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   initializeBPFMIPeepholePass(PR);
43   initializeBPFMIPeepholeTruncElimPass(PR);
44 }
45 
46 // DataLayout: little or big endian
47 static std::string computeDataLayout(const Triple &TT) {
48   if (TT.getArch() == Triple::bpfeb)
49     return "E-m:e-p:64:64-i64:64-i128:128-n32:64-S128";
50   else
51     return "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128";
52 }
53 
54 static Reloc::Model getEffectiveRelocModel(Optional<Reloc::Model> RM) {
55   if (!RM.hasValue())
56     return Reloc::PIC_;
57   return *RM;
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),
68                         getEffectiveCodeModel(CM, CodeModel::Small), OL),
69       TLOF(std::make_unique<TargetLoweringObjectFileELF>()),
70       Subtarget(TT, std::string(CPU), std::string(FS), *this) {
71   initAsmInfo();
72 
73   BPFMCAsmInfo *MAI =
74       static_cast<BPFMCAsmInfo *>(const_cast<MCAsmInfo *>(AsmInfo.get()));
75   MAI->setDwarfUsesRelocationsAcrossSections(!Subtarget.getUseDwarfRIS());
76 }
77 
78 namespace {
79 // BPF Code Generator Pass Configuration Options.
80 class BPFPassConfig : public TargetPassConfig {
81 public:
82   BPFPassConfig(BPFTargetMachine &TM, PassManagerBase &PM)
83       : TargetPassConfig(TM, PM) {}
84 
85   BPFTargetMachine &getBPFTargetMachine() const {
86     return getTM<BPFTargetMachine>();
87   }
88 
89   void addIRPasses() override;
90   bool addInstSelector() override;
91   void addMachineSSAOptimization() override;
92   void addPreEmitPass() override;
93 };
94 }
95 
96 TargetPassConfig *BPFTargetMachine::createPassConfig(PassManagerBase &PM) {
97   return new BPFPassConfig(*this, PM);
98 }
99 
100 void BPFTargetMachine::adjustPassManager(PassManagerBuilder &Builder) {
101   Builder.addExtension(
102       PassManagerBuilder::EP_Peephole,
103       [&](const PassManagerBuilder &, legacy::PassManagerBase &PM) {
104         PM.add(createCFGSimplificationPass(
105             SimplifyCFGOptions().hoistCommonInsts(true)));
106       });
107 }
108 
109 void BPFPassConfig::addIRPasses() {
110   addPass(createBPFAbstractMemberAccess(&getBPFTargetMachine()));
111   addPass(createBPFPreserveDIType());
112 
113   TargetPassConfig::addIRPasses();
114 }
115 
116 // Install an instruction selector pass using
117 // the ISelDag to gen BPF code.
118 bool BPFPassConfig::addInstSelector() {
119   addPass(createBPFISelDag(getBPFTargetMachine()));
120 
121   return false;
122 }
123 
124 void BPFPassConfig::addMachineSSAOptimization() {
125   addPass(createBPFMISimplifyPatchablePass());
126 
127   // The default implementation must be called first as we want eBPF
128   // Peephole ran at last.
129   TargetPassConfig::addMachineSSAOptimization();
130 
131   const BPFSubtarget *Subtarget = getBPFTargetMachine().getSubtargetImpl();
132   if (!DisableMIPeephole) {
133     if (Subtarget->getHasAlu32())
134       addPass(createBPFMIPeepholePass());
135     addPass(createBPFMIPeepholeTruncElimPass());
136   }
137 }
138 
139 void BPFPassConfig::addPreEmitPass() {
140   addPass(createBPFMIPreEmitCheckingPass());
141   if (getOptLevel() != CodeGenOpt::None)
142     if (!DisableMIPeephole)
143       addPass(createBPFMIPreEmitPeepholePass());
144 }
145