add diagram to test

Author: OCHyams

llvm/test/DebugInfo/KeyInstructions/Generic/simplifycfg-branch-fold.ll

@@ -1,6 +1,16 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
 ; RUN: opt %s -S -passes=simplifycfg -bonus-inst-threshold=2 | FileCheck %s
 
+;;          +---------------+
+;;          |               |
+;;     +--> b --+           |
+;;     |        v           v
+;; --> a        d --> e --> f -->
+;;     |        ^           ^
+;;     +--> c --+           |
+;;          |               |
+;;          +---------------+
+
 ;; Block d gets folded into preds b and c. Check the cloned instructions get
 ;; remapped DILocation atomGroup numbers in each of the preds. Additionally
 ;; check that the branches each inherit the atomGroup of the folded branch.