lib/Target/PowerPC/PPCVSXCopy.cpp

   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/Support/Debug.h"
  31 #include "llvm/Support/ErrorHandling.h"
  32 #include "llvm/Support/TargetRegistry.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 (MachineFunction::iterator I = MF.begin(); I != MF.end();) {
 152         MachineBasicBlock &B = *I++;
 153         if (processBlock(B))
 154           Changed = true;
 155       }
 156
 157       return Changed;
 158     }
 159
 160     void getAnalysisUsage(AnalysisUsage &AU) const override {
 161       MachineFunctionPass::getAnalysisUsage(AU);
 162     }
 163   };
 164 }
 165
 166 INITIALIZE_PASS(PPCVSXCopy, DEBUG_TYPE,
 167                 "PowerPC VSX Copy Legalization", false, false)
 168
 169 char PPCVSXCopy::ID = 0;
 170 FunctionPass*
 171 llvm::createPPCVSXCopyPass() { return new PPCVSXCopy(); }
 172