centralize conditional compilation of chaos mode

Also cleanup a few straggling dependencies on cranelift-control
that aren't needed anymore.

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

cranelift/codegen/Cargo.toml

@@ -114,8 +114,6 @@ isle-errors = ["cranelift-isle/fancy-errors"]
 # inspection, rather than inside of target/.
 isle-in-source-tree = []
 
-chaos = ["cranelift-control/chaos"]
-
 [badges]
 maintenance = { status = "experimental" }
 

cranelift/codegen/src/machinst/buffer.rs

@@ -774,9 +774,8 @@ impl<I: VCodeInst> MachBuffer<I> {
         //   fixup record referring to that last branch is removed.
     }
 
-    fn optimize_branches(&mut self, _ctrl_plane: &mut ControlPlane) {
-        #[cfg(feature = "chaos")]
-        if _ctrl_plane.get_decision() {
+    fn optimize_branches(&mut self, ctrl_plane: &mut ControlPlane) {
+        if ctrl_plane.get_decision() {
             return;
         }
 

cranelift/control/src/lib.rs

@@ -19,12 +19,12 @@
 //! [arbitrary]: ControlPlane#method.arbitrary
 //! [default]: ControlPlane#method.default
 
-#[cfg(not(any(feature = "chaos", doc)))]
+#[cfg(not(feature = "chaos"))]
 mod zero_sized;
-#[cfg(not(any(feature = "chaos", doc)))]
+#[cfg(not(feature = "chaos"))]
 pub use zero_sized::*;
 
-#[cfg(any(feature = "chaos", doc))]
+#[cfg(feature = "chaos")]
 mod chaos;
-#[cfg(any(feature = "chaos", doc))]
+#[cfg(feature = "chaos")]
 pub use chaos::*;

cranelift/control/src/zero_sized.rs

@@ -1,5 +1,28 @@
+//! Shims for ControlPlane when chaos mode is disabled. Enables
+//! unconditional use of the type and its methods throughout cranelift.
+
+/// A shim for ControlPlane when chaos mode is disabled.
+/// Please see the [crate-level documentation](crate).
 #[derive(Debug, Clone, Default)]
 pub struct ControlPlane {
     /// prevent direct instantiation (use `default` instead)
     _private: (),
 }
+
+/// A shim for ControlPlane's `Arbitrary` implementation when chaos mode is
+/// disabled. It doesn't consume any bytes and always returns a default
+/// control plane.
+impl arbitrary::Arbitrary<'_> for ControlPlane {
+    fn arbitrary<'a>(_u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
+        Ok(Self::default())
+    }
+}
+
+impl ControlPlane {
+    /// Returns a pseudo-random boolean. This variant is used when chaos
+    /// mode is disabled. It always returns `false`.
+    #[inline]
+    pub fn get_decision(&mut self) -> bool {
+        false
+    }
+}

cranelift/fuzzgen/Cargo.toml

@@ -13,12 +13,8 @@ publish = false
 [dependencies]
 cranelift = { workspace = true }
 cranelift-native = { workspace = true }
-cranelift-control = { workspace = true }
 
 anyhow = { workspace = true }
 arbitrary = "1.0.0"
 once_cell = { workspace = true }
 target-lexicon = { workspace = true, features = ["std"] }
-
-[features]
-chaos = ["cranelift-control/chaos"]

cranelift/native/Cargo.toml

@@ -12,7 +12,6 @@ edition.workspace = true
 
 [dependencies]
 cranelift-codegen = { workspace = true }
-cranelift-control = { workspace = true }
 target-lexicon = { workspace = true }
 
 [target.'cfg(any(target_arch = "s390x", target_arch = "riscv64"))'.dependencies]

cranelift/reader/Cargo.toml

@@ -12,7 +12,6 @@ edition.workspace = true
 [dependencies]
 anyhow.workspace = true
 cranelift-codegen = { workspace = true }
-cranelift-control = { workspace = true }
 smallvec = { workspace = true }
 target-lexicon = { workspace = true }
 

fuzz/Cargo.toml

@@ -37,11 +37,7 @@ component-fuzz-util = { workspace = true }
 [features]
 default = ['fuzz-spec-interpreter']
 fuzz-spec-interpreter = ['wasmtime-fuzzing/fuzz-spec-interpreter']
-chaos = [
-    "cranelift-codegen/chaos",
-    "cranelift-control/chaos",
-    "cranelift-fuzzgen/chaos",
-]
+chaos = ["cranelift-control/chaos"]
 
 [[bin]]
 name = "compile"

fuzz/fuzz_targets/cranelift-fuzzgen.rs

@@ -218,9 +218,6 @@ impl TestCase {
             )?;
             functions.push(func);
 
-            #[cfg(not(feature = "chaos"))]
-            ctrl_planes.push(ControlPlane::default());
-            #[cfg(feature = "chaos")]
             ctrl_planes.push(ControlPlane::arbitrary(gen.u)?);
         }
         // Now reverse the functions so that the main function is at the start.