Don't claim a fat IR object if no IR object should be claimed

When the linker sees an input object containing nothing but IR during
rescan, it should ignore it (LTO phase is over).  But if the input object
is a fat IR object, which has non-IR code as well, it should be used to
resolve references as if it did not contain any IR at all.  This patch
adds lto_type to bfd and linker avoids claiming a fat IR object if no IR
object should be claimed.

bfd/

	PR ld/23935
	* archive.c (_bfd_compute_and_write_armap): Check bfd_get_lto_type
	instead of lto_slim_object.
	* elflink.c (elf_link_add_object_symbols): Likewise.
	* bfd.c (bfd_lto_object_type): New.
	(bfd): Remove lto_slim_object and add lto_type.
	(bfd_get_lto_type): New function.
	* elf.c (lto_section): Removed.
	(_bfd_elf_make_section_from_shdr): Don't set lto_slim_object.
	* format.c: (lto_section): New.
	(bfd_set_lto_type): New function.
	(bfd_check_format_matches): Call bfd_set_lto_type.
	* bfd-in2.h: Regenerated.

binutils/

	PR ld/23935
	* nm.c (display_rel_file): Check bfd_get_lto_type instead of
	lto_slim_object.

ld/

	PR ld/23935
	* ldmain.c (add_archive_element): Don't claim a fat IR object if
	no IR object should be claimed.
	* testsuite/ld-plugin/lto.exp (pr20103): Adjust fat IR test.
	Add PR ld/23935 test.
	* testsuite/ld-plugin/pr23935a.c: New file.
	* testsuite/ld-plugin/pr23935b.c: Likewise.

bfd/archive.c

@@ -2355,7 +2355,8 @@ _bfd_compute_and_write_armap (bfd *arch, unsigned int elength)
 	  long symcount;
 	  long src_count;
 
-	  if (current->lto_slim_object && report_plugin_err)
+	  if (bfd_get_lto_type (current) == lto_slim_ir_object
+	      && report_plugin_err)
 	    {
 	      report_plugin_err = false;
 	      _bfd_error_handler

bfd/bfd-in2.h

@@ -1954,6 +1954,14 @@ struct bfd_build_id
     bfd_byte data[1];
   };
 
+enum bfd_lto_object_type
+  {
+    lto_non_object,            /* Not an LTO object.  */
+    lto_non_ir_object,         /* An object without LTO IR.  */
+    lto_slim_ir_object,        /* A slim LTO IR object.  */
+    lto_fat_ir_object          /* A fat LTO IR object.  */
+  };
+
 struct bfd
 {
   /* The filename the application opened the BFD with.  */
@@ -2155,13 +2163,13 @@ struct bfd
   /* Set if this is a plugin output file.  */
   unsigned int lto_output : 1;
 
-  /* Set if this is a slim LTO object not loaded with a compiler plugin.  */
-  unsigned int lto_slim_object : 1;
-
   /* Do not attempt to modify this file.  Set when detecting errors
      that BFD is not prepared to handle for objcopy/strip.  */
   unsigned int read_only : 1;
 
+  /* LTO object type.  */
+  ENUM_BITFIELD (bfd_lto_object_type) lto_type : 2;
+
   /* Set to dummy BFD created when claimed by a compiler plug-in
      library.  */
   bfd *plugin_dummy_bfd;
@@ -2303,6 +2311,12 @@ bfd_get_format (const bfd *abfd)
   return abfd->format;
 }
 
+static inline enum bfd_lto_object_type
+bfd_get_lto_type (const bfd *abfd)
+{
+  return abfd->lto_type;
+}
+
 static inline flagword
 bfd_get_file_flags (const bfd *abfd)
 {

bfd/bfd.c

@@ -74,6 +74,14 @@ EXTERNAL
 .    bfd_byte data[1];
 .  };
 .
+.enum bfd_lto_object_type
+.  {
+.    lto_non_object,		{* Not an LTO object.  *}
+.    lto_non_ir_object,		{* An object without LTO IR.  *}
+.    lto_slim_ir_object,	{* A slim LTO IR object.  *}
+.    lto_fat_ir_object		{* A fat LTO IR object.  *}
+.  };
+.
 
 CODE_FRAGMENT
 .struct bfd
@@ -278,13 +286,13 @@ CODE_FRAGMENT
 .  {* Set if this is a plugin output file.  *}
 .  unsigned int lto_output : 1;
 .
-.  {* Set if this is a slim LTO object not loaded with a compiler plugin.  *}
-.  unsigned int lto_slim_object : 1;
-.
 .  {* Do not attempt to modify this file.  Set when detecting errors
 .     that BFD is not prepared to handle for objcopy/strip.  *}
 .  unsigned int read_only : 1;
 .
+.  {* LTO object type.  *}
+.  ENUM_BITFIELD (bfd_lto_object_type) lto_type : 2;
+.
 .  {* Set to dummy BFD created when claimed by a compiler plug-in
 .     library.  *}
 .  bfd *plugin_dummy_bfd;
@@ -428,6 +436,12 @@ EXTERNAL
 .  return abfd->format;
 .}
 .
+.static inline enum bfd_lto_object_type
+.bfd_get_lto_type (const bfd *abfd)
+.{
+.  return abfd->lto_type;
+.}
+.
 .static inline flagword
 .bfd_get_file_flags (const bfd *abfd)
 .{

bfd/elf.c

@@ -970,18 +970,6 @@ bfd_elf_group_name (bfd *abfd ATTRIBUTE_UNUSED, const asection *sec)
   return NULL;
 }
 
-/* This a copy of lto_section defined in GCC (lto-streamer.h).  */
-
-struct lto_section
-{
-  int16_t major_version;
-  int16_t minor_version;
-  unsigned char slim_object;
-
-  /* Flags is a private field that is not defined publicly.  */
-  uint16_t flags;
-};
-
 /* Make a BFD section from an ELF section.  We store a pointer to the
    BFD section in the bfd_section field of the header.  */
 
@@ -1261,16 +1249,6 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
 	}
     }
 
-  /* GCC uses .gnu.lto_.lto.<some_hash> as a LTO bytecode information
-     section.  */
-  if (startswith (name, ".gnu.lto_.lto."))
-    {
-      struct lto_section lsection;
-      if (bfd_get_section_contents (abfd, newsect, &lsection, 0,
-				    sizeof (struct lto_section)))
-	abfd->lto_slim_object = lsection.slim_object;
-    }
-
   return true;
 }
 

bfd/elflink.c

@@ -4785,7 +4785,7 @@ elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
     }
 
   if (!bfd_link_relocatable (info)
-      && abfd->lto_slim_object)
+      && bfd_get_lto_type (abfd) == lto_slim_ir_object)
     {
       _bfd_error_handler
 	(_("%pB: plugin needed to handle lto object"), abfd);

bfd/format.c

@@ -278,6 +278,50 @@ null_error_handler (const char *fmt ATTRIBUTE_UNUSED,
 {
 }
 
+/* This a copy of lto_section defined in GCC (lto-streamer.h).  */
+
+struct lto_section
+{
+  int16_t major_version;
+  int16_t minor_version;
+  unsigned char slim_object;
+
+  /* Flags is a private field that is not defined publicly.  */
+  uint16_t flags;
+};
+
+/* Set lto_type in ABFD.  */
+
+static void
+bfd_set_lto_type (bfd *abfd ATTRIBUTE_UNUSED)
+{
+#if BFD_SUPPORTS_PLUGINS
+  if (abfd->format == bfd_object
+      && abfd->lto_type == lto_non_object
+      && (abfd->flags & (DYNAMIC | EXEC_P)) == 0)
+    {
+      asection *sec;
+      enum bfd_lto_object_type type = lto_non_ir_object;
+      struct lto_section lsection;
+      /* GCC uses .gnu.lto_.lto.<some_hash> as a LTO bytecode information
+	 section.  */
+      for (sec = abfd->sections; sec != NULL; sec = sec->next)
+	if (startswith (sec->name, ".gnu.lto_.lto.")
+	    && bfd_get_section_contents (abfd, sec, &lsection, 0,
+					 sizeof (struct lto_section)))
+	  {
+	    if (lsection.slim_object)
+	      type = lto_slim_ir_object;
+	    else
+	      type = lto_fat_ir_object;
+	    break;
+	  }
+
+      abfd->lto_type = type;
+    }
+#endif
+}
+
 /*
 FUNCTION
 	bfd_check_format_matches
@@ -327,7 +371,10 @@ bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
     }
 
   if (abfd->format != bfd_unknown)
-    return abfd->format == format;
+    {
+      bfd_set_lto_type (abfd);
+      return abfd->format == format;
+    }
 
   if (matching != NULL || *bfd_associated_vector != NULL)
     {
@@ -601,6 +648,8 @@ bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
 	clear_warnmsg (list++);
       --in_check_format;
 
+      bfd_set_lto_type (abfd);
+
       /* File position has moved, BTW.  */
       return true;
     }

binutils/nm.c

@@ -1466,9 +1466,9 @@ display_rel_file (bfd *abfd, bfd *archive_bfd)
 	free (dyn_syms);
     }
 
-  /* lto_slim_object is set to false when a bfd is loaded with a compiler
-     LTO plugin.  */
-  if (abfd->lto_slim_object)
+  /* lto_type is set to lto_non_ir_object when a bfd is loaded with a
+     compiler LTO plugin.  */
+  if (bfd_get_lto_type (abfd) == lto_slim_ir_object)
     {
       report_plugin_err = false;
       non_fatal (_("%s: plugin needed to handle lto object"),

ld/ldmain.c

@@ -902,7 +902,10 @@ add_archive_element (struct bfd_link_info *info,
      BFD, but we still want to output the original BFD filename.  */
   orig_input = *input;
 #if BFD_SUPPORTS_PLUGINS
-  if (link_info.lto_plugin_active)
+  /* Don't claim a fat IR object if no IR object should be claimed.  */
+  if (link_info.lto_plugin_active
+      && (!no_more_claiming
+	  || bfd_get_lto_type (abfd) != lto_fat_ir_object))
     {
       /* We must offer this archive member to the plugins to claim.  */
       plugin_maybe_claim (input);

ld/testsuite/ld-plugin/lto.exp

@@ -964,10 +964,20 @@ proc pr20103 {cflags libs} {
 
     set testname "PR ld/20103 ($cflags $libs)"
     set exec_output [run_host_cmd "$CC_FOR_TARGET" "$cflags $libs"]
-    if { [ regexp "undefined reference to `\\.?dead'" $exec_output ] } {
-        pass "$testname (1)"
+    # NB: Starting from GCC 4.9, -flto is optional for final link.
+    if { [ regexp "fatpr20103" "$libs" ] \
+	 && ([regexp " -flto" "$cflags"] \
+	     || [at_least_gcc_version 4 9]) } {
+	set result1good "fail"
+	set result1bad "pass"
     } {
-        fail "$testname (1)"
+	set result1good "pass"
+	set result1bad "fail"
+    }
+    if { [ regexp "undefined reference to `\\.?dead'" $exec_output ] } {
+	$result1good "$testname (1)"
+    } {
+	$result1bad "$testname (1)"
     }
     if { [ regexp "plugin needed to handle lto object" $exec_output ] } {
         fail "$testname (2)"
@@ -1026,6 +1036,27 @@ if { [check_lto_fat_available] } {
 	    "-O2" \
 	    {dummy.c} {} "pr20103c" \
 	] \
+	[list "Build fatpr23935.a" \
+	    "$plug_opt" \
+	    "-flto -fno-builtin -ffat-lto-objects" \
+	    {pr23935a.c} \
+	    "" \
+	    "fatpr23935.a" \
+	] \
+	[list "Build pr23935b.o" \
+	    "$plug_opt" \
+	    "-flto -fno-fat-lto-objects" \
+	    {pr23935b.c} \
+	] \
+	[list \
+	    "Build pr23935" \
+	    "-static -flto -Wl,-emain -nostdlib tmpdir/pr23935b.o \
+	     tmpdir/fatpr23935.a" \
+	    "-flto -fno-fat-lto-objects" \
+	    {dummy.c} \
+	    "" \
+	    "pr23935" \
+	] \
     ]
     pr20103 "-O2 -flto" "tmpdir/thinpr20103a.a tmpdir/thinpr20103b.a tmpdir/thinpr20103c.a"
     pr20103 "-O2 -flto" "tmpdir/fatpr20103a.a tmpdir/fatpr20103b.a tmpdir/fatpr20103c.a"

ld/testsuite/ld-plugin/pr23935a.c

@@ -0,0 +1,2 @@
+#include <stdio.h>
+int puts(const char *s) { return 0; }

ld/testsuite/ld-plugin/pr23935b.c

@@ -0,0 +1,2 @@
+#include <stdio.h>
+int main() { printf("hi\n"); return 0; }