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 static CodeModel::Model getEffectiveCodeModel(Optional<CodeModel::Model> CM) {
55   if (CM)
56     return *CM;
57   return CodeModel::Small;
58 }
59 
60 BPFTargetMachine::BPFTargetMachine(const Target &T, const Triple &TT,
61                                    StringRef CPU, StringRef FS,
62                                    const TargetOptions &Options,
63                                    Optional<Reloc::Model> RM,
64                                    Optional<CodeModel::Model> CM,
65                                    CodeGenOpt::Level OL, bool JIT)
66     : LLVMTargetMachine(T, computeDataLayout(TT), TT, CPU, FS, Options,
67                         getEffectiveRelocModel(RM), getEffectiveCodeModel(CM),
68                         OL),
69       TLOF(make_unique<TargetLoweringObjectFileELF>()),
70       Subtarget(TT, CPU, FS, *this) {
71   initAsmInfo();
72 
73   BPFMCAsmInfo *MAI = static_cast<BPFMCAsmInfo *>(const_cast<MCAsmInfo *>(AsmInfo));
74   MAI->setDwarfUsesRelocationsAcrossSections(!Subtarget.getUseDwarfRIS());
75 }
76 namespace {
77 // BPF Code Generator Pass Configuration Options.
78 class BPFPassConfig : public TargetPassConfig {
79 public:
80   BPFPassConfig(BPFTargetMachine &TM, PassManagerBase &PM)
81       : TargetPassConfig(TM, PM) {}
82 
83   BPFTargetMachine &getBPFTargetMachine() const {
84     return getTM<BPFTargetMachine>();
85   }
86 
87   bool addInstSelector() override;
88   void addMachineSSAOptimization() override;
89   void addPreEmitPass() override;
90 };
91 }
92 
93 TargetPassConfig *BPFTargetMachine::createPassConfig(PassManagerBase &PM) {
94   return new BPFPassConfig(*this, PM);
95 }
96 
97 // Install an instruction selector pass using
98 // the ISelDag to gen BPF code.
99 bool BPFPassConfig::addInstSelector() {
100   addPass(createBPFISelDag(getBPFTargetMachine()));
101 
102   return false;
103 }
104 
105 void BPFPassConfig::addMachineSSAOptimization() {
106   // The default implementation must be called first as we want eBPF
107   // Peephole ran at last.
108   TargetPassConfig::addMachineSSAOptimization();
109 
110   const BPFSubtarget *Subtarget = getBPFTargetMachine().getSubtargetImpl();
111   if (Subtarget->getHasAlu32() && !DisableMIPeephole)
112     addPass(createBPFMIPeepholePass());
113 }
114 
115 void BPFPassConfig::addPreEmitPass() {
116   const BPFSubtarget *Subtarget = getBPFTargetMachine().getSubtargetImpl();
117 
118   addPass(createBPFMIPreEmitCheckingPass());
119   if (getOptLevel() != CodeGenOpt::None)
120     if (Subtarget->getHasAlu32() && !DisableMIPeephole)
121       addPass(createBPFMIPreEmitPeepholePass());
122 }
123