1 files changed, 60 insertions, 0 deletions
diff --git a/tests/codegen-llvm/slice-iter-len-eq-zero.rs b/tests/codegen-llvm/slice-iter-len-eq-zero.rs
new file mode 100644
index 00000000000..6998d98e498
--- /dev/null
+++ b/tests/codegen-llvm/slice-iter-len-eq-zero.rs
@@ -0,0 +1,60 @@
+//@ compile-flags: -Copt-level=3
+//@ needs-deterministic-layouts (opposite scalar pair orders breaks it)
+#![crate_type = "lib"]
+
+type Demo = [u8; 3];
+
+// CHECK-LABEL: @slice_iter_len_eq_zero
+#[no_mangle]
+pub fn slice_iter_len_eq_zero(y: std::slice::Iter<'_, Demo>) -> bool {
+    // CHECK-NOT: sub
+    // CHECK: %[[RET:.+]] = icmp eq ptr {{%y.0, %y.1|%y.1, %y.0}}
+    // CHECK: ret i1 %[[RET]]
+    y.len() == 0
+}
+
+// CHECK-LABEL: @slice_iter_len_eq_zero_ref
+#[no_mangle]
+pub fn slice_iter_len_eq_zero_ref(y: &mut std::slice::Iter<'_, Demo>) -> bool {
+    // CHECK-NOT: sub
+    // CHECK: %[[A:.+]] = load ptr
+    // CHECK-SAME: !nonnull
+    // CHECK: %[[B:.+]] = load ptr
+    // CHECK-SAME: !nonnull
+    // CHECK: %[[RET:.+]] = icmp eq ptr %[[A]], %[[B]]
+    // CHECK: ret i1 %[[RET]]
+    y.len() == 0
+}
+
+struct MyZST;
+
+// CHECK-LABEL: @slice_zst_iter_len_eq_zero
+#[no_mangle]
+pub fn slice_zst_iter_len_eq_zero(y: std::slice::Iter<'_, MyZST>) -> bool {
+    // CHECK: %[[RET:.+]] = icmp eq ptr %y.1, null
+    // CHECK: ret i1 %[[RET]]
+    y.len() == 0
+}
+
+// CHECK-LABEL: @slice_zst_iter_len_eq_zero_ref
+#[no_mangle]
+pub fn slice_zst_iter_len_eq_zero_ref(y: &mut std::slice::Iter<'_, MyZST>) -> bool {
+    // CHECK: %[[LEN:.+]] = load ptr
+    // CHECK-NOT: !nonnull
+    // CHECK: %[[RET:.+]] = icmp eq ptr %[[LEN]], null
+    // CHECK: ret i1 %[[RET]]
+    y.len() == 0
+}
+
+// CHECK-LABEL: @array_into_iter_len_eq_zero
+#[no_mangle]
+pub fn array_into_iter_len_eq_zero(y: std::array::IntoIter<Demo, 123>) -> bool {
+    // This should be able to just check that the indexes are equal, and not
+    // need any subtractions or comparisons to handle `start > end`.
+
+    // CHECK-NOT: icmp
+    // CHECK-NOT: sub
+    // CHECK: %_0 = icmp eq {{i16|i32|i64}}
+    // CHECK: ret i1 %_0
+    y.len() == 0
+}