# Copyright 2015 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

if (is_android) {
  import("//build/config/android/abi.gni")
}
import("//build/config/arm.gni")
import("//build/config/chrome_build.gni")
import("//build/config/chromecast_build.gni")
import("//build/config/compiler/pgo/pgo.gni")
import("//build/config/sanitizers/sanitizers.gni")
import("//build/toolchain/goma.gni")
import("//build/toolchain/toolchain.gni")
import("//build_overrides/build.gni")

declare_args() {
  # How many symbols to include in the build. This affects the performance of
  # the build since the symbols are large and dealing with them is slow.
  #   2 means regular build with symbols.
  #   1 means minimal symbols, usually enough for backtraces only. Symbols with
  # internal linkage (static functions or those in anonymous namespaces) may not
  # appear when using this level.
  #   0 means no symbols.
  #   -1 means auto-set according to debug/release and platform.
  symbol_level = -1

  # Compile in such a way as to enable profiling of the generated code. For
  # example, don't omit the frame pointer and leave in symbols.
  enable_profiling = false

  # use_debug_fission: whether to use split DWARF debug info
  # files. This can reduce link time significantly, but is incompatible
  # with some utilities such as icecc and ccache. Requires gold and
  # gcc >= 4.8 or clang.
  # http://gcc.gnu.org/wiki/DebugFission
  #
  # This is a placeholder value indicating that the code below should set
  # the default.  This is necessary to delay the evaluation of the default
  # value expression until after its input values such as use_gold have
  # been set, e.g. by a toolchain_args() block.
  use_debug_fission = "default"

  # Enables support for ThinLTO, which links 3x-10x faster than full LTO. See
  # also http://blog.llvm.org/2016/06/thinlto-scalable-and-incremental-lto.html
  # NOTE: See http://crbug.com/871722 to understand why this is disabled for
  # 32-bit Android/ARM
  use_thin_lto =
      is_cfi || (is_android && is_official_build && target_cpu != "arm")

  # Tell VS to create a PDB that references information in .obj files rather
  # than copying it all. This should improve linker performance. mspdbcmf.exe
  # can be used to convert a fastlink pdb to a normal one.
  is_win_fastlink = false

  # Whether or not we should turn on incremental WPO. Only affects the VS
  # Windows build.
  use_incremental_wpo = false

  # Whether or not we should use position independent code.
  use_pic = true

  # Whether we're using a sample profile collected on an architecture different
  # than the one we're compiling for.
  #
  # It's currently not possible to collect AFDO profiles on anything but
  # x86{,_64}.
  using_mismatched_sample_profile = current_cpu != "x64" && current_cpu != "x86"

  # Exclude unwind tables for official builds as unwinding can be done from
  # stack dumps produced by Crashpad at a later time "offline" in the crash
  # server. For unofficial (e.g. development) builds and non-Chrome branded
  # (e.g. Cronet which doesn't use Crashpad, crbug.com/479283) builds it's
  # useful to be able to unwind at runtime.
  exclude_unwind_tables = (is_chrome_branded && is_official_build) ||
                          (is_chromecast && !is_cast_desktop_build && !is_debug)
}

assert(!is_cfi || use_thin_lto, "CFI requires ThinLTO")

# If true, optimize for size. Does not affect windows builds.
# Linux & Mac favor speed over size.
# TODO(brettw) it's weird that Mac and desktop Linux are different. We should
# explore favoring size over speed in this case as well.
optimize_for_size = is_android || is_ios || is_fuchsia

declare_args() {
  # Whether we should consider the profile we're using to be accurate. Accurate
  # profiles have the benefit of (potentially substantial) binary size
  # reductions, by instructing the compiler to optimize cold and uncovered
  # functions heavily for size. This often comes at the cost of performance.
  sample_profile_is_accurate = optimize_for_size
}

# Determine whether to enable or disable frame pointers, based on the platform
# and build arguments.
if (is_mac || is_ios || is_linux) {
  enable_frame_pointers = true
} else if (is_win) {
  # 64-bit Windows ABI doesn't support frame pointers.
  if (current_cpu == "x64") {
    enable_frame_pointers = false
  } else {
    enable_frame_pointers = true
  }
} else if (is_chromeos) {
  # ChromeOS generally prefers frame pointers, to support CWP.
  # However, Clang does not currently generate usable frame pointers in ARM
  # 32-bit builds (https://bugs.llvm.org/show_bug.cgi?id=18505) so disable them
  # there to avoid the unnecessary overhead.
  enable_frame_pointers = current_cpu != "arm"
} else if (is_android) {
  enable_frame_pointers =
      enable_profiling ||
      # Ensure that stacks from arm64 crash dumps are usable (crbug.com/391706).
      current_cpu == "arm64" ||
      # For x86 Android, unwind tables are huge without frame pointers
      # (crbug.com/762629). Enabling frame pointers grows the code size slightly
      # but overall shrinks binaries considerably by avoiding huge unwind
      # tables.
      (current_cpu == "x86" && !exclude_unwind_tables && optimize_for_size) ||
      using_sanitizer
} else {
  # Explicitly ask for frame pointers, otherwise:
  # * Stacks may be missing for sanitizer and profiling builds.
  # * Debug tcmalloc can crash (crbug.com/636489).
  enable_frame_pointers = using_sanitizer || enable_profiling || is_debug
}

# In general assume that if we have frame pointers then we can use them to
# unwind the stack. However, this requires that they are enabled by default for
# most translation units, that they are emitted correctly, and that the
# compiler or platform provides a way to access them.
can_unwind_with_frame_pointers = enable_frame_pointers
if (current_cpu == "arm" && arm_use_thumb) {
  # We cannot currently unwind ARM Thumb frame pointers correctly.
  # See https://bugs.llvm.org/show_bug.cgi?id=18505
  can_unwind_with_frame_pointers = false
} else if (is_win) {
  # Windows 32-bit does provide frame pointers, but the compiler does not
  # provide intrinsics to access them, so we don't use them.
  can_unwind_with_frame_pointers = false
}

assert(!can_unwind_with_frame_pointers || enable_frame_pointers)

# Unwinding with CFI table is only possible on static library builds and
# requried only when frame pointers are not enabled.
can_unwind_with_cfi_table = is_android && !is_component_build &&
                            !enable_frame_pointers && current_cpu == "arm"

declare_args() {
  # Whether or not the official builds should be built with full WPO. Enabled by
  # default for the PGO and the x64 builds.
  if (chrome_pgo_phase > 0) {
    full_wpo_on_official = true
  } else {
    full_wpo_on_official = false
  }
}

declare_args() {
  # Set to true to use lld, the LLVM linker. This flag may be used on Windows,
  # Linux or Fuchsia.
  # TODO(pcc): Enable lld on more architectures on Linux. E.g. we probably need
  # to fix some of crbug.com/742655 to enable it on ARM.
  use_lld =
      is_clang &&
      (is_win || is_fuchsia || (use_thin_lto && target_os != "chromeos") ||
       (is_linux && current_cpu == "x64" && target_os != "chromeos") ||
       (is_android && (current_cpu != "arm" || arm_version >= 7) &&
        current_cpu != "mipsel" && current_cpu != "mips64el"))
}

declare_args() {
  # Whether to use the gold linker from binutils instead of lld or bfd.
  use_gold = !use_lld && !(is_chromecast && is_linux &&
                           (current_cpu == "arm" || current_cpu == "mipsel")) &&
             ((is_linux && (current_cpu == "x64" || current_cpu == "x86" ||
                            current_cpu == "arm" || current_cpu == "mipsel" ||
                            current_cpu == "mips64el")) ||
              (is_android && (current_cpu == "x86" || current_cpu == "x64" ||
                              current_cpu == "arm" || current_cpu == "arm64")))
}

# If it wasn't manually set, set to an appropriate default.
assert(symbol_level >= -1 && symbol_level <= 2, "Invalid symbol_level")
if (symbol_level == -1) {
  if (is_android && use_order_profiling) {
    # With instrumentation enabled, debug info puts libchrome.so over 4gb, which
    # causes the linker to produce an invalid ELF. http://crbug.com/574476
    symbol_level = 0
  } else if (is_android && !is_component_build &&
             !(android_64bit_target_cpu && !build_apk_secondary_abi)) {
    # Reduce symbol level when it will cause invalid elf files to be created
    # (due to file size). https://crbug.com/648948.
    symbol_level = 1
  } else if (is_win && use_goma && !is_clang) {
    # goma doesn't support PDB files, so we disable symbols during goma
    # compilation because otherwise the redundant debug information generated
    # by visual studio (repeated in every .obj file) makes linker
    # memory consumption and link times unsustainable (crbug.com/630074).
    # Clang on windows does not have this issue.
    # If you use is_win_fastlink = true or lld or clang then you can set
    # symbol_level = 2 when using goma.
    symbol_level = 1
  } else if ((!is_nacl && !is_linux && !is_fuchsia) || is_debug ||
             is_official_build || is_chromecast) {
    # Linux builds slower by having symbols as part of the target binary,
    # whereas Mac and Windows have them separate, so in Release Linux, default
    # them off, but keep them on for Official builds and Chromecast builds.
    symbol_level = 2
  } else if (using_sanitizer) {
    # Sanitizers need line table info for stack traces. They don't need type
    # info or variable info, so we can leave that out to speed up the build.
    # Sanitizers also require symbols for filename suppressions to work.
    symbol_level = 1
  } else {
    symbol_level = 0
  }
} else if (symbol_level == 2) {
  if (is_win) {
    # See crbug.com/630074
    assert(is_win_fastlink || use_lld || !use_goma || is_clang,
           "VC++ goma builds that use symbol_level 2 must use " +
               "is_win_fastlink or use_lld.")
  }
}

# Assert that the configuration isn't going to hit https://crbug.com/648948.
# An exception is made when target_os == "chromeos" as we only use the Android
# toolchain there to build relatively small binaries.
assert(ignore_elf32_limitations || !is_android || target_os == "chromeos" ||
           (android_64bit_target_cpu && !build_apk_secondary_abi) ||
           is_component_build || symbol_level < 2,
       "Android 32-bit non-component builds cannot have symbol_level=2 " +
           "due to 4GiB file size limit, see https://crbug.com/648948. " +
           "If you really want to try this out, " +
           "set ignore_elf32_limitations=true.")