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llvm-mirror/tools/gold/gold-plugin.cpp
Duncan Sands d0286618b5 Remove variables that are written by not read. 
llvm-svn: 107126
2010-06-29 11:07:47 +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"
#include "plugin-api.h"
#include "llvm-c/lto.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/System/Errno.h"
#include "llvm/System/Path.h"
#include "llvm/System/Program.h"
#include <cerrno>
#include <cstdlib>
#include <cstring>
#include <fstream>
#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_add_input_library add_input_library = NULL;
ld_plugin_set_extra_library_path set_extra_library_path = 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::string output_name = "";
std::list<claimed_file> Modules;
std::vector<sys::Path> Cleanup;
}
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 as_path;
static std::vector<std::string> pass_through;
static std::string extra_library_path;
// 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("as=")) {
if (!as_path.empty()) {
(*message)(LDPL_WARNING, "Path to as specified twice. "
"Discarding %s", opt_);
} else {
as_path = opt.substr(strlen("as="));
}
} else if (opt.startswith("extra-library-path=")) {
extra_library_path = opt.substr(strlen("extra_library_path="));
} else if (opt.startswith("pass-through=")) {
llvm::StringRef item = opt.substr(strlen("pass-through="));
pass_through.push_back(item.str());
} 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
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;
} 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:
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_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) {
void *buf = NULL;
if (file->offset) {
// Gold has found what might be IR part-way inside of a file, such as
// an .a archive.
if (lseek(file->fd, file->offset, SEEK_SET) == -1) {
(*message)(LDPL_ERROR,
"Failed to seek to archive member of %s at offset %d: %s\n",
file->name,
file->offset, sys::StrError(errno).c_str());
return LDPS_ERR;
}
buf = malloc(file->filesize);
if (!buf) {
(*message)(LDPL_ERROR,
"Failed to allocate buffer for archive member of size: %d\n",
file->filesize);
return LDPS_ERR;
}
if (read(file->fd, buf, file->filesize) != file->filesize) {
(*message)(LDPL_ERROR,
"Failed to read archive member of %s at offset %d: %s\n",
file->name,
file->offset,
sys::StrError(errno).c_str());
free(buf);
return LDPS_ERR;
}
if (!lto_module_is_object_file_in_memory(buf, file->filesize)) {
free(buf);
return LDPS_OK;
}
} else 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 = buf ? lto_module_create_from_memory(buf, file->filesize) :
lto_module_create(file->name);
free(buf);
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;
case LTO_SYMBOL_DEFINITION_WEAKUNDEF:
sym.def = LDPK_WEAKUNDEF;
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.
static 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);
std::ofstream api_file;
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();
}
}
// 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.
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++) {
if (I->syms[i].resolution == LDPR_PREVAILING_DEF) {
lto_codegen_add_must_preserve_symbol(cg, I->syms[i].name);
anySymbolsPreserved = true;
if (options::generate_api_file)
api_file << I->syms[i].name << "\n";
}
}
}
if (options::generate_api_file)
api_file.close();
if (!anySymbolsPreserved) {
// All of the IL 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);
if (!options::as_path.empty()) {
sys::Path p = sys::Program::FindProgramByName(options::as_path);
lto_codegen_set_assembler_path(cg, p.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(cg, (*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(cg, path.c_str());
if (err)
(*message)(LDPL_FATAL, "Failed to write the output file.");
if (options::generate_bc_file == options::BC_ONLY)
exit(0);
}
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(uniqueObjPath.c_str(), ErrMsg,
raw_fd_ostream::F_Binary);
if (!ErrMsg.empty()) {
(*message)(LDPL_ERROR, "%s", ErrMsg.c_str());
return LDPS_ERR;
}
objFile.write(buffer, bufsize);
objFile.close();
lto_codegen_dispose(cg);
if ((*add_input_file)(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;
}
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;
}
for (std::vector<std::string>::iterator i = options::pass_through.begin(),
e = options::pass_through.end();
i != e; ++i) {
std::string &item = *i;
const char *item_p = item.c_str();
if (llvm::StringRef(item).startswith("-l")) {
if (add_input_library(item_p + 2) != LDPS_OK) {
(*message)(LDPL_ERROR, "Unable to add library to the link.");
return LDPS_ERR;
}
} else {
if (add_input_file(item_p) != LDPS_OK) {
(*message)(LDPL_ERROR, "Unable to add .o file to the link.");
return LDPS_ERR;
}
}
}
Cleanup.push_back(uniqueObjPath);
return LDPS_OK;
}
static 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;
}
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