gccrs: intrinsics: Add early implementation for atomic_store_{seqcst, relaxed, release}

gcc/rust/ChangeLog:

	* backend/rust-builtins.cc (BuiltinsContext::setup_atomic_fns): New function.
	(BuiltinsContext::setup): Call `setup_atomic_fns`.
	* backend/rust-builtins.h: Declare `setup_atomic_fns`.
	* backend/rust-compile-intrinsic.cc (atomic_store_handler_inner): New function.
	(atomic_store_handler): New handler.
	(make_unsigned_long_tree): Add helper around making unsigned long trees.
	(prefetch_data_handler): Use `make_unsigned_long_tree`.
	(build_atomic_builtin_name): New function.

gcc/testsuite/ChangeLog:

	* rust/compile/torture/intrinsics-4.rs: New test.
	* rust/compile/torture/intrinsics-5.rs: New test.
	* rust/execute/torture/atomic_store.rs: New test.

1 files changed, 32 insertions, 0 deletions

diff --git a/gcc/testsuite/rust/execute/torture/atomic_store.rs b/gcc/testsuite/rust/execute/torture/atomic_store.rs
new file mode 100644
index 0000000..9f248b4
--- /dev/null
+++ b/gcc/testsuite/rust/execute/torture/atomic_store.rs
@@ -0,0 +1,32 @@
+trait Copy {}
+
+extern "rust-intrinsic" {
+    pub fn atomic_store_seqcst<T: Copy>(dst: *mut T, val: T);
+    pub fn atomic_store_release<T: Copy>(dst: *mut T, val: T);
+    pub fn atomic_store_relaxed<T: Copy>(dst: *mut T, val: T);
+    pub fn atomic_store_unordered<T: Copy>(dst: *mut T, val: T);
+}
+
+fn main() -> i32 {
+    let mut dst = 15;
+    let one;
+    let two;
+    let three;
+    let four;
+
+    unsafe {
+        atomic_store_seqcst(&mut dst, 1);
+        one = dst;
+
+        atomic_store_release(&mut dst, 2);
+        two = dst;
+
+        atomic_store_relaxed(&mut dst, 3);
+        three = dst;
+
+        atomic_store_unordered(&mut dst, 4);
+        four = dst;
+    }
+
+    (four + three + two + one) - 10
+}