"
16#include "llvm/DerivedTypes.h"
17#include "llvm/CodeGen/SelectionDAG.h"
18using namespace llvm;
19
20X86SelectionDAGInfo::X86SelectionDAGInfo(const X86TargetMachine &TM) :
21  TargetSelectionDAGInfo(TM),
22  Subtarget(&TM.getSubtarget<X86Subtarget>()),
23  TLI(*TM.getTargetLowering()) {
24}
25
26X86SelectionDAGInfo::~X86SelectionDAGInfo() {
27}
28
29SDValue
30X86SelectionDAGInfo::EmitTargetCodeForMemset(SelectionDAG &DAG, DebugLoc dl,
31                                             SDValue Chain,
32                                             SDValue Dst, SDValue Src,
33                                             SDValue Size, unsigned Align,
34                                             bool isVolatile,
35                                         MachinePointerInfo DstPtrInfo) const {
36  ConstantSDNode *ConstantSize = dyn_cast<ConstantSDNode>(Size);
37
38  // If to a segment-relative address space, use the default lowering.
39  if (DstPtrInfo.getAddrSpace() >= 256)
40    return SDValue();
41
42  // If not DWORD aligned or size is more than the threshold, call the library.
43  // The libc version is likely to be faster for these cases. It can use the
44  // address value and run time information about the CPU.
45  if ((Align & 3) != 0 ||
46      !ConstantSize ||
47      ConstantSize->getZExtValue() >
48        Subtarget->getMaxInlineSizeThreshold()) {
49    SDValue InFlag(0, 0);
50
51    // Check to see if there is a specialized entry-point for memory zeroing.
52    ConstantSDNode *V = dyn_cast<ConstantSDNode>(Src);
53
54    if (const char *bzeroEntry =  V &&
55        V->isNullValue() ? Subtarget->getBZeroEntry() : 0) {
56      EVT IntPtr = TLI.getPointerTy();
57      Type *IntPtrTy = getTargetData()->getIntPtrType(*DAG.getContext());
58      TargetLowering::ArgListTy Args;
59      TargetLowering::ArgListEntry Entry;
60      Entry.Node = Dst;
61      Entry.Ty = IntPtrTy;
62      Args.push_back(Entry);
63      Entry.Node = Size;
64      Args.push_back(Entry);
65      TargetLowering::
66      CallLoweringInfo CLI(Chain, Type::getVoidTy(*DAG.getContext()),
67                        false, false, false, false,
68                        0, CallingConv::C, /*isTailCall=*/false,
69                        /*doesNotRet=*/false, /*isReturnValueUsed=*/false,
70                        DAG.getExternalSymbol(bzeroEntry, IntPtr), Args,
71                        DAG, dl);
72      std::pair<SDValue,SDValue> CallResult =
73        TLI.LowerCallTo(CLI);
74      return CallResult.second;
75    }
76
77    // Otherwise have the target-independent code call memset.
78    return SDValue();
79  }
80
81  uint64_t SizeVal = ConstantSize->getZExtValue();
82  SDValue InFlag(0, 0);
83  EVT AVT;
84  SDValue Count;
85  ConstantSDNode *ValC = dyn_cast<ConstantSDNode>(Src);
86  unsigned BytesLeft = 0;
87  bool TwoRepStos = false;
88  if (ValC) {
89    unsigned ValReg;
90    uint64_t Val = ValC->getZExtValue() & 255;
91
92    // If the value is a constant, then we can potentially use larger sets.
93    switch (Align & 3) {
94    case 2:   // WORD aligned
95      AVT = MVT::i16;
96      ValReg = X86::AX;
97      Val = (Val << 8) | Val;
98      break;
99    case 0:  // DWORD aligned
100      AVT = MVT::i32;
101      ValReg = X86::EAX;
102      Val = (Val << 8)  | Val;
103      Val = (Val << 16) | Val;
104      if (Subtarget->is64Bit() && ((Align & 0x7) == 0)) {  // QWORD aligned
105        AVT = MVT::i64;
106        ValReg = X86::RAX;
107        Val = (Val << 32) | Val;
108      }
109      break;
110    default:  // Byte aligned
111      AVT = MVT::i8;
112      ValReg = X86::AL;
113      Count = DAG.getIntPtrConstant(SizeVal);
114      break;
115    }
116
117    if (AVT.bitsGT(MVT::i8)) {
118      unsigned UBytes = AVT.getSizeInBits() / 8;
119      Count = DAG.getIntPtrConstant(SizeVal / UBytes);
120      BytesLeft = SizeVal % UBytes;
121    }
122
123    Chain  = DAG.getCopyToReg(Chain, dl, ValReg, DAG.getConstant(Val, AVT),
124                              InFlag);
125    InFlag = Chain.getValue(1);
126  } else {
127    AVT = MVT::i8;
128    Count  = DAG.getIntPtrConstant(SizeVal);
129    Chain  = DAG.getCopyToReg(Chain, dl, X86::AL, Src, InFlag);
130    InFlag = Chain.getValue(1);
131  }
132
133  Chain  = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RCX :
134                                                              X86::ECX,
135                            Count, InFlag);
136  InFlag = Chain.getValue(1);
137  Chain  = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RDI :
138                                                              X86::EDI,
139                            Dst, InFlag);
140  InFlag = Chain.getValue(1);
141
142  SDVTList Tys = DAG.getVTList(MVT::Other, MVT::Glue);
143  SDValue Ops[] = { Chain, DAG.getValueType(AVT), InFlag };
144  Chain = DAG.getNode(X86ISD::REP_STOS, dl, Tys, Ops, array_lengthof(Ops));
145
146  if (TwoRepStos) {
147    InFlag = Chain.getValue(1);
148    Count  = Size;
149    EVT CVT = Count.getValueType();
150    SDValue Left = DAG.getNode(ISD::AND, dl, CVT, Count,
151                               DAG.getConstant((AVT == MVT::i64) ? 7 : 3, CVT));
152    Chain  = DAG.getCopyToReg(Chain, dl, (CVT == MVT::i64) ? X86::RCX :
153                                                             X86::ECX,
154                              Left, InFlag);
155    InFlag = Chain.getValue(1);
156    Tys = DAG.getVTList(MVT::Other, MVT::Glue);
157    SDValue Ops[] = { Chain, DAG.getValueType(MVT::i8), InFlag };
158    Chain = DAG.getNode(X86ISD::REP_STOS, dl, Tys, Ops, array_lengthof(Ops));
159  } else if (BytesLeft) {
160    // Handle the last 1 - 7 bytes.
161    unsigned Offset = SizeVal - BytesLeft;
162    EVT AddrVT = Dst.getValueType();
163    EVT SizeVT = Size.getValueType();
164
165    Chain = DAG.getMemset(Chain, dl,
166                          DAG.getNode(ISD::ADD, dl, AddrVT, Dst,
167                                      DAG.getConstant(Offset, AddrVT)),
168                          Src,
169                          DAG.getConstant(BytesLeft, SizeVT),
170                          Align, isVolatile, DstPtrInfo.getWithOffset(Offset));
171  }
172
173  // TODO: Use a Tokenfactor, as in memcpy, instead of a single chain.
174  return Chain;
175}
176
177SDValue
178X86SelectionDAGInfo::EmitTargetCodeForMemcpy(SelectionDAG &DAG, DebugLoc dl,
179                                        SDValue Chain, SDValue Dst, SDValue Src,
180                                        SDValue Size, unsigned Align,
181                                        bool isVolatile, bool AlwaysInline,
182                                         MachinePointerInfo DstPtrInfo,
183                                         MachinePointerInfo SrcPtrInfo) const {
184  // This requires the copy size to be a constant, preferably
185  // within a subtarget-specific limit.
186  ConstantSDNode *ConstantSize = dyn_cast<ConstantSDNode>(Size);
187  if (!ConstantSize)
188    return SDValue();
189  uint64_t SizeVal = ConstantSize->getZExtValue();
190  if (!AlwaysInline && SizeVal > Subtarget->getMaxInlineSizeThreshold())
191    return SDValue();
192
193  /// If not DWORD aligned, it is more efficient to call the library.  However
194  /// if calling the library is not allowed (AlwaysInline), then soldier on as
195  /// the code generated here is better than the long load-store sequence we
196  /// would otherwise get.
197  if (!AlwaysInline && (Align & 3) != 0)
198    return SDValue();
199
200  // If to a segment-relative address space, use the default lowering.
201  if (DstPtrInfo.getAddrSpace() >= 256 ||
202      SrcPtrInfo.getAddrSpace() >= 256)
203    return SDValue();
204
205  MVT AVT;
206  if (Align & 1)
207    AVT = MVT::i8;
208  else if (Align & 2)
209    AVT = MVT::i16;
210  else if (Align & 4)
211    // DWORD aligned
212    AVT = MVT::i32;
213  else
214    // QWORD aligned
215    AVT = Subtarget->is64Bit() ? MVT::i64 : MVT::i32;
216
217  unsigned UBytes = AVT.getSizeInBits() / 8;
218  unsigned CountVal = SizeVal / UBytes;
219  SDValue Count = DAG.getIntPtrConstant(CountVal);
220  unsigned BytesLeft = SizeVal % UBytes;
221
222  SDValue InFlag(0, 0);
223  Chain  = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RCX :
224                                                              X86::ECX,
225                            Count, InFlag);
226  InFlag = Chain.getValue(1);
227  Chain  = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RDI :
228                                                              X86::EDI,
229                            Dst, InFlag);
230  InFlag = Chain.getValue(1);
231  Chain  = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RSI :
232                                                              X86::ESI,
233                            Src, InFlag);
234  InFlag = Chain.getValue(1);
235
236  SDVTList Tys = DAG.getVTList(MVT::Other, MVT::Glue);
237  SDValue Ops[] = { Chain, DAG.getValueType(AVT), InFlag };
238  SDValue RepMovs = DAG.getNode(X86ISD::REP_MOVS, dl, Tys, Ops,
239                                array_lengthof(Ops));
240
241  SmallVector<SDValue, 4> Results;
242  Results.push_back(RepMovs);
243  if (BytesLeft) {
244    // Handle the last 1 - 7 bytes.
245    unsigned Offset = SizeVal - BytesLeft;
246    EVT DstVT = Dst.getValueType();
247    EVT SrcVT = Src.getValueType();
248    EVT SizeVT = Size.getValueType();
249    Results.push_back(DAG.getMemcpy(Chain, dl,
250                                    DAG.getNode(ISD::ADD, dl, DstVT, Dst,
251                                                DAG.getConstant(Offset, DstVT)),
252                                    DAG.getNode(ISD::ADD, dl, SrcVT, Src,
253                                                DAG.getConstant(Offset, SrcVT)),
254                                    DAG.getConstant(BytesLeft, SizeVT),
255                                    Align, isVolatile, AlwaysInline,
256                                    DstPtrInfo.getWithOffset(Offset),
257                                    SrcPtrInfo.getWithOffset(Offset)));
258  }
259
260  return DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
261                     &Results[0], Results.size());
262}
263