Add codegen test for issue 138497

tests/codegen-llvm/issues/issue-138497-nonzero-remove-trailing-zeroes.rs

@@ -0,0 +1,17 @@
+//! This test checks that removing trailing zeroes from a `NonZero`,
+//! then creating a new `NonZero` from the result does not panic.
+
+//@ min-llvm-version: 21
+//@ compile-flags: -O -Zmerge-functions=disabled
+#![crate_type = "lib"]
+
+use std::num::NonZero;
+
+// CHECK-LABEL: @remove_trailing_zeros
+#[no_mangle]
+pub fn remove_trailing_zeros(x: NonZero<u8>) -> NonZero<u8> {
+    // CHECK: %[[TRAILING:[a-z0-9_-]+]] = {{.*}} call {{.*}} i8 @llvm.cttz.i8(i8 %x, i1 true)
+    // CHECK-NEXT: %[[RET:[a-z0-9_-]+]] = lshr exact i8 %x, %[[TRAILING]]
+    // CHECK-NEXT: ret i8 %[[RET]]
+    NonZero::new(x.get() >> x.trailing_zeros()).unwrap()
+}