use `assume(idx < self.len())` in `[T]::get_unchecked`

1 files changed, 13 insertions, 0 deletions

diff --git a/tests/codegen/issues/issue-116878.rs b/tests/codegen/issues/issue-116878.rs
new file mode 100644
index 00000000000..d5f679459f7
--- /dev/null
+++ b/tests/codegen/issues/issue-116878.rs
@@ -0,0 +1,13 @@
+// no-system-llvm
+// compile-flags: -O
+// ignore-debug: the debug assertions get in the way
+#![crate_type = "lib"]
+
+/// Make sure no bounds checks are emitted after a `get_unchecked`.
+// CHECK-LABEL: @unchecked_slice_no_bounds_check
+#[no_mangle]
+pub unsafe fn unchecked_slice_no_bounds_check(s: &[u8]) -> u8 {
+    let a = *s.get_unchecked(1);
+    // CHECK-NOT: panic_bounds_check
+    a + s[0]
+}