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 PPCTargetMachine *TM;
50     const PPCInstrInfo *TII;
51     LiveIntervals *LIS;
52 
53 protected:
54     bool processBlock(MachineBasicBlock &MBB) {
55       bool Changed = false;
56       bool Is64Bit = TM->getSubtargetImpl()->isPPC64();
57 
58       for (MachineBasicBlock::iterator I = MBB.begin(), IE = MBB.end();
59            I != IE; ++I) {
60         MachineInstr *MI = I;
61 
62         if (MI->getOpcode() != PPC::ADDItlsgdLADDR &&
63             MI->getOpcode() != PPC::ADDItlsldLADDR &&
64             MI->getOpcode() != PPC::ADDItlsgdLADDR32 &&
65             MI->getOpcode() != PPC::ADDItlsldLADDR32)
66           continue;
67 
68         DEBUG(dbgs() << "TLS Dynamic Call Fixup:\n    " << *MI;);
69 
70         unsigned OutReg = MI->getOperand(0).getReg();
71         unsigned InReg  = MI->getOperand(1).getReg();
72         DebugLoc DL = MI->getDebugLoc();
73         unsigned GPR3 = Is64Bit ? PPC::X3 : PPC::R3;
74         unsigned Opc1, Opc2;
75         SmallVector<unsigned, 4> OrigRegs;
76         OrigRegs.push_back(OutReg);
77         OrigRegs.push_back(InReg);
78         OrigRegs.push_back(GPR3);
79 
80         switch (MI->getOpcode()) {
81         default:
82           llvm_unreachable("Opcode inconsistency error");
83         case PPC::ADDItlsgdLADDR:
84           Opc1 = PPC::ADDItlsgdL;
85           Opc2 = PPC::GETtlsADDR;
86           break;
87         case PPC::ADDItlsldLADDR:
88           Opc1 = PPC::ADDItlsldL;
89           Opc2 = PPC::GETtlsldADDR;
90           break;
91         case PPC::ADDItlsgdLADDR32:
92           Opc1 = PPC::ADDItlsgdL32;
93           Opc2 = PPC::GETtlsADDR32;
94           break;
95         case PPC::ADDItlsldLADDR32:
96           Opc1 = PPC::ADDItlsldL32;
97           Opc2 = PPC::GETtlsldADDR32;
98           break;
99         }
100 
101         // Expand into two ops built prior to the existing instruction.
102         MachineInstr *Addi = BuildMI(MBB, I, DL, TII->get(Opc1), GPR3)
103           .addReg(InReg);
104         Addi->addOperand(MI->getOperand(2));
105 
106         // The ADDItls* instruction is the first instruction in the
107         // repair range.
108         MachineBasicBlock::iterator First = I;
109         --First;
110 
111         MachineInstr *Call = (BuildMI(MBB, I, DL, TII->get(Opc2), GPR3)
112                               .addReg(GPR3));
113         Call->addOperand(MI->getOperand(3));
114 
115         BuildMI(MBB, I, DL, TII->get(TargetOpcode::COPY), OutReg)
116           .addReg(GPR3);
117 
118         // The COPY is the last instruction in the repair range.
119         MachineBasicBlock::iterator Last = I;
120         --Last;
121 
122         // Move past the original instruction and remove it.
123         ++I;
124         MI->removeFromParent();
125 
126         // Repair the live intervals.
127         LIS->repairIntervalsInRange(&MBB, First, Last, OrigRegs);
128         Changed = true;
129       }
130 
131       return Changed;
132     }
133 
134 public:
135     bool runOnMachineFunction(MachineFunction &MF) override {
136       TM = static_cast<const PPCTargetMachine *>(&MF.getTarget());
137       TII = TM->getSubtargetImpl()->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