[libclc] [libclc] Skip opt command if opt_flags is empty (PR #130882)

[Fraser Cormack via cfe-commits]

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@@ -342,22 +342,32 @@ function(add_libclc_builtin_set)
 
   set( builtins_opt_lib_tgt builtins.opt.${ARG_ARCH_SUFFIX} )
 
-  # Add opt target
-  add_custom_command( OUTPUT ${builtins_opt_lib_tgt}.bc
-    COMMAND ${opt_exe} ${ARG_OPT_FLAGS} -o ${builtins_opt_lib_tgt}.bc
-      ${builtins_link_lib}
-    DEPENDS ${opt_target} ${builtins_link_lib} ${builtins_link_lib_tgt}
-  )
-  add_custom_target( ${builtins_opt_lib_tgt}
-    ALL DEPENDS ${builtins_opt_lib_tgt}.bc
-  )
+  if( ${ARG_OPT_FLAGS} STREQUAL "" )
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frasercrmck wrote:

Yes, that might be good actually. Then if SPIR-V did ever want to apply optimizations, it could do so, and it ensures this path is tested.

Note though we'd still need the special-case after the opt target, because SPIR-V will continue to want to run `llvm-spirv` and exit. It also doesn't run the `${prepare_builtins_exe}` utility so needs to exit before that point. I don't know enough about `prepare-builtins` to say whether SPIR-V *could* also make use of it: it seems to strip `opencl.ocl.version` metadata and set every external definition to `linkonce_odr` linkage. I'd need to investigate what's going on there.

https://github.com/llvm/llvm-project/pull/130882