Prevent creating the same Instance::mono multiple times

compiler/rustc_codegen_llvm/src/consts.rs

@@ -246,7 +246,8 @@ impl<'ll> CodegenCx<'ll, '_> {
 
  #[instrument(level = "debug", skip(self, llty))]
  pub(crate) fn get_static_inner(&self, def_id: DefId, llty: &'ll Type) -> &'ll Value {
- if let Some(&g) = self.instances.borrow().get(&Instance::mono(self.tcx, def_id)) {
+ let instance = Instance::mono(self.tcx, def_id);
+ if let Some(&g) = self.instances.borrow().get(&instance) {
  trace!("used cached value");
  return g;
  }
@@ -259,7 +260,7 @@ impl<'ll> CodegenCx<'ll, '_> {
  statics defined in the same CGU, but did not for `{def_id:?}`"
  );
 
- let sym = self.tcx.symbol_name(Instance::mono(self.tcx, def_id)).name;
+ let sym = self.tcx.symbol_name(instance).name;
  let fn_attrs = self.tcx.codegen_fn_attrs(def_id);
 
  debug!(?sym, ?fn_attrs);
@@ -349,7 +350,7 @@ impl<'ll> CodegenCx<'ll, '_> {
  }
  }
 
- self.instances.borrow_mut().insert(Instance::mono(self.tcx, def_id), g);
+ self.instances.borrow_mut().insert(instance, g);
  g
  }