Directly raise fatal errors inside the codegen backends

As opposed to passing it around through Result.

compiler/rustc_codegen_gcc/src/lib.rs

@@ -110,7 +110,6 @@ use rustc_middle::util::Providers;
 use rustc_session::Session;
 use rustc_session::config::{OptLevel, OutputFilenames};
 use rustc_span::Symbol;
-use rustc_span::fatal_error::FatalError;
 use rustc_target::spec::RelocModel;
 use tempfile::TempDir;
 
@@ -362,7 +361,7 @@ impl WriteBackendMethods for GccCodegenBackend {
         _exported_symbols_for_lto: &[String],
         each_linked_rlib_for_lto: &[PathBuf],
         modules: Vec<FatLtoInput<Self>>,
-    ) -> Result<ModuleCodegen<Self::Module>, FatalError> {
+    ) -> ModuleCodegen<Self::Module> {
         back::lto::run_fat(cgcx, each_linked_rlib_for_lto, modules)
     }
 
@@ -373,7 +372,7 @@ impl WriteBackendMethods for GccCodegenBackend {
         each_linked_rlib_for_lto: &[PathBuf],
         modules: Vec<(String, Self::ThinBuffer)>,
         cached_modules: Vec<(SerializedModule<Self::ModuleBuffer>, WorkProduct)>,
-    ) -> Result<(Vec<ThinModule<Self>>, Vec<WorkProduct>), FatalError> {
+    ) -> (Vec<ThinModule<Self>>, Vec<WorkProduct>) {
         back::lto::run_thin(cgcx, each_linked_rlib_for_lto, modules, cached_modules)
     }
 
@@ -390,15 +389,14 @@ impl WriteBackendMethods for GccCodegenBackend {
         _dcx: DiagCtxtHandle<'_>,
         module: &mut ModuleCodegen<Self::Module>,
         config: &ModuleConfig,
-    ) -> Result<(), FatalError> {
+    ) {
         module.module_llvm.context.set_optimization_level(to_gcc_opt_level(config.opt_level));
-        Ok(())
     }
 
     fn optimize_thin(
         cgcx: &CodegenContext<Self>,
         thin: ThinModule<Self>,
-    ) -> Result<ModuleCodegen<Self::Module>, FatalError> {
+    ) -> ModuleCodegen<Self::Module> {
         back::lto::optimize_thin_module(thin, cgcx)
     }
 
@@ -406,7 +404,7 @@ impl WriteBackendMethods for GccCodegenBackend {
         cgcx: &CodegenContext<Self>,
         module: ModuleCodegen<Self::Module>,
         config: &ModuleConfig,
-    ) -> Result<CompiledModule, FatalError> {
+    ) -> CompiledModule {
         back::write::codegen(cgcx, module, config)
     }