>
> The following patch addresses the common (?) issue of people
> omitting -flto from the linker command-line which gets more
> severe with GCC 4.9 where slim LTO objects are emitted by
> default. The patch simply _always_ arranges for the linker
> plugin to be used, so if there are any (slim) LTO objects
> on the link LTO will be done on them. Similarly the
> non-linker-plugin path in collect2 is adjusted.
>
> You can still disable this by specifying -fno-lto on the
> linker command-line.
>
> One side-effect of enabling the linker-plugin by default
> (for HAVE_LTO_PLUGIN == 2) is that collect2 will then
> use the configured plugin ld rather than the default ld.
> Not sure if that is desired.
>
> Comments?
I like it; it was on my TODO list, but I was only worried about
--with-plugin-ld and did not find time, yet, to look into the consequences.
These days, I do not think we need to worry much aboud --with-plugin-ld.
Honza
>
> Thanks,
> Richard.
>
> 2014-03-04 Richard Biener <rguent...@suse.de>
>
> * gcc.c (PLUGIN_COND): Always enable unless -fno-use-linker-plugin
> or -fno-lto is specified and the linker has full plugin support.
> * collect2.c (lto_mode): Default to LTO_MODE_WHOPR if LTO is
> enabled.
> (main): Remove -flto processing, adjust lto_mode using
> use_plugin late.
>
> Index: gcc/gcc.c
> ===================================================================
> --- gcc/gcc.c (revision 208310)
> +++ gcc/gcc.c (working copy)
> @@ -695,7 +695,7 @@ proper position among the other output f
> #if HAVE_LTO_PLUGIN > 0
> /* The linker used has full plugin support, use LTO plugin by default. */
> #if HAVE_LTO_PLUGIN == 2
> -#define PLUGIN_COND "!fno-use-linker-plugin:%{flto|flto=*|fuse-linker-plugin"
> +#define PLUGIN_COND "!fno-use-linker-plugin:%{!fno-lto"
> #define PLUGIN_COND_CLOSE "}"
> #else
> /* The linker used has limited plugin support, use LTO plugin with explicit
> Index: gcc/collect2.c
> ===================================================================
> --- gcc/collect2.c (revision 208310)
> +++ gcc/collect2.c (working copy)
> @@ -192,7 +192,11 @@ enum lto_mode_d {
> };
>
> /* Current LTO mode. */
> +#ifdef ENABLE_LTO
> +static enum lto_mode_d lto_mode = LTO_MODE_WHOPR;
> +#else
> static enum lto_mode_d lto_mode = LTO_MODE_NONE;
> +#endif
>
> bool debug; /* true if -debug */
> bool helpflag; /* true if --help */
> @@ -1018,15 +1022,11 @@ main (int argc, char **argv)
> debug = true;
> else if (! strcmp (argv[i], "-flto-partition=none"))
> no_partition = true;
> - else if ((! strncmp (argv[i], "-flto=", 6)
> - || ! strcmp (argv[i], "-flto")) && ! use_plugin)
> - lto_mode = LTO_MODE_WHOPR;
> else if (!strncmp (argv[i], "-fno-lto", 8))
> lto_mode = LTO_MODE_NONE;
> else if (! strcmp (argv[i], "-plugin"))
> {
> use_plugin = true;
> - lto_mode = LTO_MODE_NONE;
> if (selected_linker == USE_DEFAULT_LD)
> selected_linker = USE_PLUGIN_LD;
> }
> @@ -1056,6 +1056,8 @@ main (int argc, char **argv)
> }
> vflag = debug;
> find_file_set_debug (debug);
> + if (use_plugin)
> + lto_mode = LTO_MODE_NONE;
> if (no_partition && lto_mode == LTO_MODE_WHOPR)
> lto_mode = LTO_MODE_LTO;
> }
