x86: Skip __[start|stop]_SECNAME for --gc-sections -z start-stop-gc

Don't convert memory load to immediate load on __start_SECNAME and
__stop_SECNAME for --gc-sections -z start-stop-gc if all SECNAME
sections been garbage collected.

bfd/

	PR ld/27491
	* elf32-i386.c (elf_i386_convert_load_reloc): Skip __start_SECNAME
	and __stop_SECNAME for --gc-sections -z start-stop-gc if the input
	section been garbage collected.
	* elf64-x86-64.c (elf_x86_64_convert_load_reloc): Likewise.
	* elfxx-x86.h (elf_x86_start_stop_gc_p): New function.

ld/
	PR ld/27491
	* testsuite/ld-i386/i386.exp: Run PR ld/27491 tests.
	* testsuite/ld-x86-64/x86-64.exp: Likewise.
	* testsuite/ld-i386/pr27491-1.s: New file.
	* testsuite/ld-i386/pr27491-1a.d: Likewise.
	* testsuite/ld-i386/pr27491-1b.d: Likewise.
	* testsuite/ld-i386/pr27491-1c.d: Likewise.
	* testsuite/ld-i386/pr27491-2.d: Likewise.
	* testsuite/ld-i386/pr27491-2.s: Likewise.
	* testsuite/ld-i386/pr27491-3.d: Likewise.
	* testsuite/ld-i386/pr27491-3.s: Likewise.
	* testsuite/ld-i386/pr27491-4.d: Likewise.
	* testsuite/ld-i386/pr27491-4a.s: Likewise.
	* testsuite/ld-i386/pr27491-4b.s: Likewise.
	* testsuite/ld-x86-64/pr27491-1.s: Likewise.
	* testsuite/ld-x86-64/pr27491-1a.d: Likewise.
	* testsuite/ld-x86-64/pr27491-1b.d: Likewise.
	* testsuite/ld-x86-64/pr27491-1c.d: Likewise.
	* testsuite/ld-x86-64/pr27491-2.d: Likewise.
	* testsuite/ld-x86-64/pr27491-2.s: Likewise.
	* testsuite/ld-x86-64/pr27491-3.d: Likewise.
	* testsuite/ld-x86-64/pr27491-3.s: Likewise.
	* testsuite/ld-x86-64/pr27491-4.d: Likewise.
	* testsuite/ld-x86-64/pr27491-4a.s: Likewise.
	* testsuite/ld-x86-64/pr27491-4b.s: Likewise.

3 files changed, 43 insertions, 0 deletions

diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c
index 0d7f290..db6d1ac 100644
--- a/bfd/elf32-i386.c
+++ b/bfd/elf32-i386.c
@@ -1393,6 +1393,11 @@ elf_i386_convert_load_reloc (bfd *abfd, Elf_Internal_Shdr *symtab_hdr,
 	       || h->root.type == bfd_link_hash_defweak)
 	      && local_ref))
 	{
+	  /* Skip __start_SECNAME/__stop_SECNAME when --gc-sections
+	     -z start-stop-gc are used.  */
+	  if (elf_x86_start_stop_gc_p (link_info, h))
+	    return true;
+
 	convert_load:
 	  if (opcode == 0x8b)
 	    {
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index 25e2bb1..bb6df79 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -1643,6 +1643,11 @@ elf_x86_64_convert_load_reloc (bfd *abfd,
 			   || h->root.type == bfd_link_hash_defweak)
 			  && h->root.u.def.section == bfd_und_section_ptr))))
 	    {
+	      /* Skip __start_SECNAME/__stop_SECNAME when --gc-sections
+	         -z start-stop-gc are used.  */
+	      if (elf_x86_start_stop_gc_p (link_info, h))
+		return true;
+
 	      /* Skip since R_X86_64_32/R_X86_64_32S may overflow.  */
 	      if (no_overflow)
 		return true;
diff --git a/bfd/elfxx-x86.h b/bfd/elfxx-x86.h
index 8251f64..aab641a 100644
--- a/bfd/elfxx-x86.h
+++ b/bfd/elfxx-x86.h
@@ -731,3 +731,36 @@ extern void _bfd_x86_elf_link_report_relative_reloc
   _bfd_x86_elf_merge_gnu_properties
 #define elf_backend_fixup_gnu_properties \
   _bfd_x86_elf_link_fixup_gnu_properties
+
+/* Return true if H is a __start_SECNAME/__stop_SECNAME symbol for the
+   SECNAME section which has been garbage collected by --gc-sections
+   -z start-stop-gc.  */
+
+static inline bool
+elf_x86_start_stop_gc_p (struct bfd_link_info *link_info,
+			 struct elf_link_hash_entry *h)
+{
+  if (h->start_stop
+      && link_info->gc_sections
+      && link_info->start_stop_gc)
+    {
+      asection *s = h->root.u.def.section;
+
+      do
+	{
+	  /* Return false if any SECNAME section is kept.  */
+	  if (s->gc_mark)
+	    return false;
+	  s = bfd_get_next_section_by_name (s->owner, s);
+	}
+      while (s != NULL);
+
+      /* Return true only if all SECNAME sections have been garbage
+	 collected.  */
+      return true;
+    }
+
+  /* Return false if H isn't a __start_SECNAME/__stop_SECNAME symbol or
+     --gc-sections or -z start-stop-gc isn't used.  */
+  return false;
+}