Auto merge of #84507 - crlf0710:codegen_nonlocal_main_wrapper, r=nagisa

Add primary marker on codegen unit and generate main wrapper on primary codegen.

This is the codegen part of changes extracted from #84062.

This add a marker called `primary` on each codegen units, where exactly one codegen unit will be `primary = true` at a time. This specific codegen unit will take charge of generating `main` wrapper when `main` is imported from a foreign crate after the implementation of RFC 1260.

cc #28937

I'm not sure who should i ask for review for codegen changes, so feel free to reassign.
r? `@nagisa`

1 files changed, 11 insertions, 1 deletions

diff --git a/compiler/rustc_middle/src/mir/mono.rs b/compiler/rustc_middle/src/mir/mono.rs
index 77f38e52ad2..67440e6e0ed 100644
--- a/compiler/rustc_middle/src/mir/mono.rs
+++ b/compiler/rustc_middle/src/mir/mono.rs
@@ -229,6 +229,7 @@ pub struct CodegenUnit<'tcx> {
     name: Symbol,
     items: FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)>,
     size_estimate: Option<usize>,
+    primary: bool,
 }
 
 /// Specifies the linkage type for a `MonoItem`.
@@ -258,7 +259,7 @@ pub enum Visibility {
 
 impl<'tcx> CodegenUnit<'tcx> {
     pub fn new(name: Symbol) -> CodegenUnit<'tcx> {
-        CodegenUnit { name, items: Default::default(), size_estimate: None }
+        CodegenUnit { name, items: Default::default(), size_estimate: None, primary: false }
     }
 
     pub fn name(&self) -> Symbol {
@@ -269,6 +270,14 @@ impl<'tcx> CodegenUnit<'tcx> {
         self.name = name;
     }
 
+    pub fn is_primary(&self) -> bool {
+        self.primary
+    }
+
+    pub fn make_primary(&mut self) {
+        self.primary = true;
+    }
+
     pub fn items(&self) -> &FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
         &self.items
     }
@@ -378,6 +387,7 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for CodegenUnit<'tcx> {
             name,
             // The size estimate is not relevant to the hash
             size_estimate: _,
+            primary: _,
         } = *self;
 
         name.hash_stable(hcx, hasher);