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 "TargetInfo/BPFTargetInfo.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/IR/PassManager.h"
22 #include "llvm/Passes/PassBuilder.h"
23 #include "llvm/Support/FormattedStream.h"
24 #include "llvm/Support/TargetRegistry.h"
25 #include "llvm/Target/TargetOptions.h"
26 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
27 #include "llvm/Transforms/Scalar.h"
28 #include "llvm/Transforms/Scalar/SimplifyCFG.h"
29 #include "llvm/Transforms/Utils/SimplifyCFGOptions.h"
30 using namespace llvm;
31 
32 static cl::
33 opt<bool> DisableMIPeephole("disable-bpf-peephole", cl::Hidden,
34                             cl::desc("Disable machine peepholes for BPF"));
35 
36 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeBPFTarget() {
37   // Register the target.
38   RegisterTargetMachine<BPFTargetMachine> X(getTheBPFleTarget());
39   RegisterTargetMachine<BPFTargetMachine> Y(getTheBPFbeTarget());
40   RegisterTargetMachine<BPFTargetMachine> Z(getTheBPFTarget());
41 
42   PassRegistry &PR = *PassRegistry::getPassRegistry();
43   initializeBPFAbstractMemberAccessLegacyPassPass(PR);
44   initializeBPFPreserveDITypePass(PR);
45   initializeBPFCheckAndAdjustIRPass(PR);
46   initializeBPFMIPeepholePass(PR);
47   initializeBPFMIPeepholeTruncElimPass(PR);
48 }
49 
50 // DataLayout: little or big endian
51 static std::string computeDataLayout(const Triple &TT) {
52   if (TT.getArch() == Triple::bpfeb)
53     return "E-m:e-p:64:64-i64:64-i128:128-n32:64-S128";
54   else
55     return "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128";
56 }
57 
58 static Reloc::Model getEffectiveRelocModel(Optional<Reloc::Model> RM) {
59   if (!RM.hasValue())
60     return Reloc::PIC_;
61   return *RM;
62 }
63 
64 BPFTargetMachine::BPFTargetMachine(const Target &T, const Triple &TT,
65                                    StringRef CPU, StringRef FS,
66                                    const TargetOptions &Options,
67                                    Optional<Reloc::Model> RM,
68                                    Optional<CodeModel::Model> CM,
69                                    CodeGenOpt::Level OL, bool JIT)
70     : LLVMTargetMachine(T, computeDataLayout(TT), TT, CPU, FS, Options,
71                         getEffectiveRelocModel(RM),
72                         getEffectiveCodeModel(CM, CodeModel::Small), OL),
73       TLOF(std::make_unique<TargetLoweringObjectFileELF>()),
74       Subtarget(TT, std::string(CPU), std::string(FS), *this) {
75   initAsmInfo();
76 
77   BPFMCAsmInfo *MAI =
78       static_cast<BPFMCAsmInfo *>(const_cast<MCAsmInfo *>(AsmInfo.get()));
79   MAI->setDwarfUsesRelocationsAcrossSections(!Subtarget.getUseDwarfRIS());
80 }
81 
82 namespace {
83 // BPF Code Generator Pass Configuration Options.
84 class BPFPassConfig : public TargetPassConfig {
85 public:
86   BPFPassConfig(BPFTargetMachine &TM, PassManagerBase &PM)
87       : TargetPassConfig(TM, PM) {}
88 
89   BPFTargetMachine &getBPFTargetMachine() const {
90     return getTM<BPFTargetMachine>();
91   }
92 
93   void addIRPasses() override;
94   bool addInstSelector() override;
95   void addMachineSSAOptimization() override;
96   void addPreEmitPass() override;
97 };
98 }
99 
100 TargetPassConfig *BPFTargetMachine::createPassConfig(PassManagerBase &PM) {
101   return new BPFPassConfig(*this, PM);
102 }
103 
104 void BPFTargetMachine::adjustPassManager(PassManagerBuilder &Builder) {
105  Builder.addExtension(
106       PassManagerBuilder::EP_EarlyAsPossible,
107       [&](const PassManagerBuilder &, legacy::PassManagerBase &PM) {
108         PM.add(createBPFAbstractMemberAccess(this));
109         PM.add(createBPFPreserveDIType());
110       });
111 
112   Builder.addExtension(
113       PassManagerBuilder::EP_Peephole,
114       [&](const PassManagerBuilder &, legacy::PassManagerBase &PM) {
115         PM.add(createCFGSimplificationPass(
116             SimplifyCFGOptions().hoistCommonInsts(true)));
117       });
118 }
119 
120 void BPFTargetMachine::registerPassBuilderCallbacks(PassBuilder &PB,
121                                                     bool DebugPassManager) {
122   PB.registerPipelineStartEPCallback([=](ModulePassManager &MPM) {
123     FunctionPassManager FPM(DebugPassManager);
124     FPM.addPass(BPFAbstractMemberAccessPass(this));
125     FPM.addPass(BPFPreserveDITypePass());
126     MPM.addPass(createModuleToFunctionPassAdaptor(std::move(FPM)));
127   });
128   PB.registerPeepholeEPCallback([=](FunctionPassManager &FPM,
129                                     PassBuilder::OptimizationLevel Level) {
130     FPM.addPass(SimplifyCFGPass(SimplifyCFGOptions().hoistCommonInsts(true)));
131   });
132 }
133 
134 void BPFPassConfig::addIRPasses() {
135   addPass(createBPFCheckAndAdjustIR());
136   TargetPassConfig::addIRPasses();
137 }
138 
139 // Install an instruction selector pass using
140 // the ISelDag to gen BPF code.
141 bool BPFPassConfig::addInstSelector() {
142   addPass(createBPFISelDag(getBPFTargetMachine()));
143 
144   return false;
145 }
146 
147 void BPFPassConfig::addMachineSSAOptimization() {
148   addPass(createBPFMISimplifyPatchablePass());
149 
150   // The default implementation must be called first as we want eBPF
151   // Peephole ran at last.
152   TargetPassConfig::addMachineSSAOptimization();
153 
154   const BPFSubtarget *Subtarget = getBPFTargetMachine().getSubtargetImpl();
155   if (!DisableMIPeephole) {
156     if (Subtarget->getHasAlu32())
157       addPass(createBPFMIPeepholePass());
158     addPass(createBPFMIPeepholeTruncElimPass());
159   }
160 }
161 
162 void BPFPassConfig::addPreEmitPass() {
163   addPass(createBPFMIPreEmitCheckingPass());
164   if (getOptLevel() != CodeGenOpt::None)
165     if (!DisableMIPeephole)
166       addPass(createBPFMIPreEmitPeepholePass());
167 }
168