1 //===-- BPFTargetMachine.cpp - Define TargetMachine for BPF ---------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // Implements the info about BPF target spec.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "BPFTargetMachine.h"
14 #include "BPF.h"
15 #include "MCTargetDesc/BPFMCAsmInfo.h"
16 #include "llvm/CodeGen/Passes.h"
17 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
18 #include "llvm/CodeGen/TargetPassConfig.h"
19 #include "llvm/IR/LegacyPassManager.h"
20 #include "llvm/Support/FormattedStream.h"
21 #include "llvm/Support/TargetRegistry.h"
22 #include "llvm/Target/TargetOptions.h"
23 using namespace llvm;
24 
25 static cl::
26 opt<bool> DisableMIPeephole("disable-bpf-peephole", cl::Hidden,
27                             cl::desc("Disable machine peepholes for BPF"));
28 
29 extern "C" void LLVMInitializeBPFTarget() {
30   // Register the target.
31   RegisterTargetMachine<BPFTargetMachine> X(getTheBPFleTarget());
32   RegisterTargetMachine<BPFTargetMachine> Y(getTheBPFbeTarget());
33   RegisterTargetMachine<BPFTargetMachine> Z(getTheBPFTarget());
34 
35   PassRegistry &PR = *PassRegistry::getPassRegistry();
36   initializeBPFMIPeepholePass(PR);
37 }
38 
39 // DataLayout: little or big endian
40 static std::string computeDataLayout(const Triple &TT) {
41   if (TT.getArch() == Triple::bpfeb)
42     return "E-m:e-p:64:64-i64:64-n32:64-S128";
43   else
44     return "e-m:e-p:64:64-i64:64-n32:64-S128";
45 }
46 
47 static Reloc::Model getEffectiveRelocModel(Optional<Reloc::Model> RM) {
48   if (!RM.hasValue())
49     return Reloc::PIC_;
50   return *RM;
51 }
52 
53 BPFTargetMachine::BPFTargetMachine(const Target &T, const Triple &TT,
54                                    StringRef CPU, StringRef FS,
55                                    const TargetOptions &Options,
56                                    Optional<Reloc::Model> RM,
57                                    Optional<CodeModel::Model> CM,
58                                    CodeGenOpt::Level OL, bool JIT)
59     : LLVMTargetMachine(T, computeDataLayout(TT), TT, CPU, FS, Options,
60                         getEffectiveRelocModel(RM),
61                         getEffectiveCodeModel(CM, CodeModel::Small), OL),
62       TLOF(make_unique<TargetLoweringObjectFileELF>()),
63       Subtarget(TT, CPU, FS, *this) {
64   initAsmInfo();
65 
66   BPFMCAsmInfo *MAI =
67       static_cast<BPFMCAsmInfo *>(const_cast<MCAsmInfo *>(AsmInfo.get()));
68   MAI->setDwarfUsesRelocationsAcrossSections(!Subtarget.getUseDwarfRIS());
69 }
70 namespace {
71 // BPF Code Generator Pass Configuration Options.
72 class BPFPassConfig : public TargetPassConfig {
73 public:
74   BPFPassConfig(BPFTargetMachine &TM, PassManagerBase &PM)
75       : TargetPassConfig(TM, PM) {}
76 
77   BPFTargetMachine &getBPFTargetMachine() const {
78     return getTM<BPFTargetMachine>();
79   }
80 
81   bool addInstSelector() override;
82   void addMachineSSAOptimization() override;
83   void addPreEmitPass() override;
84 };
85 }
86 
87 TargetPassConfig *BPFTargetMachine::createPassConfig(PassManagerBase &PM) {
88   return new BPFPassConfig(*this, PM);
89 }
90 
91 // Install an instruction selector pass using
92 // the ISelDag to gen BPF code.
93 bool BPFPassConfig::addInstSelector() {
94   addPass(createBPFISelDag(getBPFTargetMachine()));
95 
96   return false;
97 }
98 
99 void BPFPassConfig::addMachineSSAOptimization() {
100   // The default implementation must be called first as we want eBPF
101   // Peephole ran at last.
102   TargetPassConfig::addMachineSSAOptimization();
103 
104   const BPFSubtarget *Subtarget = getBPFTargetMachine().getSubtargetImpl();
105   if (Subtarget->getHasAlu32() && !DisableMIPeephole)
106     addPass(createBPFMIPeepholePass());
107 }
108 
109 void BPFPassConfig::addPreEmitPass() {
110   const BPFSubtarget *Subtarget = getBPFTargetMachine().getSubtargetImpl();
111 
112   addPass(createBPFMIPreEmitCheckingPass());
113   if (getOptLevel() != CodeGenOpt::None)
114     if (Subtarget->getHasAlu32() && !DisableMIPeephole)
115       addPass(createBPFMIPreEmitPeepholePass());
116 }
117