Tiny optimization for into_vec (#1931)

* Tiny optimization for into_vec

* fix bug

libafl/src/mutators/mod.rs

@@ -175,6 +175,9 @@ pub trait MutatorsTuple<I, S>: HasLen {
         corpus_idx: Option<CorpusId>,
     ) -> Result<(), Error>;
 
+    /// Gets all names of the wrapped [`Mutator`]`s`, reversed.
+    fn names_reversed(&self) -> Vec<&str>;
+
     /// Gets all names of the wrapped [`Mutator`]`s`.
     fn names(&self) -> Vec<&str>;
 }
@@ -222,6 +225,11 @@ impl<I, S> MutatorsTuple<I, S> for () {
         Ok(())
     }
 
+    #[inline]
+    fn names_reversed(&self) -> Vec<&str> {
+        Vec::new()
+    }
+
     #[inline]
     fn names(&self) -> Vec<&str> {
         Vec::new()
@@ -287,9 +295,15 @@ where
         }
     }
 
+    fn names_reversed(&self) -> Vec<&str> {
+        let mut ret = self.1.names_reversed();
+        ret.push(self.0.name());
+        ret
+    }
+
     fn names(&self) -> Vec<&str> {
-        let mut ret = self.1.names();
+        let mut ret = self.names_reversed();
-        ret.insert(0, self.0.name());
+        ret.reverse();
         ret
     }
 }
@@ -299,10 +313,16 @@ where
     Head: Mutator<I, S> + 'static,
     Tail: IntoVec<Box<dyn Mutator<I, S>>>,
 {
-    fn into_vec(self) -> Vec<Box<dyn Mutator<I, S>>> {
+    fn into_vec_reversed(self) -> Vec<Box<dyn Mutator<I, S>>> {
         let (head, tail) = self.uncons();
-        let mut ret = tail.into_vec();
+        let mut ret = tail.into_vec_reversed();
-        ret.insert(0, Box::new(head));
+        ret.push(Box::new(head));
+        ret
+    }
+
+    fn into_vec(self) -> Vec<Box<dyn Mutator<I, S>>> {
+        let mut ret = self.into_vec_reversed();
+        ret.reverse();
         ret
     }
 }
@@ -353,6 +373,10 @@ where
     fn names(&self) -> Vec<&str> {
         self.0.names()
     }
+
+    fn names_reversed(&self) -> Vec<&str> {
+        self.0.names_reversed()
+    }
 }
 
 impl<Tail, I, S> IntoVec<Box<dyn Mutator<I, S>>> for (Tail,)
@@ -419,6 +443,10 @@ impl<I, S> MutatorsTuple<I, S> for Vec<Box<dyn Mutator<I, S>>> {
         mutator.post_exec(state, stage_idx, new_corpus_idx)
     }
 
+    fn names_reversed(&self) -> Vec<&str> {
+        self.iter().rev().map(|x| x.name()).collect()
+    }
+
     fn names(&self) -> Vec<&str> {
         self.iter().map(|x| x.name()).collect()
     }

libafl/src/stages/mod.rs

@@ -222,10 +222,18 @@ where
     Z: UsesState<State = Head::State>,
     Head::State: HasCurrentStage,
 {
-    fn into_vec(self) -> Vec<Box<dyn Stage<E, EM, Z, State = Head::State, Input = Head::Input>>> {
+    fn into_vec_reversed(
+        self,
+    ) -> Vec<Box<dyn Stage<E, EM, Z, State = Head::State, Input = Head::Input>>> {
         let (head, tail) = self.uncons();
-        let mut ret = tail.0.into_vec();
+        let mut ret = tail.0.into_vec_reversed();
-        ret.insert(0, Box::new(head));
+        ret.push(Box::new(head));
+        ret
+    }
+
+    fn into_vec(self) -> Vec<Box<dyn Stage<E, EM, Z, State = Head::State, Input = Head::Input>>> {
+        let mut ret = self.into_vec_reversed();
+        ret.reverse();
         ret
     }
 }

libafl_bolts/src/tuples.rs

@@ -94,6 +94,17 @@ where
 /// (We need this trait since we cannot implement `Into` for foreign types)
 #[cfg(feature = "alloc")]
 pub trait IntoVec<T> {
+    /// Convert this into a [`Vec`], reversed.
+    /// (Having this method around makes some implementations more performant)
+    fn into_vec_reversed(self) -> Vec<T>
+    where
+        Self: Sized,
+    {
+        let mut ret = self.into_vec();
+        ret.reverse();
+        ret
+    }
+
     /// Convert this into a [`Vec`].
     fn into_vec(self) -> Vec<T>;
 }