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 "BPFTargetTransformInfo.h"
16 #include "MCTargetDesc/BPFMCAsmInfo.h"
17 #include "TargetInfo/BPFTargetInfo.h"
18 #include "llvm/CodeGen/Passes.h"
19 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
20 #include "llvm/CodeGen/TargetPassConfig.h"
21 #include "llvm/IR/LegacyPassManager.h"
22 #include "llvm/IR/PassManager.h"
23 #include "llvm/Passes/PassBuilder.h"
24 #include "llvm/Support/FormattedStream.h"
25 #include "llvm/Support/TargetRegistry.h"
26 #include "llvm/Target/TargetOptions.h"
27 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
28 #include "llvm/Transforms/Scalar.h"
29 #include "llvm/Transforms/Scalar/SimplifyCFG.h"
30 #include "llvm/Transforms/Utils/SimplifyCFGOptions.h"
31 using namespace llvm;
32 
33 static cl::
34 opt<bool> DisableMIPeephole("disable-bpf-peephole", cl::Hidden,
35                             cl::desc("Disable machine peepholes for BPF"));
36 
37 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeBPFTarget() {
38   // Register the target.
39   RegisterTargetMachine<BPFTargetMachine> X(getTheBPFleTarget());
40   RegisterTargetMachine<BPFTargetMachine> Y(getTheBPFbeTarget());
41   RegisterTargetMachine<BPFTargetMachine> Z(getTheBPFTarget());
42 
43   PassRegistry &PR = *PassRegistry::getPassRegistry();
44   initializeBPFAbstractMemberAccessLegacyPassPass(PR);
45   initializeBPFPreserveDITypePass(PR);
46   initializeBPFAdjustOptPass(PR);
47   initializeBPFCheckAndAdjustIRPass(PR);
48   initializeBPFMIPeepholePass(PR);
49   initializeBPFMIPeepholeTruncElimPass(PR);
50 }
51 
52 // DataLayout: little or big endian
53 static std::string computeDataLayout(const Triple &TT) {
54   if (TT.getArch() == Triple::bpfeb)
55     return "E-m:e-p:64:64-i64:64-i128:128-n32:64-S128";
56   else
57     return "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128";
58 }
59 
60 static Reloc::Model getEffectiveRelocModel(Optional<Reloc::Model> RM) {
61   return RM.getValueOr(Reloc::PIC_);
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   Builder.addExtension(
119       PassManagerBuilder::EP_ModuleOptimizerEarly,
120       [&](const PassManagerBuilder &, legacy::PassManagerBase &PM) {
121         PM.add(createBPFAdjustOpt());
122       });
123 }
124 
125 void BPFTargetMachine::registerPassBuilderCallbacks(PassBuilder &PB) {
126   PB.registerPipelineStartEPCallback(
127       [=](ModulePassManager &MPM, PassBuilder::OptimizationLevel) {
128         FunctionPassManager FPM;
129         FPM.addPass(BPFAbstractMemberAccessPass(this));
130         FPM.addPass(BPFPreserveDITypePass());
131         MPM.addPass(createModuleToFunctionPassAdaptor(std::move(FPM)));
132       });
133   PB.registerPeepholeEPCallback([=](FunctionPassManager &FPM,
134                                     PassBuilder::OptimizationLevel Level) {
135     FPM.addPass(SimplifyCFGPass(SimplifyCFGOptions().hoistCommonInsts(true)));
136   });
137   PB.registerPipelineEarlySimplificationEPCallback(
138       [=](ModulePassManager &MPM, PassBuilder::OptimizationLevel) {
139         MPM.addPass(BPFAdjustOptPass());
140       });
141 }
142 
143 void BPFPassConfig::addIRPasses() {
144   addPass(createBPFCheckAndAdjustIR());
145   TargetPassConfig::addIRPasses();
146 }
147 
148 TargetTransformInfo
149 BPFTargetMachine::getTargetTransformInfo(const Function &F) {
150   return TargetTransformInfo(BPFTTIImpl(this, F));
151 }
152 
153 // Install an instruction selector pass using
154 // the ISelDag to gen BPF code.
155 bool BPFPassConfig::addInstSelector() {
156   addPass(createBPFISelDag(getBPFTargetMachine()));
157 
158   return false;
159 }
160 
161 void BPFPassConfig::addMachineSSAOptimization() {
162   addPass(createBPFMISimplifyPatchablePass());
163 
164   // The default implementation must be called first as we want eBPF
165   // Peephole ran at last.
166   TargetPassConfig::addMachineSSAOptimization();
167 
168   const BPFSubtarget *Subtarget = getBPFTargetMachine().getSubtargetImpl();
169   if (!DisableMIPeephole) {
170     if (Subtarget->getHasAlu32())
171       addPass(createBPFMIPeepholePass());
172     addPass(createBPFMIPeepholeTruncElimPass());
173   }
174 }
175 
176 void BPFPassConfig::addPreEmitPass() {
177   addPass(createBPFMIPreEmitCheckingPass());
178   if (getOptLevel() != CodeGenOpt::None)
179     if (!DisableMIPeephole)
180       addPass(createBPFMIPreEmitPeepholePass());
181 }
182