Revert "implement export all symbols"

This reverts commit aaef5c6.

Author: sgasho

compiler/rustc_codegen_ssa/src/back/linker.rs

@@ -800,10 +800,6 @@ impl<'a> Linker for GccLinker<'a> {
         // The object files have far more public symbols than we actually want to export,
         // so we hide them all here.
 
-        if self.sess.opts.unstable_opts.export_all_symbols {
-            return;
-        }
-
         if !self.sess.target.limit_rdylib_exports {
             return;
         }
@@ -1142,10 +1138,6 @@ impl<'a> Linker for MsvcLinker<'a> {
             }
         }
 
-        if self.sess.opts.unstable_opts.export_all_symbols {
-            return;
-        }
-
         let path = tmpdir.join("lib.def");
         let res = try {
             let mut f = File::create_buffered(&path)?;

compiler/rustc_session/src/options.rs

@@ -2343,8 +2343,6 @@ options! {
         "enforce the type length limit when monomorphizing instances in codegen"),
     experimental_default_bounds: bool = (false, parse_bool, [TRACKED],
         "enable default bounds for experimental group of auto traits"),
-    export_all_symbols: bool = (false, parse_bool, [TRACKED],
-        "disable symbol export filtering for dylibs and cdylibs, exporting all symbols"),
     export_executable_symbols: bool = (false, parse_bool, [TRACKED],
         "export symbols from executables, as if they were dynamic libraries"),
     external_clangrt: bool = (false, parse_bool, [UNTRACKED],

src/bootstrap/src/core/build_steps/compile.rs

@@ -1243,13 +1243,6 @@ pub fn rustc_cargo(
         cargo.rustflag("-Zdefault-visibility=protected");
     }
 
-    // On Apple, Enzyme can hang if rustc and Enzyme each embed their own LLVM.
-    // Export all symbols from rustc_driver so Enzyme reuses rustc's LLVM.
-    // Related: https://github.com/rust-lang/enzyme/pull/31
-    if builder.config.llvm_enzyme && target.contains("apple") && build_compiler.stage != 0 {
-        cargo.rustflag("-Zexport-all-symbols");
-    }
-
     if is_lto_stage(build_compiler) {
         match builder.config.rust_lto {
             RustcLto::Thin | RustcLto::Fat => {