src/librustc_trans/back/lto.rs

   1 // Copyright 2013 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use super::link;
  12 use super::write;
  13 use rustc::session::{mod, config};
  14 use llvm;
  15 use llvm::archive_ro::ArchiveRO;
  16 use llvm::{ModuleRef, TargetMachineRef, True, False};
  17 use rustc::metadata::cstore;
  18 use rustc::util::common::time;
  19
  20 use libc;
  21 use flate;
  22
  23 use std::iter;
  24 use std::mem;
  25 use std::num::Int;
  26
  27 pub fn run(sess: &session::Session, llmod: ModuleRef,
  28            tm: TargetMachineRef, reachable: &[String]) {
  29     if sess.opts.cg.prefer_dynamic {
  30         sess.err("cannot prefer dynamic linking when performing LTO");
  31         sess.note("only 'staticlib' and 'bin' outputs are supported with LTO");
  32         sess.abort_if_errors();
  33     }
  34
  35     // Make sure we actually can run LTO
  36     for crate_type in sess.crate_types.borrow().iter() {
  37         match *crate_type {
  38             config::CrateTypeExecutable | config::CrateTypeStaticlib => {}
  39             _ => {
  40                 sess.fatal("lto can only be run for executables and \
  41                             static library outputs");
  42             }
  43         }
  44     }
  45
  46     // For each of our upstream dependencies, find the corresponding rlib and
  47     // load the bitcode from the archive. Then merge it into the current LLVM
  48     // module that we've got.
  49     let crates = sess.cstore.get_used_crates(cstore::RequireStatic);
  50     for (cnum, path) in crates.into_iter() {
  51         let name = sess.cstore.get_crate_data(cnum).name.clone();
  52         let path = match path {
  53             Some(p) => p,
  54             None => {
  55                 sess.fatal(format!("could not find rlib for: `{}`",
  56                                    name).as_slice());
  57             }
  58         };
  59
  60         let archive = ArchiveRO::open(&path).expect("wanted an rlib");
  61         let file = path.filename_str().unwrap();
  62         let file = file.slice(3, file.len() - 5); // chop off lib/.rlib
  63         debug!("reading {}", file);
  64         for i in iter::count(0u, 1) {
  65             let bc_encoded = time(sess.time_passes(),
  66                                   format!("check for {}.{}.bytecode.deflate", name, i).as_slice(),
  67                                   (),
  68                                   |_| {
  69                                       archive.read(format!("{}.{}.bytecode.deflate",
  70                                                            file, i).as_slice())
  71                                   });
  72             let bc_encoded = match bc_encoded {
  73                 Some(data) => data,
  74                 None => {
  75                     if i == 0 {
  76                         // No bitcode was found at all.
  77                         sess.fatal(format!("missing compressed bytecode in {}",
  78                                            path.display()).as_slice());
  79                     }
  80                     // No more bitcode files to read.
  81                     break;
  82                 },
  83             };
  84             let bc_extractor = if is_versioned_bytecode_format(bc_encoded) {
  85                 |_| {
  86                     // Read the version
  87                     let version = extract_bytecode_format_version(bc_encoded);
  88
  89                     if version == 1 {
  90                         // The only version existing so far
  91                         let data_size = extract_compressed_bytecode_size_v1(bc_encoded);
  92                         let compressed_data = bc_encoded[
  93                             link::RLIB_BYTECODE_OBJECT_V1_DATA_OFFSET..
  94                             link::RLIB_BYTECODE_OBJECT_V1_DATA_OFFSET + data_size as uint];
  95
  96                         match flate::inflate_bytes(compressed_data) {
  97                             Some(inflated) => inflated,
  98                             None => {
  99                                 sess.fatal(format!("failed to decompress bc of `{}`",
 100                                                    name).as_slice())
 101                             }
 102                         }
 103                     } else {
 104                         sess.fatal(format!("Unsupported bytecode format version {}",
 105                                            version).as_slice())
 106                     }
 107                 }
 108             } else {
 109                 // the object must be in the old, pre-versioning format, so simply
 110                 // inflate everything and let LLVM decide if it can make sense of it
 111                 |_| {
 112                     match flate::inflate_bytes(bc_encoded) {
 113                         Some(bc) => bc,
 114                         None => {
 115                             sess.fatal(format!("failed to decompress bc of `{}`",
 116                                                name).as_slice())
 117                         }
 118                     }
 119                 }
 120             };
 121
 122             let bc_decoded = time(sess.time_passes(),
 123                                   format!("decode {}.{}.bc", file, i).as_slice(),
 124                                   (),
 125                                   bc_extractor);
 126
 127             let ptr = bc_decoded.as_slice().as_ptr();
 128             debug!("linking {}, part {}", name, i);
 129             time(sess.time_passes(),
 130                  format!("ll link {}.{}", name, i).as_slice(),
 131                  (),
 132                  |()| unsafe {
 133                 if !llvm::LLVMRustLinkInExternalBitcode(llmod,
 134                                                         ptr as *const libc::c_char,
 135                                                         bc_decoded.len() as libc::size_t) {
 136                     write::llvm_err(sess.diagnostic().handler(),
 137                                     format!("failed to load bc of `{}`",
 138                                             name.as_slice()));
 139                 }
 140             });
 141         }
 142     }
 143
 144     // Internalize everything but the reachable symbols of the current module
 145     let cstrs: Vec<::std::c_str::CString> =
 146         reachable.iter().map(|s| s.to_c_str()).collect();
 147     let arr: Vec<*const i8> = cstrs.iter().map(|c| c.as_ptr()).collect();
 148     let ptr = arr.as_ptr();
 149     unsafe {
 150         llvm::LLVMRustRunRestrictionPass(llmod,
 151                                          ptr as *const *const libc::c_char,
 152                                          arr.len() as libc::size_t);
 153     }
 154
 155     if sess.no_landing_pads() {
 156         unsafe {
 157             llvm::LLVMRustMarkAllFunctionsNounwind(llmod);
 158         }
 159     }
 160
 161     // Now we have one massive module inside of llmod. Time to run the
 162     // LTO-specific optimization passes that LLVM provides.
 163     //
 164     // This code is based off the code found in llvm's LTO code generator:
 165     //      tools/lto/LTOCodeGenerator.cpp
 166     debug!("running the pass manager");
 167     unsafe {
 168         let pm = llvm::LLVMCreatePassManager();
 169         llvm::LLVMRustAddAnalysisPasses(tm, pm, llmod);
 170         "verify".with_c_str(|s| llvm::LLVMRustAddPass(pm, s));
 171
 172         let builder = llvm::LLVMPassManagerBuilderCreate();
 173         llvm::LLVMPassManagerBuilderPopulateLTOPassManager(builder, pm,
 174             /* Internalize = */ False,
 175             /* RunInliner = */ True);
 176         llvm::LLVMPassManagerBuilderDispose(builder);
 177
 178         "verify".with_c_str(|s| llvm::LLVMRustAddPass(pm, s));
 179
 180         time(sess.time_passes(), "LTO passes", (), |()|
 181              llvm::LLVMRunPassManager(pm, llmod));
 182
 183         llvm::LLVMDisposePassManager(pm);
 184     }
 185     debug!("lto done");
 186 }
 187
 188 fn is_versioned_bytecode_format(bc: &[u8]) -> bool {
 189     let magic_id_byte_count = link::RLIB_BYTECODE_OBJECT_MAGIC.len();
 190     return bc.len() > magic_id_byte_count &&
 191            bc[..magic_id_byte_count] == link::RLIB_BYTECODE_OBJECT_MAGIC;
 192 }
 193
 194 fn extract_bytecode_format_version(bc: &[u8]) -> u32 {
 195     return read_from_le_bytes::<u32>(bc, link::RLIB_BYTECODE_OBJECT_VERSION_OFFSET);
 196 }
 197
 198 fn extract_compressed_bytecode_size_v1(bc: &[u8]) -> u64 {
 199     return read_from_le_bytes::<u64>(bc, link::RLIB_BYTECODE_OBJECT_V1_DATASIZE_OFFSET);
 200 }
 201
 202 fn read_from_le_bytes<T: Int>(bytes: &[u8], position_in_bytes: uint) -> T {
 203     let byte_data = bytes[position_in_bytes..
 204                           position_in_bytes + mem::size_of::<T>()];
 205     let data = unsafe {
 206         *(byte_data.as_ptr() as *const T)
 207     };
 208
 209     Int::from_le(data)
 210 }
 211