[libclc] [libclc] [cmake] Fix per-target *_convert.cl dependencies (PR #127315)

[Fraser Cormack via cfe-commits]

================
@@ -249,13 +249,19 @@ function(add_libclc_builtin_set)
 
     get_filename_component( file_dir ${file} DIRECTORY )
 
+    if( ARG_ARCH STREQUAL spirv OR ARG_ARCH STREQUAL spirv64 )
+      set(CONVERT_DEP clspv-generate_convert.cl)
+    else()
+      set(CONVERT_DEP generate_convert.cl)
+    endif()
+
     compile_to_bc(
       TRIPLE ${ARG_TRIPLE}
       INPUT ${input_file}
       OUTPUT ${output_file}
       EXTRA_OPTS -fno-builtin -nostdlib
         "${ARG_COMPILE_FLAGS}" -I${CMAKE_CURRENT_SOURCE_DIR}/${file_dir}
-      DEPENDENCIES generate_convert.cl clspv-generate_convert.cl
+      DEPENDENCIES ${CONVERT_DEP}
----------------
frasercrmck wrote:

I think really we should be passing in dependencies as an ARG. I've never like the hard-coding of the `*convert.cl` files here in a helper function.

I also have the feeling that CMake should be able to automatically infer the right dependencies transitively, given that it knows that `clspv-generate_convert.cl` is a `DEPENDENCY` of `clspv-convert.cl` which is an `INPUT`. I'd have to do some experimentation, though. I always forget exactly how CMake works in this regard.

The way we're currently specifying dependencies on `generate_convert.cl` et al is far too coarse, and means we unnecessary rebuild all libclc files when the conversion files change.

https://github.com/llvm/llvm-project/pull/127315