[clang] [clang] Merge gtest binaries into AllClangUnitTests (PR #134196)

[Reid Kleckner via cfe-commits]

https://github.com/rnk created https://github.com/llvm/llvm-project/pull/134196

This reduces the size of the clang/unittests build directory by 64% and my overall build dir size by 5%. Static linking is the real driving factor here, but even if the default build configuration used shared libraries, I don't see why we should be building so many unit test binaries.

To make the project more approachable for new contributors, I'm attempting to make the build a bit less resource-intensive. Build directory size is a common complaint, and this is low-hanging fruit.

>From 528be44ebae8ea5cd7f23c51ad11c314a73f152b Mon Sep 17 00:00:00 2001
From: Reid Kleckner <rnk at google.com>
Date: Fri, 28 Mar 2025 22:11:05 -0700
Subject: [PATCH] [clang] Merge gtest binaries into AllClangUnitTests

This reduces the size of the clang/unittests build directory by 64% and
my overall build dir size by 5%. Static linking is the real driving
factor here, but even if the default build configuration used shared
libraries, I don't see why we should be building so many unit test
binaries.

To make the project more approachable for new contributors, I'm
attempting to make the build a bit less resource-intensive. Build
directory size is a common complaint, and this is low-hanging fruit.
---
 clang/unittests/CMakeLists.txt                | 53 ++++++++++++++++++-
 clang/unittests/Driver/ModuleCacheTest.cpp    |  2 +-
 clang/unittests/Interpreter/CMakeLists.txt    |  2 +-
 .../Interpreter/ExceptionTests/CMakeLists.txt |  2 +-
 4 files changed, 54 insertions(+), 5 deletions(-)

diff --git a/clang/unittests/CMakeLists.txt b/clang/unittests/CMakeLists.txt
index f3823ba309420..8d4476761e03e 100644
--- a/clang/unittests/CMakeLists.txt
+++ b/clang/unittests/CMakeLists.txt
@@ -15,11 +15,11 @@ if(CLANG_BUILT_STANDALONE)
   endif()
 endif()
 
-# add_clang_unittest(test_name file1.cpp file2.cpp)
+# add_distinct_clang_unittest(test_name file1.cpp file2.cpp)
 #
 # Will compile the list of files together and link against the clang
 # Produces a binary named 'basename(test_name)'.
-function(add_clang_unittest test_name)
+function(add_distinct_clang_unittest test_name)
   cmake_parse_arguments(ARG
     ""
     ""
@@ -47,6 +47,33 @@ function(add_clang_unittest test_name)
   target_link_libraries(${test_name} PRIVATE ${ARG_LINK_LIBS})
 endfunction()
 
+define_property(GLOBAL PROPERTY CLANG_UNITTEST_SRCS)
+define_property(GLOBAL PROPERTY CLANG_UNITTEST_LLVM_COMPONENTS)
+define_property(GLOBAL PROPERTY CLANG_UNITTEST_CLANG_LIBS)
+define_property(GLOBAL PROPERTY CLANG_UNITTEST_LINK_LIBS)
+
+# add_clang_unittest(test_name file1.cpp file2.cpp)
+#
+# Adds unittests to the combined AllClangUnitTests binary. The unittest binary
+# is defined after adding all unittest subdirectories.
+function(add_clang_unittest test_name)
+  cmake_parse_arguments(ARG
+    ""
+    ""
+    "CLANG_LIBS;LINK_LIBS;LLVM_COMPONENTS"
+    ${ARGN})
+
+  file(RELATIVE_PATH src_prefix "${CMAKE_CURRENT_FUNCTION_LIST_DIR}" "${CMAKE_CURRENT_SOURCE_DIR}")
+  set(srcs_prefixed)
+  foreach(src ${ARG_UNPARSED_ARGUMENTS})
+    set(srcs_prefixed ${srcs_prefixed} "${src_prefix}/${src}")
+  endforeach()
+  set_property(GLOBAL APPEND PROPERTY CLANG_UNITTEST_SRCS ${srcs_prefixed})
+  set_property(GLOBAL APPEND PROPERTY CLANG_UNITTEST_CLANG_LIBS ${ARG_CLANG_LIBS})
+  set_property(GLOBAL APPEND PROPERTY CLANG_UNITTEST_LINK_LIBS ${ARG_LINK_LIBS})
+  set_property(GLOBAL APPEND PROPERTY CLANG_UNITTEST_LLVM_COMPONENTS ${ARG_LLVM_COMPONENTS})
+endfunction()
+
 add_subdirectory(Basic)
 add_subdirectory(Lex)
 add_subdirectory(Parse)
@@ -77,3 +104,25 @@ add_subdirectory(Index)
 add_subdirectory(InstallAPI)
 add_subdirectory(Serialization)
 add_subdirectory(Support)
+
+
+# If we're doing a single merged clang unit test binary, add that target after
+# all the previous subdirectories have been processed.
+get_property(SRCS GLOBAL PROPERTY CLANG_UNITTEST_SRCS)
+get_property(CLANG_LIBS GLOBAL PROPERTY CLANG_UNITTEST_CLANG_LIBS)
+get_property(LINK_LIBS GLOBAL PROPERTY CLANG_UNITTEST_LINK_LIBS)
+get_property(LLVM_COMPONENTS GLOBAL PROPERTY CLANG_UNITTEST_LLVM_COMPONENTS)
+add_distinct_clang_unittest(AllClangUnitTests
+  ${SRCS}
+  CLANG_LIBS
+  ${CLANG_LIBS}
+  LINK_LIBS
+  ${LINK_LIBS}
+  LLVM_COMPONENTS
+  ${LLVM_COMPONENTS}
+)
+
+# The Tooling library has some internal headers. Make those work. If we like
+# the merged clang unit test binary, we can udpate the include paths and make
+# this the default.
+include_directories(Tooling)
diff --git a/clang/unittests/Driver/ModuleCacheTest.cpp b/clang/unittests/Driver/ModuleCacheTest.cpp
index 48744415647e6..7aa5047c59bd3 100644
--- a/clang/unittests/Driver/ModuleCacheTest.cpp
+++ b/clang/unittests/Driver/ModuleCacheTest.cpp
@@ -17,7 +17,7 @@ using namespace clang::driver;
 
 namespace {
 
-TEST(ModuleCacheTest, GetTargetAndMode) {
+TEST(DriverModuleCacheTest, GetTargetAndMode) {
   SmallString<128> Buf;
   Driver::getDefaultModuleCachePath(Buf);
   StringRef Path = Buf;
diff --git a/clang/unittests/Interpreter/CMakeLists.txt b/clang/unittests/Interpreter/CMakeLists.txt
index 9df1a4b03da47..1dda9024075a1 100644
--- a/clang/unittests/Interpreter/CMakeLists.txt
+++ b/clang/unittests/Interpreter/CMakeLists.txt
@@ -1,4 +1,4 @@
-add_clang_unittest(ClangReplInterpreterTests
+add_distinct_clang_unittest(ClangReplInterpreterTests
   IncrementalCompilerBuilderTest.cpp
   IncrementalProcessingTest.cpp
   InterpreterTest.cpp
diff --git a/clang/unittests/Interpreter/ExceptionTests/CMakeLists.txt b/clang/unittests/Interpreter/ExceptionTests/CMakeLists.txt
index eb366a860661c..dfd94d8e6442c 100644
--- a/clang/unittests/Interpreter/ExceptionTests/CMakeLists.txt
+++ b/clang/unittests/Interpreter/ExceptionTests/CMakeLists.txt
@@ -3,7 +3,7 @@
 set(LLVM_REQUIRES_EH ON)
 set(LLVM_REQUIRES_RTTI ON)
 
-add_clang_unittest(ClangReplInterpreterExceptionTests
+add_distinct_clang_unittest(ClangReplInterpreterExceptionTests
   InterpreterExceptionTest.cpp
   EXPORT_SYMBOLS