fuzz: cleanup control plane

Co-authored-by: Falk Zwimpfer <[email protected]>
Co-authored-by: Moritz Waser <[email protected]>

cranelift/codegen/src/machinst/buffer.rs

@@ -776,10 +776,7 @@ impl<I: VCodeInst> MachBuffer<I> {
 
     fn optimize_branches(&mut self, ctrl_plane: &mut ControlPlane) {
         #[cfg(feature = "chaos")]
-        if let Some(true) = ctrl_plane.get_decision() {
-            println!("");
-            println!("");
-            println!("branch optimizations skipped");
+        if ctrl_plane.get_decision() {
             return;
         }
 

cranelift/control/src/chaos.rs

@@ -1,58 +1,28 @@
-use std::{backtrace, fmt::Debug};
-
 use arbitrary::Arbitrary;
 
 /// The control plane of chaos mode.
 /// Please see the [crate-level documentation](crate).
-///
-/// **Clone liberally!** The chaos engine is reference counted.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Default)]
 pub struct ControlPlane {
     data: Vec<bool>,
-    is_noop: bool,
 }
 
 impl Arbitrary<'_> for ControlPlane {
     fn arbitrary<'a>(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
-        Ok(Self::new(u.arbitrary()?, false))
-    }
-}
-
-impl ControlPlane {
-    fn new(data: Vec<bool>, is_noop: bool) -> Self {
-        Self {
-            data: data,
-            is_noop,
-        }
-    }
-
-    /// TODO chaos: should be explained
-    pub fn no_chaos() -> Self {
-        Self::new(Vec::new(), false)
-    }
-
-    pub fn todo() -> Self {
-        Self::new(Vec::new(), false)
-    }
-}
-
-impl Default for ControlPlane {
-    fn default() -> Self {
-        Self::new(Vec::new(), true)
+        Ok(Self {
+            data: u.arbitrary()?,
+        })
     }
 }
 
 impl ControlPlane {
-    pub fn get_decision(&mut self) -> Option<bool> {
-        if self.is_noop {
-            //println!(
-            //    "try to get a decision from a noop chaos engine at {} ",
-            //    backtrace::Backtrace::force_capture()
-            //);
-            //None
-            panic!("trying to get a decision from a noop chaos engine");
-        } else {
-            self.data.pop()
-        }
+    /// Returns a pseudo-random boolean if the control plane was constructed
+    /// with `arbitrary`.
+    ///
+    /// The default value `false` will always be returned if the
+    /// pseudo-random data is exhausted or the control plane was constructed
+    /// with `default`.
+    pub fn get_decision(&mut self) -> bool {
+        self.data.pop().unwrap_or_default()
     }
 }

cranelift/control/src/lib.rs

@@ -11,17 +11,13 @@
 //! e.g. manipulate heuristic optimizations, clobber undefined register bits
 //! etc.
 //!
-//! There are three ways to acquire a [ControlPlane]:
+//! There are two ways to acquire a [ControlPlane]:
 //! - [arbitrary] for the real deal
-//! - [noop] for the zero-sized type when `chaos` is disabled
-//! - [todo] for stubbing out code paths during development
-//!
-//! The reason both [noop] and [todo] exist is so that [todo] can easily
-//! be searched for and removed later.
+//! - [default] for an "empty" control plane which always returns default
+//!   values
 //!
 //! [arbitrary]: ControlPlane#method.arbitrary
-//! [noop]: ControlPlane::noop
-//! [todo]: ControlPlane::todo
+//! [default]: ControlPlane#method.default
 
 #[cfg(not(any(feature = "chaos", doc)))]
 mod zero_sized;

cranelift/control/src/zero_sized.rs

@@ -1,20 +1,5 @@
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Default)]
 pub struct ControlPlane {
-    /// prevent direct instantiation (use `noop` or `todo` instead)
+    /// prevent direct instantiation (use `default` instead)
     _private: (),
 }
-
-impl ControlPlane {
-    pub fn no_chaos() -> Self {
-        Self { _private: () }
-    }
-
-    // get_decision function is not implemented here because it should only be called within
-    // conditional compiled code blocks. In that case the other implementation would be used anyway.
-}
-
-impl Default for ControlPlane {
-    fn default() -> Self {
-        Self::no_chaos()
-    }
-}