halide.cmake

include(CMakeParseArguments)

# ----------------------- Public Functions.
# These are all documented in README_cmake.md.
#
# Note that certain CMake variables may need to be set correctly to use these rules:
#
# - If you are using a Halide distribution, simply set HALIDE_DISTRIB_DIR
# to the path to the distrib directory.
#
# - More complex usages (mainly, internal-to-Halide users) may, instead, set some combination
# of HALIDE_TOOLS_DIR, HALIDE_INCLUDE_DIR, and HALIDE_COMPILER_LIB.
#

# Add the include paths and link dependencies for halide_image_io.
add_library(halide_image_io INTERFACE)
foreach(LIB IN ITEMS PNG JPEG)
  find_package(${LIB} QUIET)
  if(${LIB}_FOUND)
    message(STATUS "Found ${LIB} version ${${LIB}_VERSION}")
    target_link_libraries(halide_image_io INTERFACE ${LIB}::${LIB})
    else()
    message(STATUS "${LIB} not found; compiling with -DHALIDE_NO_${LIB}")
    target_compile_definitions(halide_image_io INTERFACE HALIDE_NO_${LIB})
  endif()
endforeach()
add_library(Halide::ImageIO ALIAS halide_image_io)

function(halide_use_image_io TARGET)
  message(DEPRECATION "Use: target_link_libraries(${TARGET} PRIVATE Halide::ImageIO)")
  target_link_libraries(${TARGET} PRIVATE Halide::ImageIO)
endfunction()

# Make a build target for a Generator.
function(halide_generator NAME)
  set(oneValueArgs GENERATOR_NAME)
  set(multiValueArgs SRCS DEPS INCLUDES)
  cmake_parse_arguments(args "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})

  if(NOT ${NAME} MATCHES "^.*\\.generator$")
    message(FATAL_ERROR "halide_generator rules must have names that end in .generator (${NAME})")
  endif()

  string(REGEX REPLACE "\\.generator*$" "" BASENAME ${NAME})

  if ("${args_GENERATOR_NAME}" STREQUAL "")
    set(args_GENERATOR_NAME "${BASENAME}")
  endif()

  # We could precompile GenGen.cpp, but add_executable() requires
  # at least one source file, and this is the cheapest one we're going to have.
  add_executable("${NAME}_binary" "${HALIDE_TOOLS_DIR}/GenGen.cpp")
  _halide_set_cxx_options("${NAME}_binary")
  target_include_directories("${NAME}_binary" PRIVATE "${HALIDE_INCLUDE_DIR}" "${HALIDE_TOOLS_DIR}")
  target_link_libraries("${NAME}_binary" PRIVATE ${HALIDE_SYSTEM_LIBS} ${CMAKE_DL_LIBS} ${CMAKE_THREAD_LIBS_INIT})
  if (MSVC)
    target_link_libraries("${NAME}_binary" PRIVATE Kernel32)
  endif()

  list(LENGTH args_SRCS SRCSLEN)
  # Don't create an empty object-library: that can cause quiet failures in MSVC builds.
  if("${SRCSLEN}" GREATER 0)
    set(GENLIB "${NAME}_library")
    # Use Shared Libraries for all Generators to ensure that the RegisterGenerator
    # code is not dead-stripped.
    add_library("${GENLIB}" STATIC ${args_SRCS})
    _halide_set_cxx_options("${GENLIB}")
    target_link_libraries("${GENLIB}" ${args_DEPS})
    target_include_directories("${GENLIB}" PRIVATE ${args_INCLUDES} "${HALIDE_INCLUDE_DIR}" "${HALIDE_TOOLS_DIR}")
    foreach(DEP ${args_DEPS})
      target_include_directories("${GENLIB}" PRIVATE
                                 $<TARGET_PROPERTY:${DEP},INTERFACE_INCLUDE_DIRECTORIES>)
    endforeach()
    # Ensure that Halide.h is built prior to any Generator
    add_dependencies("${GENLIB}" ${HALIDE_COMPILER_LIB})
    _halide_force_link_library("${NAME}_binary" "${GENLIB}")
  endif()

  get_target_property(TARGET_TYPE "${HALIDE_COMPILER_LIB}" TYPE)
  if("${TARGET_TYPE}" STREQUAL "STATIC_LIBRARY")
    # Getting link order correct for static libraries is nearly impossible in CMake;
    # to avoid flakiness, always link libHalide via --whole-archive
    # when in static-library mode.
    _halide_force_link_library("${NAME}_binary" "${HALIDE_COMPILER_LIB}")
  else()
    target_link_libraries("${NAME}_binary" PRIVATE "${HALIDE_COMPILER_LIB}")
  endif()

  _halide_genfiles_dir(${BASENAME} GENFILES_DIR)
  set(STUB_HDR "${GENFILES_DIR}/${BASENAME}.stub.h")
  set(GENERATOR_EXEC_ARGS "-g" "${args_GENERATOR_NAME}" "-o" "${GENFILES_DIR}" "-e" "cpp_stub" "-n" "${BASENAME}")

  _halide_add_exec_generator_target(
    "${NAME}_stub_gen"
    GENERATOR_BINARY "${NAME}_binary"
    GENERATOR_ARGS   "${GENERATOR_EXEC_ARGS}"
    OUTPUTS          "${STUB_HDR}"
  )
  set_property(TARGET "${NAME}_stub_gen" PROPERTY _HALIDE_GENERATOR_NAME "${args_GENERATOR_NAME}")

  if("${SRCSLEN}" GREATER 0)
    _halide_get_static_library_actual_path(${GENLIB} GENLIB_ACTUAL_PATH)
    add_library("${NAME}" STATIC IMPORTED)
    set_target_properties("${NAME}" PROPERTIES IMPORTED_LOCATION "${GENLIB_ACTUAL_PATH}")
  else()
    add_library("${NAME}" INTERFACE)
  endif()
  add_dependencies("${NAME}" "${NAME}_stub_gen")
  set_target_properties("${NAME}" PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "${GENFILES_DIR}")
endfunction()

# Use a Generator target to emit a code library.
function(halide_library_from_generator BASENAME)
  set(options )
  set(oneValueArgs FUNCTION_NAME GENERATOR HALIDE_TARGET GRADIENT_DESCENT)
  set(multiValueArgs EXTRA_OUTPUTS FILTER_DEPS GENERATOR_ARGS HALIDE_TARGET_FEATURES INCLUDES)
  cmake_parse_arguments(args "" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})

  if ("${args_GENERATOR}" STREQUAL "")
    set(args_GENERATOR "${BASENAME}.generator")
  endif()
  if ("${args_FUNCTION_NAME}" STREQUAL "")
    set(args_FUNCTION_NAME "${BASENAME}")
  endif()
  if ("${args_HALIDE_TARGET}" STREQUAL "")
    set(args_HALIDE_TARGET "host")
  endif()
  if ("${args_GRADIENT_DESCENT}" STREQUAL "")
    set(args_GRADIENT_DESCENT "0")
  endif()
  # It's fine for EXTRA_OUTPUTS, GENERATOR_ARGS, FILTER_DEPS, HALIDE_TARGET_FEATURES to be empty

  # Some sanity checking
  if("${args_HALIDE_TARGET}" MATCHES "^target=")
    message(FATAL_ERROR "HALIDE_TARGET should not begin with 'target='.")
  endif()
  foreach(FEATURE ${args_HALIDE_TARGET_FEATURES})
    if("${FEATURE}" STREQUAL "no_runtime")
      message(FATAL_ERROR "HALIDE_TARGET_FEATURES may not contain 'no_runtime'.")
    endif()
    # Note that this list isn't exhaustive, but will check enough of the likely
    # common cases to enforce proper usage.
    if("${FEATURE}" STREQUAL "host" OR
       "${FEATURE}" STREQUAL "x86" OR
       "${FEATURE}" STREQUAL "arm" OR
       "${FEATURE}" STREQUAL "32" OR
       "${FEATURE}" STREQUAL "64" OR
       "${FEATURE}" STREQUAL "linux" OR
       "${FEATURE}" STREQUAL "osx" OR
       "${FEATURE}" STREQUAL "windows" OR
       "${FEATURE}" STREQUAL "ios" OR
       "${FEATURE}" STREQUAL "android")
      message(FATAL_ERROR "HALIDE_TARGET_FEATURES may not the Arch/OS/Bits string '${FEATURE}'; use HALIDE_TARGET instead.")
    endif()
  endforeach()
  foreach(ARG ${args_GENERATOR_ARGS})
    if("${ARG}" MATCHES "^target=")
      message(FATAL_ERROR "GENERATOR_ARGS may not include 'target=whatever'; use HALIDE_TARGET instead.")
    endif()
  endforeach()

  set(OUTPUTS static_library c_header registration compiler_log)
  foreach(E ${args_EXTRA_OUTPUTS})
    # Convert legacy aliases
    set(cpp_current "c_source")
    set(h_current "c_header")
    set(html_current "stmt_html")
    set(o_current "object")
    set(py.c_current "python_extension")
    if (DEFINED ${E}_current)
      message(DEPRECATION "'${E}' in EXTRA_OUTPUTS is deprecated, please use ${${E}_current}")
      set(E ${${E}_current})
    endif()

    if("${E}" STREQUAL "c_source")
      message(FATAL_ERROR "halide_library('${BASENAME}') doesn't support '${E}' in EXTRA_OUTPUTS; please depend on '${BASENAME}_cc' instead.")
    endif()
    if("${E}" STREQUAL "cpp_stub")
      message(FATAL_ERROR "halide_library('${BASENAME}') doesn't support '${E}' in EXTRA_OUTPUTS; please depend on '${BASENAME}.generator' instead.")
    endif()
    list(FIND OUTPUTS ${E} index)
    if (${index} GREATER -1)
      message(FATAL_ERROR "Duplicate entry ${E} in extra_outputs.")
    endif()
    list(APPEND OUTPUTS ${E})
  endforeach()

  get_property(GENERATOR_NAME TARGET "${args_GENERATOR}_stub_gen" PROPERTY _HALIDE_GENERATOR_NAME)

  # Create a directory to contain generator specific intermediate files
  _halide_genfiles_dir(${BASENAME} GENFILES_DIR)

  # Append HALIDE_TARGET_FEATURES to the target(s)
  set(TARGET_WITH_FEATURES "${args_HALIDE_TARGET}")
  foreach(FEATURE ${args_HALIDE_TARGET_FEATURES})
    _halide_add_target_features("${TARGET_WITH_FEATURES}" ${FEATURE} TARGET_WITH_FEATURES)
  endforeach()
  # Select the runtime to use *before* adding no_runtime
  _halide_library_runtime("${TARGET_WITH_FEATURES}" RUNTIME_NAME)
  _halide_add_target_features("${TARGET_WITH_FEATURES}" "no_runtime" TARGET_WITH_FEATURES)

  set(GENERATOR_EXEC_ARGS "-o" "${GENFILES_DIR}")
  list(APPEND GENERATOR_EXEC_ARGS "-d" "${args_GRADIENT_DESCENT}")
  list(APPEND GENERATOR_EXEC_ARGS "-g" "${GENERATOR_NAME}")
  list(APPEND GENERATOR_EXEC_ARGS "-f" "${args_FUNCTION_NAME}" )
  list(APPEND GENERATOR_EXEC_ARGS "target=${TARGET_WITH_FEATURES}")
  # GENERATOR_ARGS always come last
  list(APPEND GENERATOR_EXEC_ARGS ${args_GENERATOR_ARGS})

  set(assembly_ext ".s")
  set(bitcode_ext ".bc")
  set(c_header_ext ".h")
  set(featurization_ext ".featurization")
  set(llvm_assembly_ext ".ll")
  set(object_ext ${CMAKE_C_OUTPUT_EXTENSION})
  set(python_extension_ext ".py.cpp")
  set(pytorch_wrapper_ext ".pytorch.h")
  set(registration_ext ".registration.cpp")
  set(schedule_ext ".schedule.h")
  set(static_library_ext ${CMAKE_STATIC_LIBRARY_SUFFIX})
  set(stmt_ext ".stmt")
  set(stmt_html_ext ".stmt.html")
  set(compiler_log_ext ".halide_compiler_log")

  set(OUTPUT_FILES )
  foreach(OUTPUT ${OUTPUTS})
    if(NOT DEFINED ${OUTPUT}_ext)
        message(FATAL_ERROR "halide_library('${BASENAME}'): output '${OUTPUT}' is not supported!")
    endif()

    list(APPEND OUTPUT_FILES "${GENFILES_DIR}/${BASENAME}${${OUTPUT}_ext}")
  endforeach()

  # Output everything (except for the generated .cpp file)
  string(REPLACE ";" "," OUTPUTS_COMMA "${OUTPUTS}")
  set(ARGS_WITH_OUTPUTS "-e" ${OUTPUTS_COMMA} ${GENERATOR_EXEC_ARGS})
  _halide_add_exec_generator_target(
    "${BASENAME}_lib_gen"
    GENERATOR_BINARY "${args_GENERATOR}_binary"
    GENERATOR_ARGS   "${ARGS_WITH_OUTPUTS}"
    OUTPUTS          ${OUTPUT_FILES}
  )

  add_library("${BASENAME}" STATIC IMPORTED)
  add_dependencies("${BASENAME}" "${BASENAME}_lib_gen" "${RUNTIME_NAME}")
  set_target_properties("${BASENAME}" PROPERTIES
    IMPORTED_LOCATION "${GENFILES_DIR}/${BASENAME}${CMAKE_STATIC_LIBRARY_SUFFIX}"
    INTERFACE_INCLUDE_DIRECTORIES "${GENFILES_DIR}" ${args_INCLUDES}
    INTERFACE_LINK_LIBRARIES "${RUNTIME_NAME};${args_FILTER_DEPS};${CMAKE_DL_LIBS};${CMAKE_THREAD_LIBS_INIT}")

  # A separate invocation for the generated .cpp file,
  # since it's rarely used, and some code will fail at Generation
  # time at present (e.g. code with predicated loads or stores).
  set(ARGS_WITH_OUTPUTS "-e" "c_source" ${GENERATOR_EXEC_ARGS})
  _halide_add_exec_generator_target(
    "${BASENAME}_cc_gen"
    GENERATOR_BINARY "${args_GENERATOR}_binary"
    GENERATOR_ARGS   "${ARGS_WITH_OUTPUTS}"
    OUTPUTS          "${GENFILES_DIR}/${BASENAME}.halide_generated.cpp"
  )

  add_library("${BASENAME}_cc" STATIC "${GENFILES_DIR}/${BASENAME}.halide_generated.cpp")
  # Needs _lib_gen as well, to get the .h file
  add_dependencies("${BASENAME}_cc" "${BASENAME}_lib_gen" "${BASENAME}_cc_gen")
  target_link_libraries("${BASENAME}_cc" PRIVATE ${args_FILTER_DEPS})
  target_include_directories("${BASENAME}_cc" PRIVATE "${HALIDE_INCLUDE_DIR}")
  target_include_directories("${BASENAME}_cc" PUBLIC "${GENFILES_DIR}" ${args_INCLUDES})
  # Very few of the cc_libs are needed, so exclude from "all".
  set_target_properties("${BASENAME}_cc" PROPERTIES EXCLUDE_FROM_ALL TRUE)

  # Code to build the BASENAME.rungen target
  set(RUNGEN "${BASENAME}.rungen")
  add_executable("${RUNGEN}" "${GENFILES_DIR}/${BASENAME}.registration.cpp")
  target_link_libraries("${RUNGEN}" PRIVATE _halide_library_from_generator_rungen "${BASENAME}")
  # Not all Generators will build properly with RunGen (e.g., missing
  # external dependencies), so exclude them from the "ALL" targets
  set_target_properties("${RUNGEN}" PROPERTIES EXCLUDE_FROM_ALL TRUE)

  # BASENAME.run simply runs the BASENAME.rungen target
  add_custom_target("${BASENAME}.run"
                    COMMAND "${RUNGEN}" "${RUNARGS}"
                    DEPENDS "${RUNGEN}")
  set_target_properties("${BASENAME}.run" PROPERTIES EXCLUDE_FROM_ALL TRUE)
endfunction()

# Rule to build and use a Generator; it's convenient sugar around
# halide_generator() + halide_library_from_generator().
function(halide_library NAME)
  set(oneValueArgs FUNCTION_NAME HALIDE_TARGET GENERATOR GENERATOR_NAME)
  set(multiValueArgs EXTRA_OUTPUTS FILTER_DEPS GENERATOR_DEPS HALIDE_TARGET_FEATURES INCLUDES GENERATOR_ARGS SRCS)
  cmake_parse_arguments(args "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})

  if (NOT "${args_GENERATOR}" STREQUAL "")
    message(FATAL_ERROR "halide_library('${BASENAME}') doesn't take a GENERATOR argument. Did you mean to use GENERATOR_NAME, or the halide_library_from_generator() rule?")
  endif()

  halide_generator("${NAME}.generator"
                   SRCS ${args_SRCS}
                   DEPS ${args_GENERATOR_DEPS}
                   INCLUDES ${args_INCLUDES}
                   GENERATOR_NAME ${args_GENERATOR_NAME})

  halide_library_from_generator("${NAME}"
                   DEPS ${args_FILTER_DEPS}
                   INCLUDES ${args_INCLUDES}
                   GENERATOR "${NAME}.generator"
                   FUNCTION_NAME ${args_FUNCTION_NAME}
                   HALIDE_TARGET ${args_HALIDE_TARGET}
                   HALIDE_TARGET_FEATURES ${args_HALIDE_TARGET_FEATURES}
                   GENERATOR_ARGS ${args_GENERATOR_ARGS}
                   EXTRA_OUTPUTS ${args_EXTRA_OUTPUTS})
endfunction()

# ----------------------- Private Functions.
# All functions, properties, variables, etc. that begin with an underscore
# should be assumed to be private implementation details; don't rely on them externally.

# Set the C++ options necessary for using libHalide.
function(_halide_set_cxx_options TARGET)
  if (MSVC)
    target_compile_definitions("${TARGET}" PRIVATE "-D_CRT_SECURE_NO_WARNINGS" "-D_SCL_SECURE_NO_WARNINGS")
  endif()
  if(NOT HALIDE_ENABLE_RTTI)
    if(MSVC)
      target_compile_options("${TARGET}" PRIVATE "/GR-")
    else()
      target_compile_options("${TARGET}" PRIVATE "-fno-rtti")
    endif()
  endif()
endfunction()

# Get (and lazily create) the generated-files directory for Generators.
function(_halide_genfiles_dir NAME OUTVAR)
  set(GENFILES_DIR "${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/genfiles/${NAME}")
  file(MAKE_DIRECTORY "${GENFILES_DIR}")
  set(${OUTVAR} "${GENFILES_DIR}" PARENT_SCOPE)
endfunction()

# Given the target of a static library, return the path to the actual .a file
function(_halide_get_static_library_actual_path TARGET OUTVAR)
  get_target_property(DIR ${TARGET} LIBRARY_OUTPUT_DIRECTORY)
  if (DIR)
    set(DIR "${DIR}/")
  else()
    # Set to empty string since it could be "DIR-NOTFOUND"
    set(DIR "")
  endif()
  set(${OUTVAR} "${DIR}${CMAKE_CFG_INTDIR}/${CMAKE_STATIC_LIBRARY_PREFIX}${TARGET}${CMAKE_STATIC_LIBRARY_SUFFIX}" PARENT_SCOPE)
endfunction()

# Adds features to a target string, canonicalizing the result.
# If multitarget, features are added to all.
function(_halide_add_target_features HALIDE_TARGET HALIDE_FEATURES OUTVAR)
  string(REPLACE "," ";" MULTITARGETS "${HALIDE_TARGET}")
  foreach(T ${MULTITARGETS})
    string(REPLACE "-" ";" NEW_T "${T}")
    foreach(F ${HALIDE_FEATURES})
      list(APPEND NEW_T ${F})
    endforeach()
    string(REPLACE ";" "-" NEW_T "${NEW_T}")
    _halide_canonicalize_target("${NEW_T}" NEW_T)
    list(APPEND NEW_MULTITARGETS ${NEW_T})
  endforeach()
  string(REPLACE ";" "," NEW_MULTITARGETS "${NEW_MULTITARGETS}")
  set(${OUTVAR} "${NEW_MULTITARGETS}" PARENT_SCOPE)
endfunction()

# If any of the (multi) targets have the feature specified, set outvar to true.
# Otherwise set outvar to false.
function(_halide_has_target_feature HALIDE_TARGET HALIDE_FEATURE OUTVAR)
  set(${OUTVAR} FALSE PARENT_SCOPE)
  string(REPLACE "," ";" FEATURES "${HALIDE_TARGET}")
  string(REPLACE "-" ";" FEATURES "${HALIDE_TARGET}")
  foreach(F ${FEATURES})
    if("${F}" STREQUAL "${HALIDE_FEATURE}")
      set(${OUTVAR} TRUE PARENT_SCOPE)
    endif()
  endforeach()
endfunction()

# Split the target into base and feature lists.
function(_halide_split_target HALIDE_TARGET OUTVAR_BASE OUTVAR_FEATURES)
  if("${HALIDE_TARGET}" MATCHES ".*,.*")
    message(FATAL_ERROR "Multitarget may not be specified in _halide_split_target(${HALIDE_TARGET})")
  endif()

  string(REPLACE "-" ";" FEATURES "${HALIDE_TARGET}")
  list(LENGTH FEATURES LEN)
  if("${LEN}" EQUAL 0)
    message(FATAL_ERROR "Empty target")
  endif()

  list(GET FEATURES 0 BASE)
  if ("${BASE}" STREQUAL "host")
    list(REMOVE_AT FEATURES 0)
  else()
    if("${LEN}" LESS 3)
      message(FATAL_ERROR "Illegal target (${HALIDE_TARGET})")
    endif()
    list(GET FEATURES 0 1 2 BASE)
    list(REMOVE_AT FEATURES 0 1 2)
  endif()
  set(${OUTVAR_BASE} "${BASE}" PARENT_SCOPE)
  set(${OUTVAR_FEATURES} "${FEATURES}" PARENT_SCOPE)
endfunction()

# Join base and feature lists back into a target. Do not canonicalize.
function(_halide_join_target BASE FEATURES OUTVAR)
  foreach(F ${FEATURES})
    list(APPEND BASE ${F})
  endforeach()
  string(REPLACE ";" "-" BASE "${BASE}")
  set(${OUTVAR} "${BASE}" PARENT_SCOPE)
endfunction()

# Alphabetizes the features part of the target to make sure they always match no
# matter the concatenation order of the target string pieces. Remove duplicates.
function(_halide_canonicalize_target HALIDE_TARGET OUTVAR)
  if("${HALIDE_TARGET}" MATCHES ".*,.*")
    message(FATAL_ERROR "Multitarget may not be specified in _halide_canonicalize_target(${HALIDE_TARGET})")
  endif()
  _halide_split_target("${HALIDE_TARGET}" BASE FEATURES)
  list(REMOVE_DUPLICATES FEATURES)
  list(SORT FEATURES)
  _halide_join_target("${BASE}" "${FEATURES}" HALIDE_TARGET)
  set(${OUTVAR} "${HALIDE_TARGET}" PARENT_SCOPE)
endfunction()

# Given a HALIDE_TARGET, return the CMake target name for the runtime.
function(_halide_runtime_target_name HALIDE_TARGET OUTVAR)
  # MULTITARGETS = HALIDE_TARGET.split(",")
  string(REPLACE "," ";" MULTITARGETS "${HALIDE_TARGET}")
  # HALIDE_TARGET = MULTITARGETS.final_element()
  list(GET MULTITARGETS -1 HALIDE_TARGET)
  _halide_canonicalize_target("${HALIDE_TARGET}" HALIDE_TARGET)
  _halide_split_target("${HALIDE_TARGET}" BASE FEATURES)
  # Discard target features which do not affect the contents of the runtime.
  list(REMOVE_DUPLICATES FEATURES)
  list(REMOVE_ITEM FEATURES "user_context" "no_asserts" "no_bounds_query" "no_runtime" "profile")
  list(SORT FEATURES)
  # Now build up the name
  set(RESULT "halide_rt")
  foreach(B ${BASE})
    list(APPEND RESULT ${B})
  endforeach()
  if(${CMAKE_SYSTEM_NAME} MATCHES "Windows")
    set(HALIDE_ABBREVIATE_TARGETS TRUE)
  endif()
  if(HALIDE_ABBREVIATE_TARGETS)
    # Windows systems still have limits of 260-character pathnames in
    # lots of situations, and CMake can replicate project names multiple times
    # in the same path, so long target strings can cause us to overflow
    # this limit, even if CMAKE_OBJECT_PATH_MAX is set. So here we make
    # algorithmically-generated abbreviations for all the feature strings
    # and use those for external cmaketarget/filenames.

    # Halide Target Features we know about. (This need not be exact, but should
    # be close for best compression.)
    list(APPEND KNOWN_FEATURES
        jit
        debug
        no_asserts
        no_bounds_query
        sse41
        avx
        avx2
        fma
        fma4
        f16c
        armv7s
        no_neon
        vsx
        power_arch_2_07
        cuda
        cuda_capability_30
        cuda_capability_32
        cuda_capability_35
        cuda_capability_50
        cuda_capability_61
        opencl
        cl_doubles
        cl_half
        cl_atomics64
        opengl
        openglcompute
        egl
        user_context
        matlab
        profile
        no_runtime
        metal
        c_plus_plus_name_mangling
        large_buffers
        hvx_64
        hvx_128
        hvx_v62
        hvx_v65
        hvx_v66
        hvx_shared_object
        fuzz_float_stores
        soft_float_abi
        msan
        avx512
        avx512_knl
        avx512_skylake
        avx512_cannonlake
        trace_loads
        trace_stores
        trace_realizations
        d3d12compute
        strict_float
        tsan
        asan
        check_unsafe_promises
        hexagon_dma
        embed_bitcode
        disable_llvm_loop_opt
        enable_llvm_loop_opt
        wasm_simd128
        wasm_signext
        sve
        sve2
      )
    # Synthesize a one-or-two-char abbreviation based on the feature's position
    # in the KNOWN_FEATURES list.
    set(I 0)
    foreach(F ${KNOWN_FEATURES})
      math(EXPR II "97 + (${I} / 26)")
      if("${II}" GREATER 97)
        string(ASCII ${II} C1)
      else()
        set(C1 "")
      endif()
      math(EXPR II "97 + (${I} % 26)")
      string(ASCII ${II} C2)
      # CMake has no map-like structure; we'll fake it using synthesized variable names.
      set(HALIDE_TARGET_FEATURE_ABBREVIATION_${F} ${C1}${C2})
      math(EXPR I "${I} + 1")
    endforeach()
  endif()

  foreach(F ${FEATURES})
    if(DEFINED HALIDE_TARGET_FEATURE_ABBREVIATION_${F})
      list(APPEND RESULT ${HALIDE_TARGET_FEATURE_ABBREVIATION_${F}})
    else()
      # Unknown features get appended to the end
      list(APPEND RESULT ${F})
    endif()
  endforeach()

  # Finally, convert from a list into a _ separated name
  string(REPLACE ";" "_" RESULT "${RESULT}")
  set(${OUTVAR} "${RESULT}" PARENT_SCOPE)
endfunction()

# Generate the runtime library for the given halide_target; return
# its cmake target name in outvar.
function(_halide_library_runtime HALIDE_TARGET OUTVAR)
  if(NOT TARGET halide_library_runtime.generator)
    halide_generator(halide_library_runtime.generator SRCS "")
  endif()

  string(REPLACE "," ";" MULTITARGETS "${HALIDE_TARGET}")
  list(GET MULTITARGETS -1 HALIDE_TARGET)
  _halide_runtime_target_name("${HALIDE_TARGET}" RUNTIME_NAME)
  if(NOT TARGET "${RUNTIME_NAME}_runtime_gen")
    set(RUNTIME_LIB "${RUNTIME_NAME}${CMAKE_STATIC_LIBRARY_SUFFIX}")

    _halide_genfiles_dir(${RUNTIME_NAME} GENFILES_DIR)
    set(GENERATOR_EXEC_ARGS "-o" "${GENFILES_DIR}")
    list(APPEND GENERATOR_EXEC_ARGS "-r" "${RUNTIME_NAME}")
    list(APPEND GENERATOR_EXEC_ARGS "target=${HALIDE_TARGET}")

    _halide_add_exec_generator_target(
      "${RUNTIME_NAME}_runtime_gen"
      GENERATOR_BINARY "halide_library_runtime.generator_binary"
      GENERATOR_ARGS   "${GENERATOR_EXEC_ARGS}"
      OUTPUTS          "${GENFILES_DIR}/${RUNTIME_LIB}"
    )

    # By default, IMPORTED libraries are only visible to the declaration
    # directories (and subdirectories); since runtime libraries are declared
    # lazily, we need to ensure they are globally visible to avoid ordering issues.
    add_library("${RUNTIME_NAME}" STATIC IMPORTED GLOBAL)
    add_dependencies("${RUNTIME_NAME}" "${RUNTIME_NAME}_runtime_gen")
    set_target_properties("${RUNTIME_NAME}" PROPERTIES
      IMPORTED_LOCATION "${GENFILES_DIR}/${RUNTIME_LIB}")

    # It's hard to force specific system libraries to the end of link order
    # in CMake, because of course it is; to mitigate this, we do snooping
    # here for common targets with extra dependencies and add them to
    # the dependencies for runtime, to ensure that they get sorted into
    # an appropriate spot in link order.
    set(RT_LIBS )

    # opengl
    _halide_has_target_feature("${HALIDE_TARGET}" opengl HAS_OPENGL)
    if("${HAS_OPENGL}")
      find_package(OpenGL QUIET)
      if (OpenGL_FOUND)
        list(APPEND RT_LIBS ${OPENGL_LIBRARIES})
      endif()
      if(${CMAKE_SYSTEM_NAME} MATCHES "Linux")
        # Linux systems need X11 for OpenGL as well
        find_package(X11 QUIET)
        if (X11_FOUND)
          list(APPEND RT_LIBS ${X11_LIBRARIES})
        endif()
      endif()
    endif()

    set_target_properties("${RUNTIME_NAME}" PROPERTIES
      INTERFACE_LINK_LIBRARIES "${RT_LIBS}")

  endif()
  set(${OUTVAR} "${RUNTIME_NAME}" PARENT_SCOPE)
endfunction()

function(_halide_add_exec_generator_target EXEC_TARGET)
  set(options )
  set(oneValueArgs GENERATOR_BINARY)
  set(multiValueArgs OUTPUTS GENERATOR_ARGS)
  cmake_parse_arguments(args "" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})

  set(EXTRA_OUTPUTS_COMMENT )
  foreach(OUTPUT ${args_OUTPUTS})
    if((${OUTPUT} MATCHES "^.*\\.h$")
       OR (${OUTPUT} MATCHES "^.*${CMAKE_STATIC_LIBRARY_SUFFIX}$")
       OR (${OUTPUT} MATCHES "^.*\\.registration\\.cpp$"))
      # Ignore
    else()
      set(EXTRA_OUTPUTS_COMMENT "${EXTRA_OUTPUTS_COMMENT}\nEmitting extra Halide output: ${OUTPUT}")
    endif()
  endforeach()

  add_custom_target(${EXEC_TARGET} DEPENDS ${args_OUTPUTS})

  # LLVM may leak memory during generator execution. If projects are built with address sanitizer enabled,
  # this may cause generators to fail, making it hard to use Halide and address sanitizer at the same time.
  # To work around this, we execute generators with an environment setting to disable leak checking.
  set(RUN_WITHOUT_LEAKCHECK ${CMAKE_COMMAND} -E env "ASAN_OPTIONS=detect_leaks=0")

  if(NOT WIN32)
    add_custom_command(
      OUTPUT ${args_OUTPUTS}
      DEPENDS ${args_GENERATOR_BINARY}
      # Reduce noise during build; uncomment for debugging
      # COMMAND ${CMAKE_COMMAND} -E echo Running $<TARGET_FILE:${args_GENERATOR_BINARY}> ${args_GENERATOR_ARGS}
      COMMAND ${RUN_WITHOUT_LEAKCHECK} $<TARGET_FILE:${args_GENERATOR_BINARY}> ${args_GENERATOR_ARGS}
      COMMENT "${EXTRA_OUTPUTS_COMMENT}"
    )
  else()
    add_custom_command(
      OUTPUT ${args_OUTPUTS}
      DEPENDS ${args_GENERATOR_BINARY}
      # Reduce noise during build; uncomment for debugging
      # COMMAND ${CMAKE_COMMAND} -E echo copying $<TARGET_FILE:${HALIDE_COMPILER_LIB}> to "$<TARGET_FILE_DIR:${args_GENERATOR_BINARY}>"
      COMMAND ${CMAKE_COMMAND} -E copy_if_different $<TARGET_FILE:${HALIDE_COMPILER_LIB}> "$<TARGET_FILE_DIR:${args_GENERATOR_BINARY}>"
      # Reduce noise during build; uncomment for debugging
      # COMMAND ${CMAKE_COMMAND} -E echo Running $<TARGET_FILE:${args_GENERATOR_BINARY}> ${args_GENERATOR_ARGS}
      COMMAND ${RUN_WITHOUT_LEAKCHECK} $<TARGET_FILE:${args_GENERATOR_BINARY}> ${args_GENERATOR_ARGS}
      COMMENT "${EXTRA_OUTPUTS_COMMENT}"
    )
  endif()
  foreach(OUT ${args_OUTPUTS})
    set_source_files_properties(${OUT} PROPERTIES GENERATED TRUE)
  endforeach()
endfunction()

function(_halide_force_link_library NAME LIB)
  # We need to ensure that the libraries are linked in with --whole-archive
  # (or the equivalent), to ensure that the Generator-registration code
  # isn't omitted. Sadly, there's no portable way to do this, so we do some
  # special-casing here:
  if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
    _halide_get_static_library_actual_path("${LIB}" LIB_ACTUAL_PATH)
    target_link_libraries("${NAME}" PRIVATE "${LIB}")
    # Append to LINK_FLAGS, since we may call this multiple times
    get_property(flags TARGET "${NAME}" PROPERTY LINK_FLAGS)
    set(flags "${flags} -Wl,-force_load,${LIB_ACTUAL_PATH}")
    set_target_properties("${NAME}" PROPERTIES LINK_FLAGS ${flags})
  elseif(MSVC)
    # Note that this requires VS2015 R2+
    target_link_libraries("${NAME}" PRIVATE "${LIB}")
    # Append to LINK_FLAGS, since we may call this multiple times
    get_property(flags TARGET "${NAME}" PROPERTY LINK_FLAGS)
    set(flags "${flags} /WHOLEARCHIVE:${LIB}.lib")
    set_target_properties("${NAME}" PROPERTIES LINK_FLAGS ${flags})
  else()
    # Assume Linux or similar
    target_link_libraries("${NAME}" PRIVATE -Wl,--whole-archive "${LIB}" -Wl,-no-whole-archive)
  endif()
endfunction()

# ----------------------- Configuration code

# If paths to tools, include, and libHalide aren't specified, infer them
# based on the path to the distrib folder. If the path to the distrib
# folder isn't specified, fail.
if("${HALIDE_TOOLS_DIR}" STREQUAL "" OR
    "${HALIDE_INCLUDE_DIR}" STREQUAL "" OR
    "${HALIDE_COMPILER_LIB}" STREQUAL "")
  if("${HALIDE_DISTRIB_DIR}" STREQUAL "")
    message(FATAL_ERROR "HALIDE_DISTRIB_DIR must point to the Halide distribution directory.")
  endif()
  set(HALIDE_INCLUDE_DIR "${HALIDE_DISTRIB_DIR}/include")
  set(HALIDE_TOOLS_DIR "${HALIDE_DISTRIB_DIR}/tools")
  if(${HALIDE_DISTRIB_USE_STATIC_LIBRARY})
    message(STATUS "Using ${HALIDE_DISTRIB_DIR}/lib/${CMAKE_STATIC_LIBRARY_PREFIX}Halide${CMAKE_STATIC_LIBRARY_SUFFIX}")
    add_library(_halide_compiler_lib STATIC IMPORTED)
    set_target_properties(_halide_compiler_lib PROPERTIES
      IMPORTED_LOCATION "${HALIDE_DISTRIB_DIR}/lib/${CMAKE_STATIC_LIBRARY_PREFIX}Halide${CMAKE_STATIC_LIBRARY_SUFFIX}"
      INTERFACE_INCLUDE_DIRECTORIES ${HALIDE_INCLUDE_DIR})
    set(HALIDE_COMPILER_LIB _halide_compiler_lib)
  else()
    message(STATUS "Using ${HALIDE_DISTRIB_DIR}/bin/${CMAKE_SHARED_LIBRARY_PREFIX}Halide${CMAKE_SHARED_LIBRARY_SUFFIX}")
    add_library(_halide_compiler_lib SHARED IMPORTED)
    set_target_properties(_halide_compiler_lib PROPERTIES
      IMPORTED_LOCATION "${HALIDE_DISTRIB_DIR}/bin/${CMAKE_SHARED_LIBRARY_PREFIX}Halide${CMAKE_SHARED_LIBRARY_SUFFIX}"
      INTERFACE_INCLUDE_DIRECTORIES ${HALIDE_INCLUDE_DIR})
    if(WIN32)
      set_target_properties(_halide_compiler_lib PROPERTIES
        IMPORTED_IMPLIB "${HALIDE_DISTRIB_DIR}/lib/${CMAKE_STATIC_LIBRARY_PREFIX}Halide${CMAKE_STATIC_LIBRARY_SUFFIX}")
    endif()
    set(HALIDE_COMPILER_LIB _halide_compiler_lib)
  endif()
endif()

if(NOT DEFINED HALIDE_SYSTEM_LIBS)
  # If HALIDE_SYSTEM_LIBS isn't defined, we are compiling against a Halide distribution
  # folder; this is normally captured in the halide_config.cmake file. If that file
  # exists in the same directory as this one, just include it here.
  if(EXISTS "${CMAKE_CURRENT_LIST_DIR}/halide_config.cmake")
    include("${CMAKE_CURRENT_LIST_DIR}/halide_config.cmake")
  else()
    message(WARNING "HALIDE_SYSTEM_LIBS is not set and we could not find halide_config.cmake")
  endif()
endif()

define_property(TARGET PROPERTY _HALIDE_GENERATOR_NAME
                BRIEF_DOCS "Internal use by Halide build rules: do not use externally"
                FULL_DOCS "Internal use by Halide build rules: do not use externally")

add_library(_halide_library_from_generator_rungen "${HALIDE_TOOLS_DIR}/RunGenMain.cpp")
target_include_directories(_halide_library_from_generator_rungen PRIVATE "${HALIDE_INCLUDE_DIR}" "${HALIDE_TOOLS_DIR}")
target_link_libraries(_halide_library_from_generator_rungen PRIVATE Halide::ImageIO)
_halide_set_cxx_options(_halide_library_from_generator_rungen)
set_target_properties(_halide_library_from_generator_rungen PROPERTIES EXCLUDE_FROM_ALL TRUE)