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