Only export the sanitizer symbols for LTO and move export code to cg_llvm

Don't export them from cdylibs. There is no need to do so and it
complicates exported_non_generic_symbols. In addition the GCC backend
likely uses different symbols and may potentially not even need us to
explicitly tell it to export the symbols it needs.

Author: bjorn3

compiler/rustc_codegen_llvm/src/back/lto.rs

@@ -15,6 +15,7 @@ use rustc_codegen_ssa::{ModuleCodegen, ModuleKind, looks_like_rust_object_file};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::memmap::Mmap;
 use rustc_errors::DiagCtxtHandle;
+use rustc_hir::attrs::SanitizerSet;
 use rustc_middle::bug;
 use rustc_middle::dep_graph::WorkProduct;
 use rustc_session::config::{self, Lto};
@@ -42,6 +43,33 @@ fn prepare_lto(
         .map(|symbol| CString::new(symbol.to_owned()).unwrap())
         .collect::<Vec<CString>>();
 
+    if cgcx.regular_module_config.instrument_coverage
+        || cgcx.regular_module_config.pgo_gen.enabled()
+    {
+        // These are weak symbols that point to the profile version and the
+        // profile name, which need to be treated as exported so LTO doesn't nix
+        // them.
+        const PROFILER_WEAK_SYMBOLS: [&CStr; 2] =
+            [c"__llvm_profile_raw_version", c"__llvm_profile_filename"];
+
+        symbols_below_threshold.extend(PROFILER_WEAK_SYMBOLS.iter().map(|&sym| sym.to_owned()));
+    }
+
+    if cgcx.regular_module_config.sanitizer.contains(SanitizerSet::MEMORY) {
+        let mut msan_weak_symbols = Vec::new();
+
+        // Similar to profiling, preserve weak msan symbol during LTO.
+        if cgcx.regular_module_config.sanitizer_recover.contains(SanitizerSet::MEMORY) {
+            msan_weak_symbols.push(c"__msan_keep_going");
+        }
+
+        if cgcx.regular_module_config.sanitizer_memory_track_origins != 0 {
+            msan_weak_symbols.push(c"__msan_track_origins");
+        }
+
+        symbols_below_threshold.extend(msan_weak_symbols.into_iter().map(|sym| sym.to_owned()));
+    }
+
     // __llvm_profile_counter_bias is pulled in at link time by an undefined reference to
     // __llvm_profile_runtime, therefore we won't know until link time if this symbol
     // should have default visibility.

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -15,7 +15,7 @@ use rustc_middle::ty::{self, GenericArgKind, GenericArgsRef, Instance, SymbolNam
 use rustc_middle::util::Providers;
 use rustc_session::config::{CrateType, OomStrategy};
 use rustc_symbol_mangling::mangle_internal_symbol;
-use rustc_target::spec::{SanitizerSet, TlsModel};
+use rustc_target::spec::TlsModel;
 use tracing::debug;
 
 use crate::base::allocator_kind_for_codegen;
@@ -242,53 +242,6 @@ fn exported_non_generic_symbols_provider_local<'tcx>(
         }
     }
 
-    if tcx.sess.instrument_coverage() || tcx.sess.opts.cg.profile_generate.enabled() {
-        // These are weak symbols that point to the profile version and the
-        // profile name, which need to be treated as exported so LTO doesn't nix
-        // them.
-        const PROFILER_WEAK_SYMBOLS: [&str; 2] =
-            ["__llvm_profile_raw_version", "__llvm_profile_filename"];
-
-        symbols.extend(PROFILER_WEAK_SYMBOLS.iter().map(|sym| {
-            let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(tcx, sym));
-            (
-                exported_symbol,
-                SymbolExportInfo {
-                    level: SymbolExportLevel::C,
-                    kind: SymbolExportKind::Data,
-                    used: false,
-                    rustc_std_internal_symbol: false,
-                },
-            )
-        }));
-    }
-
-    if tcx.sess.opts.unstable_opts.sanitizer.contains(SanitizerSet::MEMORY) {
-        let mut msan_weak_symbols = Vec::new();
-
-        // Similar to profiling, preserve weak msan symbol during LTO.
-        if tcx.sess.opts.unstable_opts.sanitizer_recover.contains(SanitizerSet::MEMORY) {
-            msan_weak_symbols.push("__msan_keep_going");
-        }
-
-        if tcx.sess.opts.unstable_opts.sanitizer_memory_track_origins != 0 {
-            msan_weak_symbols.push("__msan_track_origins");
-        }
-
-        symbols.extend(msan_weak_symbols.into_iter().map(|sym| {
-            let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(tcx, sym));
-            (
-                exported_symbol,
-                SymbolExportInfo {
-                    level: SymbolExportLevel::C,
-                    kind: SymbolExportKind::Data,
-                    used: false,
-                    rustc_std_internal_symbol: false,
-                },
-            )
-        }));
-    }
-
     // Sort so we get a stable incr. comp. hash.
     symbols.sort_by_cached_key(|s| s.0.symbol_name_for_local_instance(tcx));