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438900938c
llvm/tools/gold/gold-plugin.cpp
Rafael Espindola 438900938c Optimize linkonce_odr unnamed_addr functions during LTO. 
Generalize the API so we can distinguish symbols that are needed just for a DSO
symbol table from those that are used from some native .o.

The symbols that are only wanted for the dso symbol table can be dropped if
llvm can prove every other dso has a copy (linkonce_odr) and the address is not
important (unnamed_addr).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191922 91177308-0d34-0410-b5e6-96231b3b80d8
2013-10-03 18:29:09 +00:00

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//===-- 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 "llvm/Config/config.h" // plugin-api.h requires HAVE_STDINT_H
#include "plugin-api.h"
#include "llvm-c/lto.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/Support/Errno.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/ToolOutputFile.h"
#include "llvm/Support/system_error.h"
#include <cerrno>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <list>
#include <vector>
// Support Windows/MinGW crazyness.
#ifdef _WIN32
# include <io.h>
# define lseek _lseek
# define read _read
#endif
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_add_input_library add_input_library = NULL;
ld_plugin_set_extra_library_path set_extra_library_path = NULL;
ld_plugin_get_view get_view = NULL;
ld_plugin_message message = discard_message;
int api_version = 0;
int gold_version = 0;
struct claimed_file {
void *handle;
std::vector<ld_plugin_symbol> syms;
};
lto_codegen_model output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
std::string output_name = "";
std::list<claimed_file> Modules;
std::vector<std::string> Cleanup;
lto_code_gen_t code_gen = NULL;
}
namespace options {
enum generate_bc { BC_NO, BC_ALSO, BC_ONLY };
static bool generate_api_file = false;
static generate_bc generate_bc_file = BC_NO;
static std::string bc_path;
static std::string obj_path;
static std::string extra_library_path;
static std::string triple;
static std::string mcpu;
// Additional options to pass into the code generator.
// Note: This array will contain all plugin options which are not claimed
// as plugin exclusive to pass to the code generator.
// For example, "generate-api-file" and "as"options are for the plugin
// use only and will not be passed.
static std::vector<std::string> extra;
static void process_plugin_option(const char* opt_)
{
if (opt_ == NULL)
return;
llvm::StringRef opt = opt_;
if (opt == "generate-api-file") {
generate_api_file = true;
} else if (opt.startswith("mcpu=")) {
mcpu = opt.substr(strlen("mcpu="));
} else if (opt.startswith("extra-library-path=")) {
extra_library_path = opt.substr(strlen("extra_library_path="));
} else if (opt.startswith("mtriple=")) {
triple = opt.substr(strlen("mtriple="));
} else if (opt.startswith("obj-path=")) {
obj_path = opt.substr(strlen("obj-path="));
} else if (opt == "emit-llvm") {
generate_bc_file = BC_ONLY;
} else if (opt == "also-emit-llvm") {
generate_bc_file = BC_ALSO;
} else if (opt.startswith("also-emit-llvm=")) {
llvm::StringRef path = opt.substr(strlen("also-emit-llvm="));
generate_bc_file = BC_ALSO;
if (!bc_path.empty()) {
(*message)(LDPL_WARNING, "Path to the output IL file specified twice. "
"Discarding %s", opt_);
} else {
bc_path = path;
}
} else {
// Save this option to pass to the code generator.
extra.push_back(opt);
}
}
}
static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
int *claimed);
static ld_plugin_status all_symbols_read_hook(void);
static 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;
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_OUTPUT_NAME:
output_name = tv->tv_u.tv_string;
break;
case LDPT_LINKER_OUTPUT:
switch (tv->tv_u.tv_val) {
case LDPO_REL: // .o
case LDPO_DYN: // .so
// FIXME: Replace 3 with LDPO_PIE once that is in a released binutils.
case 3: // position independent executable
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:
options::process_plugin_option(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;
code_gen = lto_codegen_create();
} 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;
} break;
case LDPT_ADD_SYMBOLS:
add_symbols = tv->tv_u.tv_add_symbols;
break;
case LDPT_GET_SYMBOLS_V2:
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_ADD_INPUT_LIBRARY:
add_input_library = tv->tv_u.tv_add_input_file;
break;
case LDPT_SET_EXTRA_LIBRARY_PATH:
set_extra_library_path = tv->tv_u.tv_set_extra_library_path;
break;
case LDPT_GET_VIEW:
get_view = tv->tv_u.tv_get_view;
break;
case LDPT_MESSAGE:
message = tv->tv_u.tv_message;
break;
default:
break;
}
}
if (!registeredClaimFile) {
(*message)(LDPL_ERROR, "register_claim_file not passed to LLVMgold.");
return LDPS_ERR;
}
if (!add_symbols) {
(*message)(LDPL_ERROR, "add_symbols not passed to 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.
static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
int *claimed) {
lto_module_t M;
const void *view;
OwningPtr<MemoryBuffer> buffer;
if (get_view) {
if (get_view(file->handle, &view) != LDPS_OK) {
(*message)(LDPL_ERROR, "Failed to get a view of %s", file->name);
return LDPS_ERR;
}
} else {
int64_t offset = 0;
// Gold has found what might be IR part-way inside of a file, such as
// an .a archive.
if (file->offset) {
offset = file->offset;
}
if (error_code ec = MemoryBuffer::getOpenFileSlice(
file->fd, file->name, buffer, file->filesize, offset)) {
(*message)(LDPL_ERROR, ec.message().c_str());
return LDPS_ERR;
}
view = buffer->getBufferStart();
}
if (!lto_module_is_object_file_in_memory(view, file->filesize))
return LDPS_OK;
M = lto_module_create_from_memory(view, file->filesize);
if (!M) {
if (const char* msg = lto_get_error_message()) {
(*message)(LDPL_ERROR,
"LLVM gold plugin has failed to create LTO module: %s",
msg);
return LDPS_ERR;
}
return LDPS_OK;
}
*claimed = 1;
Modules.resize(Modules.size() + 1);
claimed_file &cf = Modules.back();
if (!options::triple.empty())
lto_module_set_target_triple(M, options::triple.c_str());
cf.handle = file->handle;
unsigned sym_count = lto_module_get_num_symbols(M);
cf.syms.reserve(sym_count);
for (unsigned i = 0; i != sym_count; ++i) {
lto_symbol_attributes attrs = lto_module_get_symbol_attribute(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(M, i));
sym.name = strdup(sym.name);
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;
sym.comdat_key = NULL;
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.comdat_key = sym.name;
sym.def = LDPK_WEAKDEF;
break;
case LTO_SYMBOL_DEFINITION_WEAKUNDEF:
sym.def = LDPK_WEAKUNDEF;
break;
default:
(*message)(LDPL_ERROR, "Unknown definition attribute: %d", definition);
return LDPS_ERR;
}
sym.size = 0;
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;
}
}
if (code_gen)
lto_codegen_add_module(code_gen, M);
lto_module_dispose(M);
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.
static ld_plugin_status all_symbols_read_hook(void) {
std::ofstream api_file;
assert(code_gen);
if (options::generate_api_file) {
api_file.open("apifile.txt", std::ofstream::out | std::ofstream::trunc);
if (!api_file.is_open()) {
(*message)(LDPL_FATAL, "Unable to open apifile.txt for writing.");
abort();
}
}
for (std::list<claimed_file>::iterator I = Modules.begin(),
E = Modules.end(); I != E; ++I) {
if (I->syms.empty())
continue;
(*get_symbols)(I->handle, I->syms.size(), &I->syms[0]);
for (unsigned i = 0, e = I->syms.size(); i != e; i++) {
if (I->syms[i].resolution == LDPR_PREVAILING_DEF) {
lto_codegen_add_must_preserve_symbol(code_gen, I->syms[i].name);
if (options::generate_api_file)
api_file << I->syms[i].name << "\n";
} else if (I->syms[i].resolution == LDPR_PREVAILING_DEF_IRONLY_EXP) {
lto_codegen_add_dso_symbol(code_gen, I->syms[i].name);
if (options::generate_api_file)
api_file << I->syms[i].name << " dso only\n";
}
}
}
if (options::generate_api_file)
api_file.close();
lto_codegen_set_pic_model(code_gen, output_type);
lto_codegen_set_debug_model(code_gen, LTO_DEBUG_MODEL_DWARF);
if (!options::mcpu.empty())
lto_codegen_set_cpu(code_gen, options::mcpu.c_str());
// Pass through extra options to the code generator.
if (!options::extra.empty()) {
for (std::vector<std::string>::iterator it = options::extra.begin();
it != options::extra.end(); ++it) {
lto_codegen_debug_options(code_gen, (*it).c_str());
}
}
if (options::generate_bc_file != options::BC_NO) {
std::string path;
if (options::generate_bc_file == options::BC_ONLY)
path = output_name;
else if (!options::bc_path.empty())
path = options::bc_path;
else
path = output_name + ".bc";
bool err = lto_codegen_write_merged_modules(code_gen, path.c_str());
if (err)
(*message)(LDPL_FATAL, "Failed to write the output file.");
if (options::generate_bc_file == options::BC_ONLY) {
lto_codegen_dispose(code_gen);
exit(0);
}
}
const char *objPath;
if (lto_codegen_compile_to_file(code_gen, &objPath)) {
(*message)(LDPL_ERROR, "Could not produce a combined object file\n");
}
lto_codegen_dispose(code_gen);
for (std::list<claimed_file>::iterator I = Modules.begin(),
E = Modules.end(); I != E; ++I) {
for (unsigned i = 0; i != I->syms.size(); ++i) {
ld_plugin_symbol &sym = I->syms[i];
free(sym.name);
}
}
if ((*add_input_file)(objPath) != LDPS_OK) {
(*message)(LDPL_ERROR, "Unable to add .o file to the link.");
(*message)(LDPL_ERROR, "File left behind in: %s", objPath);
return LDPS_ERR;
}
if (!options::extra_library_path.empty() &&
set_extra_library_path(options::extra_library_path.c_str()) != LDPS_OK) {
(*message)(LDPL_ERROR, "Unable to set the extra library path.");
return LDPS_ERR;
}
if (options::obj_path.empty())
Cleanup.push_back(objPath);
return LDPS_OK;
}
static ld_plugin_status cleanup_hook(void) {
for (int i = 0, e = Cleanup.size(); i != e; ++i) {
error_code EC = sys::fs::remove(Cleanup[i]);
if (EC)
(*message)(LDPL_ERROR, "Failed to delete '%s': %s", Cleanup[i].c_str(),
EC.message().c_str());
}
return LDPS_OK;
}
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