commit 26c2ff33f8fcd57d52194a159226b639a4fee00c
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Tue Mar 25 13:33:51 2014 -0700

    Don't issue a warning for reference in LTO IR
    
    References in LTO IR may be removed by LTO later.  Instead, make a
    warning symbol if needed.  Warnings will be handled after LTO resolves
    all references.
    
    bfd/
    
    	PR ld/16746
    	* linker.c (_bfd_generic_link_add_one_symbol): Don't issue a
    	warning for reference in LTO IR which may be removed by LTO later.
    
    ld/testsuite/
    
    	PR ld/16746
    	* ld-plugin/lto.exp: Add 4 tests for PR ld/16746.
    	* ld-plugin/pr16746a.c: New file.
    	* ld-plugin/pr16746b.c: Likewise.
    	* ld-plugin/pr16746c.c: Likewise.
    	* ld-plugin/pr16746d.c: Likewise.

Index: binutils-2.24/bfd/linker.c
===================================================================
--- binutils-2.24.orig/bfd/linker.c	2014-05-06 16:08:45.649990914 +0200
+++ binutils-2.24/bfd/linker.c	2014-05-06 16:08:49.819990627 +0200
@@ -1904,8 +1904,10 @@ _bfd_generic_link_add_one_symbol (struct
 	  break;
 
 	case WARNC:
-	  /* Issue a warning and cycle.  */
-	  if (h->u.i.warning != NULL)
+	  /* Issue a warning and cycle.  Don't issue a warning for
+	     reference in LTO IR which may be removed by LTO later. */
+	  if (h->u.i.warning != NULL
+	      && (abfd->flags & BFD_PLUGIN) == 0)
 	    {
 	      if (! (*info->callbacks->warning) (info, h->u.i.warning,
 						 h->root.string, abfd,
@@ -1930,6 +1932,11 @@ _bfd_generic_link_add_one_symbol (struct
 	  break;
 
 	case WARN:
+	  /* Don't issue a warning for reference in LTO IR which may be
+	     removed by LTO later.  Make a warning symbol instead.  */
+	  if ((hash_entry_bfd (h)->flags & BFD_PLUGIN) != 0)
+	    goto mwarn;
+
 	  /* Issue a warning.  */
 	  if (! (*info->callbacks->warning) (info, string, h->root.string,
 					     hash_entry_bfd (h), NULL, 0))
@@ -1951,6 +1958,7 @@ _bfd_generic_link_add_one_symbol (struct
 	    }
 	  /* Fall through.  */
 	case MWARN:
+mwarn:
 	  /* Make a warning symbol.  */
 	  {
 	    struct bfd_link_hash_entry *sub;
Index: binutils-2.24/ld/testsuite/ld-plugin/lto.exp
===================================================================
--- binutils-2.24.orig/ld/testsuite/ld-plugin/lto.exp	2014-05-06 16:08:45.649990914 +0200
+++ binutils-2.24/ld/testsuite/ld-plugin/lto.exp	2014-05-06 16:10:14.334984808 +0200
@@ -206,6 +206,18 @@ set lto_link_elf_tests {
   {"Build libpr15146d.a"
    "" "-flto -O2"
    {pr15146d.c} {} "lib15146d.a"}
+  {"Build libpr16746a.a"
+   "" ""
+   {pr16746a.c pr16746b.c} {} "lib16746a.a"}
+  {"Build libpr16746b.a"
+   "" "-O2 -flto"
+   {pr16746c.c pr16746d.c} {} "lib16746b.a"}
+  {"PR ld/16746 (1)"
+   "-O2 -flto -fuse-linker-plugin tmpdir/pr16746a.o tmpdir/pr16746c.o" "-O2 -flto"
+   {dummy.c} {} "pr16746a.exe"}
+  {"PR ld/16746 (2)"
+   "-O2 -flto -fuse-linker-plugin tmpdir/pr16746c.o tmpdir/pr16746a.o" "-O2 -flto"
+   {dummy.c} {} "pr16746b.exe"}
 }
 
 # Check final symbols in executables.
@@ -309,6 +321,20 @@ if { [is_elf_format]
 	pass $testname
     } {
 	fail $testname
+    }
+    set testname "PR ld/16746 (3)"
+    set exec_output [run_host_cmd "$CC" "$gcc_gas_flag $gcc_ld_flag -O2 -flto -fuse-linker-plugin tmpdir/pr16746b.o tmpdir/pr16746d.o"]
+    if { [ regexp "warning: foobar" $exec_output ] && ![ regexp "symbol from plugin" $exec_output ] } {
+	pass $testname
+    } {
+	fail $testname
+    }
+    set testname "PR ld/16746 (4)"
+    set exec_output [run_host_cmd "$CC" "$gcc_gas_flag $gcc_ld_flag -O2 -flto -fuse-linker-plugin tmpdir/pr16746d.o tmpdir/pr16746b.o"]
+    if { [ regexp "warning: foobar" $exec_output ] && ![ regexp "symbol from plugin" $exec_output ] } {
+	pass $testname
+    } {
+	fail $testname
     }
 }
 
Index: binutils-2.24/ld/testsuite/ld-plugin/pr16746a.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-2.24/ld/testsuite/ld-plugin/pr16746a.c	2014-05-06 16:08:49.819990627 +0200
@@ -0,0 +1,3 @@
+static const char __evoke_link_warning_foobar[]
+ __attribute__ ((used, section (".gnu.warning.foobar\n\t#")))
+ = "foobar";
Index: binutils-2.24/ld/testsuite/ld-plugin/pr16746b.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-2.24/ld/testsuite/ld-plugin/pr16746b.c	2014-05-06 16:08:49.820990627 +0200
@@ -0,0 +1,5 @@
+static const char __evoke_link_warning_foobar[]
+ __attribute__ ((used, section (".gnu.warning.foobar\n\t#")))
+ = "foobar";
+
+void foobar (void) {}
Index: binutils-2.24/ld/testsuite/ld-plugin/pr16746c.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-2.24/ld/testsuite/ld-plugin/pr16746c.c	2014-05-06 16:08:49.820990627 +0200
@@ -0,0 +1,8 @@
+extern void foobar (void);
+int
+main (int argc, char **argv)
+{
+  if (__builtin_constant_p (argc))
+    foobar ();
+  return 0;
+}
Index: binutils-2.24/ld/testsuite/ld-plugin/pr16746d.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-2.24/ld/testsuite/ld-plugin/pr16746d.c	2014-05-06 16:08:49.820990627 +0200
@@ -0,0 +1,8 @@
+extern void foobar (void);
+int
+main (int argc, char **argv)
+{
+  if (!__builtin_constant_p (argc))
+    foobar ();
+  return 0;
+}