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/* LTO IL options.

   Copyright 2009 Free Software Foundation, Inc.

   Contributed by Simon Baldwin <simonb@google.com>

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under

the terms of the GNU General Public License as published by the Free

Software Foundation; either version 3, or (at your option) any later

version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY

WARRANTY; without even the implied warranty of MERCHANTABILITY or

FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

for more details.

You should have received a copy of the GNU General Public License

along with GCC; see the file COPYING3.  If not see

<http://www.gnu.org/licenses/>.  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tree.h"

#include "hashtab.h"

#include "ggc.h"

#include "vec.h"

#include "bitmap.h"

#include "flags.h"

#include "opts.h"

#include "options.h"

#include "target.h"

#include "toplev.h"

#include "lto-streamer.h"

/* When a file is initially compiled, the options used when generating

   the IL are not necessarily the same as those used when linking the

   objects into the final executable.  In general, most build systems

   will proceed with something along the lines of:

        $ gcc <cc-flags> -flto -c f1.c -o f1.o

        $ gcc <cc-flags> -flto -c f2.c -o f2.o

        ...

        $ gcc <cc-flags> -flto -c fN.c -o fN.o

   And the final link may or may not include the same <cc-flags> used

   to generate the initial object files:

        $ gcc <ld-flags> -flto -o prog f1.o ... fN.o

   Since we will be generating final code during the link step, some

   of the flags used during the compile step need to be re-applied

   during the link step.  For instance, flags in the -m family.

   The idea is to save a selected set of <cc-flags> in a special

   section of the initial object files.  This section is then read

   during linking and the options re-applied.

   FIXME lto.  Currently the scheme is limited in that only the

   options saved on the first object file (f1.o) are read back during

   the link step.  This means that the options used to compile f1.o

   will be applied to ALL the object files in the final link step.

   More work needs to be done to implement a merging and validation

   mechanism, as this will not be enough for all cases.  */

/* Saved options hold the type of the option (currently CL_TARGET or

   CL_COMMON), and the code, argument, and value.  */

typedef struct GTY(()) opt_d

{

  unsigned int type;

  size_t code;

  char *arg;

  int value;

} opt_t;

DEF_VEC_O (opt_t);

DEF_VEC_ALLOC_O (opt_t, heap);

/* Options are held in two vectors, one for those registered by

   command line handling code, and the other for those read in from

   any LTO IL input.  */

static VEC(opt_t, heap) *user_options = NULL;

static VEC(opt_t, heap) *file_options = NULL;

/* Iterate FROM in reverse, writing option codes not yet in CODES into *TO.

   Mark each new option code encountered in CODES.  */

static void

reverse_iterate_options (VEC(opt_t, heap) *from, VEC(opt_t, heap) **to,

                         bitmap codes)

{

  int i;

  for (i = VEC_length (opt_t, from); i > 0; i--)

    {

      const opt_t *const o = VEC_index (opt_t, from, i - 1);

      if (bitmap_set_bit (codes, o->code))

        VEC_safe_push (opt_t, heap, *to, o);

    }

}

/* Concatenate options vectors FIRST and SECOND, rationalize so that only the

   final of any given option remains, and return the result.  */

static VEC(opt_t, heap) *

concatenate_options (VEC(opt_t, heap) *first, VEC(opt_t, heap) *second)

{

  VEC(opt_t, heap) *results = NULL;

  bitmap codes = lto_bitmap_alloc ();

  reverse_iterate_options (second, &results, codes);

  reverse_iterate_options (first, &results, codes);

  lto_bitmap_free (codes);

  return results;

}

/* Clear the options vector in *OPTS_P and set it to NULL.  */

static void

clear_options (VEC(opt_t, heap) **opts_p)

{

  int i;

  opt_t *o;

  for (i = 0; VEC_iterate (opt_t, *opts_p, i, o); i++)

    free (o->arg);

  VEC_free (opt_t, heap, *opts_p);

}

/* Write LENGTH bytes from ADDR to STREAM.  */

static void

output_data_stream (struct lto_output_stream *stream,

                    const void *addr, size_t length)

{

  lto_output_data_stream (stream, addr, length);

}

/* Write string STRING to STREAM.  */

static void

output_string_stream (struct lto_output_stream *stream, const char *string)

{

  bool flag = false;

  if (string != NULL)

    {

      const size_t length = strlen (string);

      flag = true;

      output_data_stream (stream, &flag, sizeof (flag));

      output_data_stream (stream, &length, sizeof (length));

      output_data_stream (stream, string, length);

    }

  else

    output_data_stream (stream, &flag, sizeof (flag));

}

/* Read LENGTH bytes from STREAM to ADDR.  */

static void

input_data_block (struct lto_input_block *ib, void *addr, size_t length)

{

  size_t i;

  unsigned char *const buffer = (unsigned char *const) addr;

  for (i = 0; i < length; i++)

    buffer[i] = lto_input_1_unsigned (ib);

}

/* Return a string from IB.  The string is allocated, and the caller is

   responsible for freeing it.  */

static char *

input_string_block (struct lto_input_block *ib)

{

  bool flag;

  input_data_block (ib, &flag, sizeof (flag));

  if (flag)

    {

      size_t length;

      char *string;

      input_data_block (ib, &length, sizeof (length));

      string = (char *) xcalloc (1, length + 1);

      input_data_block (ib, string, length);

      return string;

    }

  else

    return NULL;

}

/* Return true if this option is one we need to save in LTO output files.

   At present, we pass along all target options, and common options that

   involve position independent code.

   TODO This list of options requires expansion and rationalization.

   Among others, optimization options may well be appropriate here.  */

static bool

register_user_option_p (size_t code, int type)

{

  if (type == CL_TARGET)

    return true;

  else if (type == CL_COMMON)

    {

      return (code == OPT_fPIC

              || code == OPT_fpic

              || code == OPT_fPIE

              || code == OPT_fpie

              || code == OPT_fcommon

              || code == OPT_fexceptions);

    }

  return false;

}

/* Note command line option with the given TYPE and CODE, ARG, and VALUE.

   If relevant to LTO, save it in the user options vector.  */

void

lto_register_user_option (size_t code, const char *arg, int value, int type)

{

  if (register_user_option_p (code, type))

    {

      opt_t o;

      o.type = type;

      o.code = code;

      if (arg != NULL)

        {

          o.arg = (char *) xmalloc (strlen (arg) + 1);

          strcpy (o.arg, arg);

        }

      else

        o.arg = NULL;

      o.value = value;

      VEC_safe_push (opt_t, heap, user_options, &o);

    }

}

/* Empty the saved user options vector.  */

void

lto_clear_user_options (void)

{

  clear_options (&user_options);

}

/* Empty the saved file options vector.  */

void

lto_clear_file_options (void)

{

  clear_options (&file_options);

}

/* Concatenate the user options and any file options read from an LTO IL

   file, and serialize them to STREAM.  File options precede user options

   so that the latter override the former when reissued.  */

static void

output_options (struct lto_output_stream *stream)

{

  VEC(opt_t, heap) *opts = concatenate_options (file_options, user_options);

  const size_t length = VEC_length (opt_t, opts);

  int i;

  opt_t *o;

  output_data_stream (stream, &length, sizeof (length));

  for (i = 0; VEC_iterate (opt_t, opts, i, o); i++)

    {

      output_data_stream (stream, &o->type, sizeof (o->type));

      output_data_stream (stream, &o->code, sizeof (o->code));

      output_string_stream (stream, o->arg);

      output_data_stream (stream, &o->value, sizeof (o->value));

    }

  VEC_free (opt_t, heap, opts);

}

/* Write currently held options to an LTO IL section.  */

void

lto_write_options (void)

{

  char *const section_name = lto_get_section_name (LTO_section_opts, NULL);

  struct lto_output_stream stream;

  struct lto_simple_header header;

  struct lto_output_stream *header_stream;

  lto_begin_section (section_name, !flag_wpa);

  free (section_name);

  memset (&stream, 0, sizeof (stream));

  output_options (&stream);

  memset (&header, 0, sizeof (header));

  header.lto_header.major_version = LTO_major_version;

  header.lto_header.minor_version = LTO_minor_version;

  header.lto_header.section_type = LTO_section_opts;

  header.compressed_size = 0;

  header.main_size = stream.total_size;

  header_stream = ((struct lto_output_stream *)

                   xcalloc (1, sizeof (*header_stream)));

  lto_output_data_stream (header_stream, &header, sizeof (header));

  lto_write_stream (header_stream);

  free (header_stream);

  lto_write_stream (&stream);

  lto_end_section ();

}

/* Unserialize an options vector from IB, and append to file_options.  */

static void

input_options (struct lto_input_block *ib)

{

  size_t length, i;

  input_data_block (ib, &length, sizeof (length));

  for (i = 0; i < length; i++)

    {

      opt_t o;

      input_data_block (ib, &o.type, sizeof (o.type));

      input_data_block (ib, &o.code, sizeof (o.code));

      o.arg = input_string_block (ib);

      input_data_block (ib, &o.value, sizeof (o.value));

      VEC_safe_push (opt_t, heap, file_options, &o);

    }

}

/* Read options from an LTO IL section.  */

void

lto_read_file_options (struct lto_file_decl_data *file_data)

{

  size_t len;

  const char *data;

  const struct lto_simple_header *header;

  int32_t opts_offset;

  struct lto_input_block ib;

  data = lto_get_section_data (file_data, LTO_section_opts, NULL, &len);

  header = (const struct lto_simple_header *) data;

  opts_offset = sizeof (*header);

  lto_check_version (header->lto_header.major_version,

                     header->lto_header.minor_version);

  LTO_INIT_INPUT_BLOCK (ib, data + opts_offset, 0, header->main_size);

  input_options (&ib);

  lto_free_section_data (file_data, LTO_section_opts, 0, data, len);

}

/* Concatenate the user options and any file options read from an LTO IL

   file, and reissue them as if all had just been read in from the command

   line.  As with serialization, file options precede user options.  */

void

lto_reissue_options (void)

{

  VEC(opt_t, heap) *opts = concatenate_options (file_options, user_options);

  int i;

  opt_t *o;

  for (i = 0; VEC_iterate (opt_t, opts, i, o); i++)

    {

      const struct cl_option *option = &cl_options[o->code];

      if (option->flag_var)

        set_option (option, o->value, o->arg);

      if (o->type == CL_TARGET)

        targetm.handle_option (o->code, o->arg, o->value);

      else if (o->type == CL_COMMON)

        gcc_assert (option->flag_var);

      else

        gcc_unreachable ();

    }

  VEC_free (opt_t, heap, opts);

}