[ORC] Add MaterializationUnit::Interface parameter to ObjectLayer::add.

Also moves object interface building functions out of Mangling.h and in to the
new ObjectFileInterfaces.h header, and updates the llvm-jitlink tool to use
custom object interfaces rather than a custom link layer.

ObjectLayer::add overloads are added to match the old signatures (which
do not take a MaterializationUnit::Interface). These overloads use the
standard getObjectFileInterface function to build an interface.

Passing a MaterializationUnit::Interface explicitly makes it easier to alter
the effective interface of the object file being added, e.g. by changing symbol
visibility/linkage, or renaming symbols (in both cases the changes will need to
be mirrored by a JITLink pass at link time to update the LinkGraph to match the
explicit interface). Altering interfaces in this way can be useful when lazily
compiling (e.g. for renaming function bodies) or emulating linker options (e.g.
demoting all symbols to hidden visibility to emulate -load_hidden).

1 files changed, 205 insertions, 0 deletions

diff --git a/llvm/lib/ExecutionEngine/Orc/ObjectFileInterface.cpp b/llvm/lib/ExecutionEngine/Orc/ObjectFileInterface.cpp
new file mode 100644
index 0000000..c1ad569d
--- /dev/null
+++ b/llvm/lib/ExecutionEngine/Orc/ObjectFileInterface.cpp
@@ -0,0 +1,205 @@
+//===------ ObjectFileInterface.cpp - MU interface utils for objects ------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ExecutionEngine/Orc/ObjectFileInterface.h"
+#include "llvm/ExecutionEngine/Orc/ELFNixPlatform.h"
+#include "llvm/ExecutionEngine/Orc/MachOPlatform.h"
+#include "llvm/Object/ELFObjectFile.h"
+#include "llvm/Object/MachO.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/Support/Debug.h"
+
+#define DEBUG_TYPE "orc"
+
+namespace llvm {
+namespace orc {
+
+void addInitSymbol(MaterializationUnit::Interface &I, ExecutionSession &ES,
+                   StringRef ObjFileName) {
+  assert(!I.InitSymbol && "I already has an init symbol");
+  size_t Counter = 0;
+
+  do {
+    std::string InitSymString;
+    raw_string_ostream(InitSymString)
+        << "$." << ObjFileName << ".__inits." << Counter++;
+    I.InitSymbol = ES.intern(InitSymString);
+  } while (I.SymbolFlags.count(I.InitSymbol));
+
+  I.SymbolFlags[I.InitSymbol] = JITSymbolFlags::MaterializationSideEffectsOnly;
+}
+
+static Expected<MaterializationUnit::Interface>
+getMachOObjectFileSymbolInfo(ExecutionSession &ES,
+                             const object::MachOObjectFile &Obj) {
+  MaterializationUnit::Interface I;
+
+  for (auto &Sym : Obj.symbols()) {
+    Expected<uint32_t> SymFlagsOrErr = Sym.getFlags();
+    if (!SymFlagsOrErr)
+      // TODO: Test this error.
+      return SymFlagsOrErr.takeError();
+
+    // Skip symbols not defined in this object file.
+    if (*SymFlagsOrErr & object::BasicSymbolRef::SF_Undefined)
+      continue;
+
+    // Skip symbols that are not global.
+    if (!(*SymFlagsOrErr & object::BasicSymbolRef::SF_Global))
+      continue;
+
+    // Skip symbols that have type SF_File.
+    if (auto SymType = Sym.getType()) {
+      if (*SymType == object::SymbolRef::ST_File)
+        continue;
+    } else
+      return SymType.takeError();
+
+    auto Name = Sym.getName();
+    if (!Name)
+      return Name.takeError();
+    auto InternedName = ES.intern(*Name);
+    auto SymFlags = JITSymbolFlags::fromObjectSymbol(Sym);
+    if (!SymFlags)
+      return SymFlags.takeError();
+
+    // Strip the 'exported' flag from MachO linker-private symbols.
+    if (Name->startswith("l"))
+      *SymFlags &= ~JITSymbolFlags::Exported;
+
+    I.SymbolFlags[InternedName] = std::move(*SymFlags);
+  }
+
+  for (auto &Sec : Obj.sections()) {
+    auto SecType = Obj.getSectionType(Sec);
+    if ((SecType & MachO::SECTION_TYPE) == MachO::S_MOD_INIT_FUNC_POINTERS) {
+      addInitSymbol(I, ES, Obj.getFileName());
+      break;
+    }
+    auto SegName = Obj.getSectionFinalSegmentName(Sec.getRawDataRefImpl());
+    auto SecName = cantFail(Obj.getSectionName(Sec.getRawDataRefImpl()));
+    if (MachOPlatform::isInitializerSection(SegName, SecName)) {
+      addInitSymbol(I, ES, Obj.getFileName());
+      break;
+    }
+  }
+
+  return I;
+}
+
+static Expected<MaterializationUnit::Interface>
+getELFObjectFileSymbolInfo(ExecutionSession &ES,
+                           const object::ELFObjectFileBase &Obj) {
+  MaterializationUnit::Interface I;
+
+  for (auto &Sym : Obj.symbols()) {
+    Expected<uint32_t> SymFlagsOrErr = Sym.getFlags();
+    if (!SymFlagsOrErr)
+      // TODO: Test this error.
+      return SymFlagsOrErr.takeError();
+
+    // Skip symbols not defined in this object file.
+    if (*SymFlagsOrErr & object::BasicSymbolRef::SF_Undefined)
+      continue;
+
+    // Skip symbols that are not global.
+    if (!(*SymFlagsOrErr & object::BasicSymbolRef::SF_Global))
+      continue;
+
+    // Skip symbols that have type SF_File.
+    if (auto SymType = Sym.getType()) {
+      if (*SymType == object::SymbolRef::ST_File)
+        continue;
+    } else
+      return SymType.takeError();
+
+    auto Name = Sym.getName();
+    if (!Name)
+      return Name.takeError();
+    auto InternedName = ES.intern(*Name);
+    auto SymFlags = JITSymbolFlags::fromObjectSymbol(Sym);
+    if (!SymFlags)
+      return SymFlags.takeError();
+
+    // ELF STB_GNU_UNIQUE should map to Weak for ORC.
+    if (Sym.getBinding() == ELF::STB_GNU_UNIQUE)
+      *SymFlags |= JITSymbolFlags::Weak;
+
+    I.SymbolFlags[InternedName] = std::move(*SymFlags);
+  }
+
+  SymbolStringPtr InitSymbol;
+  for (auto &Sec : Obj.sections()) {
+    if (auto SecName = Sec.getName()) {
+      if (ELFNixPlatform::isInitializerSection(*SecName)) {
+        addInitSymbol(I, ES, Obj.getFileName());
+        break;
+      }
+    }
+  }
+
+  return I;
+}
+
+Expected<MaterializationUnit::Interface>
+getGenericObjectFileSymbolInfo(ExecutionSession &ES,
+                               const object::ObjectFile &Obj) {
+  MaterializationUnit::Interface I;
+
+  for (auto &Sym : Obj.symbols()) {
+    Expected<uint32_t> SymFlagsOrErr = Sym.getFlags();
+    if (!SymFlagsOrErr)
+      // TODO: Test this error.
+      return SymFlagsOrErr.takeError();
+
+    // Skip symbols not defined in this object file.
+    if (*SymFlagsOrErr & object::BasicSymbolRef::SF_Undefined)
+      continue;
+
+    // Skip symbols that are not global.
+    if (!(*SymFlagsOrErr & object::BasicSymbolRef::SF_Global))
+      continue;
+
+    // Skip symbols that have type SF_File.
+    if (auto SymType = Sym.getType()) {
+      if (*SymType == object::SymbolRef::ST_File)
+        continue;
+    } else
+      return SymType.takeError();
+
+    auto Name = Sym.getName();
+    if (!Name)
+      return Name.takeError();
+    auto InternedName = ES.intern(*Name);
+    auto SymFlags = JITSymbolFlags::fromObjectSymbol(Sym);
+    if (!SymFlags)
+      return SymFlags.takeError();
+
+    I.SymbolFlags[InternedName] = std::move(*SymFlags);
+  }
+
+  return I;
+}
+
+Expected<MaterializationUnit::Interface>
+getObjectFileInterface(ExecutionSession &ES, MemoryBufferRef ObjBuffer) {
+  auto Obj = object::ObjectFile::createObjectFile(ObjBuffer);
+
+  if (!Obj)
+    return Obj.takeError();
+
+  if (auto *MachOObj = dyn_cast<object::MachOObjectFile>(Obj->get()))
+    return getMachOObjectFileSymbolInfo(ES, *MachOObj);
+  else if (auto *ELFObj = dyn_cast<object::ELFObjectFileBase>(Obj->get()))
+    return getELFObjectFileSymbolInfo(ES, *ELFObj);
+
+  return getGenericObjectFileSymbolInfo(ES, **Obj);
+}
+
+} // End namespace orc.
+} // End namespace llvm.