Start to reduce libdevice dependencies on libclc (#19340)

The libdevice project included a CMake file from libclc to complete some
work. This is an undesirable link for several reasons.

For one, libclc is upstream and libdevice isn't. This means that it's
easy to accidentally pull in changes from upstream that alter how
libdevice is built. We can see this in the FOLDER property of the
link_bc target, which was set to 'libclc/Device IR/Linking'. This would
be confusing for any user building DPC++ in an IDE.

For two, this sharing of code also necessitated making downstream
changes to libclc, which make maintenance more difficult. This can be
seen in the RSP_DIR argument to link_bc, which was never set in libclc
to anything other than the upstream value.

This commit therefore starts to sever this dependency by just copying
over the two utility functions to libdevice's CMake. They aren't very
big and it should make any existing dependencies clearer. For example,
we implicitly are relying on libclc being built so that the
prepare-bultins target and executable are set up. This isn't an ideal
situation but is left for future work.

Author: frasercrmck

libclc/cmake/modules/AddLibclc.cmake

@@ -96,15 +96,12 @@ endfunction()
 #     Custom target to create
 # * INPUT <string> ...
 #     List of bytecode files to link together
-# * RSP_DIR <string>
-#     Directory where a response file should be placed
-#     (Only needed for WIN32 or CYGWIN)
 # * DEPENDENCIES <string> ...
 #     List of extra dependencies to inject
 function(link_bc)
   cmake_parse_arguments(ARG
     "INTERNALIZE"
-    "TARGET;RSP_DIR"
+    "TARGET"
     "INPUTS;DEPENDENCIES"
     ${ARGN}
   )
@@ -113,7 +110,7 @@ function(link_bc)
   if( WIN32 OR CYGWIN )
     # Create a response file in case the number of inputs exceeds command-line
     # character limits on certain platforms.
-    file( TO_CMAKE_PATH ${ARG_RSP_DIR}/${ARG_TARGET}.rsp RSP_FILE )
+    file( TO_CMAKE_PATH ${LIBCLC_ARCH_OBJFILE_DIR}/${ARG_TARGET}.rsp RSP_FILE )
     # Turn it into a space-separate list of input files
     list( JOIN ARG_INPUTS " " RSP_INPUT )
     file( GENERATE OUTPUT ${RSP_FILE} CONTENT ${RSP_INPUT} )
@@ -414,7 +411,6 @@ function(add_libclc_builtin_set)
     link_bc(
       TARGET ${builtins_link_lib_tgt}
       INPUTS ${bytecode_files}
-      RSP_DIR ${LIBCLC_ARCH_OBJFILE_DIR}
       DEPENDENCIES ${builtins_comp_lib_tgt}
     )
   else()
@@ -425,7 +421,6 @@ function(add_libclc_builtin_set)
     link_bc(
       TARGET ${builtins_link_lib_tmp_tgt}
       INPUTS ${bytecode_files}
-      RSP_DIR ${LIBCLC_ARCH_OBJFILE_DIR}
       DEPENDENCIES ${builtins_comp_lib_tgt}
     )
     set( internal_link_depend_files )
@@ -437,7 +432,6 @@ function(add_libclc_builtin_set)
       TARGET ${builtins_link_lib_tgt}
       INPUTS $<TARGET_PROPERTY:${builtins_link_lib_tmp_tgt},TARGET_FILE>
         ${internal_link_depend_files}
-      RSP_DIR ${LIBCLC_ARCH_OBJFILE_DIR}
       DEPENDENCIES ${builtins_link_lib_tmp_tgt} ${ARG_INTERNAL_LINK_DEPENDENCIES}
     )
   endif()

libdevice/CMakeLists.txt

@@ -1,8 +1,6 @@
 # Utility project providing various functionalities for SPIR-V devices
 # without native support of these functionalities.
 
-include(${CMAKE_CURRENT_SOURCE_DIR}/../libclc/cmake/modules/AddLibclc.cmake)
-
 set(CMAKE_MODULE_PATH
   ${CMAKE_MODULE_PATH}
   "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules"

libdevice/cmake/modules/SYCLLibdevice.cmake

@@ -161,6 +161,105 @@ function(compile_lib_ext filename)
            COMPONENT libsycldevice)
 endfunction()
 
+# Links together one or more bytecode files
+#
+# Arguments:
+# * INTERNALIZE
+#     Set if -internalize flag should be passed when linking
+# * TARGET <string>
+#     Custom target to create
+# * INPUT <string> ...
+#     List of bytecode files to link together
+# * RSP_DIR <string>
+#     Directory where a response file should be placed
+#     (Only needed for WIN32 or CYGWIN)
+# * DEPENDENCIES <string> ...
+#     List of extra dependencies to inject
+function(link_bc)
+  cmake_parse_arguments(ARG
+    "INTERNALIZE"
+    "TARGET;RSP_DIR"
+    "INPUTS;DEPENDENCIES"
+    ${ARGN}
+  )
+
+  set( LINK_INPUT_ARG ${ARG_INPUTS} )
+  if( WIN32 OR CYGWIN )
+    # Create a response file in case the number of inputs exceeds command-line
+    # character limits on certain platforms.
+    file( TO_CMAKE_PATH ${ARG_RSP_DIR}/${ARG_TARGET}.rsp RSP_FILE )
+    # Turn it into a space-separate list of input files
+    list( JOIN ARG_INPUTS " " RSP_INPUT )
+    file( GENERATE OUTPUT ${RSP_FILE} CONTENT ${RSP_INPUT} )
+    # Ensure that if this file is removed, we re-run CMake
+    set_property( DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS
+      ${RSP_FILE}
+    )
+    set( LINK_INPUT_ARG "@${RSP_FILE}" )
+  endif()
+
+  if( ARG_INTERNALIZE )
+    set( link_flags --internalize --only-needed )
+  endif()
+
+  add_custom_command(
+    OUTPUT ${ARG_TARGET}.bc
+    COMMAND ${llvm-link_exe} ${link_flags} -o ${ARG_TARGET}.bc ${LINK_INPUT_ARG}
+    DEPENDS ${llvm-link_target} ${ARG_DEPENDENCIES} ${ARG_INPUTS} ${RSP_FILE}
+  )
+
+  add_custom_target( ${ARG_TARGET} ALL DEPENDS ${ARG_TARGET}.bc )
+  set_target_properties( ${ARG_TARGET} PROPERTIES
+    TARGET_FILE ${CMAKE_CURRENT_BINARY_DIR}/${ARG_TARGET}.bc
+  )
+endfunction()
+
+# Runs opt and prepare-builtins on a bitcode file specified by lib_tgt
+#
+# ARGUMENTS:
+# * LIB_TGT string
+#     Target name that becomes dependent on the out file named LIB_TGT.bc
+# * IN_FILE string
+#     Target name of the input bytecode file
+# * OUT_DIR string
+#     Name of the directory where the output should be placed
+# *  DEPENDENCIES <string> ...
+#     List of extra dependencies to inject
+function(process_bc out_file)
+  cmake_parse_arguments(ARG
+    ""
+    "LIB_TGT;IN_FILE;OUT_DIR"
+    "OPT_FLAGS;DEPENDENCIES"
+    ${ARGN})
+  add_custom_command( OUTPUT ${ARG_LIB_TGT}.bc
+    COMMAND ${opt_exe} ${ARG_OPT_FLAGS} -o ${ARG_LIB_TGT}.bc
+    ${ARG_IN_FILE}
+    DEPENDS ${opt_target} ${ARG_IN_FILE} ${ARG_DEPENDENCIES}
+  )
+  add_custom_target( ${ARG_LIB_TGT}
+    ALL DEPENDS ${ARG_LIB_TGT}.bc
+  )
+  set_target_properties( ${ARG_LIB_TGT}
+    PROPERTIES TARGET_FILE ${ARG_LIB_TGT}.bc
+  )
+
+  set( builtins_opt_lib $<TARGET_PROPERTY:${ARG_LIB_TGT},TARGET_FILE> )
+
+  # Add prepare target
+  # FIXME: prepare_builtins_exe comes from having included libclc before this.
+  # This is brittle.
+  add_custom_command( OUTPUT ${ARG_OUT_DIR}/${out_file}
+    COMMAND ${prepare_builtins_exe} -o ${ARG_OUT_DIR}/${out_file}
+      ${builtins_opt_lib}
+      DEPENDS ${builtins_opt_lib} ${ARG_LIB_TGT} ${prepare_builtins_target} )
+  add_custom_target( prepare-${out_file} ALL
+    DEPENDS ${ARG_OUT_DIR}/${out_file}
+  )
+  set_target_properties( prepare-${out_file}
+    PROPERTIES TARGET_FILE ${ARG_OUT_DIR}/${out_file}
+  )
+endfunction()
+
 # Appends a list to a global property.
 #
 # Arguments: