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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"
18 using namespace llvm;
19 
X86SelectionDAGInfo(const X86TargetMachine & TM)20 X86SelectionDAGInfo::X86SelectionDAGInfo(const X86TargetMachine &TM) :
21   TargetSelectionDAGInfo(TM),
22   Subtarget(&TM.getSubtarget<X86Subtarget>()),
23   TLI(*TM.getTargetLowering()) {
24 }
25 
~X86SelectionDAGInfo()26 X86SelectionDAGInfo::~X86SelectionDAGInfo() {
27 }
28 
29 SDValue
EmitTargetCodeForMemset(SelectionDAG & DAG,DebugLoc dl,SDValue Chain,SDValue Dst,SDValue Src,SDValue Size,unsigned Align,bool isVolatile,MachinePointerInfo DstPtrInfo) const30 X86SelectionDAGInfo::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       std::pair<SDValue,SDValue> CallResult =
66         TLI.LowerCallTo(Chain, Type::getVoidTy(*DAG.getContext()),
67                         false, false, false, false,
68                         0, CallingConv::C, false, /*isReturnValueUsed=*/false,
69                         DAG.getExternalSymbol(bzeroEntry, IntPtr), Args,
70                         DAG, dl);
71       return CallResult.second;
72     }
73 
74     // Otherwise have the target-independent code call memset.
75     return SDValue();
76   }
77 
78   uint64_t SizeVal = ConstantSize->getZExtValue();
79   SDValue InFlag(0, 0);
80   EVT AVT;
81   SDValue Count;
82   ConstantSDNode *ValC = dyn_cast<ConstantSDNode>(Src);
83   unsigned BytesLeft = 0;
84   bool TwoRepStos = false;
85   if (ValC) {
86     unsigned ValReg;
87     uint64_t Val = ValC->getZExtValue() & 255;
88 
89     // If the value is a constant, then we can potentially use larger sets.
90     switch (Align & 3) {
91     case 2:   // WORD aligned
92       AVT = MVT::i16;
93       ValReg = X86::AX;
94       Val = (Val << 8) | Val;
95       break;
96     case 0:  // DWORD aligned
97       AVT = MVT::i32;
98       ValReg = X86::EAX;
99       Val = (Val << 8)  | Val;
100       Val = (Val << 16) | Val;
101       if (Subtarget->is64Bit() && ((Align & 0x7) == 0)) {  // QWORD aligned
102         AVT = MVT::i64;
103         ValReg = X86::RAX;
104         Val = (Val << 32) | Val;
105       }
106       break;
107     default:  // Byte aligned
108       AVT = MVT::i8;
109       ValReg = X86::AL;
110       Count = DAG.getIntPtrConstant(SizeVal);
111       break;
112     }
113 
114     if (AVT.bitsGT(MVT::i8)) {
115       unsigned UBytes = AVT.getSizeInBits() / 8;
116       Count = DAG.getIntPtrConstant(SizeVal / UBytes);
117       BytesLeft = SizeVal % UBytes;
118     }
119 
120     Chain  = DAG.getCopyToReg(Chain, dl, ValReg, DAG.getConstant(Val, AVT),
121                               InFlag);
122     InFlag = Chain.getValue(1);
123   } else {
124     AVT = MVT::i8;
125     Count  = DAG.getIntPtrConstant(SizeVal);
126     Chain  = DAG.getCopyToReg(Chain, dl, X86::AL, Src, InFlag);
127     InFlag = Chain.getValue(1);
128   }
129 
130   Chain  = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RCX :
131                                                               X86::ECX,
132                             Count, InFlag);
133   InFlag = Chain.getValue(1);
134   Chain  = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RDI :
135                                                               X86::EDI,
136                             Dst, InFlag);
137   InFlag = Chain.getValue(1);
138 
139   SDVTList Tys = DAG.getVTList(MVT::Other, MVT::Glue);
140   SDValue Ops[] = { Chain, DAG.getValueType(AVT), InFlag };
141   Chain = DAG.getNode(X86ISD::REP_STOS, dl, Tys, Ops, array_lengthof(Ops));
142 
143   if (TwoRepStos) {
144     InFlag = Chain.getValue(1);
145     Count  = Size;
146     EVT CVT = Count.getValueType();
147     SDValue Left = DAG.getNode(ISD::AND, dl, CVT, Count,
148                                DAG.getConstant((AVT == MVT::i64) ? 7 : 3, CVT));
149     Chain  = DAG.getCopyToReg(Chain, dl, (CVT == MVT::i64) ? X86::RCX :
150                                                              X86::ECX,
151                               Left, InFlag);
152     InFlag = Chain.getValue(1);
153     Tys = DAG.getVTList(MVT::Other, MVT::Glue);
154     SDValue Ops[] = { Chain, DAG.getValueType(MVT::i8), InFlag };
155     Chain = DAG.getNode(X86ISD::REP_STOS, dl, Tys, Ops, array_lengthof(Ops));
156   } else if (BytesLeft) {
157     // Handle the last 1 - 7 bytes.
158     unsigned Offset = SizeVal - BytesLeft;
159     EVT AddrVT = Dst.getValueType();
160     EVT SizeVT = Size.getValueType();
161 
162     Chain = DAG.getMemset(Chain, dl,
163                           DAG.getNode(ISD::ADD, dl, AddrVT, Dst,
164                                       DAG.getConstant(Offset, AddrVT)),
165                           Src,
166                           DAG.getConstant(BytesLeft, SizeVT),
167                           Align, isVolatile, DstPtrInfo.getWithOffset(Offset));
168   }
169 
170   // TODO: Use a Tokenfactor, as in memcpy, instead of a single chain.
171   return Chain;
172 }
173 
174 SDValue
EmitTargetCodeForMemcpy(SelectionDAG & DAG,DebugLoc dl,SDValue Chain,SDValue Dst,SDValue Src,SDValue Size,unsigned Align,bool isVolatile,bool AlwaysInline,MachinePointerInfo DstPtrInfo,MachinePointerInfo SrcPtrInfo) const175 X86SelectionDAGInfo::EmitTargetCodeForMemcpy(SelectionDAG &DAG, DebugLoc dl,
176                                         SDValue Chain, SDValue Dst, SDValue Src,
177                                         SDValue Size, unsigned Align,
178                                         bool isVolatile, bool AlwaysInline,
179                                          MachinePointerInfo DstPtrInfo,
180                                          MachinePointerInfo SrcPtrInfo) const {
181   // This requires the copy size to be a constant, preferably
182   // within a subtarget-specific limit.
183   ConstantSDNode *ConstantSize = dyn_cast<ConstantSDNode>(Size);
184   if (!ConstantSize)
185     return SDValue();
186   uint64_t SizeVal = ConstantSize->getZExtValue();
187   if (!AlwaysInline && SizeVal > Subtarget->getMaxInlineSizeThreshold())
188     return SDValue();
189 
190   /// If not DWORD aligned, it is more efficient to call the library.  However
191   /// if calling the library is not allowed (AlwaysInline), then soldier on as
192   /// the code generated here is better than the long load-store sequence we
193   /// would otherwise get.
194   if (!AlwaysInline && (Align & 3) != 0)
195     return SDValue();
196 
197   // If to a segment-relative address space, use the default lowering.
198   if (DstPtrInfo.getAddrSpace() >= 256 ||
199       SrcPtrInfo.getAddrSpace() >= 256)
200     return SDValue();
201 
202   MVT AVT;
203   if (Align & 1)
204     AVT = MVT::i8;
205   else if (Align & 2)
206     AVT = MVT::i16;
207   else if (Align & 4)
208     // DWORD aligned
209     AVT = MVT::i32;
210   else
211     // QWORD aligned
212     AVT = Subtarget->is64Bit() ? MVT::i64 : MVT::i32;
213 
214   unsigned UBytes = AVT.getSizeInBits() / 8;
215   unsigned CountVal = SizeVal / UBytes;
216   SDValue Count = DAG.getIntPtrConstant(CountVal);
217   unsigned BytesLeft = SizeVal % UBytes;
218 
219   SDValue InFlag(0, 0);
220   Chain  = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RCX :
221                                                               X86::ECX,
222                             Count, InFlag);
223   InFlag = Chain.getValue(1);
224   Chain  = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RDI :
225                                                               X86::EDI,
226                             Dst, InFlag);
227   InFlag = Chain.getValue(1);
228   Chain  = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RSI :
229                                                               X86::ESI,
230                             Src, InFlag);
231   InFlag = Chain.getValue(1);
232 
233   SDVTList Tys = DAG.getVTList(MVT::Other, MVT::Glue);
234   SDValue Ops[] = { Chain, DAG.getValueType(AVT), InFlag };
235   SDValue RepMovs = DAG.getNode(X86ISD::REP_MOVS, dl, Tys, Ops,
236                                 array_lengthof(Ops));
237 
238   SmallVector<SDValue, 4> Results;
239   Results.push_back(RepMovs);
240   if (BytesLeft) {
241     // Handle the last 1 - 7 bytes.
242     unsigned Offset = SizeVal - BytesLeft;
243     EVT DstVT = Dst.getValueType();
244     EVT SrcVT = Src.getValueType();
245     EVT SizeVT = Size.getValueType();
246     Results.push_back(DAG.getMemcpy(Chain, dl,
247                                     DAG.getNode(ISD::ADD, dl, DstVT, Dst,
248                                                 DAG.getConstant(Offset, DstVT)),
249                                     DAG.getNode(ISD::ADD, dl, SrcVT, Src,
250                                                 DAG.getConstant(Offset, SrcVT)),
251                                     DAG.getConstant(BytesLeft, SizeVT),
252                                     Align, isVolatile, AlwaysInline,
253                                     DstPtrInfo.getWithOffset(Offset),
254                                     SrcPtrInfo.getWithOffset(Offset)));
255   }
256 
257   return DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
258                      &Results[0], Results.size());
259 }
260