build/config/compiler/compiler.gni - gn - Git at Google

 # 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
   use_thin_lto = is_cfi

   # 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"
 }

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

 # 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 && !is_fuchsia)

 # 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

 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 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.")
	# 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
	use_thin_lto = is_cfi

	# 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"
	}

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

	# 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 && !is_fuchsia)

	# 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

	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 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.")