Avoid attempting to export allocator shim during LTO

The allocator shim no longer participates in LTO.

Author: bjorn3

compiler/rustc_codegen_ssa/src/back/linker.rs

@@ -5,6 +5,7 @@ use std::path::{Path, PathBuf};
 use std::{env, io, iter, mem, str};
 
 use cc::windows_registry;
+use rustc_ast::expand::allocator::{ALLOCATOR_METHODS, NO_ALLOC_SHIM_IS_UNSTABLE, global_fn_name};
 use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
 use rustc_metadata::{
     find_native_static_library, try_find_native_dynamic_library, try_find_native_static_library,
@@ -16,14 +17,16 @@ use rustc_middle::middle::exported_symbols::{
 };
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
-use rustc_session::config::{self, CrateType, DebugInfo, LinkerPluginLto, Lto, OptLevel, Strip};
+use rustc_session::config::{
+    self, CrateType, DebugInfo, LinkerPluginLto, Lto, OomStrategy, OptLevel, Strip,
+};
 use rustc_span::sym;
+use rustc_symbol_mangling::mangle_internal_symbol;
 use rustc_target::spec::{Cc, LinkOutputKind, LinkerFlavor, Lld};
 use tracing::{debug, warn};
 
 use super::command::Command;
 use super::symbol_export;
-use crate::back::symbol_export::allocator_shim_symbols;
 use crate::base::needs_allocator_shim_for_linking;
 use crate::errors;
 
@@ -1846,7 +1849,17 @@ fn exported_symbols_for_non_proc_macro(
         && needs_allocator_shim_for_linking(tcx.dependency_formats(()), crate_type)
         && tcx.allocator_kind(()).is_some()
     {
-        symbols.extend(allocator_shim_symbols(tcx));
+        for symbol_name in ALLOCATOR_METHODS
+            .iter()
+            .map(|method| mangle_internal_symbol(tcx, global_fn_name(method.name).as_str()))
+            .chain([
+                mangle_internal_symbol(tcx, "__rust_alloc_error_handler"),
+                mangle_internal_symbol(tcx, OomStrategy::SYMBOL),
+                mangle_internal_symbol(tcx, NO_ALLOC_SHIM_IS_UNSTABLE),
+            ])
+        {
+            symbols.push((symbol_name, SymbolExportKind::Text));
+        }
     }
 
     symbols

compiler/rustc_codegen_ssa/src/back/lto.rs

@@ -9,7 +9,7 @@ use rustc_middle::ty::TyCtxt;
 use rustc_session::config::{CrateType, Lto};
 use tracing::info;
 
-use crate::back::symbol_export::{self, allocator_shim_symbols, symbol_name_for_instance_in_crate};
+use crate::back::symbol_export::{self, symbol_name_for_instance_in_crate};
 use crate::back::write::CodegenContext;
 use crate::base::allocator_kind_for_codegen;
 use crate::errors::{DynamicLinkingWithLTO, LtoDisallowed, LtoDylib, LtoProcMacro};
@@ -130,11 +130,6 @@ pub(super) fn exported_symbols_for_lto(
         }
     }
 
-    // Mark allocator shim symbols as exported only if they were generated.
-    if export_threshold == SymbolExportLevel::Rust && allocator_kind_for_codegen(tcx).is_some() {
-        symbols_below_threshold.extend(allocator_shim_symbols(tcx).map(|(name, _kind)| name));
-    }
-
     symbols_below_threshold
 }
 

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -1,7 +1,6 @@
 use std::collections::hash_map::Entry::*;
 
 use rustc_abi::{CanonAbi, X86Call};
-use rustc_ast::expand::allocator::{ALLOCATOR_METHODS, NO_ALLOC_SHIM_IS_UNSTABLE, global_fn_name};
 use rustc_data_structures::unord::UnordMap;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LOCAL_CRATE, LocalDefId};
@@ -13,13 +12,10 @@ use rustc_middle::middle::exported_symbols::{
 use rustc_middle::query::LocalCrate;
 use rustc_middle::ty::{self, GenericArgKind, GenericArgsRef, Instance, SymbolName, Ty, TyCtxt};
 use rustc_middle::util::Providers;
-use rustc_session::config::{CrateType, OomStrategy};
-use rustc_symbol_mangling::mangle_internal_symbol;
+use rustc_session::config::CrateType;
 use rustc_target::spec::TlsModel;
 use tracing::debug;
 
-use crate::back::symbol_export;
-
 fn threshold(tcx: TyCtxt<'_>) -> SymbolExportLevel {
     crates_export_threshold(tcx.crate_types())
 }
@@ -491,31 +487,6 @@ pub(crate) fn provide(providers: &mut Providers) {
         upstream_monomorphizations_for_provider;
 }
 
-pub(crate) fn allocator_shim_symbols(
-    tcx: TyCtxt<'_>,
-) -> impl Iterator<Item = (String, SymbolExportKind)> {
-    ALLOCATOR_METHODS
-        .iter()
-        .map(move |method| mangle_internal_symbol(tcx, global_fn_name(method.name).as_str()))
-        .chain([
-            mangle_internal_symbol(tcx, "__rust_alloc_error_handler"),
-            mangle_internal_symbol(tcx, OomStrategy::SYMBOL),
-            mangle_internal_symbol(tcx, NO_ALLOC_SHIM_IS_UNSTABLE),
-        ])
-        .map(move |symbol_name| {
-            let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(tcx, &symbol_name));
-
-            (
-                symbol_export::exporting_symbol_name_for_instance_in_crate(
-                    tcx,
-                    exported_symbol,
-                    LOCAL_CRATE,
-                ),
-                SymbolExportKind::Text,
-            )
-        })
-}
-
 fn symbol_export_level(tcx: TyCtxt<'_>, sym_def_id: DefId) -> SymbolExportLevel {
     // We export anything that's not mangled at the "C" layer as it probably has
     // to do with ABI concerns. We do not, however, apply such treatment to