[gcc/devel/rust/master] Add execute test for black_box intrinsic

[Thomas Schwinge via Gcc-cvs]

https://gcc.gnu.org/g:78fcf63b606343f6fe837b933b8fadccf0f49e87

commit 78fcf63b606343f6fe837b933b8fadccf0f49e87
Author: Pierre-Emmanuel Patry <pierre-emmanuel.pa...@embecosm.com>
Date:   Thu Apr 17 17:53:15 2025 +0200

    Add execute test for black_box intrinsic
    
    gcc/testsuite/ChangeLog:
    
            * rust/execute/black_box.rs: New test.
    
    Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.pa...@embecosm.com>

Diff:
---
 gcc/testsuite/rust/execute/black_box.rs | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/gcc/testsuite/rust/execute/black_box.rs 
b/gcc/testsuite/rust/execute/black_box.rs
new file mode 100644
index 000000000000..7a9920eba947
--- /dev/null
+++ b/gcc/testsuite/rust/execute/black_box.rs
@@ -0,0 +1,30 @@
+/* { dg-output "Value is: 42\r*\n" } */
+#![feature(rustc_attrs)]
+
+extern "C" {
+    fn printf(s: *const i8, ...);
+}
+
+#[lang = "sized"]
+pub trait Sized {}
+
+#[rustc_builtin_macro]
+macro_rules! llvm_asm {
+    () => {};
+}
+
+pub fn black_box<T>(mut dummy: T) -> T {
+    unsafe {
+        llvm_asm!("" : : "r"(&mut dummy) : "memory" : "volatile");
+    }
+
+    dummy
+}
+
+fn main() {
+    let dummy: i32 = 42;
+    let result = black_box(dummy);
+    unsafe {
+        printf("Value is: %i\n\0" as *const str as *const i8, result);
+    }
+}