Fuzzer: differential comparison of opt/no-opt

Cargo.toml

@@ -19,3 +19,11 @@ rayon = "1.5"
 lazy_static = "1.4"
 libc = "0.2"
 addr2line = "0.19"
+
+# For fuzzing only. Versions must match those in fuzz/Cargo.toml.
+libfuzzer-sys = { version = "0.4", optional = true }
+wasm-smith = { version = "0.8", optional = true }
+
+[features]
+default = []
+fuzzing = ["libfuzzer-sys", "wasm-smith"]

fuzz/Cargo.toml

@@ -19,6 +19,7 @@ wasmtime = "3.0"
 
 [dependencies.waffle]
 path = ".."
+features = ["fuzzing"]
 
 # Prevent this from interfering with workspaces
 [workspace]
@@ -47,3 +48,9 @@ name = "differential"
 path = "fuzz_targets/differential.rs"
 test = false
 doc = false
+
+[[bin]]
+name = "opt_diff"
+path = "fuzz_targets/opt_diff.rs"
+test = false
+doc = false

fuzz/fuzz_targets/differential.rs

@@ -1,116 +1,17 @@
 #![no_main]
-use libfuzzer_sys::{arbitrary, fuzz_target};
+use libfuzzer_sys::fuzz_target;
 use std::sync::atomic::{AtomicU64, Ordering};
 
 use waffle::{FrontendOptions, Module};
 
-fn reject(bytes: &[u8]) -> bool {
-    let parser = wasmparser::Parser::new(0);
-    let mut has_start = false;
-    let mut has_global_set = false;
-    let mut num_globals = 0;
-    for payload in parser.parse_all(bytes) {
-        match payload.unwrap() {
-            wasmparser::Payload::CodeSectionEntry(body) => {
-                for op in body.get_operators_reader().unwrap() {
-                    let op = op.unwrap();
-                    match op {
-                        wasmparser::Operator::GlobalSet { .. } => {
-                            has_global_set = true;
-                        }
-                        _ => {}
-                    }
-                }
-            }
-            wasmparser::Payload::StartSection { .. } => {
-                has_start = true;
-            }
-            wasmparser::Payload::ExportSection(mut reader) => {
-                for _ in 0..reader.get_count() {
-                    let e = reader.read().unwrap();
-                    match &e.kind {
-                        &wasmparser::ExternalKind::Global => {
-                            num_globals += 1;
-                        }
-                        _ => {}
-                    }
-                }
-            }
-            _ => {}
-        }
-    }
-
-    if !has_start || !has_global_set || num_globals < 1 {
-        return true;
-    }
-
-    false
-}
-
-#[derive(Debug)]
-struct Config;
-
-impl<'a> arbitrary::Arbitrary<'a> for Config {
-    fn arbitrary(_u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
-        Ok(Config)
-    }
-}
-
-impl wasm_smith::Config for Config {
-    fn min_funcs(&self) -> usize {
-        1
-    }
-    fn max_funcs(&self) -> usize {
-        1
-    }
-    fn min_memories(&self) -> u32 {
-        1
-    }
-    fn max_memories(&self) -> usize {
-        1
-    }
-    fn min_globals(&self) -> usize {
-        10
-    }
-    fn max_globals(&self) -> usize {
-        10
-    }
-    fn min_tables(&self) -> u32 {
-        0
-    }
-    fn max_tables(&self) -> usize {
-        0
-    }
-    fn min_imports(&self) -> usize {
-        0
-    }
-    fn max_imports(&self) -> usize {
-        0
-    }
-    fn min_exports(&self) -> usize {
-        12
-    }
-    fn max_exports(&self) -> usize {
-        12
-    }
-    fn allow_start_export(&self) -> bool {
-        true
-    }
-    fn canonicalize_nans(&self) -> bool {
-        true
-    }
-    fn max_memory_pages(&self, _is_64: bool) -> u64 {
-        1
-    }
-}
-
-fuzz_target!(|module: wasm_smith::ConfiguredModule<Config>| {
+fuzz_target!(
+    |module: wasm_smith::ConfiguredModule<waffle::fuzzing::Config>| {
         let _ = env_logger::try_init();
         log::debug!("original module: {:?}", module.module);
 
         let orig_bytes = module.module.to_bytes();
 
-    if reject(&orig_bytes[..]) {
+        if waffle::fuzzing::reject(&orig_bytes[..]) {
             log::debug!("Discarding fuzz run. Body:\n{:?}", module);
             return;
         } else {
@@ -155,7 +56,8 @@ fuzz_target!(|module: wasm_smith::ConfiguredModule<Config>| {
         // what matters is that it terminated above without a trap (hence
         // halts in a reasonable time).
         roundtrip_store.add_fuel(u64::MAX).unwrap();
-    let roundtrip_instance = wasmtime::Instance::new(&mut roundtrip_store, &roundtrip_module, &[])
+        let roundtrip_instance =
+            wasmtime::Instance::new(&mut roundtrip_store, &roundtrip_module, &[])
                 .expect("cannot instantiate roundtripped wasm");
 
         // Ensure exports are equal.
@@ -208,7 +110,8 @@ fuzz_target!(|module: wasm_smith::ConfiguredModule<Config>| {
         }
 
         success(total);
-});
+    }
+);
 
 static TOTAL: AtomicU64 = AtomicU64::new(0);
 static SUCCESS: AtomicU64 = AtomicU64::new(0);

fuzz/fuzz_targets/opt_diff.rs

@@ -0,0 +1,56 @@
+#![no_main]
+use libfuzzer_sys::fuzz_target;
+
+use waffle::{FrontendOptions, InterpContext, InterpResult, Module};
+
+fuzz_target!(
+    |module: wasm_smith::ConfiguredModule<waffle::fuzzing::Config>| {
+        let _ = env_logger::try_init();
+        log::debug!("original module: {:?}", module.module);
+
+        let orig_bytes = module.module.to_bytes();
+
+        if waffle::fuzzing::reject(&orig_bytes[..]) {
+            log::debug!("Discarding fuzz run. Body:\n{:?}", module);
+            return;
+        } else {
+            log::info!("body: {:?}", module);
+        }
+
+        let mut parsed_module =
+            Module::from_wasm_bytes(&orig_bytes[..], &FrontendOptions::default()).unwrap();
+        parsed_module.expand_all_funcs().unwrap();
+
+        let start = parsed_module.start_func.unwrap();
+
+        let mut orig_ctx = InterpContext::new(&parsed_module);
+        orig_ctx.fuel = 10000;
+
+        match orig_ctx.call(&parsed_module, start, &[]) {
+            InterpResult::OutOfFuel => {
+                // Silently reject.
+                log::trace!("Rejecting due to timeout in orig");
+                return;
+            }
+            InterpResult::Ok(_) => {}
+            ret => panic!("Bad result: {:?}", ret),
+        }
+
+        let mut opt_module = parsed_module.clone();
+        opt_module.per_func_body(|body| body.optimize());
+
+        let mut opt_ctx = InterpContext::new(&opt_module);
+        // Allow a little leeway for opts to not actually optimize.
+        opt_ctx.fuel = 20000;
+        opt_ctx.call(&opt_module, start, &[]).ok().unwrap();
+
+        log::trace!(
+            "Orig ran in {} fuel; opt ran in {} fuel",
+            10000 - orig_ctx.fuel,
+            20000 - opt_ctx.fuel
+        );
+
+        assert_eq!(orig_ctx.memories, opt_ctx.memories);
+        assert_eq!(orig_ctx.globals, opt_ctx.globals);
+    }
+);

src/entity.rs

@@ -171,3 +171,10 @@ impl<Idx: EntityRef, T: Clone + Debug + Default> IndexMut<Idx> for PerEntity<Idx
         &mut self.0[idx.index()]
     }
 }
+
+impl<Idx: EntityRef, T: Clone + Debug + Default + PartialEq> PartialEq for PerEntity<Idx, T> {
+    fn eq(&self, other: &Self) -> bool {
+        self.0 == other.0
+    }
+}
+impl<Idx: EntityRef, T: Clone + Debug + Default + PartialEq + Eq> Eq for PerEntity<Idx, T> {}

src/interp.rs

@@ -11,9 +11,10 @@ mod wasi;
 
 #[derive(Debug, Clone)]
 pub struct InterpContext {
-    memories: PerEntity<Memory, InterpMemory>,
-    tables: PerEntity<Table, InterpTable>,
-    globals: PerEntity<Global, ConstVal>,
+    pub memories: PerEntity<Memory, InterpMemory>,
+    pub tables: PerEntity<Table, InterpTable>,
+    pub globals: PerEntity<Global, ConstVal>,
+    pub fuel: u64,
 }
 
 type MultiVal = SmallVec<[ConstVal; 2]>;
@@ -23,6 +24,7 @@ pub enum InterpResult {
     Ok(MultiVal),
     Exit,
     Trap,
+    OutOfFuel,
 }
 
 impl InterpResult {
@@ -72,6 +74,7 @@ impl InterpContext {
             memories,
             tables,
             globals,
+            fuel: u64::MAX,
         }
     }
 
@@ -105,6 +108,11 @@ impl InterpContext {
         }
 
         loop {
+            self.fuel -= 1;
+            if self.fuel == 0 {
+                return InterpResult::OutOfFuel;
+            }
+
             log::trace!("Interpreting block {}", frame.cur_block);
             for &inst in &body.blocks[frame.cur_block].insts {
                 log::trace!("Evaluating inst {}", inst);
@@ -290,15 +298,15 @@ impl InterpStackFrame {
     }
 }
 
-#[derive(Debug, Clone, Default)]
+#[derive(Debug, Clone, Default, PartialEq, Eq)]
 pub struct InterpMemory {
-    data: Vec<u8>,
-    max_pages: usize,
+    pub data: Vec<u8>,
+    pub max_pages: usize,
 }
 
-#[derive(Debug, Clone, Default)]
+#[derive(Debug, Clone, Default, PartialEq, Eq)]
 pub struct InterpTable {
-    elements: Vec<Func>,
+    pub elements: Vec<Func>,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Default)]

src/lib.rs

@@ -22,3 +22,6 @@ pub use ops::{Ieee32, Ieee64, Operator};
 
 mod interp;
 pub use interp::*;
+
+#[cfg(feature = "fuzzing")]
+pub mod fuzzing;