Add LLVM plugin for gold.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63623 91177308-0d34-0410-b5e6-96231b3b80d8

tools/Makefile

@@ -27,6 +27,10 @@ include $(LEVEL)/Makefile.config
 
 ifeq ($(ENABLE_PIC),1)
 PARALLEL_DIRS += lto
+
+ifdef BINUTILS_INCDIR
+PARALLEL_DIRS += gold
+endif
 endif
 
 include $(LEVEL)/Makefile.common

tools/gold/Makefile

@@ -0,0 +1,29 @@
+#===- tools/gold/Makefile ----------------------------------*- Makefile -*-===##
+# 
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+# 
+##===----------------------------------------------------------------------===##
+
+LEVEL = ../..
+LIBRARYNAME = LLVMgold
+
+# Include this here so we can get the configuration of the targets
+# that have been configured for construction. We have to do this 
+# early so we can set up LINK_COMPONENTS before including Makefile.rules
+include $(LEVEL)/Makefile.config
+
+LINK_LIBS_IN_SHARED=1
+SHARED_LIBRARY = 1
+BUILD_ARCHIVE = 0
+DONT_BUILD_RELINKED = 1
+
+LINK_COMPONENTS :=
+
+include $(LEVEL)/Makefile.common
+
+# Because off_t is used in the public API, the largefile parts are required for
+# ABI compatibility.
+CXXFLAGS+=-I$(BINUTILS_INCDIR) -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -lLTO

tools/gold/README.txt

@@ -0,0 +1,17 @@
+This directory contains a plugin that is designed to work with binutils
+gold linker. At present time, this is not the default linker in
+binutils, and the default build of gold does not support plugins.
+
+Obtaining binutils:
+
+  cvs -z 9 -d :pserver:anoncvs@sourceware.org:/cvs/src login
+  {enter "anoncvs" as the password}
+  cvs -z 9 -d :pserver:anoncvs@sourceware.org:/cvs/src co binutils
+
+This will create a src/ directory. Make a build/ directory and from
+there configure binutils with "../src/configure --enable-gold --enable-plugins".
+Then build binutils with "make all-gold".
+
+To build the LLVMgold plugin, configure LLVM with the option
+--with-binutils-include=/path/to/binutils/src/include/ . To use the
+plugin, run "ld-new --plugin /path/to/libLLVMgold.so".

tools/gold/gold-plugin.cpp

@@ -0,0 +1,327 @@
+//===-- gold-plugin.cpp - Plugin to gold for Link Time Optimization  ------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This is a gold plugin for LLVM. It provides an LLVM implementation of the
+// interface described in http://gcc.gnu.org/wiki/whopr/driver .
+//
+//===----------------------------------------------------------------------===//
+
+#include "plugin-api.h"
+
+#include "llvm-c/lto.h"
+
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/System/Path.h"
+
+#include <cstdlib>
+#include <cstring>
+#include <list>
+#include <vector>
+
+using namespace llvm;
+
+namespace {
+  ld_plugin_status discard_message(int level, const char *format, ...) {
+    // Die loudly. Recent versions of Gold pass ld_plugin_message as the first
+    // callback in the transfer vector. This should never be called.
+    abort();
+  }
+
+  ld_plugin_add_symbols add_symbols = NULL;
+  ld_plugin_get_symbols get_symbols = NULL;
+  ld_plugin_add_input_file add_input_file = NULL;
+  ld_plugin_message message = discard_message;
+
+  int api_version = 0;
+  int gold_version = 0;
+
+  struct claimed_file {
+    lto_module_t M;
+    void *handle;
+    std::vector<ld_plugin_symbol> syms;
+  };
+
+  lto_codegen_model output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
+  std::list<claimed_file> Modules;
+  std::vector<sys::Path> Cleanup;
+}
+
+ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
+                                 int *claimed);
+ld_plugin_status all_symbols_read_hook(void);
+ld_plugin_status cleanup_hook(void);
+
+extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
+ld_plugin_status onload(ld_plugin_tv *tv) {
+  // We're given a pointer to the first transfer vector. We read through them
+  // until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
+  // contain pointers to functions that we need to call to register our own
+  // hooks. The others are addresses of functions we can use to call into gold
+  // for services.
+
+  bool registeredClaimFile = false;
+  bool registeredAllSymbolsRead = false;
+  bool registeredCleanup = false;
+
+  for (; tv->tv_tag != LDPT_NULL; ++tv) {
+    switch (tv->tv_tag) {
+      case LDPT_API_VERSION:
+        api_version = tv->tv_u.tv_val;
+        break;
+      case LDPT_GOLD_VERSION:  // major * 100 + minor
+        gold_version = tv->tv_u.tv_val;
+        break;
+      case LDPT_LINKER_OUTPUT:
+        switch (tv->tv_u.tv_val) {
+          case LDPO_REL:  // .o
+          case LDPO_DYN:  // .so
+            output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC;
+            break;
+          case LDPO_EXEC:  // .exe
+            output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
+            break;
+          default:
+            (*message)(LDPL_ERROR, "Unknown output file type %d",
+                       tv->tv_u.tv_val);
+            return LDPS_ERR;
+        }
+        // TODO: add an option to disable PIC.
+        //output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC;
+        break;
+      case LDPT_OPTION:
+        (*message)(LDPL_WARNING, "Ignoring flag %s", tv->tv_u.tv_string);
+        break;
+      case LDPT_REGISTER_CLAIM_FILE_HOOK: {
+        ld_plugin_register_claim_file callback;
+        callback = tv->tv_u.tv_register_claim_file;
+
+        if ((*callback)(claim_file_hook) != LDPS_OK)
+          return LDPS_ERR;
+
+        registeredClaimFile = true;
+      } break;
+      case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
+        ld_plugin_register_all_symbols_read callback;
+        callback = tv->tv_u.tv_register_all_symbols_read;
+
+        if ((*callback)(all_symbols_read_hook) != LDPS_OK)
+          return LDPS_ERR;
+
+        registeredAllSymbolsRead = true;
+      } break;
+      case LDPT_REGISTER_CLEANUP_HOOK: {
+        ld_plugin_register_cleanup callback;
+        callback = tv->tv_u.tv_register_cleanup;
+
+        if ((*callback)(cleanup_hook) != LDPS_OK)
+          return LDPS_ERR;
+
+        registeredCleanup = true;
+      } break;
+      case LDPT_ADD_SYMBOLS:
+        add_symbols = tv->tv_u.tv_add_symbols;
+        break;
+      case LDPT_GET_SYMBOLS:
+        get_symbols = tv->tv_u.tv_get_symbols;
+        break;
+      case LDPT_ADD_INPUT_FILE:
+        add_input_file = tv->tv_u.tv_add_input_file;
+        break;
+      case LDPT_MESSAGE:
+        message = tv->tv_u.tv_message;
+        break;
+      default:
+        break;
+    }
+  }
+
+  if (!registeredClaimFile || !registeredAllSymbolsRead || !registeredCleanup ||
+      !add_symbols || !get_symbols || !add_input_file) {
+    (*message)(LDPL_ERROR, "Not all hooks registered for LLVMgold.");
+    return LDPS_ERR;
+  }
+
+  return LDPS_OK;
+}
+
+/// claim_file_hook - called by gold to see whether this file is one that
+/// our plugin can handle. We'll try to open it and register all the symbols
+/// with add_symbol if possible.
+ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
+                                 int *claimed) {
+  // If set, this means gold found IR in an ELF section. LLVM doesn't wrap its
+  // IR in ELF, so we know it's not us.
+  if (file->offset)
+    return LDPS_OK;
+
+  if (!lto_module_is_object_file(file->name))
+    return LDPS_OK;
+
+  *claimed = 1;
+  Modules.resize(Modules.size() + 1);
+  claimed_file &cf = Modules.back();
+
+  cf.M = lto_module_create(file->name);
+  if (!cf.M) {
+    (*message)(LDPL_ERROR, "Failed to create LLVM module: %s",
+               lto_get_error_message());
+    return LDPS_ERR;
+  }
+  cf.handle = file->handle;
+  unsigned sym_count = lto_module_get_num_symbols(cf.M);
+  cf.syms.reserve(sym_count);
+
+  for (unsigned i = 0; i != sym_count; ++i) {
+    lto_symbol_attributes attrs = lto_module_get_symbol_attribute(cf.M, i);
+    if ((attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL)
+      continue;
+
+    cf.syms.push_back(ld_plugin_symbol());
+    ld_plugin_symbol &sym = cf.syms.back();
+    sym.name = const_cast<char *>(lto_module_get_symbol_name(cf.M, i));
+    sym.version = NULL;
+
+    int scope = attrs & LTO_SYMBOL_SCOPE_MASK;
+    switch (scope) {
+      case LTO_SYMBOL_SCOPE_HIDDEN:
+        sym.visibility = LDPV_HIDDEN;
+        break;
+      case LTO_SYMBOL_SCOPE_PROTECTED:
+        sym.visibility = LDPV_PROTECTED;
+        break;
+      case 0: // extern
+      case LTO_SYMBOL_SCOPE_DEFAULT:
+        sym.visibility = LDPV_DEFAULT;
+        break;
+      default:
+        (*message)(LDPL_ERROR, "Unknown scope attribute: %d", scope);
+        return LDPS_ERR;
+    }
+
+    int definition = attrs & LTO_SYMBOL_DEFINITION_MASK;
+    switch (definition) {
+      case LTO_SYMBOL_DEFINITION_REGULAR:
+        sym.def = LDPK_DEF;
+        break;
+      case LTO_SYMBOL_DEFINITION_UNDEFINED:
+        sym.def = LDPK_UNDEF;
+        break;
+      case LTO_SYMBOL_DEFINITION_TENTATIVE:
+        sym.def = LDPK_COMMON;
+        break;
+      case LTO_SYMBOL_DEFINITION_WEAK:
+        sym.def = LDPK_WEAKDEF;
+        break;
+      default:
+        (*message)(LDPL_ERROR, "Unknown definition attribute: %d", definition);
+        return LDPS_ERR;
+    }
+
+    // LLVM never emits COMDAT.
+    sym.size = 0;
+    sym.comdat_key = NULL;
+
+    sym.resolution = LDPR_UNKNOWN;
+  }
+
+  cf.syms.reserve(cf.syms.size());
+
+  if (!cf.syms.empty()) {
+    if ((*add_symbols)(cf.handle, cf.syms.size(), &cf.syms[0]) != LDPS_OK) {
+      (*message)(LDPL_ERROR, "Unable to add symbols!");
+      return LDPS_ERR;
+    }
+  }
+
+  return LDPS_OK;
+}
+
+/// all_symbols_read_hook - gold informs us that all symbols have been read.
+/// At this point, we use get_symbols to see if any of our definitions have
+/// been overridden by a native object file. Then, perform optimization and
+/// codegen.
+ld_plugin_status all_symbols_read_hook(void) {
+  lto_code_gen_t cg = lto_codegen_create();
+
+  for (std::list<claimed_file>::iterator I = Modules.begin(),
+       E = Modules.end(); I != E; ++I)
+    lto_codegen_add_module(cg, I->M);
+
+  // If we don't preserve any symbols, libLTO will assume that all symbols are
+  // needed. Keep all symbols unless we're producing a final executable.
+  if (output_type == LTO_CODEGEN_PIC_MODEL_STATIC) {
+    bool anySymbolsPreserved = false;
+    for (std::list<claimed_file>::iterator I = Modules.begin(),
+         E = Modules.end(); I != E; ++I) {
+      (*get_symbols)(I->handle, I->syms.size(), &I->syms[0]);
+      for (unsigned i = 0, e = I->syms.size(); i != e; i++) {
+        (*message)(LDPL_WARNING, "def: %d visibility: %d resolution %d",
+                   I->syms[i].def, I->syms[i].visibility, I->syms[i].resolution);
+        if (I->syms[i].resolution == LDPR_PREVAILING_DEF) {
+          lto_codegen_add_must_preserve_symbol(cg, I->syms[i].name);
+          anySymbolsPreserved = true;
+        }
+      }
+    }
+
+    if (!anySymbolsPreserved) {
+      // This entire file is unnecessary!
+      lto_codegen_dispose(cg);
+      return LDPS_OK;
+    }
+  }
+
+  lto_codegen_set_pic_model(cg, output_type);
+  lto_codegen_set_debug_model(cg, LTO_DEBUG_MODEL_DWARF);
+
+  size_t bufsize = 0;
+  const char *buffer = static_cast<const char *>(lto_codegen_compile(cg,
+                                                                     &bufsize));
+
+  std::string ErrMsg;
+
+  sys::Path uniqueObjPath("/tmp/llvmgold.o");
+  if (uniqueObjPath.createTemporaryFileOnDisk(true, &ErrMsg)) {
+    (*message)(LDPL_ERROR, "%s", ErrMsg.c_str());
+    return LDPS_ERR;
+  }
+  raw_fd_ostream *objFile = new raw_fd_ostream(uniqueObjPath.c_str(), true,
+                                               ErrMsg);
+  if (!ErrMsg.empty()) {
+    delete objFile;
+    (*message)(LDPL_ERROR, "%s", ErrMsg.c_str());
+    return LDPS_ERR;
+  }
+
+  objFile->write(buffer, bufsize);
+  objFile->close();
+
+  lto_codegen_dispose(cg);
+
+  if ((*add_input_file)(const_cast<char*>(uniqueObjPath.c_str())) != LDPS_OK) {
+    (*message)(LDPL_ERROR, "Unable to add .o file to the link.");
+    (*message)(LDPL_ERROR, "File left behind in: %s", uniqueObjPath.c_str());
+    return LDPS_ERR;
+  }
+
+  Cleanup.push_back(uniqueObjPath);
+
+  return LDPS_OK;
+}
+
+ld_plugin_status cleanup_hook(void) {
+  std::string ErrMsg;
+
+  for (int i = 0, e = Cleanup.size(); i != e; ++i)
+    if (Cleanup[i].eraseFromDisk(false, &ErrMsg))
+      (*message)(LDPL_ERROR, "Failed to delete '%s': %s", Cleanup[i].c_str(),
+                 ErrMsg.c_str());
+
+  return LDPS_OK;
+}