[JITLink] Switch from an atom-based model to a "blocks and symbols" model.

In the Atom model the symbols, content and relocations of a relocatable object
file are represented as a graph of atoms, where each Atom represents a
contiguous block of content with a single name (or no name at all if the
content is anonymous), and where edges between Atoms represent relocations.
If more than one symbol is associated with a contiguous block of content then
the content is broken into multiple atoms and layout constraints (represented by
edges) are introduced to ensure that the content remains effectively contiguous.
These layout constraints must be kept in mind when examining the content
associated with a symbol (it may be spread over multiple atoms) or when applying
certain relocation types (e.g. MachO subtractors).

This patch replaces the Atom model in JITLink with a blocks-and-symbols model.
The blocks-and-symbols model represents relocatable object files as bipartite
graphs, with one set of nodes representing contiguous content (Blocks) and
another representing named or anonymous locations (Symbols) within a Block.
Relocations are represented as edges from Blocks to Symbols. This scheme
removes layout constraints (simplifying handling of MachO alt-entry symbols,
and hopefully ELF sections at some point in the future) and simplifies some
relocation logic.

llvm-svn: 373689

1 files changed, 0 insertions, 138 deletions

diff --git a/llvm/lib/ExecutionEngine/JITLink/MachOAtomGraphBuilder.h b/llvm/lib/ExecutionEngine/JITLink/MachOAtomGraphBuilder.h
deleted file mode 100644
index 72d441b24d0..00000000000
--- a/llvm/lib/ExecutionEngine/JITLink/MachOAtomGraphBuilder.h
+++ /dev/null
@@ -1,138 +0,0 @@
-//===----- MachOAtomGraphBuilder.h - MachO AtomGraph builder ----*- C++ -*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-// Generic MachO AtomGraph building code.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LIB_EXECUTIONENGINE_JITLINK_MACHOATOMGRAPHBUILDER_H
-#define LIB_EXECUTIONENGINE_JITLINK_MACHOATOMGRAPHBUILDER_H
-
-#include "llvm/ExecutionEngine/JITLink/JITLink.h"
-
-#include "JITLinkGeneric.h"
-
-#include "llvm/Object/MachO.h"
-
-namespace llvm {
-namespace jitlink {
-
-class MachOAtomGraphBuilder {
-public:
-  virtual ~MachOAtomGraphBuilder();
-  Expected<std::unique_ptr<AtomGraph>> buildGraph();
-
-protected:
-  using OffsetToAtomMap = std::map<JITTargetAddress, DefinedAtom *>;
-
-  class MachOSection {
-  public:
-    MachOSection() = default;
-
-    /// Create a MachO section with the given address and alignment.
-    MachOSection(Section &GenericSection, JITTargetAddress Address,
-                 unsigned Alignment)
-        : Address(Address), GenericSection(&GenericSection),
-          Alignment(Alignment) {}
-
-    /// Create a section without address, content or size (used for common
-    /// symbol sections).
-    MachOSection(Section &GenericSection) : GenericSection(&GenericSection) {}
-
-    Section &getGenericSection() const {
-      assert(GenericSection && "Section is null");
-      return *GenericSection;
-    }
-
-    StringRef getName() const {
-      assert(GenericSection && "No generic section attached");
-      return GenericSection->getName();
-    }
-
-    MachOSection &setContent(StringRef Content) {
-      assert(!ContentPtr && !Size && "Content/zeroFill already set");
-      ContentPtr = Content.data();
-      Size = Content.size();
-      return *this;
-    }
-
-    MachOSection &setZeroFill(uint64_t Size) {
-      assert(!ContentPtr && !this->Size && "Content/zeroFill already set");
-      this->Size = Size;
-      return *this;
-    }
-
-    bool isZeroFill() const { return !ContentPtr; }
-
-    bool empty() const { return getSize() == 0; }
-
-    size_t getSize() const { return Size; }
-
-    StringRef getContent() const {
-      assert(ContentPtr && "getContent() called on zero-fill section");
-      return {ContentPtr, static_cast<size_t>(Size)};
-    }
-
-    JITTargetAddress getAddress() const { return Address; }
-
-    unsigned getAlignment() const { return Alignment; }
-
-    MachOSection &setNoDeadStrip(bool NoDeadStrip) {
-      this->NoDeadStrip = NoDeadStrip;
-      return *this;
-    }
-
-    bool isNoDeadStrip() const { return NoDeadStrip; }
-
-  private:
-    JITTargetAddress Address = 0;
-    Section *GenericSection = nullptr;
-    const char *ContentPtr = nullptr;
-    uint64_t Size = 0;
-    unsigned Alignment = 0;
-    bool NoDeadStrip = false;
-  };
-
-  using CustomAtomizeFunction = std::function<Error(MachOSection &S)>;
-
-  MachOAtomGraphBuilder(const object::MachOObjectFile &Obj);
-
-  AtomGraph &getGraph() const { return *G; }
-
-  const object::MachOObjectFile &getObject() const { return Obj; }
-
-  void addCustomAtomizer(StringRef SectionName, CustomAtomizeFunction Atomizer);
-
-  virtual Error addRelocations() = 0;
-
-  /// Returns true if Atom A and Atom B are at a fixed offset from one another
-  /// (i.e. if they're part of the same alt-entry chain).
-  bool areLayoutLocked(const Atom &A, const Atom &B);
-
-private:
-  static unsigned getPointerSize(const object::MachOObjectFile &Obj);
-  static support::endianness getEndianness(const object::MachOObjectFile &Obj);
-
-  MachOSection &getCommonSection();
-
-  Error parseSections();
-  Error addNonCustomAtoms();
-  Error addAtoms();
-
-  const object::MachOObjectFile &Obj;
-  std::unique_ptr<AtomGraph> G;
-  DenseMap<const DefinedAtom *, const DefinedAtom *> AltEntryStarts;
-  DenseMap<unsigned, MachOSection> Sections;
-  StringMap<CustomAtomizeFunction> CustomAtomizeFunctions;
-  Optional<MachOSection> CommonSymbolsSection;
-};
-
-} // end namespace jitlink
-} // end namespace llvm
-
-#endif // LIB_EXECUTIONENGINE_JITLINK_MACHOATOMGRAPHBUILDER_H