1 //===-- SystemZSelectionDAGInfo.cpp - SystemZ SelectionDAG Info -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the SystemZSelectionDAGInfo class.
12 //===----------------------------------------------------------------------===//
14 #include "SystemZTargetMachine.h"
15 #include "llvm/CodeGen/SelectionDAG.h"
19 #define DEBUG_TYPE "systemz-selectiondag-info"
21 SystemZSelectionDAGInfo::SystemZSelectionDAGInfo(const DataLayout &DL)
22 : TargetSelectionDAGInfo(&DL) {}
24 SystemZSelectionDAGInfo::~SystemZSelectionDAGInfo() {
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.
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));
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 {
64 if (auto *CSize = dyn_cast<ConstantSDNode>(Size))
65 return emitMemMem(DAG, DL, SystemZISD::MVC, SystemZISD::MVC_LOOP,
66 Chain, Dst, Src, CSize->getZExtValue());
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,
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);
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();
95 if (auto *CSize = dyn_cast<ConstantSDNode>(Size)) {
96 uint64_t Bytes = CSize->getZExtValue();
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 :
108 unsigned Size1 = Bytes == 16 ? 8 : 1 << findLastSet(Bytes);
109 unsigned Size2 = Bytes - Size1;
110 SDValue Chain1 = memsetStore(DAG, DL, Chain, Dst, ByteVal, Size1,
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);
122 // Handle one and two bytes using STC.
124 SDValue Chain1 = DAG.getStore(Chain, DL, Byte, Dst, DstPtrInfo,
125 false, false, Align);
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),
133 return DAG.getNode(ISD::TokenFactor, DL, MVT::Other, Chain1, Chain2);
136 assert(Bytes >= 2 && "Should have dealt with 0- and 1-byte cases already");
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);
144 // Copy the byte to the first location and then use MVC to copy
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);
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.
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));
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));
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);
203 return std::make_pair(SDValue(), SDValue());
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,
220 Chain = End.getValue(1);
221 SDValue Glue = End.getValue(2);
223 // Now select between End and null, depending on whether the character
225 SmallVector<SDValue, 5> Ops;
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));
231 VTs = DAG.getVTList(PtrVT, MVT::Glue);
232 End = DAG.getNode(SystemZISD::SELECT_CCMASK, DL, VTs, Ops);
233 return std::make_pair(End, Chain);
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));
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);
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.
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,
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);
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));
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);