Update comments about the partitioning inefficiency

src/librustc_mir/monomorphize/partitioning.rs

@@ -427,8 +427,6 @@ fn merge_codegen_units<'tcx>(initial_partitioning: &mut PreInliningPartitioning<
     codegen_units.sort_by_key(|cgu| cgu.name().clone());
 
     // Merge the two smallest codegen units until the target size is reached.
-    // Note that "size" is estimated here rather inaccurately as the number of
-    // translation items in a given unit. This could be improved on.
     while codegen_units.len() > target_cgu_count {
         // Sort small cgus to the back
         codegen_units.sort_by_key(|cgu| usize::MAX - cgu.size_estimate());

src/librustc_trans/base.rs

@@ -824,9 +824,7 @@ pub fn trans_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     ongoing_translation.submit_pre_translated_module_to_llvm(tcx, metadata_module);
 
     // We sort the codegen units by size. This way we can schedule work for LLVM
-    // a bit more efficiently. Note that "size" is defined rather crudely at the
-    // moment as it is just the number of TransItems in the CGU, not taking into
-    // account the size of each TransItem.
+    // a bit more efficiently.
     let codegen_units = {
         let mut codegen_units = codegen_units;
         codegen_units.sort_by_key(|cgu| usize::MAX - cgu.size_estimate());