[WIP] Support hybrid LTO/non-LTO rlibs.

Author: bjorn3

build_system/build_sysroot.rs

@@ -243,8 +243,6 @@ fn build_clif_sysroot_for_triple(
             prefix.to_str().unwrap()
         ));
     }
-    rustflags.push("-Clto=thin".to_owned());
-    rustflags.push("-Zdylib-lto".to_owned());
     rustflags.push("-Cembed-bitcode=yes".to_owned());
     compiler.rustflags.extend(rustflags);
     let mut build_cmd = STANDARD_LIBRARY.build(&compiler, dirs);
@@ -256,7 +254,6 @@ fn build_clif_sysroot_for_triple(
     if compiler.triple.contains("apple") {
         build_cmd.env("CARGO_PROFILE_RELEASE_SPLIT_DEBUGINFO", "packed");
     }
-    build_cmd.env("CARGO_PROFILE_RELEASE_LTO", "thin");
     spawn_and_wait(build_cmd);
 
     for entry in fs::read_dir(build_dir.join("deps")).unwrap() {

src/lib.rs

@@ -207,23 +207,30 @@ impl CodegenBackend for CraneliftCodegenBackend {
                 .unwrap_or_else(|err| tcx.sess.dcx().fatal(err))
         });
         match config.codegen_mode {
-            CodegenMode::Aot => match tcx.sess.lto() {
-                Lto::No | Lto::ThinLocal => {
-                    driver::aot::run_aot(tcx, metadata, need_metadata_module)
-                }
-                Lto::Thin | Lto::Fat => {
-                    if tcx.crate_name(LOCAL_CRATE) == sym::compiler_builtins {
-                        return driver::aot::run_aot(tcx, metadata, need_metadata_module);
-                    }
-
+            CodegenMode::Aot => {
+                if tcx.sess.opts.cg.linker_plugin_lto.enabled() {
                     #[cfg(feature = "lto")]
                     return driver::lto::run_aot(tcx, metadata, need_metadata_module);
 
                     #[cfg(not(feature = "lto"))]
                     tcx.dcx()
                         .fatal("LTO support was disabled when compiling rustc_codegen_cranelift");
                 }
-            },
+                match tcx.sess.lto() {
+                    Lto::No | Lto::ThinLocal => {
+                        driver::aot::run_aot(tcx, metadata, need_metadata_module)
+                    }
+                    Lto::Thin | Lto::Fat => {
+                        #[cfg(feature = "lto")]
+                        return driver::lto::run_aot(tcx, metadata, need_metadata_module);
+
+                        #[cfg(not(feature = "lto"))]
+                        tcx.dcx().fatal(
+                            "LTO support was disabled when compiling rustc_codegen_cranelift",
+                        );
+                    }
+                }
+            }
             CodegenMode::Jit | CodegenMode::JitLazy => {
                 #[cfg(feature = "jit")]
                 driver::jit::run_jit(tcx, config.codegen_mode, config.jit_args);