[libclc] [libclc] Improve dependencies to avoid build errors (PR #95018)

[Tim Creech via cfe-commits]

https://github.com/tcreech-intel created https://github.com/llvm/llvm-project/pull/95018

With the Makefile generator and particularly high build parallelism some intermediate dependencies may be generated redundantly and concurrently, leading to build failures.

To fix this, arrange for libclc's add_custom_commands to depend on targets rather than directly on files.

This follows CMake documentation's[^1] guidance on add_custom_command:

> Do not list the output in more than one independent target that may
> build in parallel or the instances of the rule may conflict. Instead,
> use the add_custom_target() command to drive the command and make the
> other targets depend on that one.

Eliminating the redundant commands also improves build times.

[^1]: https://cmake.org/cmake/help/v3.29/command/add_custom_command.html

>From 3e85695cc62abf8fe0943421708b5db67750b4ea Mon Sep 17 00:00:00 2001
From: Tim Creech <timothy.m.creech at intel.com>
Date: Mon, 10 Jun 2024 11:07:55 -0400
Subject: [PATCH] [libclc] Improve dependencies to avoid build errors

With the Makefile generator and particularly high build parallelism some
intermediate dependencies may be generated redundantly and concurrently,
leading to build failures.

To fix this, arrange for libclc's add_custom_commands to depend on
targets rather than directly on files.

This follows CMake documentation's [1] guidance on add_custom_command:

> Do not list the output in more than one independent target that may
> build in parallel or the instances of the rule may conflict. Instead,
> use the add_custom_target() command to drive the command and make the
> other targets depend on that one.

Eliminating the redundant commands also improves build times.

1. https://cmake.org/cmake/help/v3.29/command/add_custom_command.html
---
 libclc/CMakeLists.txt                | 14 ++++++++++----
 libclc/cmake/modules/AddLibclc.cmake |  6 ++++--
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/libclc/CMakeLists.txt b/libclc/CMakeLists.txt
index 9858ae905983f..ba4561d941e90 100644
--- a/libclc/CMakeLists.txt
+++ b/libclc/CMakeLists.txt
@@ -374,15 +374,21 @@ foreach( t ${LIBCLC_TARGETS_TO_BUILD} )
         OUTPUT ${output_file}
         EXTRA_OPTS "${mcpu}" -fno-builtin -nostdlib
                    "${build_flags}" -I${PROJECT_SOURCE_DIR}/${file_dir}
+        DEPENDENCIES generate_convert.cl clspv-generate_convert.cl
       )
       list( APPEND bytecode_files ${output_file} )
     endforeach()
 
-    set( builtins_link_lib_tgt builtins.link.${arch_suffix} )
+    set( builtins_comp_lib_tgt builtins.comp.${arch_suffix} )
+    add_custom_target( ${builtins_comp_lib_tgt}
+      DEPENDS ${bytecode_files}
+    )
 
+    set( builtins_link_lib_tgt builtins.link.${arch_suffix} )
     link_bc(
       TARGET ${builtins_link_lib_tgt}
       INPUTS ${bytecode_files}
+      DEPENDENCIES ${builtins_comp_lib_tgt}
     )
 
     set( builtins_link_lib $<TARGET_PROPERTY:${builtins_link_lib_tgt},TARGET_FILE> )
@@ -391,7 +397,7 @@ foreach( t ${LIBCLC_TARGETS_TO_BUILD} )
       set( spv_suffix ${arch_suffix}.spv )
       add_custom_command( OUTPUT ${spv_suffix}
         COMMAND libclc::llvm-spirv ${spvflags} -o ${spv_suffix} ${builtins_link_lib}
-        DEPENDS ${builtins_link_lib}
+        DEPENDS ${builtins_link_lib_tgt}
       )
       add_custom_target( "prepare-${spv_suffix}" ALL DEPENDS "${spv_suffix}" )
       install( FILES ${CMAKE_CURRENT_BINARY_DIR}/${spv_suffix}
@@ -403,7 +409,7 @@ foreach( t ${LIBCLC_TARGETS_TO_BUILD} )
       add_custom_command( OUTPUT ${builtins_opt_lib_tgt}.bc
         COMMAND libclc::opt ${opt_flags} -o ${builtins_opt_lib_tgt}.bc
           ${builtins_link_lib}
-        DEPENDS libclc::opt ${builtins_link_lib}
+        DEPENDS libclc::opt ${builtins_link_lib_tgt}
       )
       add_custom_target( ${builtins_opt_lib_tgt}
         ALL DEPENDS ${builtins_opt_lib_tgt}.bc
@@ -418,7 +424,7 @@ foreach( t ${LIBCLC_TARGETS_TO_BUILD} )
       set( obj_suffix ${arch_suffix}.bc )
       add_custom_command( OUTPUT ${obj_suffix}
         COMMAND prepare_builtins -o ${obj_suffix} ${builtins_opt_lib}
-        DEPENDS ${builtins_opt_lib} prepare_builtins )
+        DEPENDS ${builtins_opt_lib_tgt} prepare_builtins )
       add_custom_target( prepare-${obj_suffix} ALL DEPENDS ${obj_suffix} )
 
       # nvptx-- targets don't include workitem builtins
diff --git a/libclc/cmake/modules/AddLibclc.cmake b/libclc/cmake/modules/AddLibclc.cmake
index 7f4620fa6a21d..e70be31f4480b 100644
--- a/libclc/cmake/modules/AddLibclc.cmake
+++ b/libclc/cmake/modules/AddLibclc.cmake
@@ -80,11 +80,13 @@ endfunction()
 #     Custom target to create
 # * INPUT <string> ...
 #     List of bytecode files to link together
+# * DEPENDENCIES <string> ...
+#     List of extra dependencies to inject
 function(link_bc)
   cmake_parse_arguments(ARG
     ""
     "TARGET"
-    "INPUTS"
+    "INPUTS;DEPENDENCIES"
     ${ARGN}
   )
 
@@ -106,7 +108,7 @@ function(link_bc)
   add_custom_command(
     OUTPUT ${ARG_TARGET}.bc
     COMMAND libclc::llvm-link -o ${ARG_TARGET}.bc ${LINK_INPUT_ARG}
-    DEPENDS libclc::llvm-link ${ARG_INPUTS} ${RSP_FILE}
+    DEPENDS libclc::llvm-link ${ARG_DEPENDENCIES} ${RSP_FILE}
   )
 
   add_custom_target( ${ARG_TARGET} ALL DEPENDS ${ARG_TARGET}.bc )