[libclc] Fix data races in libclc/libspirv LIT tests (#17902)

Multiple libclc test targets were running essentially the same test
suite in parallel. This could result in data races when one target
writes a file another target is reading.

This commit fixes the issue by creating a unique test execution
directory per target. We already have a unique libclc target known as an
'arch suffix' in CMake. This suffix is used as the unique builtins file
name. We pass this through to LIT via a parameter to create the
execution directory. Note this use of LIT (i.e., having one suite called
multiple times in different configurations) is unconventional so there
aren't many similar examples in LLVM.

Patch proposed by @bader.

Author: frasercrmck

libclc/test/CMakeLists.txt

@@ -19,7 +19,7 @@ set(LIBCLC_TEST_DEPS
 add_custom_target(check-libclc)
 
 foreach( t ${LIBCLC_TARGET_TO_TEST} )
-	foreach( d ${${t}_devices} )
+  foreach( d ${${t}_devices} )
     if( ${d} STREQUAL "none" )
       set( mcpu )
       set( arch_suffix "${t}" )
@@ -29,11 +29,13 @@ foreach( t ${LIBCLC_TARGET_TO_TEST} )
     endif()
     message( " Testing : ${arch_suffix}" )
 
-    add_lit_testsuite(check-libclc-spirv-${arch_suffix} "Running libclc spirv-${arch_suffix} regression tests"
+    add_lit_testsuite(check-libclc-spirv-${arch_suffix}
+      "Running libclc spirv-${arch_suffix} regression tests"
       ${CMAKE_CURRENT_BINARY_DIR}
       ARGS
         --verbose
-      PARAMS "target=${t}" ${mcpu} "builtins=libspirv-${arch_suffix}.bc"
+      PARAMS "target=${t}" ${mcpu} "libclc-arch-suffix=${arch_suffix}"
+             "builtins=libspirv-${arch_suffix}.bc"
       DEPENDS
         ${LIBCLC_TEST_DEPS}
         libspirv-builtins

libclc/test/lit.cfg.py

@@ -26,15 +26,18 @@
 # test_source_root: The root path where tests are located.
 config.test_source_root = os.path.join(os.path.dirname(__file__), "binding")
 
-# test_exec_root: The root path where tests should be run.
-config.test_exec_root = os.path.join(config.test_run_dir, "test")
-
 libclc_inc = os.path.join(config.libclc_root, "libspirv", "include")
 
 target = lit_config.params.get("target", "")
 builtins = lit_config.params.get("builtins", "")
 cpu = lit_config.params.get("cpu", "")
 cpu = [] if cpu == "" else ["-mcpu=" + cpu]
+libclc_arch_suffix = lit_config.params.get("libclc-arch-suffix", "")
+
+# test_exec_root: The root path where tests should be run. We create a unique
+# test directory per libclc target to test to avoid data races when multiple
+# targets try and access the the same libclc test files.
+config.test_exec_root = os.path.join(config.test_run_dir, "test", libclc_arch_suffix)
 
 llvm_config.use_default_substitutions()