Move LTO support library to a component, allowing it to be tested

more reliably across platforms.  Patch by Tom Roeder!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191343 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/LTO/LTOCodeGenerator.h

@@ -0,0 +1,130 @@
+//===-LTOCodeGenerator.h - LLVM Link Time Optimizer -----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the LTOCodeGenerator class.
+//
+//   LTO compilation consists of three phases: Pre-IPO, IPO and Post-IPO. 
+//
+//   The Pre-IPO phase compiles source code into bitcode file. The resulting
+// bitcode files, along with object files and libraries, will be fed to the
+// linker to through the IPO and Post-IPO phases. By using obj-file extension,
+// the resulting bitcode file disguises itself as an object file, and therefore
+// obviates the need of writing a special set of the make-rules only for LTO
+// compilation.
+//
+//   The IPO phase perform inter-procedural analyses and optimizations, and
+// the Post-IPO consists two sub-phases: intra-procedural scalar optimizations
+// (SOPT), and intra-procedural target-dependent code generator (CG).
+// 
+//   As of this writing, we don't separate IPO and the Post-IPO SOPT. They
+// are intermingled together, and are driven by a single pass manager (see
+// PassManagerBuilder::populateLTOPassManager()).
+// 
+//   The "LTOCodeGenerator" is the driver for the IPO and Post-IPO stages. 
+// The "CodeGenerator" here is bit confusing. Don't confuse the "CodeGenerator"
+// with the machine specific code generator.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LTO_CODE_GENERATOR_H
+#define LTO_CODE_GENERATOR_H
+
+#include "llvm-c/lto.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/Linker.h"
+#include <string>
+#include <vector>
+
+namespace llvm {
+  class LLVMContext;
+  class GlobalValue;
+  class Mangler;
+  class MemoryBuffer;
+  class TargetMachine;
+  class raw_ostream;
+}
+
+//===----------------------------------------------------------------------===//
+/// LTOCodeGenerator - C++ class which implements the opaque lto_code_gen_t
+/// type.
+///
+struct LTOCodeGenerator {
+  static const char *getVersionString();
+
+  LTOCodeGenerator();
+  ~LTOCodeGenerator();
+
+  // Merge given module, return true on success.
+  bool addModule(struct LTOModule*, std::string &errMsg);
+
+  void setDebugInfo(lto_debug_model);
+  void setCodePICModel(lto_codegen_model);
+
+  void setCpu(const char *mCpu) { MCpu = mCpu; }
+
+  void addMustPreserveSymbol(const char *sym) { MustPreserveSymbols[sym] = 1; }
+
+  // To pass options to the driver and optimization passes. These options are
+  // not necessarily for debugging purpose (The function name is misleading).
+  // This function should be called before LTOCodeGenerator::compilexxx(),
+  // and LTOCodeGenerator::writeMergedModules().
+  //
+  void setCodeGenDebugOptions(const char *opts);
+
+  // Write the merged module to the file specified by the given path.
+  // Return true on success.
+  bool writeMergedModules(const char *path, std::string &errMsg);
+
+  // Compile the merged module into a *single* object file; the path to object
+  // file is returned to the caller via argument "name". Return true on
+  // success.
+  //
+  // NOTE that it is up to the linker to remove the intermediate object file.
+  //  Do not try to remove the object file in LTOCodeGenerator's destructor
+  //  as we don't who (LTOCodeGenerator or the obj file) will last longer.
+  // 
+  bool compile_to_file(const char **name, std::string &errMsg);
+
+  // As with compile_to_file(), this function compiles the merged module into
+  // single object file. Instead of returning the object-file-path to the caller
+  // (linker), it brings the object to a buffer, and return the buffer to the
+  // caller. This function should delete intermediate object file once its content
+  // is brought to memory. Return NULL if the compilation was not successful. 
+  //
+  const void *compile(size_t *length, std::string &errMsg);
+
+private:
+  void initializeLTOPasses();
+
+  bool generateObjectFile(llvm::raw_ostream &out, std::string &errMsg);
+  void applyScopeRestrictions();
+  void applyRestriction(llvm::GlobalValue &GV,
+                        std::vector<const char*> &MustPreserveList,
+                        llvm::SmallPtrSet<llvm::GlobalValue*, 8> &AsmUsed,
+                        llvm::Mangler &Mangler);
+  bool determineTarget(std::string &errMsg);
+
+  typedef llvm::StringMap<uint8_t> StringSet;
+
+  llvm::LLVMContext &Context;
+  llvm::Linker Linker;
+  llvm::TargetMachine *TargetMach;
+  bool EmitDwarfDebugInfo;
+  bool ScopeRestrictionsDone;
+  lto_codegen_model CodeModel;
+  StringSet MustPreserveSymbols;
+  StringSet AsmUndefinedRefs;
+  llvm::MemoryBuffer *NativeObjectFile;
+  std::vector<char *> CodegenOptions;
+  std::string MCpu;
+  std::string NativeObjectPath;
+};
+
+#endif // LTO_CODE_GENERATOR_H