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Auto merge of #103092 - petrochenkov:weaklto, r=wesleywiser

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linker: Fix weak lang item linking with combination windows-gnu + LLD + LTO

In https://github.com/rust-lang/rust/pull/100404 this logic was originally disabled for MSVC due to issues with LTO, but the same issues appear on windows-gnu with LLD because that LLD uses the same underlying logic as MSVC LLD, just with re-syntaxed command line options.

So this PR just disables it for LTO builds in general.
This commit is contained in:
bors 2022-10-20 16:20:50 +00:00
commit 5ffa67d730
2 changed files with 9 additions and 4 deletions
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2
compiler/rustc_codegen_ssa/src/back/link.rs
View File

@ -2715,7 +2715,7 @@ fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool {
}
}
fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
pub(crate) fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
match sess.lto() {
config::Lto::Fat => true,
config::Lto::Thin => {

11
compiler/rustc_codegen_ssa/src/base.rs
View File

@ -1,3 +1,4 @@
use crate::back::link::are_upstream_rust_objects_already_included;
use crate::back::metadata::create_compressed_metadata_file;
use crate::back::write::{
compute_per_cgu_lto_type, start_async_codegen, submit_codegened_module_to_llvm,
@ -892,10 +893,14 @@ impl CrateInfo {
// Handle circular dependencies in the standard library.
// See comment before `add_linked_symbol_object` function for the details.
// With msvc-like linkers it's both unnecessary (they support circular dependencies),
// and causes linking issues (when weak lang item symbols are "privatized" by LTO).
// If global LTO is enabled then almost everything (*) is glued into a single object file,
// so this logic is not necessary and can cause issues on some targets (due to weak lang
// item symbols being "privatized" to that object file), so we disable it.
// (*) Native libs, and `#[compiler_builtins]` and `#[no_builtins]` crates are not glued,
// and we assume that they cannot define weak lang items. This is not currently enforced
// by the compiler, but that's ok because all this stuff is unstable anyway.
let target = &tcx.sess.target;
if !target.is_like_msvc {
if !are_upstream_rust_objects_already_included(tcx.sess) {
let missing_weak_lang_items: FxHashSet<&Symbol> = info
.used_crates
.iter()