Add new tool, lto, to do link time optimization. This tool installs

dynamic library that linker can use to optimize llvm byte codes at
link time.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29494 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 99 insertions, 0 deletions

diff --git a/include/llvm/LinkTimeOptimizer.h b/include/llvm/LinkTimeOptimizer.h
new file mode 100644
index 0000000000..52532b1947
--- /dev/null
+++ b/include/llvm/LinkTimeOptimizer.h
@@ -0,0 +1,99 @@
+//===-- llvm/LinkTimeOptimizer.h - Public Interface  ------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Devang Patel and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// 
+//===----------------------------------------------------------------------===//
+//
+// This header provides public interface to use LLVM link time optimization
+// library. This is intended to be used by linker to do link time optimization.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __LTO_H__
+#define __LTO_H__
+
+#include <string>
+#include <vector>
+#include <set>
+#include <llvm/ADT/hash_map>
+
+namespace llvm {
+
+  class Module;
+  class GlobalValue;
+
+  enum LTOStatus {
+    LTO_UNKNOWN,
+    LTO_OPT_SUCCESS,
+    LTO_READ_SUCCESS,
+    LTO_READ_FAILURE,
+    LTO_WRITE_FAILURE,
+    LTO_NO_TARGET,
+    LTO_NO_WORK,
+    LTO_MODULE_MERGE_FAILURE,
+    LTO_ASM_FAILURE
+  };
+ 
+  enum LTOLinkageTypes {
+    LTOExternalLinkage, // Externally visible function
+    LTOLinkOnceLinkage, // Keep one copy of named function when linking (inline)
+    LTOWeakLinkage,     // Keep one copy of named function when linking (weak)
+    LTOInternalLinkage  // Rename collisions when linking (static functions)
+  };
+
+  /// This class representes LLVM symbol information without exposing details
+  /// of LLVM global values. It encapsulates symbol linkage information. This
+  /// is typically used in hash_map where associated name identifies the 
+  /// the symbol name.
+  class LLVMSymbol {
+
+  public:
+
+    LTOLinkageTypes getLinkage() const { return linkage; }
+    void mayBeNotUsed();
+
+  LLVMSymbol (enum LTOLinkageTypes lt, GlobalValue *g) : linkage(lt), gv(g) {}
+
+  private:
+    enum LTOLinkageTypes linkage;
+    GlobalValue *gv;
+  };
+
+  class string_compare {
+  public:
+    bool operator()(const char* left, const char* right) const { 
+      return (strcmp(left, right) == 0); 
+    }
+  };
+  
+  /// This is the main link time optimization class. It exposes simple API
+  /// to perform link time optimization using LLVM intermodular optimizer.
+  class LinkTimeOptimizer {
+
+  public:
+    typedef hash_map<const char*, LLVMSymbol*, hash<const char*>, 
+		     string_compare> NameToSymbolMap;
+
+    enum LTOStatus readLLVMObjectFile(const std::string &InputFilename,
+				      NameToSymbolMap &symbols,
+				      std::set<const char*> &references);
+    enum LTOStatus optimizeModules(const std::string &OutputFilename,
+				   std::vector<const char*> &exportList);
+
+  private:
+    std::vector<Module *> modules;
+    NameToSymbolMap allSymbols;
+  };
+
+} // End llvm namespace
+
+/// This provides C interface to initialize link time optimizer. This allows
+/// linker to use dlopen() interface to dynamically load LinkTimeOptimizer.
+/// extern "C" helps, because dlopen() interface uses name to find the symbol.
+extern "C"
+llvm::LinkTimeOptimizer *createLLVMOptimizer();
+
+#endif