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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         const unsigned OrigRegs[] = {OutReg, InReg, GPR3};
     77 
     78         switch (MI->getOpcode()) {
     79         default:
     80           llvm_unreachable("Opcode inconsistency error");
     81         case PPC::ADDItlsgdLADDR:
     82           Opc1 = PPC::ADDItlsgdL;
     83           Opc2 = PPC::GETtlsADDR;
     84           break;
     85         case PPC::ADDItlsldLADDR:
     86           Opc1 = PPC::ADDItlsldL;
     87           Opc2 = PPC::GETtlsldADDR;
     88           break;
     89         case PPC::ADDItlsgdLADDR32:
     90           Opc1 = PPC::ADDItlsgdL32;
     91           Opc2 = PPC::GETtlsADDR32;
     92           break;
     93         case PPC::ADDItlsldLADDR32:
     94           Opc1 = PPC::ADDItlsldL32;
     95           Opc2 = PPC::GETtlsldADDR32;
     96           break;
     97         }
     98 
     99         // Don't really need to save data to the stack - the clobbered
    100         // registers are already saved when the SDNode (e.g. PPCaddiTlsgdLAddr)
    101         // gets translated to the pseudo instruction (e.g. ADDItlsgdLADDR).
    102         BuildMI(MBB, I, DL, TII->get(PPC::ADJCALLSTACKDOWN)).addImm(0);
    103 
    104         // Expand into two ops built prior to the existing instruction.
    105         MachineInstr *Addi = BuildMI(MBB, I, DL, TII->get(Opc1), GPR3)
    106           .addReg(InReg);
    107         Addi->addOperand(MI->getOperand(2));
    108 
    109         // The ADDItls* instruction is the first instruction in the
    110         // repair range.
    111         MachineBasicBlock::iterator First = I;
    112         --First;
    113 
    114         MachineInstr *Call = (BuildMI(MBB, I, DL, TII->get(Opc2), GPR3)
    115                               .addReg(GPR3));
    116         Call->addOperand(MI->getOperand(3));
    117 
    118         BuildMI(MBB, I, DL, TII->get(PPC::ADJCALLSTACKUP)).addImm(0).addImm(0);
    119 
    120         BuildMI(MBB, I, DL, TII->get(TargetOpcode::COPY), OutReg)
    121           .addReg(GPR3);
    122 
    123         // The COPY is the last instruction in the repair range.
    124         MachineBasicBlock::iterator Last = I;
    125         --Last;
    126 
    127         // Move past the original instruction and remove it.
    128         ++I;
    129         MI->removeFromParent();
    130 
    131         // Repair the live intervals.
    132         LIS->repairIntervalsInRange(&MBB, First, Last, OrigRegs);
    133         Changed = true;
    134       }
    135 
    136       return Changed;
    137     }
    138 
    139 public:
    140     bool runOnMachineFunction(MachineFunction &MF) override {
    141       TII = MF.getSubtarget<PPCSubtarget>().getInstrInfo();
    142       LIS = &getAnalysis<LiveIntervals>();
    143 
    144       bool Changed = false;
    145 
    146       for (MachineFunction::iterator I = MF.begin(); I != MF.end();) {
    147         MachineBasicBlock &B = *I++;
    148         if (processBlock(B))
    149           Changed = true;
    150       }
    151 
    152       return Changed;
    153     }
    154 
    155     void getAnalysisUsage(AnalysisUsage &AU) const override {
    156       AU.addRequired<LiveIntervals>();
    157       AU.addPreserved<LiveIntervals>();
    158       AU.addRequired<SlotIndexes>();
    159       AU.addPreserved<SlotIndexes>();
    160       MachineFunctionPass::getAnalysisUsage(AU);
    161     }
    162   };
    163 }
    164 
    165 INITIALIZE_PASS_BEGIN(PPCTLSDynamicCall, DEBUG_TYPE,
    166                       "PowerPC TLS Dynamic Call Fixup", false, false)
    167 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
    168 INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
    169 INITIALIZE_PASS_END(PPCTLSDynamicCall, DEBUG_TYPE,
    170                     "PowerPC TLS Dynamic Call Fixup", false, false)
    171 
    172 char PPCTLSDynamicCall::ID = 0;
    173 FunctionPass*
    174 llvm::createPPCTLSDynamicCallPass() { return new PPCTLSDynamicCall(); }
    175