diff --git a/llvm/runtimes/CMakeLists.txt b/llvm/runtimes/CMakeLists.txt
--- a/llvm/runtimes/CMakeLists.txt
+++ b/llvm/runtimes/CMakeLists.txt
@@ -530,4 +530,23 @@
 
     set_property(GLOBAL APPEND PROPERTY LLVM_ALL_ADDITIONAL_TEST_TARGETS runtimes ${RUNTIMES_TEST_DEPENDS})
   endif()
+
+  # Attempt to merge the runtimes' compile_commands.json file into the main
+  # file.
+  if(CMAKE_EXPORT_COMPILE_COMMANDS AND TARGET runtimes AND TARGET runtimes-configure)
+    set(files_to_concat
+        ${LLVM_BINARY_DIR}/compile_commands.json
+        ${LLVM_BINARY_DIR}/runtimes/runtimes-bins/compile_commands.json
+    )
+    set(output_file ${LLVM_BINARY_DIR}/compile_commands.json)
+    add_custom_command(
+      OUTPUT ${output_file}
+      COMMAND "${Python3_EXECUTABLE}" ${LLVM_MAIN_SRC_DIR}/utils/concat-compile-commands.py ${files_to_concat} -o ${output_file}
+      COMMENT "Merging the LLVM runtimes 'compile_commands.json' file"
+      DEPENDS runtimes-configure ${LLVM_BINARY_DIR}/runtimes/runtimes-bins/compile_commands.json
+      VERBATIM
+    )
+    add_custom_target(merge-compile-commands DEPENDS ${output_file})
+    add_dependencies(runtimes merge-compile-commands)
+  endif()
 endif()
diff --git a/llvm/utils/concat-compile-commands.py b/llvm/utils/concat-compile-commands.py
new file mode 100755
--- /dev/null
+++ b/llvm/utils/concat-compile-commands.py
@@ -0,0 +1,30 @@
+#!/usr/bin/env python
+
+import argparse
+import json
+
+desc = '''Concatenate JSON files generated by CMake tools.'''
+
+def main():
+    parser = argparse.ArgumentParser(description=desc)
+    parser.add_argument(
+        'json_files',
+        nargs='+',
+        help='list of JSON files to concatenate.')
+    parser.add_argument(
+        '--output',
+        '-o',
+        required=True,
+        help='Filename to output the merged JSON file to.')
+    
+    data = []
+    args = parser.parse_args()
+    for json_file in args.json_files:
+        with open(json_file) as file:
+            data.extend(json.load(file))
+
+    with open(args.output, 'w') as file:
+        json.dump(data, file, indent=2)
+
+if __name__ == '__main__':
+    main()