From 0cdd7f50b06fb363a2e8b0f6d270e0ed14476af8 Mon Sep 17 00:00:00 2001 From: bjorn3 <17426603+bjorn3@users.noreply.github.com> Date: Thu, 8 May 2025 14:34:40 +0000 Subject: Add all rustc_std_internal_symbol to symbols.o rustc_std_internal_symbol is meant to call functions from crates where there is no direct dependency on said crate. As they either have to be added to symbols.o or rustc has to introduce an implicit dependency on them to avoid linker errors. The latter is done for some things like the panic runtime, but adding these symbols to symbols.o allows removing those implicit dependencies. --- compiler/rustc_codegen_ssa/src/back/linker.rs | 1 + .../rustc_codegen_ssa/src/back/symbol_export.rs | 16 ++++++++++++++++ compiler/rustc_codegen_ssa/src/base.rs | 22 +--------------------- 3 files changed, 18 insertions(+), 21 deletions(-) (limited to 'compiler/rustc_codegen_ssa/src') diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs index b6892bb63e8..8138fd788cf 100644 --- a/compiler/rustc_codegen_ssa/src/back/linker.rs +++ b/compiler/rustc_codegen_ssa/src/back/linker.rs @@ -1882,6 +1882,7 @@ pub(crate) fn linked_symbols( for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| { if info.level.is_below_threshold(export_threshold) && !tcx.is_compiler_builtins(cnum) || info.used + || info.rustc_std_internal_symbol { symbols.push(( symbol_export::linking_symbol_name_for_instance_in_crate( diff --git a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs index 19c005d418e..75f7a463556 100644 --- a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs +++ b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs @@ -131,6 +131,9 @@ fn reachable_non_generics_provider(tcx: TyCtxt<'_>, _: LocalCrate) -> DefIdMap, _: LocalCrate) -> DefIdMap( level: info.level, kind: SymbolExportKind::Text, used: info.used, + rustc_std_internal_symbol: info.rustc_std_internal_symbol, }, ) }) @@ -207,6 +212,7 @@ fn exported_symbols_provider_local<'tcx>( level: SymbolExportLevel::C, kind: SymbolExportKind::Text, used: false, + rustc_std_internal_symbol: false, }, )); } @@ -230,6 +236,7 @@ fn exported_symbols_provider_local<'tcx>( level: SymbolExportLevel::Rust, kind: SymbolExportKind::Text, used: false, + rustc_std_internal_symbol: true, }, )); } @@ -250,6 +257,7 @@ fn exported_symbols_provider_local<'tcx>( level: SymbolExportLevel::C, kind: SymbolExportKind::Data, used: false, + rustc_std_internal_symbol: false, }, ) })); @@ -275,6 +283,7 @@ fn exported_symbols_provider_local<'tcx>( level: SymbolExportLevel::C, kind: SymbolExportKind::Data, used: false, + rustc_std_internal_symbol: false, }, ) })); @@ -292,6 +301,7 @@ fn exported_symbols_provider_local<'tcx>( level: SymbolExportLevel::C, kind: SymbolExportKind::Data, used: true, + rustc_std_internal_symbol: false, }, )); } @@ -367,6 +377,8 @@ fn exported_symbols_provider_local<'tcx>( } } + // Note: These all set rustc_std_internal_symbol to false as generic functions must not + // be marked with this attribute and we are only handling generic functions here. match *mono_item { MonoItem::Fn(Instance { def: InstanceKind::Item(def), args }) => { let has_generics = args.non_erasable_generics().next().is_some(); @@ -382,6 +394,7 @@ fn exported_symbols_provider_local<'tcx>( level: SymbolExportLevel::Rust, kind: SymbolExportKind::Text, used: false, + rustc_std_internal_symbol: false, }, )); } @@ -404,6 +417,7 @@ fn exported_symbols_provider_local<'tcx>( level: SymbolExportLevel::Rust, kind: SymbolExportKind::Text, used: false, + rustc_std_internal_symbol: false, }, )); } @@ -420,6 +434,7 @@ fn exported_symbols_provider_local<'tcx>( level: SymbolExportLevel::Rust, kind: SymbolExportKind::Text, used: false, + rustc_std_internal_symbol: false, }, )); } @@ -430,6 +445,7 @@ fn exported_symbols_provider_local<'tcx>( level: SymbolExportLevel::Rust, kind: SymbolExportKind::Text, used: false, + rustc_std_internal_symbol: false, }, )); } diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs index cc90271cd0c..b06cfd1e473 100644 --- a/compiler/rustc_codegen_ssa/src/base.rs +++ b/compiler/rustc_codegen_ssa/src/base.rs @@ -6,7 +6,7 @@ use std::time::{Duration, Instant}; use itertools::Itertools; use rustc_abi::FIRST_VARIANT; use rustc_ast as ast; -use rustc_ast::expand::allocator::{ALLOCATOR_METHODS, AllocatorKind, global_fn_name}; +use rustc_ast::expand::allocator::AllocatorKind; use rustc_attr_data_structures::OptimizeAttr; use rustc_data_structures::fx::{FxHashMap, FxIndexSet}; use rustc_data_structures::profiling::{get_resident_set_size, print_time_passes_entry}; @@ -1056,26 +1056,6 @@ impl CrateInfo { .collect::>(); symbols.sort_unstable_by(|a, b| a.0.cmp(&b.0)); linked_symbols.extend(symbols); - if tcx.allocator_kind(()).is_some() { - // At least one crate needs a global allocator. This crate may be placed - // after the crate that defines it in the linker order, in which case some - // linkers return an error. By adding the global allocator shim methods to - // the linked_symbols list, linking the generated symbols.o will ensure that - // circular dependencies involving the global allocator don't lead to linker - // errors. - linked_symbols.extend(ALLOCATOR_METHODS.iter().map(|method| { - ( - add_prefix( - mangle_internal_symbol( - tcx, - global_fn_name(method.name).as_str(), - ), - SymbolExportKind::Text, - ), - SymbolExportKind::Text, - ) - })); - } }); } -- cgit 1.4.1-3-g733a5 From b9c0f15486326e127987d79883921a1591405118 Mon Sep 17 00:00:00 2001 From: bjorn3 <17426603+bjorn3@users.noreply.github.com> Date: Tue, 17 Jun 2025 16:47:55 +0000 Subject: Fix LTO for internalizing rustc_std_internal_symbol symbols --- compiler/rustc_codegen_ssa/src/back/linker.rs | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'compiler/rustc_codegen_ssa/src') diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs index 8138fd788cf..3d8ff3fbf56 100644 --- a/compiler/rustc_codegen_ssa/src/back/linker.rs +++ b/compiler/rustc_codegen_ssa/src/back/linker.rs @@ -1876,6 +1876,21 @@ pub(crate) fn linked_symbols( } } + match tcx.sess.lto() { + Lto::No | Lto::ThinLocal => {} + Lto::Thin | Lto::Fat => { + // We really only need symbols from upstream rlibs to end up in the linked symbols list. + // The rest are in separate object files which the linker will always link in and + // doesn't have rules around the order in which they need to appear. + // When doing LTO, some of the symbols in the linked symbols list may end up getting + // internalized, which then prevents referencing them from symbols.o. When doing LTO, + // all object files that get linked in will be local object files rather than pulled in + // from rlibs, so an empty linked symbols list works fine to avoid referencing all those + // internalized symbols from symbols.o. + return Vec::new(); + } + } + let mut symbols = Vec::new(); let export_threshold = symbol_export::crates_export_threshold(&[crate_type]); -- cgit 1.4.1-3-g733a5 From 4b7711520bc1a04b05252e59c4c371aa0bcc6793 Mon Sep 17 00:00:00 2001 From: bjorn3 <17426603+bjorn3@users.noreply.github.com> Date: Fri, 27 Jun 2025 09:49:18 +0000 Subject: Update comments --- compiler/rustc_codegen_ssa/src/back/linker.rs | 10 +++++----- compiler/rustc_middle/src/middle/exported_symbols.rs | 3 +++ 2 files changed, 8 insertions(+), 5 deletions(-) (limited to 'compiler/rustc_codegen_ssa/src') diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs index 3d8ff3fbf56..556aa4ed616 100644 --- a/compiler/rustc_codegen_ssa/src/back/linker.rs +++ b/compiler/rustc_codegen_ssa/src/back/linker.rs @@ -1882,11 +1882,11 @@ pub(crate) fn linked_symbols( // We really only need symbols from upstream rlibs to end up in the linked symbols list. // The rest are in separate object files which the linker will always link in and // doesn't have rules around the order in which they need to appear. - // When doing LTO, some of the symbols in the linked symbols list may end up getting - // internalized, which then prevents referencing them from symbols.o. When doing LTO, - // all object files that get linked in will be local object files rather than pulled in - // from rlibs, so an empty linked symbols list works fine to avoid referencing all those - // internalized symbols from symbols.o. + // When doing LTO, some of the symbols in the linked symbols list happen to be + // internalized by LTO, which then prevents referencing them from symbols.o. When doing + // LTO, all object files that get linked in will be local object files rather than + // pulled in from rlibs, so an empty linked symbols list works fine to avoid referencing + // all those internalized symbols from symbols.o. return Vec::new(); } } diff --git a/compiler/rustc_middle/src/middle/exported_symbols.rs b/compiler/rustc_middle/src/middle/exported_symbols.rs index 491bba98c19..c70ff398cea 100644 --- a/compiler/rustc_middle/src/middle/exported_symbols.rs +++ b/compiler/rustc_middle/src/middle/exported_symbols.rs @@ -31,6 +31,9 @@ pub enum SymbolExportKind { /// The `SymbolExportInfo` of a symbols specifies symbol-related information /// that is relevant to code generation and linking. +/// +/// The difference between `used` and `rustc_std_internal_symbol` is that the +/// former is exported by LTO while the latter isn't. #[derive(Eq, PartialEq, Debug, Copy, Clone, TyEncodable, TyDecodable, HashStable)] pub struct SymbolExportInfo { pub level: SymbolExportLevel, -- cgit 1.4.1-3-g733a5