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Auto merge of #35637 - japaric:no-builtins-lto, r=alexcrichton
exclude `#![no_builtins]` crates from LTO this prevents intrinsics like `memcpy` from being mis-optimized to infinite recursive calls when LTO is used. fixes #31544 closes #35540 --- r? @alexcrichton cc @Amanieu
2 parents 1de5b7e + e996405 commit db7300d

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+61
-10
lines changed

7 files changed

+61
-10
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‎src/librustc/middle/cstore.rs

+2
Original file line numberDiff line numberDiff line change
@@ -227,6 +227,7 @@ pub trait CrateStore<'tcx> {
227227
fn plugin_registrar_fn(&self, cnum: ast::CrateNum) -> Option<DefId>;
228228
fn native_libraries(&self, cnum: ast::CrateNum) -> Vec<(NativeLibraryKind, String)>;
229229
fn reachable_ids(&self, cnum: ast::CrateNum) -> Vec<DefId>;
230+
fn is_no_builtins(&self, cnum: ast::CrateNum) -> bool;
230231

231232
// resolve
232233
fn def_index_for_def_key(&self,
@@ -428,6 +429,7 @@ impl<'tcx> CrateStore<'tcx> for DummyCrateStore {
428429
fn native_libraries(&self, cnum: ast::CrateNum) -> Vec<(NativeLibraryKind, String)>
429430
{ bug!("native_libraries") }
430431
fn reachable_ids(&self, cnum: ast::CrateNum) -> Vec<DefId> { bug!("reachable_ids") }
432+
fn is_no_builtins(&self, cnum: ast::CrateNum) -> bool { bug!("is_no_builtins") }
431433

432434
// resolve
433435
fn def_key(&self, def: DefId) -> hir_map::DefKey { bug!("def_key") }

‎src/librustc_metadata/csearch.rs

+4
Original file line numberDiff line numberDiff line change
@@ -409,6 +409,10 @@ impl<'tcx> CrateStore<'tcx> for cstore::CStore {
409409
decoder::get_reachable_ids(&cdata)
410410
}
411411

412+
fn is_no_builtins(&self, cnum: ast::CrateNum) -> bool {
413+
attr::contains_name(&self.crate_attrs(cnum), "no_builtins")
414+
}
415+
412416
fn def_index_for_def_key(&self,
413417
cnum: ast::CrateNum,
414418
def: DefKey)

‎src/librustc_trans/back/link.rs

+15-9
Original file line numberDiff line numberDiff line change
@@ -940,7 +940,7 @@ fn add_upstream_rust_crates(cmd: &mut Linker,
940940
Linkage::IncludedFromDylib => {}
941941
Linkage::Static => {
942942
add_static_crate(cmd, sess, tmpdir, crate_type,
943-
&src.rlib.unwrap().0)
943+
&src.rlib.unwrap().0, sess.cstore.is_no_builtins(cnum))
944944
}
945945
Linkage::Dynamic => {
946946
add_dynamic_crate(cmd, sess, &src.dylib.unwrap().0)
@@ -964,12 +964,16 @@ fn add_upstream_rust_crates(cmd: &mut Linker,
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// * For LTO, we remove upstream object files.
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// * For dylibs we remove metadata and bytecode from upstream rlibs
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//
967-
// When performing LTO, all of the bytecode from the upstream libraries has
968-
// already been included in our object file output. As a result we need to
969-
// remove the object files in the upstream libraries so the linker doesn't
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// try to include them twice (or whine about duplicate symbols). We must
971-
// continue to include the rest of the rlib, however, as it may contain
972-
// static native libraries which must be linked in.
967+
// When performing LTO, almost(*) all of the bytecode from the upstream
968+
// libraries has already been included in our object file output. As a
969+
// result we need to remove the object files in the upstream libraries so
970+
// the linker doesn't try to include them twice (or whine about duplicate
971+
// symbols). We must continue to include the rest of the rlib, however, as
972+
// it may contain static native libraries which must be linked in.
973+
//
974+
// (*) Crates marked with `#![no_builtins]` don't participate in LTO and
975+
// their bytecode wasn't included. The object files in those libraries must
976+
// still be passed to the linker.
973977
//
974978
// When making a dynamic library, linkers by default don't include any
975979
// object files in an archive if they're not necessary to resolve the link.
@@ -989,7 +993,8 @@ fn add_upstream_rust_crates(cmd: &mut Linker,
989993
sess: &Session,
990994
tmpdir: &Path,
991995
crate_type: config::CrateType,
992-
cratepath: &Path) {
996+
cratepath: &Path,
997+
is_a_no_builtins_crate: bool) {
993998
if !sess.lto() && crate_type != config::CrateTypeDylib {
994999
cmd.link_rlib(&fix_windows_verbatim_for_gcc(cratepath));
9951000
return
@@ -1013,7 +1018,8 @@ fn add_upstream_rust_crates(cmd: &mut Linker,
10131018
}
10141019
let canonical = f.replace("-", "_");
10151020
let canonical_name = name.replace("-", "_");
1016-
if sess.lto() && canonical.starts_with(&canonical_name) &&
1021+
if sess.lto() && !is_a_no_builtins_crate &&
1022+
canonical.starts_with(&canonical_name) &&
10171023
canonical.ends_with(".o") {
10181024
let num = &f[name.len()..f.len() - 2];
10191025
if num.len() > 0 && num[1..].parse::<u32>().is_ok() {

‎src/librustc_trans/back/lto.rs

+6-1
Original file line numberDiff line numberDiff line change
@@ -52,7 +52,12 @@ pub fn run(sess: &session::Session, llmod: ModuleRef,
5252
// For each of our upstream dependencies, find the corresponding rlib and
5353
// load the bitcode from the archive. Then merge it into the current LLVM
5454
// module that we've got.
55-
link::each_linked_rlib(sess, &mut |_, path| {
55+
link::each_linked_rlib(sess, &mut |cnum, path| {
56+
// `#![no_builtins]` crates don't participate in LTO.
57+
if sess.cstore.is_no_builtins(cnum) {
58+
return;
59+
}
60+
5661
let archive = ArchiveRO::open(&path).expect("wanted an rlib");
5762
let bytecodes = archive.iter().filter_map(|child| {
5863
child.ok().and_then(|c| c.name().map(|name| (name, c)))

‎src/test/run-make/no-builtins-lto/Makefile

+9
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@@ -0,0 +1,9 @@
1+
-include ../tools.mk
2+
3+
all:
4+
# Compile a `#![no_builtins]` rlib crate
5+
$(RUSTC) no_builtins.rs
6+
# Build an executable that depends on that crate using LTO. The no_builtins crate doesn't
7+
# participate in LTO, so its rlib must be explicitly linked into the final binary. Verify this by
8+
# grepping the linker arguments.
9+
$(RUSTC) main.rs -C lto -Z print-link-args | grep 'libno_builtins.rlib'

‎src/test/run-make/no-builtins-lto/main.rs

+13
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,13 @@
1+
// Copyright 2016 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+
extern crate no_builtins;
12+
13+
fn main() {}

‎src/test/run-make/no-builtins-lto/no_builtins.rs

+12
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,12 @@
1+
// Copyright 2016 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+
#![crate_type = "lib"]
12+
#![no_builtins]

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