1 //===-- BPFTargetMachine.cpp - Define TargetMachine for BPF ---------------===//
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 // Implements the info about BPF target spec.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "BPFTargetMachine.h"
15 #include "BPF.h"
16 #include "MCTargetDesc/BPFMCAsmInfo.h"
17 #include "llvm/CodeGen/Passes.h"
18 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
19 #include "llvm/CodeGen/TargetPassConfig.h"
20 #include "llvm/IR/LegacyPassManager.h"
21 #include "llvm/Support/FormattedStream.h"
22 #include "llvm/Support/TargetRegistry.h"
23 #include "llvm/Target/TargetOptions.h"
24 using namespace llvm;
25 
26 static cl::
27 opt<bool> DisableMIPeephole("disable-bpf-peephole", cl::Hidden,
28                             cl::desc("Disable machine peepholes for BPF"));
29 
30 extern "C" void LLVMInitializeBPFTarget() {
31   // Register the target.
32   RegisterTargetMachine<BPFTargetMachine> X(getTheBPFleTarget());
33   RegisterTargetMachine<BPFTargetMachine> Y(getTheBPFbeTarget());
34   RegisterTargetMachine<BPFTargetMachine> Z(getTheBPFTarget());
35 
36   PassRegistry &PR = *PassRegistry::getPassRegistry();
37   initializeBPFMIPeepholePass(PR);
38 }
39 
40 // DataLayout: little or big endian
41 static std::string computeDataLayout(const Triple &TT) {
42   if (TT.getArch() == Triple::bpfeb)
43     return "E-m:e-p:64:64-i64:64-n32:64-S128";
44   else
45     return "e-m:e-p:64:64-i64:64-n32:64-S128";
46 }
47 
48 static Reloc::Model getEffectiveRelocModel(Optional<Reloc::Model> RM) {
49   if (!RM.hasValue())
50     return Reloc::PIC_;
51   return *RM;
52 }
53 
54 BPFTargetMachine::BPFTargetMachine(const Target &T, const Triple &TT,
55                                    StringRef CPU, StringRef FS,
56                                    const TargetOptions &Options,
57                                    Optional<Reloc::Model> RM,
58                                    Optional<CodeModel::Model> CM,
59                                    CodeGenOpt::Level OL, bool JIT)
60     : LLVMTargetMachine(T, computeDataLayout(TT), TT, CPU, FS, Options,
61                         getEffectiveRelocModel(RM),
62                         getEffectiveCodeModel(CM, CodeModel::Small), OL),
63       TLOF(make_unique<TargetLoweringObjectFileELF>()),
64       Subtarget(TT, CPU, FS, *this) {
65   initAsmInfo();
66 
67   BPFMCAsmInfo *MAI =
68       static_cast<BPFMCAsmInfo *>(const_cast<MCAsmInfo *>(AsmInfo.get()));
69   MAI->setDwarfUsesRelocationsAcrossSections(!Subtarget.getUseDwarfRIS());
70 }
71 namespace {
72 // BPF Code Generator Pass Configuration Options.
73 class BPFPassConfig : public TargetPassConfig {
74 public:
75   BPFPassConfig(BPFTargetMachine &TM, PassManagerBase &PM)
76       : TargetPassConfig(TM, PM) {}
77 
78   BPFTargetMachine &getBPFTargetMachine() const {
79     return getTM<BPFTargetMachine>();
80   }
81 
82   bool addInstSelector() override;
83   void addMachineSSAOptimization() override;
84   void addPreEmitPass() override;
85 };
86 }
87 
88 TargetPassConfig *BPFTargetMachine::createPassConfig(PassManagerBase &PM) {
89   return new BPFPassConfig(*this, PM);
90 }
91 
92 // Install an instruction selector pass using
93 // the ISelDag to gen BPF code.
94 bool BPFPassConfig::addInstSelector() {
95   addPass(createBPFISelDag(getBPFTargetMachine()));
96 
97   return false;
98 }
99 
100 void BPFPassConfig::addMachineSSAOptimization() {
101   // The default implementation must be called first as we want eBPF
102   // Peephole ran at last.
103   TargetPassConfig::addMachineSSAOptimization();
104 
105   const BPFSubtarget *Subtarget = getBPFTargetMachine().getSubtargetImpl();
106   if (Subtarget->getHasAlu32() && !DisableMIPeephole)
107     addPass(createBPFMIPeepholePass());
108 }
109 
110 void BPFPassConfig::addPreEmitPass() {
111   const BPFSubtarget *Subtarget = getBPFTargetMachine().getSubtargetImpl();
112 
113   addPass(createBPFMIPreEmitCheckingPass());
114   if (getOptLevel() != CodeGenOpt::None)
115     if (Subtarget->getHasAlu32() && !DisableMIPeephole)
116       addPass(createBPFMIPreEmitPeepholePass());
117 }
118