1 files changed, 63 insertions, 0 deletions
diff --git a/tests/codegen/swap-small-types.rs b/tests/codegen/swap-small-types.rs
new file mode 100644
index 000000000..03e2a2327
--- /dev/null
+++ b/tests/codegen/swap-small-types.rs
@@ -0,0 +1,63 @@
+// compile-flags: -O
+// only-x86_64
+// ignore-debug: the debug assertions get in the way
+
+#![crate_type = "lib"]
+
+use std::mem::swap;
+
+type RGB48 = [u16; 3];
+
+// CHECK-LABEL: @swap_rgb48
+#[no_mangle]
+pub fn swap_rgb48(x: &mut RGB48, y: &mut RGB48) {
+    // FIXME MIR inlining messes up LLVM optimizations.
+// WOULD-CHECK-NOT: alloca
+// WOULD-CHECK: load i48
+// WOULD-CHECK: store i48
+    swap(x, y)
+}
+
+// LLVM doesn't vectorize a loop over 3-byte elements,
+// so we chunk it down to bytes and loop over those instead.
+type RGB24 = [u8; 3];
+
+// CHECK-LABEL: @swap_rgb24_slices
+#[no_mangle]
+pub fn swap_rgb24_slices(x: &mut [RGB24], y: &mut [RGB24]) {
+// CHECK-NOT: alloca
+// CHECK: load <{{[0-9]+}} x i8>
+// CHECK: store <{{[0-9]+}} x i8>
+    if x.len() == y.len() {
+        x.swap_with_slice(y);
+    }
+}
+
+// This one has a power-of-two size, so we iterate over it directly
+type RGBA32 = [u8; 4];
+
+// CHECK-LABEL: @swap_rgba32_slices
+#[no_mangle]
+pub fn swap_rgba32_slices(x: &mut [RGBA32], y: &mut [RGBA32]) {
+// CHECK-NOT: alloca
+// CHECK: load <{{[0-9]+}} x i32>
+// CHECK: store <{{[0-9]+}} x i32>
+    if x.len() == y.len() {
+        x.swap_with_slice(y);
+    }
+}
+
+// Strings have a non-power-of-two size, but have pointer alignment,
+// so we swap usizes instead of dropping all the way down to bytes.
+const _: () = assert!(!std::mem::size_of::<String>().is_power_of_two());
+
+// CHECK-LABEL: @swap_string_slices
+#[no_mangle]
+pub fn swap_string_slices(x: &mut [String], y: &mut [String]) {
+// CHECK-NOT: alloca
+// CHECK: load <{{[0-9]+}} x i64>
+// CHECK: store <{{[0-9]+}} x i64>
+    if x.len() == y.len() {
+        x.swap_with_slice(y);
+    }
+}