diff --git a/.gitmodules b/.gitmodules
index 47273304..55e073c2 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -4,3 +4,6 @@
 [submodule "tools/asm-processor"]
 	path = tools/asm-processor
 	url = https://github.com/simonlindholm/asm-processor
+[submodule "tools/asm-differ"]
+	path = tools/asm-differ
+	url = https://github.com/simonlindholm/asm-differ
diff --git a/tools/asm-differ b/tools/asm-differ
new file mode 160000
index 00000000..e8bddb02
--- /dev/null
+++ b/tools/asm-differ
@@ -0,0 +1 @@
+Subproject commit e8bddb02576e73aecb90f813bfb452417c37b257