1 //===- RDFCopy.cpp --------------------------------------------------------===//
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 // RDF-based copy propagation.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "RDFCopy.h"
15 #include "RDFGraph.h"
16 #include "RDFLiveness.h"
17 #include "RDFRegisters.h"
18 #include "llvm/CodeGen/MachineDominators.h"
19 #include "llvm/CodeGen/MachineInstr.h"
20 #include "llvm/CodeGen/MachineOperand.h"
21 #include "llvm/CodeGen/MachineRegisterInfo.h"
22 #include "llvm/CodeGen/TargetOpcodes.h"
23 #include "llvm/CodeGen/TargetRegisterInfo.h"
24 #include "llvm/MC/MCRegisterInfo.h"
25 #include "llvm/Support/CommandLine.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/raw_ostream.h"
29 #include <cassert>
30 #include <cstdint>
31 #include <utility>
32
33 using namespace llvm;
34 using namespace rdf;
35
36 #ifndef NDEBUG
37 static cl::opt<unsigned> CpLimit("rdf-cp-limit", cl::init(0), cl::Hidden);
38 static unsigned CpCount = 0;
39 #endif
40
interpretAsCopy(const MachineInstr * MI,EqualityMap & EM)41 bool CopyPropagation::interpretAsCopy(const MachineInstr *MI, EqualityMap &EM) {
42 unsigned Opc = MI->getOpcode();
43 switch (Opc) {
44 case TargetOpcode::COPY: {
45 const MachineOperand &Dst = MI->getOperand(0);
46 const MachineOperand &Src = MI->getOperand(1);
47 RegisterRef DstR = DFG.makeRegRef(Dst.getReg(), Dst.getSubReg());
48 RegisterRef SrcR = DFG.makeRegRef(Src.getReg(), Src.getSubReg());
49 assert(TargetRegisterInfo::isPhysicalRegister(DstR.Reg));
50 assert(TargetRegisterInfo::isPhysicalRegister(SrcR.Reg));
51 const TargetRegisterInfo &TRI = DFG.getTRI();
52 if (TRI.getMinimalPhysRegClass(DstR.Reg) !=
53 TRI.getMinimalPhysRegClass(SrcR.Reg))
54 return false;
55 EM.insert(std::make_pair(DstR, SrcR));
56 return true;
57 }
58 case TargetOpcode::REG_SEQUENCE:
59 llvm_unreachable("Unexpected REG_SEQUENCE");
60 }
61 return false;
62 }
63
recordCopy(NodeAddr<StmtNode * > SA,EqualityMap & EM)64 void CopyPropagation::recordCopy(NodeAddr<StmtNode*> SA, EqualityMap &EM) {
65 CopyMap.insert(std::make_pair(SA.Id, EM));
66 Copies.push_back(SA.Id);
67 }
68
scanBlock(MachineBasicBlock * B)69 bool CopyPropagation::scanBlock(MachineBasicBlock *B) {
70 bool Changed = false;
71 NodeAddr<BlockNode*> BA = DFG.findBlock(B);
72
73 for (NodeAddr<InstrNode*> IA : BA.Addr->members(DFG)) {
74 if (DFG.IsCode<NodeAttrs::Stmt>(IA)) {
75 NodeAddr<StmtNode*> SA = IA;
76 EqualityMap EM;
77 if (interpretAsCopy(SA.Addr->getCode(), EM))
78 recordCopy(SA, EM);
79 }
80 }
81
82 MachineDomTreeNode *N = MDT.getNode(B);
83 for (auto I : *N)
84 Changed |= scanBlock(I->getBlock());
85
86 return Changed;
87 }
88
getLocalReachingDef(RegisterRef RefRR,NodeAddr<InstrNode * > IA)89 NodeId CopyPropagation::getLocalReachingDef(RegisterRef RefRR,
90 NodeAddr<InstrNode*> IA) {
91 NodeAddr<RefNode*> RA = L.getNearestAliasedRef(RefRR, IA);
92 if (RA.Id != 0) {
93 if (RA.Addr->getKind() == NodeAttrs::Def)
94 return RA.Id;
95 assert(RA.Addr->getKind() == NodeAttrs::Use);
96 if (NodeId RD = RA.Addr->getReachingDef())
97 return RD;
98 }
99 return 0;
100 }
101
run()102 bool CopyPropagation::run() {
103 scanBlock(&DFG.getMF().front());
104
105 if (trace()) {
106 dbgs() << "Copies:\n";
107 for (NodeId I : Copies) {
108 dbgs() << "Instr: " << *DFG.addr<StmtNode*>(I).Addr->getCode();
109 dbgs() << " eq: {";
110 for (auto J : CopyMap[I])
111 dbgs() << ' ' << Print<RegisterRef>(J.first, DFG) << '='
112 << Print<RegisterRef>(J.second, DFG);
113 dbgs() << " }\n";
114 }
115 }
116
117 bool Changed = false;
118 #ifndef NDEBUG
119 bool HasLimit = CpLimit.getNumOccurrences() > 0;
120 #endif
121
122 auto MinPhysReg = [this] (RegisterRef RR) -> unsigned {
123 const TargetRegisterInfo &TRI = DFG.getTRI();
124 const TargetRegisterClass &RC = *TRI.getMinimalPhysRegClass(RR.Reg);
125 if ((RC.LaneMask & RR.Mask) == RC.LaneMask)
126 return RR.Reg;
127 for (MCSubRegIndexIterator S(RR.Reg, &TRI); S.isValid(); ++S)
128 if (RR.Mask == TRI.getSubRegIndexLaneMask(S.getSubRegIndex()))
129 return S.getSubReg();
130 llvm_unreachable("Should have found a register");
131 return 0;
132 };
133
134 for (NodeId C : Copies) {
135 #ifndef NDEBUG
136 if (HasLimit && CpCount >= CpLimit)
137 break;
138 #endif
139 auto SA = DFG.addr<InstrNode*>(C);
140 auto FS = CopyMap.find(SA.Id);
141 if (FS == CopyMap.end())
142 continue;
143
144 EqualityMap &EM = FS->second;
145 for (NodeAddr<DefNode*> DA : SA.Addr->members_if(DFG.IsDef, DFG)) {
146 RegisterRef DR = DA.Addr->getRegRef(DFG);
147 auto FR = EM.find(DR);
148 if (FR == EM.end())
149 continue;
150 RegisterRef SR = FR->second;
151 if (DR == SR)
152 continue;
153
154 NodeId AtCopy = getLocalReachingDef(SR, SA);
155
156 for (NodeId N = DA.Addr->getReachedUse(), NextN; N; N = NextN) {
157 auto UA = DFG.addr<UseNode*>(N);
158 NextN = UA.Addr->getSibling();
159 uint16_t F = UA.Addr->getFlags();
160 if ((F & NodeAttrs::PhiRef) || (F & NodeAttrs::Fixed))
161 continue;
162 if (UA.Addr->getRegRef(DFG) != DR)
163 continue;
164
165 NodeAddr<InstrNode*> IA = UA.Addr->getOwner(DFG);
166 assert(DFG.IsCode<NodeAttrs::Stmt>(IA));
167 NodeId AtUse = getLocalReachingDef(SR, IA);
168 if (AtCopy != AtUse)
169 continue;
170
171 MachineOperand &Op = UA.Addr->getOp();
172 if (Op.isTied())
173 continue;
174 if (trace()) {
175 dbgs() << "Can replace " << Print<RegisterRef>(DR, DFG)
176 << " with " << Print<RegisterRef>(SR, DFG) << " in "
177 << *NodeAddr<StmtNode*>(IA).Addr->getCode();
178 }
179
180 unsigned NewReg = MinPhysReg(SR);
181 Op.setReg(NewReg);
182 Op.setSubReg(0);
183 DFG.unlinkUse(UA, false);
184 if (AtCopy != 0) {
185 UA.Addr->linkToDef(UA.Id, DFG.addr<DefNode*>(AtCopy));
186 } else {
187 UA.Addr->setReachingDef(0);
188 UA.Addr->setSibling(0);
189 }
190
191 Changed = true;
192 #ifndef NDEBUG
193 if (HasLimit && CpCount >= CpLimit)
194 break;
195 CpCount++;
196 #endif
197
198 auto FC = CopyMap.find(IA.Id);
199 if (FC != CopyMap.end()) {
200 // Update the EM map in the copy's entry.
201 auto &M = FC->second;
202 for (auto &J : M) {
203 if (J.second != DR)
204 continue;
205 J.second = SR;
206 break;
207 }
208 }
209 } // for (N in reached-uses)
210 } // for (DA in defs)
211 } // for (C in Copies)
212
213 return Changed;
214 }
215