rewrite and rename issue-46239

Author: Oneirical

src/tools/run-make-support/src/rustc.rs

@@ -64,6 +64,12 @@ impl Rustc {
         self
     }
 
+    /// Specify a specific optimization level.
+    pub fn opt_level(&mut self, option: &str) -> &mut Self {
+        self.cmd.arg(format!("-Copt-level={option}"));
+        self
+    }
+
     /// Specify type(s) of output files to generate.
     pub fn emit(&mut self, kinds: &str) -> &mut Self {
         self.cmd.arg(format!("--emit={kinds}"));

src/tools/tidy/src/allowed_run_make_makefiles.txt

@@ -112,7 +112,6 @@ run-make/issue-37839/Makefile
 run-make/issue-37893/Makefile
 run-make/issue-38237/Makefile
 run-make/issue-40535/Makefile
-run-make/issue-46239/Makefile
 run-make/issue-47384/Makefile
 run-make/issue-47551/Makefile
 run-make/issue-51671/Makefile

tests/codegen/noalias-freeze.rs

@@ -0,0 +1,21 @@
+//@ compile-flags: -Copt-level=1
+
+// References returned by a Frozen pointer type
+// could be marked as "noalias", which caused miscompilation errors.
+// This test runs the most minimal possible code that can reproduce this bug,
+// and checks that noalias does not appear.
+// See https://github.com/rust-lang/rust/issues/46239
+
+#![crate_type = "lib"]
+
+fn project<T>(x: &(T,)) -> &T { &x.0 }
+
+fn dummy() {}
+
+// CHECK-LABEL: @foo(
+// CHECK-NOT: noalias
+#[no_mangle]
+pub fn foo() {
+    let f = (dummy as fn(),);
+    (*project(&f))();
+}