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      1 //===---------- PPCTLSDynamicCall.cpp - TLS Dynamic Call Fixup ------------===//
      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 // This pass expands ADDItls{ld,gd}LADDR[32] machine instructions into
     11 // separate ADDItls[gd]L[32] and GETtlsADDR[32] instructions, both of
     12 // which define GPR3.  A copy is added from GPR3 to the target virtual
     13 // register of the original instruction.  The GETtlsADDR[32] is really
     14 // a call instruction, so its target register is constrained to be GPR3.
     15 // This is not true of ADDItls[gd]L[32], but there is a legacy linker
     16 // optimization bug that requires the target register of the addi of
     17 // a local- or general-dynamic TLS access sequence to be GPR3.
     18 //
     19 // This is done in a late pass so that TLS variable accesses can be
     20 // fully commoned by MachineCSE.
     21 //
     22 //===----------------------------------------------------------------------===//
     23 
     24 #include "PPCInstrInfo.h"
     25 #include "PPC.h"
     26 #include "PPCInstrBuilder.h"
     27 #include "PPCTargetMachine.h"
     28 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
     29 #include "llvm/CodeGen/MachineFunctionPass.h"
     30 #include "llvm/CodeGen/MachineInstrBuilder.h"
     31 #include "llvm/Support/Debug.h"
     32 #include "llvm/Support/raw_ostream.h"
     33 
     34 using namespace llvm;
     35 
     36 #define DEBUG_TYPE "ppc-tls-dynamic-call"
     37 
     38 namespace llvm {
     39   void initializePPCTLSDynamicCallPass(PassRegistry&);
     40 }
     41 
     42 namespace {
     43   struct PPCTLSDynamicCall : public MachineFunctionPass {
     44     static char ID;
     45     PPCTLSDynamicCall() : MachineFunctionPass(ID) {
     46       initializePPCTLSDynamicCallPass(*PassRegistry::getPassRegistry());
     47     }
     48 
     49     const PPCInstrInfo *TII;
     50     LiveIntervals *LIS;
     51 
     52 protected:
     53     bool processBlock(MachineBasicBlock &MBB) {
     54       bool Changed = false;
     55       bool Is64Bit = MBB.getParent()->getSubtarget<PPCSubtarget>().isPPC64();
     56 
     57       for (MachineBasicBlock::iterator I = MBB.begin(), IE = MBB.end();
     58            I != IE;) {
     59         MachineInstr *MI = I;
     60 
     61         if (MI->getOpcode() != PPC::ADDItlsgdLADDR &&
     62             MI->getOpcode() != PPC::ADDItlsldLADDR &&
     63             MI->getOpcode() != PPC::ADDItlsgdLADDR32 &&
     64             MI->getOpcode() != PPC::ADDItlsldLADDR32) {
     65           ++I;
     66           continue;
     67         }
     68 
     69         DEBUG(dbgs() << "TLS Dynamic Call Fixup:\n    " << *MI;);
     70 
     71         unsigned OutReg = MI->getOperand(0).getReg();
     72         unsigned InReg  = MI->getOperand(1).getReg();
     73         DebugLoc DL = MI->getDebugLoc();
     74         unsigned GPR3 = Is64Bit ? PPC::X3 : PPC::R3;
     75         unsigned Opc1, Opc2;
     76         SmallVector<unsigned, 4> OrigRegs;
     77         OrigRegs.push_back(OutReg);
     78         OrigRegs.push_back(InReg);
     79         OrigRegs.push_back(GPR3);
     80 
     81         switch (MI->getOpcode()) {
     82         default:
     83           llvm_unreachable("Opcode inconsistency error");
     84         case PPC::ADDItlsgdLADDR:
     85           Opc1 = PPC::ADDItlsgdL;
     86           Opc2 = PPC::GETtlsADDR;
     87           break;
     88         case PPC::ADDItlsldLADDR:
     89           Opc1 = PPC::ADDItlsldL;
     90           Opc2 = PPC::GETtlsldADDR;
     91           break;
     92         case PPC::ADDItlsgdLADDR32:
     93           Opc1 = PPC::ADDItlsgdL32;
     94           Opc2 = PPC::GETtlsADDR32;
     95           break;
     96         case PPC::ADDItlsldLADDR32:
     97           Opc1 = PPC::ADDItlsldL32;
     98           Opc2 = PPC::GETtlsldADDR32;
     99           break;
    100         }
    101 
    102         // Expand into two ops built prior to the existing instruction.
    103         MachineInstr *Addi = BuildMI(MBB, I, DL, TII->get(Opc1), GPR3)
    104           .addReg(InReg);
    105         Addi->addOperand(MI->getOperand(2));
    106 
    107         // The ADDItls* instruction is the first instruction in the
    108         // repair range.
    109         MachineBasicBlock::iterator First = I;
    110         --First;
    111 
    112         MachineInstr *Call = (BuildMI(MBB, I, DL, TII->get(Opc2), GPR3)
    113                               .addReg(GPR3));
    114         Call->addOperand(MI->getOperand(3));
    115 
    116         BuildMI(MBB, I, DL, TII->get(TargetOpcode::COPY), OutReg)
    117           .addReg(GPR3);
    118 
    119         // The COPY is the last instruction in the repair range.
    120         MachineBasicBlock::iterator Last = I;
    121         --Last;
    122 
    123         // Move past the original instruction and remove it.
    124         ++I;
    125         MI->removeFromParent();
    126 
    127         // Repair the live intervals.
    128         LIS->repairIntervalsInRange(&MBB, First, Last, OrigRegs);
    129         Changed = true;
    130       }
    131 
    132       return Changed;
    133     }
    134 
    135 public:
    136     bool runOnMachineFunction(MachineFunction &MF) override {
    137       TII = MF.getSubtarget<PPCSubtarget>().getInstrInfo();
    138       LIS = &getAnalysis<LiveIntervals>();
    139 
    140       bool Changed = false;
    141 
    142       for (MachineFunction::iterator I = MF.begin(); I != MF.end();) {
    143         MachineBasicBlock &B = *I++;
    144         if (processBlock(B))
    145           Changed = true;
    146       }
    147 
    148       return Changed;
    149     }
    150 
    151     void getAnalysisUsage(AnalysisUsage &AU) const override {
    152       AU.addRequired<LiveIntervals>();
    153       AU.addPreserved<LiveIntervals>();
    154       AU.addRequired<SlotIndexes>();
    155       AU.addPreserved<SlotIndexes>();
    156       MachineFunctionPass::getAnalysisUsage(AU);
    157     }
    158   };
    159 }
    160 
    161 INITIALIZE_PASS_BEGIN(PPCTLSDynamicCall, DEBUG_TYPE,
    162                       "PowerPC TLS Dynamic Call Fixup", false, false)
    163 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
    164 INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
    165 INITIALIZE_PASS_END(PPCTLSDynamicCall, DEBUG_TYPE,
    166                     "PowerPC TLS Dynamic Call Fixup", false, false)
    167 
    168 char PPCTLSDynamicCall::ID = 0;
    169 FunctionPass*
    170 llvm::createPPCTLSDynamicCallPass() { return new PPCTLSDynamicCall(); }
    171