[llvm] [NFC][StructurizeCFG] Add a test that can crash StructurizeCFG pass (PR #126087)

[Shilei Tian via llvm-commits]

https://github.com/shiltian created https://github.com/llvm/llvm-project/pull/126087

I tried to fix it in #124051 but failed to do so. This PR adds the test and
marks it as xfail.

>From 6487e53143010cea327ea896f68ad4fba1b52d8a Mon Sep 17 00:00:00 2001
From: Shilei Tian <i at tianshilei.me>
Date: Thu, 6 Feb 2025 11:22:38 -0500
Subject: [PATCH] [NFC][StructurizeCFG] Add a test that can crash
 StructurizeCFG pass

I tried to fix it in #124051 but failed to do so. This PR adds the test and
marks it as xfail.
---
 .../simple-structurizecfg-crash.ll             | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 llvm/test/Transforms/StructurizeCFG/simple-structurizecfg-crash.ll

diff --git a/llvm/test/Transforms/StructurizeCFG/simple-structurizecfg-crash.ll b/llvm/test/Transforms/StructurizeCFG/simple-structurizecfg-crash.ll
new file mode 100644
index 000000000000000..745b0bdc0382ada
--- /dev/null
+++ b/llvm/test/Transforms/StructurizeCFG/simple-structurizecfg-crash.ll
@@ -0,0 +1,18 @@
+; RUN: opt -S -passes=structurizecfg %s -o -
+; XFAIL: *
+
+; FIXME: This test is expected to crash. Generate checklines after the crash is fixed.
+
+define void @foo() {
+entry:
+  br i1 false, label %cond.true, label %cond.false
+
+cond.true:                                        ; preds = %entry
+  br label %cond.end
+
+cond.false:                                       ; preds = %entry
+  br label %cond.end
+
+cond.end:                                         ; preds = %cond.false, %cond.true
+  ret void
+}