tests: Copy dont-shuffle-bswaps per tested opt level

Restore the OPT2 test annotations while doing so.

Author: workingjubilee

tests/codegen/autovec/dont-shuffle-bswaps-opt2.rs

@@ -0,0 +1,46 @@
+//@ revisions: OPT2
+//@[OPT2] compile-flags: -Copt-level=2
+
+#![crate_type = "lib"]
+#![no_std]
+
+// The code is from https://github.com/rust-lang/rust/issues/122805.
+// Ensure we do not generate the shufflevector instruction
+// to avoid complicating the code.
+
+// CHECK-LABEL: define{{.*}}void @convert(
+// CHECK-NOT: shufflevector
+
+// CHECK: store i16
+// CHECK-NEXT: getelementptr inbounds{{( nuw)?}} i8, {{.+}} 2
+// CHECK-NEXT: store i16
+// CHECK-NEXT: getelementptr inbounds{{( nuw)?}} i8, {{.+}} 4
+// CHECK-NEXT: store i16
+// CHECK-NEXT: getelementptr inbounds{{( nuw)?}} i8, {{.+}} 6
+// CHECK-NEXT: store i16
+// CHECK-NEXT: getelementptr inbounds{{( nuw)?}} i8, {{.+}} 8
+// CHECK-NEXT: store i16
+// CHECK-NEXT: getelementptr inbounds{{( nuw)?}} i8, {{.+}} 10
+// CHECK-NEXT: store i16
+// CHECK-NEXT: getelementptr inbounds{{( nuw)?}} i8, {{.+}} 12
+// CHECK-NEXT: store i16
+// CHECK-NEXT: getelementptr inbounds{{( nuw)?}} i8, {{.+}} 14
+// CHECK-NEXT: store i16
+#[no_mangle]
+pub fn convert(value: [u16; 8]) -> [u8; 16] {
+    #[cfg(target_endian = "little")]
+    let bswap = u16::to_be;
+    #[cfg(target_endian = "big")]
+    let bswap = u16::to_le;
+    let addr16 = [
+        bswap(value[0]),
+        bswap(value[1]),
+        bswap(value[2]),
+        bswap(value[3]),
+        bswap(value[4]),
+        bswap(value[5]),
+        bswap(value[6]),
+        bswap(value[7]),
+    ];
+    unsafe { core::mem::transmute::<_, [u8; 16]>(addr16) }
+}

tests/codegen/dont-shuffle-bswaps.rs renamed to tests/codegen/autovec/dont-shuffle-bswaps-opt3.rs

@@ -1,5 +1,4 @@
-//@ revisions: OPT2 OPT3 OPT3_S390X
-//@[OPT2] compile-flags: -Copt-level=2
+//@ revisions: OPT3 OPT3_S390X
 //@[OPT3] compile-flags: -C opt-level=3
 // some targets don't do the opt we are looking for
 //@[OPT3] only-64bit