1 //===-------------- PPCVSXCopy.cpp - VSX Copy Legalization ----------------===//
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 // A pass which deals with the complexity of generating legal VSX register
11 // copies to/from register classes which partially overlap with the VSX
12 // register file.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #include "PPCInstrInfo.h"
17 #include "MCTargetDesc/PPCPredicates.h"
18 #include "PPC.h"
19 #include "PPCHazardRecognizers.h"
20 #include "PPCInstrBuilder.h"
21 #include "PPCMachineFunctionInfo.h"
22 #include "PPCTargetMachine.h"
23 #include "llvm/ADT/STLExtras.h"
24 #include "llvm/ADT/Statistic.h"
25 #include "llvm/CodeGen/MachineFrameInfo.h"
26 #include "llvm/CodeGen/MachineFunctionPass.h"
27 #include "llvm/CodeGen/MachineInstrBuilder.h"
28 #include "llvm/CodeGen/MachineMemOperand.h"
29 #include "llvm/CodeGen/MachineRegisterInfo.h"
30 #include "llvm/MC/MCAsmInfo.h"
31 #include "llvm/Support/CommandLine.h"
32 #include "llvm/Support/Debug.h"
33 #include "llvm/Support/ErrorHandling.h"
34 #include "llvm/Support/TargetRegistry.h"
35 #include "llvm/Support/raw_ostream.h"
36 
37 using namespace llvm;
38 
39 #define DEBUG_TYPE "ppc-vsx-copy"
40 
41 namespace llvm {
42   void initializePPCVSXCopyPass(PassRegistry&);
43 }
44 
45 namespace {
46   // PPCVSXCopy pass - For copies between VSX registers and non-VSX registers
47   // (Altivec and scalar floating-point registers), we need to transform the
48   // copies into subregister copies with other restrictions.
49   struct PPCVSXCopy : public MachineFunctionPass {
50     static char ID;
51     PPCVSXCopy() : MachineFunctionPass(ID) {
52       initializePPCVSXCopyPass(*PassRegistry::getPassRegistry());
53     }
54 
55     const TargetInstrInfo *TII;
56 
57     bool IsRegInClass(unsigned Reg, const TargetRegisterClass *RC,
58                       MachineRegisterInfo &MRI) {
59       if (TargetRegisterInfo::isVirtualRegister(Reg)) {
60         return RC->hasSubClassEq(MRI.getRegClass(Reg));
61       } else if (RC->contains(Reg)) {
62         return true;
63       }
64 
65       return false;
66     }
67 
68     bool IsVSReg(unsigned Reg, MachineRegisterInfo &MRI) {
69       return IsRegInClass(Reg, &PPC::VSRCRegClass, MRI);
70     }
71 
72     bool IsVRReg(unsigned Reg, MachineRegisterInfo &MRI) {
73       return IsRegInClass(Reg, &PPC::VRRCRegClass, MRI);
74     }
75 
76     bool IsF8Reg(unsigned Reg, MachineRegisterInfo &MRI) {
77       return IsRegInClass(Reg, &PPC::F8RCRegClass, MRI);
78     }
79 
80 protected:
81     bool processBlock(MachineBasicBlock &MBB) {
82       bool Changed = false;
83 
84       MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
85       for (MachineBasicBlock::iterator I = MBB.begin(), IE = MBB.end();
86            I != IE; ++I) {
87         MachineInstr *MI = I;
88         if (!MI->isFullCopy())
89           continue;
90 
91         MachineOperand &DstMO = MI->getOperand(0);
92         MachineOperand &SrcMO = MI->getOperand(1);
93 
94         if ( IsVSReg(DstMO.getReg(), MRI) &&
95             !IsVSReg(SrcMO.getReg(), MRI)) {
96           // This is a copy *to* a VSX register from a non-VSX register.
97           Changed = true;
98 
99           const TargetRegisterClass *SrcRC =
100             IsVRReg(SrcMO.getReg(), MRI) ? &PPC::VSHRCRegClass :
101                                            &PPC::VSLRCRegClass;
102           assert((IsF8Reg(SrcMO.getReg(), MRI) ||
103                   IsVRReg(SrcMO.getReg(), MRI)) &&
104                  "Unknown source for a VSX copy");
105 
106           unsigned NewVReg = MRI.createVirtualRegister(SrcRC);
107           BuildMI(MBB, MI, MI->getDebugLoc(),
108                   TII->get(TargetOpcode::SUBREG_TO_REG), NewVReg)
109             .addImm(1) // add 1, not 0, because there is no implicit clearing
110                        // of the high bits.
111             .addOperand(SrcMO)
112             .addImm(IsVRReg(SrcMO.getReg(), MRI) ? PPC::sub_128 :
113                                                    PPC::sub_64);
114 
115           // The source of the original copy is now the new virtual register.
116           SrcMO.setReg(NewVReg);
117         } else if (!IsVSReg(DstMO.getReg(), MRI) &&
118                     IsVSReg(SrcMO.getReg(), MRI)) {
119           // This is a copy *from* a VSX register to a non-VSX register.
120           Changed = true;
121 
122           const TargetRegisterClass *DstRC =
123             IsVRReg(DstMO.getReg(), MRI) ? &PPC::VSHRCRegClass :
124                                            &PPC::VSLRCRegClass;
125           assert((IsF8Reg(DstMO.getReg(), MRI) ||
126                   IsVRReg(DstMO.getReg(), MRI)) &&
127                  "Unknown destination for a VSX copy");
128 
129           // Copy the VSX value into a new VSX register of the correct subclass.
130           unsigned NewVReg = MRI.createVirtualRegister(DstRC);
131           BuildMI(MBB, MI, MI->getDebugLoc(),
132                   TII->get(TargetOpcode::COPY), NewVReg)
133             .addOperand(SrcMO);
134 
135           // Transform the original copy into a subregister extraction copy.
136           SrcMO.setReg(NewVReg);
137           SrcMO.setSubReg(IsVRReg(DstMO.getReg(), MRI) ? PPC::sub_128 :
138                                                          PPC::sub_64);
139         }
140       }
141 
142       return Changed;
143     }
144 
145 public:
146     bool runOnMachineFunction(MachineFunction &MF) override {
147       // If we don't have VSX on the subtarget, don't do anything.
148       const PPCSubtarget &STI = MF.getSubtarget<PPCSubtarget>();
149       if (!STI.hasVSX())
150         return false;
151       TII = STI.getInstrInfo();
152 
153       bool Changed = false;
154 
155       for (MachineFunction::iterator I = MF.begin(); I != MF.end();) {
156         MachineBasicBlock &B = *I++;
157         if (processBlock(B))
158           Changed = true;
159       }
160 
161       return Changed;
162     }
163 
164     void getAnalysisUsage(AnalysisUsage &AU) const override {
165       MachineFunctionPass::getAnalysisUsage(AU);
166     }
167   };
168 }
169 
170 INITIALIZE_PASS(PPCVSXCopy, DEBUG_TYPE,
171                 "PowerPC VSX Copy Legalization", false, false)
172 
173 char PPCVSXCopy::ID = 0;
174 FunctionPass*
175 llvm::createPPCVSXCopyPass() { return new PPCVSXCopy(); }
176 
177