diff --git a/clambcc/clambc-compiler.py b/clambcc/clambc-compiler.py
index 5975eb92ac..a21afcbc22 100755
--- a/clambcc/clambc-compiler.py
+++ b/clambcc/clambc-compiler.py
@@ -607,7 +607,9 @@ def createInputSourceFile(clangLLVM: ClangLLVM, name: str, args: list, options:
     'clambc-lowering-notfinal',
     'verify',
 
-    # TODO: What do this do?
+    # This is an LLVM built-in pass that converts switch operations to a series of branches (ifs).
+    # This allows our runtime to get away with not implementing the switch instruction.
+    # See: https://llvm.org/docs/Passes.html#lower-switch-lower-switchinsts-to-branches
     'lowerswitch',
     'verify',