Rollup merge of #146209 - bjorn3:lto_refactors5, r=dianqk

Misc LTO cleanups

Follow up to rust-lang/rust#145955.

* Remove want_summary argument from `prepare_thin`.
   Since rust-lang/rust#133250 ThinLTO summary writing is instead done by `llvm_optimize`.
* Two minor cleanups

Author: matthiaskrgr

src/back/lto.rs

@@ -305,12 +305,9 @@ pub(crate) fn run_thin(
     )
 }
 
-pub(crate) fn prepare_thin(
-    module: ModuleCodegen<GccContext>,
-    _emit_summary: bool,
-) -> (String, ThinBuffer) {
+pub(crate) fn prepare_thin(module: ModuleCodegen<GccContext>) -> (String, ThinBuffer) {
     let name = module.name;
-    //let buffer = ThinBuffer::new(module.module_llvm.context, true, emit_summary);
+    //let buffer = ThinBuffer::new(module.module_llvm.context, true);
     let buffer = ThinBuffer::new(&module.module_llvm.context);
     (name, buffer)
 }
@@ -650,10 +647,6 @@ impl ThinBufferMethods for ThinBuffer {
     fn data(&self) -> &[u8] {
         &[]
     }
-
-    fn thin_link_data(&self) -> &[u8] {
-        unimplemented!();
-    }
 }
 
 pub struct ThinData; //(Arc<TempDir>);

src/lib.rs

@@ -408,11 +408,8 @@ impl WriteBackendMethods for GccCodegenBackend {
         back::write::codegen(cgcx, module, config)
     }
 
-    fn prepare_thin(
-        module: ModuleCodegen<Self::Module>,
-        emit_summary: bool,
-    ) -> (String, Self::ThinBuffer) {
-        back::lto::prepare_thin(module, emit_summary)
+    fn prepare_thin(module: ModuleCodegen<Self::Module>) -> (String, Self::ThinBuffer) {
+        back::lto::prepare_thin(module)
     }
 
     fn serialize_module(_module: ModuleCodegen<Self::Module>) -> (String, Self::ModuleBuffer) {