From cbf3b2432e612fca1db0f320003745d7adc431b9 Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov@redhat.com>
Date: Wed, 31 Aug 2022 13:18:46 +0200
Subject: [PATCH] Add test for #98294

Add a test to make that the failure condition for this pattern is
optimized away.

Fixes #98294.
---
 ...issue-98294-get-mut-copy-from-slice-opt.rs | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
 create mode 100644 src/test/codegen/issue-98294-get-mut-copy-from-slice-opt.rs

diff --git a/src/test/codegen/issue-98294-get-mut-copy-from-slice-opt.rs b/src/test/codegen/issue-98294-get-mut-copy-from-slice-opt.rs
new file mode 100644
index 00000000000..7da29cd7952
--- /dev/null
+++ b/src/test/codegen/issue-98294-get-mut-copy-from-slice-opt.rs
@@ -0,0 +1,19 @@
+// min-llvm-version: 15.0.0
+// ignore-debug: The debug assertions get in the way
+// compile-flags: -O
+
+#![crate_type = "lib"]
+
+// There should be no calls to panic / len_mismatch_fail.
+
+#[no_mangle]
+pub fn test(a: &mut [u8], offset: usize, bytes: &[u8]) {
+    // CHECK-LABEL: @test(
+    // CHECK-NOT: call
+    // CHECK: call void @llvm.memcpy
+    // CHECK-NOT: call
+    // CHECK: }
+    if let Some(dst) = a.get_mut(offset..offset + bytes.len()) {
+        dst.copy_from_slice(bytes);
+    }
+}