lib/ExecutionEngine/JITLink/BasicGOTAndStubsBuilder.h

   1 //===--- BasicGOTAndStubsBuilder.h - Generic GOT/Stub creation --*- C++ -*-===//
   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 // A base for simple GOT and stub creation.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef LLVM_LIB_EXECUTIONENGINE_JITLINK_BASICGOTANDSTUBSBUILDER_H
  14 #define LLVM_LIB_EXECUTIONENGINE_JITLINK_BASICGOTANDSTUBSBUILDER_H
  15
  16 #include "llvm/ExecutionEngine/JITLink/JITLink.h"
  17
  18 namespace llvm {
  19 namespace jitlink {
  20
  21 template <typename BuilderImpl> class BasicGOTAndStubsBuilder {
  22 public:
  23   BasicGOTAndStubsBuilder(LinkGraph &G) : G(G) {}
  24
  25   void run() {
  26     // We're going to be adding new blocks, but we don't want to iterate over
  27     // the newly added ones, so just copy the existing blocks out.
  28     std::vector<Block *> Blocks(G.blocks().begin(), G.blocks().end());
  29
  30     for (auto *B : Blocks)
  31       for (auto &E : B->edges())
  32         if (impl().isGOTEdge(E))
  33           impl().fixGOTEdge(E, getGOTEntrySymbol(E.getTarget()));
  34         else if (impl().isExternalBranchEdge(E))
  35           impl().fixExternalBranchEdge(E, getStubSymbol(E.getTarget()));
  36   }
  37
  38 protected:
  39   Symbol &getGOTEntrySymbol(Symbol &Target) {
  40     assert(Target.hasName() && "GOT edge cannot point to anonymous target");
  41
  42     auto GOTEntryI = GOTEntries.find(Target.getName());
  43
  44     // Build the entry if it doesn't exist.
  45     if (GOTEntryI == GOTEntries.end()) {
  46       auto &GOTEntry = impl().createGOTEntry(Target);
  47       GOTEntryI =
  48           GOTEntries.insert(std::make_pair(Target.getName(), &GOTEntry)).first;
  49     }
  50
  51     assert(GOTEntryI != GOTEntries.end() && "Could not get GOT entry symbol");
  52     return *GOTEntryI->second;
  53   }
  54
  55   Symbol &getStubSymbol(Symbol &Target) {
  56     assert(Target.hasName() &&
  57            "External branch edge can not point to an anonymous target");
  58     auto StubI = Stubs.find(Target.getName());
  59
  60     if (StubI == Stubs.end()) {
  61       auto &StubSymbol = impl().createStub(Target);
  62       StubI = Stubs.insert(std::make_pair(Target.getName(), &StubSymbol)).first;
  63     }
  64
  65     assert(StubI != Stubs.end() && "Count not get stub symbol");
  66     return *StubI->second;
  67   }
  68
  69   LinkGraph &G;
  70
  71 private:
  72   BuilderImpl &impl() { return static_cast<BuilderImpl &>(*this); }
  73
  74   DenseMap<StringRef, Symbol *> GOTEntries;
  75   DenseMap<StringRef, Symbol *> Stubs;
  76 };
  77
  78 } // end namespace jitlink
  79 } // end namespace llvm
  80
  81 #endif // LLVM_LIB_EXECUTIONENGINE_JITLINK_BASICGOTANDSTUBSBUILDER_H