[PATCH] Add -print-lto-plugin

[Andi Kleen <andi at firstfloor dot org>]

From: Andi Kleen <ak@linux.intel.com>

binutils have LTO linker plugin support now, but it requires hardcoding
the path to gcc's libexec dir in the Makefile. Add an option to the
gcc driver instead to print the full file name to avoid this.

This is especially useful for ar or nm.

Passes bootstrap and test on x86-64.

Ok to commit?

2010-10-02  Andi Kleen <ak@linux.intel.com>

	* common.opt (-print-lto-plugin): Add.
	* doc/invoke.texi (-print-lto-plugin): Document.
	* gcc.c (display_help): Describe -print-lto-plugin.
	(main.c): Handle print_lto_plugin.
---
 gcc/common.opt      |    6 ++++++
 gcc/doc/invoke.texi |    9 ++++++++-
 gcc/gcc.c           |   13 +++++++++++++
 3 files changed, 27 insertions(+), 1 deletions(-)

diff --git a/gcc/common.opt b/gcc/common.opt
index 44a3de8..fe8e718 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -157,6 +157,9 @@ Driver JoinedOrMissing Alias(print-file-name=)
 -print-libgcc-file-name
 Driver Alias(print-libgcc-file-name)
 
+-print-lto-plugin
+Driver Alias(print-lto-plugin)
+
 -print-multi-directory
 Driver Alias(print-multi-directory)
 
@@ -1902,6 +1905,9 @@ Driver JoinedOrMissing Var(print_file_name)
 print-libgcc-file-name
 Driver
 
+print-lto-plugin
+Driver Var(print_lto_plugin)
+
 print-multi-directory
 Driver Var(print_multi_directory)
 
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 057ae7d..530d4dc 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -322,7 +322,7 @@ Objective-C and Objective-C++ Dialects}.
 -fdebug-prefix-map=@var{old}=@var{new} @gol
 -femit-struct-debug-baseonly -femit-struct-debug-reduced @gol
 -femit-struct-debug-detailed@r{[}=@var{spec-list}@r{]} @gol
--p  -pg  -print-file-name=@var{library}  -print-libgcc-file-name @gol
+-p  -pg  -print-file-name=@var{library}  -print-libgcc-file-name  -print-lto-plugin @gol
 -print-multi-directory  -print-multi-lib  -print-multi-os-directory @gol
 -print-prog-name=@var{program}  -print-search-dirs  -Q @gol
 -print-sysroot -print-sysroot-headers-suffix @gol
@@ -5715,6 +5715,13 @@ Same as @option{-print-file-name=libgcc.a}.
 This is useful when you use @option{-nostdlib} or @option{-nodefaultlibs}
 but you do want to link with @file{libgcc.a}.  You can do
 
+@item -print-lto-plugin
+@opindex print-lto-plugin
+Print the path name of the LTO linker plugin used by the compiler.
+
+This is useful to pass to ar, gold, ld or other binutils with linker 
+plugin support. 
+
 @smallexample
 gcc -nostdlib @var{files}@dots{} `gcc -print-libgcc-file-name`
 @end smallexample
diff --git a/gcc/gcc.c b/gcc/gcc.c
index ef637e9..ea0987a 100644
--- a/gcc/gcc.c
+++ b/gcc/gcc.c
@@ -2937,6 +2937,7 @@ display_help (void)
   fputs (_("  -dumpmachine             Display the compiler's target processor\n"), stdout);
   fputs (_("  -print-search-dirs       Display the directories in the compiler's search path\n"), stdout);
   fputs (_("  -print-libgcc-file-name  Display the name of the compiler's companion library\n"), stdout);
+  fputs (_("  -print-lto-plugin        Display the name of the compiler's LTO plugin\n"), stdout);
   fputs (_("  -print-file-name=<lib>   Display the full path to library <lib>\n"), stdout);
   fputs (_("  -print-prog-name=<prog>  Display the full path to compiler component <prog>\n"), stdout);
   fputs (_("  -print-multi-directory   Display the root directory for versions of libgcc\n"), stdout);
@@ -3229,6 +3230,7 @@ driver_handle_option (struct gcc_options *opts,
     case OPT_print_sysroot:
     case OPT_print_multi_os_directory:
     case OPT_print_sysroot_headers_suffix:
+    case OPT_print_lto_plugin:
     case OPT_time:
     case OPT_wrapper:
       /* These options set the variables specified in common.opt
@@ -6534,6 +6536,17 @@ main (int argc, char **argv)
 	fatal_error ("not configured with sysroot headers suffix");
     }
 
+  if (print_lto_plugin)
+    {
+      char *plugin;
+
+      plugin = find_a_file (&exec_prefixes, "liblto_plugin.so", R_OK, false);
+      if (!plugin)
+        fatal_error ("-print-lto-plugin specified, but no plugin found");    
+      printf ("%s\n", plugin);
+      return (0);
+    }
+
   if (print_help_list)
     {
       display_help ();
-- 
1.7.1