1 //===-------------- PPCVSXCopy.cpp - VSX Copy Legalization ----------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // A pass which deals with the complexity of generating legal VSX register
10 // copies to/from register classes which partially overlap with the VSX
11 // register file.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "MCTargetDesc/PPCPredicates.h"
16 #include "PPC.h"
17 #include "PPCHazardRecognizers.h"
18 #include "PPCInstrBuilder.h"
19 #include "PPCInstrInfo.h"
20 #include "PPCMachineFunctionInfo.h"
21 #include "PPCTargetMachine.h"
22 #include "llvm/ADT/STLExtras.h"
23 #include "llvm/ADT/Statistic.h"
24 #include "llvm/CodeGen/MachineFrameInfo.h"
25 #include "llvm/CodeGen/MachineFunctionPass.h"
26 #include "llvm/CodeGen/MachineInstrBuilder.h"
27 #include "llvm/CodeGen/MachineMemOperand.h"
28 #include "llvm/CodeGen/MachineRegisterInfo.h"
29 #include "llvm/MC/MCAsmInfo.h"
30 #include "llvm/MC/TargetRegistry.h"
31 #include "llvm/Support/Debug.h"
32 #include "llvm/Support/ErrorHandling.h"
33 #include "llvm/Support/raw_ostream.h"
34 
35 using namespace llvm;
36 
37 #define DEBUG_TYPE "ppc-vsx-copy"
38 
39 namespace {
40   // PPCVSXCopy pass - For copies between VSX registers and non-VSX registers
41   // (Altivec and scalar floating-point registers), we need to transform the
42   // copies into subregister copies with other restrictions.
43   struct PPCVSXCopy : public MachineFunctionPass {
44     static char ID;
45     PPCVSXCopy() : MachineFunctionPass(ID) {
46       initializePPCVSXCopyPass(*PassRegistry::getPassRegistry());
47     }
48 
49     const TargetInstrInfo *TII;
50 
51     bool IsRegInClass(unsigned Reg, const TargetRegisterClass *RC,
52                       MachineRegisterInfo &MRI) {
53       if (Register::isVirtualRegister(Reg)) {
54         return RC->hasSubClassEq(MRI.getRegClass(Reg));
55       } else if (RC->contains(Reg)) {
56         return true;
57       }
58 
59       return false;
60     }
61 
62     bool IsVSReg(unsigned Reg, MachineRegisterInfo &MRI) {
63       return IsRegInClass(Reg, &PPC::VSRCRegClass, MRI);
64     }
65 
66     bool IsVRReg(unsigned Reg, MachineRegisterInfo &MRI) {
67       return IsRegInClass(Reg, &PPC::VRRCRegClass, MRI);
68     }
69 
70     bool IsF8Reg(unsigned Reg, MachineRegisterInfo &MRI) {
71       return IsRegInClass(Reg, &PPC::F8RCRegClass, MRI);
72     }
73 
74     bool IsVSFReg(unsigned Reg, MachineRegisterInfo &MRI) {
75       return IsRegInClass(Reg, &PPC::VSFRCRegClass, MRI);
76     }
77 
78     bool IsVSSReg(unsigned Reg, MachineRegisterInfo &MRI) {
79       return IsRegInClass(Reg, &PPC::VSSRCRegClass, MRI);
80     }
81 
82 protected:
83     bool processBlock(MachineBasicBlock &MBB) {
84       bool Changed = false;
85 
86       MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
87       for (MachineInstr &MI : MBB) {
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 = &PPC::VSLRCRegClass;
100           assert((IsF8Reg(SrcMO.getReg(), MRI) ||
101                   IsVSSReg(SrcMO.getReg(), MRI) ||
102                   IsVSFReg(SrcMO.getReg(), MRI)) &&
103                  "Unknown source for a VSX copy");
104 
105           Register NewVReg = MRI.createVirtualRegister(SrcRC);
106           BuildMI(MBB, MI, MI.getDebugLoc(),
107                   TII->get(TargetOpcode::SUBREG_TO_REG), NewVReg)
108               .addImm(1) // add 1, not 0, because there is no implicit clearing
109                          // of the high bits.
110               .add(SrcMO)
111               .addImm(PPC::sub_64);
112 
113           // The source of the original copy is now the new virtual register.
114           SrcMO.setReg(NewVReg);
115         } else if (!IsVSReg(DstMO.getReg(), MRI) &&
116                     IsVSReg(SrcMO.getReg(), MRI)) {
117           // This is a copy *from* a VSX register to a non-VSX register.
118           Changed = true;
119 
120           const TargetRegisterClass *DstRC = &PPC::VSLRCRegClass;
121           assert((IsF8Reg(DstMO.getReg(), MRI) ||
122                   IsVSFReg(DstMO.getReg(), MRI) ||
123                   IsVSSReg(DstMO.getReg(), MRI)) &&
124                  "Unknown destination for a VSX copy");
125 
126           // Copy the VSX value into a new VSX register of the correct subclass.
127           Register NewVReg = MRI.createVirtualRegister(DstRC);
128           BuildMI(MBB, MI, MI.getDebugLoc(), TII->get(TargetOpcode::COPY),
129                   NewVReg)
130               .add(SrcMO);
131 
132           // Transform the original copy into a subregister extraction copy.
133           SrcMO.setReg(NewVReg);
134           SrcMO.setSubReg(PPC::sub_64);
135         }
136       }
137 
138       return Changed;
139     }
140 
141 public:
142     bool runOnMachineFunction(MachineFunction &MF) override {
143       // If we don't have VSX on the subtarget, don't do anything.
144       const PPCSubtarget &STI = MF.getSubtarget<PPCSubtarget>();
145       if (!STI.hasVSX())
146         return false;
147       TII = STI.getInstrInfo();
148 
149       bool Changed = false;
150 
151       for (MachineBasicBlock &B : llvm::make_early_inc_range(MF))
152         if (processBlock(B))
153           Changed = true;
154 
155       return Changed;
156     }
157 
158     void getAnalysisUsage(AnalysisUsage &AU) const override {
159       MachineFunctionPass::getAnalysisUsage(AU);
160     }
161   };
162 }
163 
164 INITIALIZE_PASS(PPCVSXCopy, DEBUG_TYPE,
165                 "PowerPC VSX Copy Legalization", false, false)
166 
167 char PPCVSXCopy::ID = 0;
168 FunctionPass*
169 llvm::createPPCVSXCopyPass() { return new PPCVSXCopy(); }
170