include(CheckCXXCompilerFlag)
include(CheckLinkerFlag)
include(CheckIPOSupported)

# Portable IPO/LTO detection (avoid in Debug)
check_ipo_supported(RESULT _YAMS_IPO_OK OUTPUT _YAMS_IPO_MSG)

# Multi-config generators: set per-config; Single-config: respect CMAKE_BUILD_TYPE
if(_YAMS_IPO_OK)
  if(CMAKE_CONFIGURATION_TYPES)
    foreach(_cfg Release RelWithDebInfo MinSizeRel)
      string(TOUPPER "${_cfg}" _CFG_UP)
      set("CMAKE_INTERPROCEDURAL_OPTIMIZATION_${_CFG_UP}" ON CACHE BOOL "IPO for ${_cfg}" FORCE)
    endforeach()
    # Ensure Debug stays off for fast, deterministic testing
    set(CMAKE_INTERPROCEDURAL_OPTIMIZATION_DEBUG OFF CACHE BOOL "IPO for Debug" FORCE)
  else()
    if(CMAKE_BUILD_TYPE AND NOT CMAKE_BUILD_TYPE MATCHES "^[Dd]ebug$")
      set(CMAKE_INTERPROCEDURAL_OPTIMIZATION ON)
    endif()
  endif()
else()
  message(STATUS "IPO/LTO not supported: ${_YAMS_IPO_MSG}")
endif()

# Prefer LLD when available (ELF platforms)
set(_YAMS_TRY_LLD FALSE)
if(CMAKE_CXX_COMPILER_ID MATCHES "Clang|GNU")
  check_linker_flag(CXX "-fuse-ld=lld" _YAMS_LLD_OK)
  if(_YAMS_LLD_OK)
    add_link_options(-fuse-ld=lld)
    set(_YAMS_TRY_LLD TRUE)
    message(STATUS "Using LLD via -fuse-ld=lld")
  else()
    message(STATUS "LLD not available; using default linker")
  endif()
endif()

# Prefer ThinLTO under Clang for Release-like configs only
if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
  if(CMAKE_CONFIGURATION_TYPES)
    # Apply per-config using generator expressions
    add_link_options($<$<CONFIG:Release,RelWithDebInfo,MinSizeRel>:-flto=thin>)
  else()
    if(CMAKE_BUILD_TYPE AND NOT CMAKE_BUILD_TYPE MATCHES "^[Dd]ebug$")
      add_link_options(-flto=thin)
    endif()
  endif()
  message(STATUS "Clang detected; preferring ThinLTO in Release-like builds")
endif()

# Helpful defaults for Release builds
if(CMAKE_BUILD_TYPE MATCHES "^[Rr]elease$")
  add_compile_options(-ffunction-sections -fdata-sections)
  if(_YAMS_TRY_LLD)
    add_link_options(-Wl,--gc-sections)
  endif()
endif()