Added test for cold_path()

Author: x17jiri

tests/codegen/hint/cold_path.rs

@@ -0,0 +1,54 @@
+//@ compile-flags: -O
+#![crate_type = "lib"]
+#![feature(cold_path)]
+
+use std::hint::cold_path;
+
+#[inline(never)]
+#[no_mangle]
+pub fn path_a() {
+    println!("path a");
+}
+
+#[inline(never)]
+#[no_mangle]
+pub fn path_b() {
+    println!("path b");
+}
+
+#[no_mangle]
+pub fn test1(x: bool) {
+    if x {
+        path_a();
+    } else {
+        cold_path();
+        path_b();
+    }
+}
+
+#[no_mangle]
+pub fn test2(x: i32) {
+    match x > 0 {
+        true => path_a(),
+        false => {
+            cold_path();
+            path_b()
+        }
+    }
+}
+
+// CHECK-LABEL: @test1(
+// CHECK: br i1 %x, label %bb1, label %bb2, !prof ![[NUM:[0-9]+]]
+// CHECK: bb2:
+// CHECK: path_b
+// CHECK: bb1:
+// CHECK: path_a
+
+// CHECK-LABEL: @test2(
+// CHECK: br i1 %_2, label %bb2, label %bb1, !prof ![[NUM]]
+// CHECK: bb1:
+// CHECK: path_b
+// CHECK: bb2:
+// CHECK: path_a
+
+// CHECK: ![[NUM]] = !{!"branch_weights", {{(!"expected", )?}}i32 2000, i32 1}