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 "PPC.h"
17 #include "MCTargetDesc/PPCPredicates.h"
18 #include "PPCHazardRecognizers.h"
19 #include "PPCInstrBuilder.h"
20 #include "PPCInstrInfo.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/Debug.h"
32 #include "llvm/Support/ErrorHandling.h"
33 #include "llvm/Support/TargetRegistry.h"
34 #include "llvm/Support/raw_ostream.h"
35 
36 using namespace llvm;
37 
38 #define DEBUG_TYPE "ppc-vsx-copy"
39 
40 namespace llvm {
41   void initializePPCVSXCopyPass(PassRegistry&);
42 }
43 
44 namespace {
45   // PPCVSXCopy pass - For copies between VSX registers and non-VSX registers
46   // (Altivec and scalar floating-point registers), we need to transform the
47   // copies into subregister copies with other restrictions.
48   struct PPCVSXCopy : public MachineFunctionPass {
49     static char ID;
50     PPCVSXCopy() : MachineFunctionPass(ID) {
51       initializePPCVSXCopyPass(*PassRegistry::getPassRegistry());
52     }
53 
54     const TargetInstrInfo *TII;
55 
56     bool IsRegInClass(unsigned Reg, const TargetRegisterClass *RC,
57                       MachineRegisterInfo &MRI) {
58       if (TargetRegisterInfo::isVirtualRegister(Reg)) {
59         return RC->hasSubClassEq(MRI.getRegClass(Reg));
60       } else if (RC->contains(Reg)) {
61         return true;
62       }
63 
64       return false;
65     }
66 
67     bool IsVSReg(unsigned Reg, MachineRegisterInfo &MRI) {
68       return IsRegInClass(Reg, &PPC::VSRCRegClass, MRI);
69     }
70 
71     bool IsVRReg(unsigned Reg, MachineRegisterInfo &MRI) {
72       return IsRegInClass(Reg, &PPC::VRRCRegClass, MRI);
73     }
74 
75     bool IsF8Reg(unsigned Reg, MachineRegisterInfo &MRI) {
76       return IsRegInClass(Reg, &PPC::F8RCRegClass, MRI);
77     }
78 
79     bool IsVSFReg(unsigned Reg, MachineRegisterInfo &MRI) {
80       return IsRegInClass(Reg, &PPC::VSFRCRegClass, MRI);
81     }
82 
83     bool IsVSSReg(unsigned Reg, MachineRegisterInfo &MRI) {
84       return IsRegInClass(Reg, &PPC::VSSRCRegClass, MRI);
85     }
86 
87 protected:
88     bool processBlock(MachineBasicBlock &MBB) {
89       bool Changed = false;
90 
91       MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
92       for (MachineInstr &MI : MBB) {
93         if (!MI.isFullCopy())
94           continue;
95 
96         MachineOperand &DstMO = MI.getOperand(0);
97         MachineOperand &SrcMO = MI.getOperand(1);
98 
99         if ( IsVSReg(DstMO.getReg(), MRI) &&
100             !IsVSReg(SrcMO.getReg(), MRI)) {
101           // This is a copy *to* a VSX register from a non-VSX register.
102           Changed = true;
103 
104           const TargetRegisterClass *SrcRC = &PPC::VSLRCRegClass;
105           assert((IsF8Reg(SrcMO.getReg(), MRI) ||
106                   IsVSSReg(SrcMO.getReg(), MRI) ||
107                   IsVSFReg(SrcMO.getReg(), MRI)) &&
108                  "Unknown source for a VSX copy");
109 
110           unsigned NewVReg = MRI.createVirtualRegister(SrcRC);
111           BuildMI(MBB, MI, MI.getDebugLoc(),
112                   TII->get(TargetOpcode::SUBREG_TO_REG), NewVReg)
113               .addImm(1) // add 1, not 0, because there is no implicit clearing
114                          // of the high bits.
115               .addOperand(SrcMO)
116               .addImm(PPC::sub_64);
117 
118           // The source of the original copy is now the new virtual register.
119           SrcMO.setReg(NewVReg);
120         } else if (!IsVSReg(DstMO.getReg(), MRI) &&
121                     IsVSReg(SrcMO.getReg(), MRI)) {
122           // This is a copy *from* a VSX register to a non-VSX register.
123           Changed = true;
124 
125           const TargetRegisterClass *DstRC = &PPC::VSLRCRegClass;
126           assert((IsF8Reg(DstMO.getReg(), MRI) ||
127                   IsVSFReg(DstMO.getReg(), MRI) ||
128                   IsVSSReg(DstMO.getReg(), MRI)) &&
129                  "Unknown destination for a VSX copy");
130 
131           // Copy the VSX value into a new VSX register of the correct subclass.
132           unsigned NewVReg = MRI.createVirtualRegister(DstRC);
133           BuildMI(MBB, MI, MI.getDebugLoc(), TII->get(TargetOpcode::COPY),
134                   NewVReg)
135               .addOperand(SrcMO);
136 
137           // Transform the original copy into a subregister extraction copy.
138           SrcMO.setReg(NewVReg);
139           SrcMO.setSubReg(PPC::sub_64);
140         }
141       }
142 
143       return Changed;
144     }
145 
146 public:
147     bool runOnMachineFunction(MachineFunction &MF) override {
148       // If we don't have VSX on the subtarget, don't do anything.
149       const PPCSubtarget &STI = MF.getSubtarget<PPCSubtarget>();
150       if (!STI.hasVSX())
151         return false;
152       TII = STI.getInstrInfo();
153 
154       bool Changed = false;
155 
156       for (MachineFunction::iterator I = MF.begin(); I != MF.end();) {
157         MachineBasicBlock &B = *I++;
158         if (processBlock(B))
159           Changed = true;
160       }
161 
162       return Changed;
163     }
164 
165     void getAnalysisUsage(AnalysisUsage &AU) const override {
166       MachineFunctionPass::getAnalysisUsage(AU);
167     }
168   };
169 }
170 
171 INITIALIZE_PASS(PPCVSXCopy, DEBUG_TYPE,
172                 "PowerPC VSX Copy Legalization", false, false)
173 
174 char PPCVSXCopy::ID = 0;
175 FunctionPass*
176 llvm::createPPCVSXCopyPass() { return new PPCVSXCopy(); }
177 
178