Rollup merge of rust-lang#143020 - RalfJung:codegen_fn_attrs, r=oli-obk

codegen_fn_attrs: make comment more precise

Follow-up to rust-lang#142854.

r? ````@oli-obk```` or ````@workingjubilee````

Author: compiler-errors

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -412,7 +412,9 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
 
     mixed_export_name_no_mangle_lint_state.lint_if_mixed(tcx);
 
-    // Apply the minimum function alignment here, so that individual backends don't have to.
+    // Apply the minimum function alignment here. This ensures that a function's alignment is
+    // determined by the `-C` flags of the crate it is defined in, not the `-C` flags of the crate
+    // it happens to be codegen'd (or const-eval'd) in.
     codegen_fn_attrs.alignment =
         Ord::max(codegen_fn_attrs.alignment, tcx.sess.opts.unstable_opts.min_function_alignment);