Merge the intrinsic and user tests for select_unpredictable

[1] mentions that having a single test with `-Zmerge-functions=disabled`
is preferable to having two separate tests.  Apply that to the new
`select_unpredicatble` test here.

[1]: #133964 (comment)

Author: tgross35

tests/codegen/bool-select-unpredictable.rs

@@ -1,8 +1,11 @@
-//@ compile-flags: -O
+//@ compile-flags: -O -Zmerge-functions=disabled
 
 #![feature(core_intrinsics)]
+#![feature(select_unpredictable)]
 #![crate_type = "lib"]
 
+/* Test the intrinsic */
+
 #[no_mangle]
 pub fn test_int(p: bool, a: u64, b: u64) -> u64 {
     // CHECK-LABEL: define{{.*}} @test_int
@@ -33,3 +36,32 @@ pub fn test_zst(p: bool, a: (), b: ()) -> () {
     // CHECK-LABEL: define{{.*}} @test_zst
     core::intrinsics::select_unpredictable(p, a, b)
 }
+
+/* Test the user-facing version */
+
+#[no_mangle]
+pub fn test_int2(p: bool, a: u64, b: u64) -> u64 {
+    // CHECK-LABEL: define{{.*}} @test_int2
+    // CHECK: select i1 %p, i64 %a, i64 %b, !unpredictable
+    p.select_unpredictable(a, b)
+}
+
+#[no_mangle]
+pub fn test_pair2(p: bool, a: (u64, u64), b: (u64, u64)) -> (u64, u64) {
+    // CHECK-LABEL: define{{.*}} @test_pair2
+    // CHECK: select i1 %p, {{.*}}, !unpredictable
+    p.select_unpredictable(a, b)
+}
+
+#[no_mangle]
+pub fn test_struct2(p: bool, a: Large, b: Large) -> Large {
+    // CHECK-LABEL: define{{.*}} @test_struct2
+    // CHECK: select i1 %p, {{.*}}, !unpredictable
+    p.select_unpredictable(a, b)
+}
+
+#[no_mangle]
+pub fn test_zst2(p: bool, a: (), b: ()) -> () {
+    // CHECK-LABEL: define{{.*}} @test_zst2
+    p.select_unpredictable(a, b)
+}