[Driver] Add support for -fuse-ld=lld

[H.J. Lu]

On Thu, Jun 23, 2016 at 9:01 PM, Davide Italiano <dccitaliano@gmail.com> wrote:
> LLVM currently ships with a new ELF linker http://lld.llvm.org/.
> I experiment a lot with gcc and lld so it would be nice if
> -fuse-ld=lld is supported (considering the linker is now mature enough
> to link large C/C++ applications).
>
> Also, IMHO, -fuse-ld should be a generic facility which accept other
> linkers (as long as they follow the convention ld.<arg>), and should
> also support absolute path, e.g. -fuse-ld=/usr/local/bin/ld.mylinker.
> Probably outside of the scope of this patch, but I thought worth
> mentioning.
>
> Thanks,
>
> --
> Davide
>
> From 323c23d79c91d7dcee2f29b9ced8c1c00703d346 Mon Sep 17 00:00:00 2001
> From: Davide Italiano <dccitaliano@gmail.com>
> Date: Thu, 23 Jun 2016 20:51:53 -0700
> Subject: [PATCH] Driver: Add support for -fuse-ld=lld.
>
> * collect2.c  (main): Support -fuse-ld=lld.
>
> * common.opt: Add fuse-ld=lld
>
> * doc/invoke.texi:  Document -fuse-ld=lld
>
> * opts.c: Ignore -fuse-ld=lld

Remove blank line between them.

> ---
>  gcc/collect2.c      | 11 ++++++++---
>  gcc/common.opt      |  4 ++++
>  gcc/doc/invoke.texi |  4 ++++
>  gcc/opts.c          |  1 +
>  4 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/gcc/collect2.c b/gcc/collect2.c
> index bffac80..6a8387c 100644
> --- a/gcc/collect2.c
> +++ b/gcc/collect2.c
> @@ -831,6 +831,7 @@ main (int argc, char **argv)
>        USE_PLUGIN_LD,
>        USE_GOLD_LD,
>        USE_BFD_LD,
> +      USE_LLD_LD,
>        USE_LD_MAX
>      } selected_linker = USE_DEFAULT_LD;
>    static const char *const ld_suffixes[USE_LD_MAX] =
> @@ -838,7 +839,8 @@ main (int argc, char **argv)
>        "ld",
>        PLUGIN_LD_SUFFIX,
>        "ld.gold",
> -      "ld.bfd"
> +      "ld.bfd",
> +      "ld.lld"
>      };
>    static const char *const real_ld_suffix = "real-ld";
>    static const char *const collect_ld_suffix = "collect-ld";
> @@ -1004,6 +1006,8 @@ main (int argc, char **argv)
>        selected_linker = USE_BFD_LD;
>      else if (strcmp (argv[i], "-fuse-ld=gold") == 0)
>        selected_linker = USE_GOLD_LD;
> +  else if (strcmp (argv[i], "-fuse-ld=lld") == 0)
> +    selected_linker = USE_LLD_LD;
>
>  #ifdef COLLECT_EXPORT_LIST
>      /* These flags are position independent, although their order
> @@ -1093,7 +1097,8 @@ main (int argc, char **argv)
>    /* Maybe we know the right file to use (if not cross).  */
>    ld_file_name = 0;
>  #ifdef DEFAULT_LINKER
> -  if (selected_linker == USE_BFD_LD || selected_linker == USE_GOLD_LD)
> +  if (selected_linker == USE_BFD_LD || selected_linker == USE_GOLD_LD ||
> +      selected_linker == USE_LLD_LD)

Please make each condition on a separate line starting with ||.

>      {
>        char *linker_name;
>  # ifdef HOST_EXECUTABLE_SUFFIX
> @@ -1307,7 +1312,7 @@ main (int argc, char **argv)
>            else if (!use_collect_ld
>                 && strncmp (arg, "-fuse-ld=", 9) == 0)
>          {
> -          /* Do not pass -fuse-ld={bfd|gold} to the linker. */
> +          /* Do not pass -fuse-ld={bfd|gold|lld} to the linker. */
>            ld1--;
>            ld2--;
>          }
> diff --git a/gcc/common.opt b/gcc/common.opt
> index 5d90385..2a95a1f 100644
> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -2536,6 +2536,10 @@ fuse-ld=gold
>  Common Driver Negative(fuse-ld=bfd)
>  Use the gold linker instead of the default linker.
>
> +fuse-ld=lld
> +Common Driver Negative(fuse-ld=lld)
> +Use the lld LLVM linker instead of the default linker.
> +

This is wrong.  It should be

fuse-ld=bfd
Common Driver Negative(fuse-ld=gold)
Use the bfd linker instead of the default linker.

fuse-ld=gold
Common Driver Negative(fuse-ld=lld)
Use the gold linker instead of the default linker.

fuse-ld=lld
Common Driver Negative(fuse-ld=bfd)
Use the lld LLVM linker instead of the default linker.


>  fuse-linker-plugin
>  Common Undocumented Var(flag_use_linker_plugin)
>
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 2c87c53..4b8acff 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -10651,6 +10651,10 @@ Use the @command{bfd} linker instead of the
> default linker.
>  @opindex fuse-ld=gold
>  Use the @command{gold} linker instead of the default linker.
>
> +@item -fuse-ld=lld
> +@opindex fuse-ld=lld
> +Use the LLVM @command{lld} linker instead of the default linker.
> +
>  @cindex Libraries
>  @item -l@var{library}
>  @itemx -l @var{library}
> diff --git a/gcc/opts.c b/gcc/opts.c
> index 7406210..f2c86f7 100644
> --- a/gcc/opts.c
> +++ b/gcc/opts.c
> @@ -2178,6 +2178,7 @@ common_handle_option (struct gcc_options *opts,
>
>      case OPT_fuse_ld_bfd:
>      case OPT_fuse_ld_gold:
> +    case OPT_fuse_ld_lld:
>      case OPT_fuse_linker_plugin:
>        /* No-op. Used by the driver and passed to us because it starts with f.*/
>        break;
> --
> 2.5.5



-- 
H.J.