Add --relocatable-merge-sections

docs/mold.1

@@ -478,6 +478,26 @@ Instead of generating an executable or a shared object file, combine
 input object files to generate another object file that can be used as
 an input to a linker.
 .Pp
+.It Fl -relocatable-merge-sections
+By default,
+.Nm
+doesn't merge input sections by name when merging input object files into a \
+single output object file for
+.Fl r .
+For example,
+.Ar .text.foo
+and
+.Ar .text.bar
+aren't merged for
+.Fl r
+even though they are merged into
+.Ar .text
+according to the default section merging rules.
+.Pp
+This option changes the behavior so that
+.Nm
+merges input sections by name by the default section merging rules.
+.Pp
 .It Fl s , Fl -strip-all
 Omit
 .Li \.symtab

elf/cmdline.cc

@@ -697,6 +697,8 @@ std::vector<std::string> parse_nonpositional_args(Context<E> &ctx) {
       ctx.arg.relocatable = true;
       ctx.arg.emit_relocs = true;
       ctx.arg.discard_locals = false;
+    } else if (read_flag("relocatable-merge-sections")) {
+      ctx.arg.relocatable_merge_sections = true;
     } else if (read_flag("perf")) {
       ctx.arg.perf = true;
     } else if (read_flag("pack-dyn-relocs=relr")) {

elf/mold.h

@@ -1660,6 +1660,7 @@ struct Context {
     bool quick_exit = true;
     bool relax = true;
     bool relocatable = false;
+    bool relocatable_merge_sections = false;
     bool repro = false;
     bool rosegment = true;
     bool shared = false;

elf/output-chunks.cc

@@ -1857,7 +1857,9 @@ void GnuHashSection<E>::copy_buf(Context<E> &ctx) {
 template <typename E>
 std::string_view
 get_merged_output_name(Context<E> &ctx, std::string_view name, u64 flags) {
-  if (ctx.arg.relocatable || (ctx.arg.unique && ctx.arg.unique->match(name)))
+  if (ctx.arg.relocatable && !ctx.arg.relocatable_merge_sections)
+    return name;
+  if (ctx.arg.unique && ctx.arg.unique->match(name))
     return name;
   if (name == ".rodata" || name.starts_with(".rodata."))
     return (flags & SHF_STRINGS) ? ".rodata.str" : ".rodata.cst";

elf/passes.cc

@@ -412,7 +412,7 @@ struct OutputSectionKey {
 template <typename E>
 std::string_view
 get_output_name(Context<E> &ctx, std::string_view name, u64 flags) {
-  if (ctx.arg.relocatable)
+  if (ctx.arg.relocatable && !ctx.arg.relocatable_merge_sections)
     return name;
   if (ctx.arg.unique && ctx.arg.unique->match(name))
     return name;