tests/codegen-llvm/some-non-zero-from-atomic-optimization.rs: New test

Author: Enselic

tests/codegen-llvm/some-non-zero-from-atomic-optimization.rs

@@ -0,0 +1,68 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/60044>.
+
+// We want to check that the None case is optimized away
+//@ compile-flags: -O
+
+// Simplify the emitted code
+//@ compile-flags: -Cforce-unwind-tables=no
+
+// Make it easier to write FileCheck directives:
+//@ compile-flags: -Zmerge-functions=disabled
+
+#![crate_type = "lib"]
+
+use std::num::NonZeroUsize;
+use std::sync::atomic::AtomicUsize;
+use std::sync::atomic::Ordering::Relaxed;
+
+pub static X: AtomicUsize = AtomicUsize::new(1);
+
+/// This function function shall look like this:
+/// ```llvm
+/// define noundef range(i64 1, 0) i64 @some_non_zero_from_atomic_get() unnamed_addr #0 {
+/// start:
+///   %0 = load atomic i64, ptr @_ZN38some_non_zero_from_atomic_optimization1X13E monotonic, align 8
+///   %1 = icmp ne i64 %0, 0
+///   tail call void @llvm.assume(i1 %1)
+///   ret i64 %0
+/// }
+/// ; ...
+/// attributes #0 = { mustprogress nofree norecurse nounwind nonlazybind willreturn ... }
+/// ```
+// CHECK-LABEL: define noundef range(i64 1, 0) i64 @some_non_zero_from_atomic_get() unnamed_addr
+// CHECK-SAME: #[[#ATTRIBUTE_GROUP:]] {
+// CHECK: %0 = load atomic i64, ptr @{{[_a-zA-Z0-9]+}} monotonic, align 8
+// CHECK-NEXT: %1 = icmp ne i64 %0, 0
+// CHECK-NEXT: tail call void @llvm.assume(i1 %1)
+// CHECK-NEXT: ret i64 %0
+// CHECK-NEXT: }
+#[no_mangle]
+pub unsafe fn some_non_zero_from_atomic_get() -> Option<NonZeroUsize> {
+    let x = X.load(Relaxed);
+    Some(NonZeroUsize::new_unchecked(x))
+}
+
+/// This function shall be identical to the above:
+// CHECK-LABEL: define noundef range(i64 1, 0) i64 @some_non_zero_from_atomic_get2() unnamed_addr
+// CHECK-SAME: #[[#ATTRIBUTE_GROUP]] {
+// CHECK: %0 = load atomic i64, ptr @{{[_a-zA-Z0-9]+}} monotonic, align 8
+// CHECK-NEXT: %1 = icmp ne i64 %0, 0
+// CHECK-NEXT: tail call void @llvm.assume(i1 %1)
+// CHECK-NEXT: ret i64 %0
+// CHECK-NEXT: }
+#[no_mangle]
+pub unsafe fn some_non_zero_from_atomic_get2() -> usize {
+    match some_non_zero_from_atomic_get() {
+        Some(x) => x.get(),
+        None => unreachable!(), // shall be optimized out
+    }
+}
+
+// Finally make sure the attribute group looks reasonable:
+// CHECK-LABEL: attributes
+// CHECK: #[[#ATTRIBUTE_GROUP]] =
+// CHECK-SAME: mustprogress
+// CHECK-SAME: nofree
+// CHECK-SAME: norecurse
+// CHECK-SAME: nounwind
+// CHECK-SAME: willreturn