if(NOT DEFINED LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE)
  if(CMAKE_COMPILER_IS_GNUCXX)
    set(LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE ON)
  elseif( MSVC )
    set(LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE OFF)
  elseif( "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang" )
    set(LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE ON)
  elseif( "${CMAKE_CXX_COMPILER_ID}" MATCHES "Intel" )
    set(LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE ON)
  endif()
endif()

function(_get_compile_options_from_flags output_var)
  set(compile_options "")

  if(LIBC_TARGET_ARCHITECTURE_IS_RISCV64 OR(LIBC_CPU_FEATURES MATCHES "FMA"))
    check_flag(ADD_FMA_FLAG ${FMA_OPT_FLAG} ${ARGN})
  endif()
  check_flag(ADD_ROUND_OPT_FLAG ${ROUND_OPT_FLAG} ${ARGN})
  check_flag(ADD_EXPLICIT_SIMD_OPT_FLAG ${EXPLICIT_SIMD_OPT_FLAG} ${ARGN})
  check_flag(ADD_MISC_MATH_BASIC_OPS_OPT_FLAG ${MISC_MATH_BASIC_OPS_OPT_FLAG} ${ARGN})

  if(LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE)
    if(ADD_FMA_FLAG)
      if(LIBC_TARGET_ARCHITECTURE_IS_X86_64)
        list(APPEND compile_options "-mavx2")
        list(APPEND compile_options "-mfma")
      elseif(LIBC_TARGET_ARCHITECTURE_IS_RISCV64)
        list(APPEND compile_options "-D__LIBC_RISCV_USE_FMA")
      endif()
      # For clang, we will build the math functions with `-fno-math-errno` so that
      # __builtin_fma* will generate the fused-mutliply-add instructions.  We
      # don't put the control flag to the public config yet, and see if it makes
      # sense to just enable this flag by default.
      if(LIBC_ADD_FNO_MATH_ERRNO)
        list(APPEND compile_options "-fno-math-errno")
      endif()
    endif()
    if(ADD_ROUND_OPT_FLAG)
      if(LIBC_TARGET_ARCHITECTURE_IS_X86_64)
        # ROUND_OPT_FLAG is only enabled if SSE4.2 is detected, not just SSE4.1,
        # because there was code to check for SSE4.2 already, and few CPUs only
        # have SSE4.1.
        list(APPEND compile_options "-msse4.2")
      endif()
      if(LIBC_COMPILER_HAS_BUILTIN_CEIL_FLOOR_RINT_TRUNC)
        list(APPEND compile_options
             "-D__LIBC_USE_BUILTIN_CEIL_FLOOR_RINT_TRUNC")
      endif()
      if(LIBC_COMPILER_HAS_BUILTIN_ROUND)
        list(APPEND compile_options "-D__LIBC_USE_BUILTIN_ROUND")
      endif()
      if(LIBC_COMPILER_HAS_BUILTIN_ROUNDEVEN)
        list(APPEND compile_options "-D__LIBC_USE_BUILTIN_ROUNDEVEN")
      endif()
    endif()
    if(ADD_EXPLICIT_SIMD_OPT_FLAG)
      list(APPEND compile_options "-D__LIBC_EXPLICIT_SIMD_OPT")
    endif()
    if(ADD_MISC_MATH_BASIC_OPS_OPT_FLAG)
      list(APPEND compile_options "-D__LIBC_MISC_MATH_BASIC_OPS_OPT")
      if(LIBC_COMPILER_HAS_BUILTIN_FMAX_FMIN)
        list(APPEND compile_options "-D__LIBC_USE_BUILTIN_FMAX_FMIN")
      endif()
      if(LIBC_COMPILER_HAS_BUILTIN_FMAXF16_FMINF16)
        list(APPEND compile_options "-D__LIBC_USE_BUILTIN_FMAXF16_FMINF16")
      endif()
      if("FullFP16" IN_LIST LIBC_CPU_FEATURES AND
         CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
        list(APPEND compile_options
             "SHELL:-Xclang -target-feature -Xclang +fullfp16")
      endif()
    endif()
  elseif(MSVC)
    if(ADD_FMA_FLAG)
      list(APPEND compile_options "/arch:AVX2")
    endif()
    if(ADD_EXPLICIT_SIMD_OPT_FLAG)
      list(APPEND compile_options "/D__LIBC_EXPLICIT_SIMD_OPT")
    endif()
  endif()

  set(${output_var} ${compile_options} PARENT_SCOPE)
endfunction(_get_compile_options_from_flags)

function(_get_compile_options_from_config output_var)
  set(config_options "")

  if(LIBC_CONF_QSORT_IMPL)
    list(APPEND config_options "-DLIBC_QSORT_IMPL=${LIBC_CONF_QSORT_IMPL}")
  endif()

  if(LIBC_TYPES_TIME_T_IS_32_BIT AND LLVM_LIBC_FULL_BUILD)
    list(APPEND config_options "-DLIBC_TYPES_TIME_T_IS_32_BIT")
  endif()

  if(LIBC_ADD_NULL_CHECKS)
    list(APPEND config_options "-DLIBC_ADD_NULL_CHECKS")
  endif()

  if(NOT "${LIBC_CONF_FREXP_INF_NAN_EXPONENT}" STREQUAL "")
    list(APPEND config_options "-DLIBC_FREXP_INF_NAN_EXPONENT=${LIBC_CONF_FREXP_INF_NAN_EXPONENT}")
  endif()

  if(LIBC_CONF_MATH_OPTIMIZATIONS)
    list(APPEND config_options "-DLIBC_MATH=${LIBC_CONF_MATH_OPTIMIZATIONS}")
  endif()

  set(${output_var} ${config_options} PARENT_SCOPE)
endfunction(_get_compile_options_from_config)

function(_get_common_compile_options output_var flags)
  _get_compile_options_from_flags(compile_flags ${flags})
  _get_compile_options_from_config(config_flags)

  set(compile_options ${LIBC_COMPILE_OPTIONS_DEFAULT} ${compile_flags} ${config_flags})

  if(LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE)
    list(APPEND compile_options "-fpie")

    if(LLVM_LIBC_FULL_BUILD)
      # Only add -ffreestanding flag in non-GPU full build mode.
      if(NOT LIBC_TARGET_OS_IS_GPU)
        list(APPEND compile_options "-ffreestanding")
      endif()
      list(APPEND compile_options "-DLIBC_FULL_BUILD")
      # Manually disable standard include paths to prevent system headers from
      # being included.
      if(LIBC_CC_SUPPORTS_NOSTDLIBINC)
        list(APPEND compile_options "-nostdlibinc")
      elseif(COMPILER_RESOURCE_DIR)
        # TODO: We should require COMPILER_RESOURCE_DIR to be set.
        list(APPEND compile_options "-isystem${COMPILER_RESOURCE_DIR}/include")
        list(APPEND compile_options "-nostdinc")
      endif()
      # TODO: We should set this unconditionally on Linux.
      if(LIBC_TARGET_OS_IS_LINUX AND
         (LIBC_CC_SUPPORTS_NOSTDLIBINC OR COMPILER_RESOURCE_DIR))
        # We use -idirafter to avoid preempting libc's own headers in case the
        # directory (e.g. /usr/include) contains other headers.
        if(CMAKE_CROSSCOMPILING)
          list(APPEND compile_options "-idirafter=${LIBC_KERNEL_HEADERS}")
        else()
          list(APPEND compile_options "-idirafter${LIBC_KERNEL_HEADERS}")
        endif()
      endif()
    endif()

    if(LIBC_COMPILER_HAS_FIXED_POINT)
      list(APPEND compile_options "-ffixed-point")
    endif()

    if(NOT LIBC_TARGET_OS_IS_GPU)
      list(APPEND compile_options "-fno-builtin")
    endif()

    list(APPEND compile_options "-fno-exceptions")
    list(APPEND compile_options "-fno-lax-vector-conversions")
    list(APPEND compile_options "-fno-unwind-tables")
    list(APPEND compile_options "-fno-asynchronous-unwind-tables")
    list(APPEND compile_options "-fno-rtti")
    if (LIBC_CC_SUPPORTS_PATTERN_INIT)
      list(APPEND compile_options "-ftrivial-auto-var-init=pattern")
    endif()
    if (LIBC_CONF_KEEP_FRAME_POINTER)
      list(APPEND compile_options "-fno-omit-frame-pointer")
      if (LIBC_TARGET_ARCHITECTURE_IS_X86_64)
        list(APPEND compile_options "-mno-omit-leaf-frame-pointer")
      endif()
    endif()
    if (LIBC_CONF_ENABLE_STACK_PROTECTOR)
      list(APPEND compile_options "-fstack-protector-strong")
    endif()
    list(APPEND compile_options "-Wall")
    list(APPEND compile_options "-Wextra")
    # -DLIBC_WNO_ERROR=ON if you can't build cleanly with -Werror.
    if(NOT LIBC_WNO_ERROR)
      list(APPEND compile_options "-Werror")
    endif()
    list(APPEND compile_options "-Wconversion")
    list(APPEND compile_options "-Wno-sign-conversion")
    list(APPEND compile_options "-Wdeprecated")
    if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
      # Silence this warning because _Complex is a part of C99.
      list(APPEND compile_options "-fext-numeric-literals")
    else()
      list(APPEND compile_options "-Wno-c99-extensions")
      list(APPEND compile_options "-Wno-gnu-imaginary-constant")
    endif()
    list(APPEND compile_options "-Wno-pedantic")
    list(APPEND compile_options "-Wimplicit-fallthrough")
    list(APPEND compile_options "-Wwrite-strings")
    list(APPEND compile_options "-Wextra-semi")
    if(NOT CMAKE_COMPILER_IS_GNUCXX)
      list(APPEND compile_options "-Wnewline-eof")
      list(APPEND compile_options "-Wnonportable-system-include-path")
      list(APPEND compile_options "-Wstrict-prototypes")
      list(APPEND compile_options "-Wthread-safety")
      list(APPEND compile_options "-Wglobal-constructors")
    endif()
  elseif(MSVC)
    list(APPEND compile_options "/EHs-c-")
    list(APPEND compile_options "/GR-")
  endif()
  if (LIBC_TARGET_OS_IS_GPU)
    list(APPEND compile_options "-nogpulib")
    list(APPEND compile_options "-fvisibility=hidden")
    list(APPEND compile_options "-fconvergent-functions")
    list(APPEND compile_options "-flto")
    list(APPEND compile_options "-Wno-multi-gpu")

    if(LIBC_TARGET_ARCHITECTURE_IS_NVPTX)
      list(APPEND compile_options "-Wno-unknown-cuda-version")
      list(APPEND compile_options "--cuda-feature=+ptx63")
      if(LIBC_CUDA_ROOT)
        list(APPEND compile_options "--cuda-path=${LIBC_CUDA_ROOT}")
      endif()
    elseif(LIBC_TARGET_ARCHITECTURE_IS_AMDGPU)
      list(APPEND compile_options "SHELL:-Xclang -mcode-object-version=none")
    endif()
  endif()
  set(${output_var} ${compile_options} PARENT_SCOPE)
endfunction()