[ELF] Keep non-alloc orphan sections at the end

https://reviews.llvm.org/D85867 changed the way we assign file offsets
(alloc sections first, then non-alloc sections).

It also removed a non-alloc special case from `findOrphanPos`.
Looking at the memory-nonalloc-no-warn.test change, which would be
needed by #93761, it makes sense to restore the previous behavior: when
placing non-alloc orphan sections, keep these sections at the end so
that the section index order matches the file offset order.

This change is cosmetic. In sections-nonalloc.s, GNU ld places the
orphan `other3` in the middle and the orphan .symtab/.shstrtab/.strtab
at the end.

Pull Request: https://github.com/llvm/llvm-project/pull/94519

1 files changed, 4 insertions, 0 deletions

diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 0295a65..544db20 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -921,7 +921,11 @@ static bool shouldSkip(SectionCommand *cmd) {
 static SmallVectorImpl<SectionCommand *>::iterator
 findOrphanPos(SmallVectorImpl<SectionCommand *>::iterator b,
               SmallVectorImpl<SectionCommand *>::iterator e) {
+  // Place non-alloc orphan sections at the end. This matches how we assign file
+  // offsets to non-alloc sections.
   OutputSection *sec = &cast<OutputDesc>(*e)->osec;
+  if (!(sec->flags & SHF_ALLOC))
+    return e;
 
   // As a special case, place .relro_padding before the SymbolAssignment using
   // DATA_SEGMENT_RELRO_END, if present.