Parallel driver script and optimizations to reduce system time

config.toml.example

@@ -1,3 +1,4 @@
+parallel_difftest = true
 bb_max_len = 32
 max_switch_targets = 8
 max_bb_count = 50

config/src/lib.rs

@@ -9,6 +9,7 @@ pub fn load(path: impl AsRef<Path>) -> Config {
 
 #[derive(Deserialize, Clone)]
 pub struct Config {
+    pub parallel_difftest: bool,
     #[serde(flatten)]
     pub generation: GenerationConfig,
     #[serde(flatten)]

difftest/Cargo.toml

@@ -12,5 +12,4 @@ colored = "2.0.0"
 env_logger = "0.11.3"
 log = "0.4.17"
 rayon = "1.7.0"
-serde = { version = "1", features = ["derive"] }
 tempfile = "3.3.0"

difftest/src/backends.rs

@@ -174,9 +174,14 @@ impl LLVM {
 
 impl Backend for LLVM {
     fn compile(&self, source: &Source, target: &Path) -> ProcessOutput {
-        let mut command = Command::new("rustc");
-
-        command.arg(format!("+{}", self.toolchain));
+        let mut command = if let Ok(path) = std::env::var("RUSTLANTIS_RUSTC_PATH") {
+            debug!("Compiling with rustc from RUSTLANTIS_RUSTC_PATH");
+            Command::new(path)
+        } else {
+            let mut command = Command::new("rustc");
+            command.arg(format!("+{}", self.toolchain));
+            command
+        };
 
         command
             .args(["-o", target.to_str().unwrap()])
@@ -307,13 +312,18 @@ impl Miri {
 
 impl Backend for Miri {
     fn execute(&self, source: &Source, _: &Path) -> ExecResult {
-        debug!("Executing with Miri {source}");
-        let mut command = match &self.miri {
-            BackendSource::Path(binary) => Command::new(binary),
-            BackendSource::Rustup(toolchain) => {
-                let mut cmd = Command::new("rustup");
-                cmd.args(["run", &toolchain, "miri"]);
-                cmd
+        let mut command = if let Ok(path) = std::env::var("RUSTLANTIS_MIRI_PATH") {
+            debug!("Executing with Miri from RUSTLANTIS_MIRI_PATH");
+            Command::new(path)
+        } else {
+            debug!("Executing with Miri {source}");
+            match &self.miri {
+                BackendSource::Path(binary) => Command::new(binary),
+                BackendSource::Rustup(toolchain) => {
+                    let mut cmd = Command::new("rustup");
+                    cmd.args(["run", &toolchain, "miri"]);
+                    cmd
+                }
             }
         };
         command.args(self.flags.clone());

difftest/src/lib.rs

@@ -155,24 +155,28 @@ impl fmt::Display for ExecResults {
 pub fn run_diff_test<'a>(
     source: &Source,
     backends: HashMap<String, Box<dyn Backend + 'a>>,
+    parallel: bool,
 ) -> ExecResults {
     let target_dir = tempfile::tempdir().unwrap();
-    let exec_results: HashMap<String, ExecResult> = backends
-        .into_par_iter()
-        .map(|(name, b)| {
-            let target_path = target_dir.path().join(&name);
-            let result = if log_enabled!(log::Level::Debug) {
-                let time = Instant::now();
-                let result = b.execute(source, &target_path);
-                let dur = time.elapsed();
-                debug!("{name} took {}s", dur.as_secs_f32());
-                result
-            } else {
-                b.execute(source, &target_path)
-            };
-            (name.clone(), result)
-        })
-        .collect();
 
-    ExecResults::from_exec_results(exec_results.into_iter())
+    let run_test = |(name, backend): (String, Box<dyn Backend>)| -> (String, ExecResult) {
+        let target_path = target_dir.path().join(&name);
+        let result = if log_enabled!(log::Level::Debug) {
+            let time = Instant::now();
+            let result = backend.execute(source, &target_path);
+            let dur = time.elapsed();
+            debug!("{name} took {}s", dur.as_secs_f32());
+            result
+        } else {
+            backend.execute(source, &target_path)
+        };
+        (name, result)
+    };
+
+    let results: HashMap<String, ExecResult> = if parallel {
+        backends.into_par_iter().map(run_test).collect()
+    } else {
+        backends.into_iter().map(run_test).collect()
+    };
+    ExecResults::from_exec_results(results.into_iter())
 }

difftest/src/main.rs

@@ -22,6 +22,7 @@ fn main() -> ExitCode {
 
     let config_path = std::env::var("RUSTLANTIS_CONFIG").unwrap_or("config.toml".to_string());
     let config = config::load(config_path);
+    let parallel = config.parallel_difftest;
     let backends = backends::from_config(config);
 
     let source = if source == "-" {
@@ -44,7 +45,7 @@ fn main() -> ExitCode {
             .collect::<String>()
     );
 
-    let results = run_diff_test(&source, backends);
+    let results = run_diff_test(&source, backends, parallel);
     if results.all_same() && results.all_success() {
         info!("{} is all the same", source);
         debug!("{}", results);

difftest/tests/config.toml

@@ -1,3 +1,4 @@
+parallel_difftest = true
 max_fn_count = 100
 max_args_count = 0
 

difftest/tests/test.rs

@@ -6,7 +6,7 @@ fn correct_mir() {
     let config = config::load("tests/config.toml");
     let backends = backends::from_config(config);
 
-    let results = run_diff_test(&Source::File("tests/inputs/simple.rs".into()), backends);
+    let results = run_diff_test(&Source::File("tests/inputs/simple.rs".into()), backends, true);
     println!("{}", results);
     assert!(results.all_same());
     assert!(
@@ -24,6 +24,7 @@ fn invalid_mir() {
     let results = run_diff_test(
         &Source::File("tests/inputs/invalid_mir.rs".into()),
         backends,
+        false,
     );
     println!("{}", results);
     assert!(results.all_same());
@@ -36,7 +37,7 @@ fn ub() {
     let config = config::load("tests/config.toml");
     let backends = backends::from_config(config);
 
-    let results = run_diff_test(&Source::File("tests/inputs/ub.rs".into()), backends);
+    let results = run_diff_test(&Source::File("tests/inputs/ub.rs".into()), backends, false);
     println!("{}", results);
     assert_eq!(results.has_ub(), Some(true));
 }

fuzz.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+set -eu
+
+cargo build --release
+export MIRI_SYSROOT=$(cargo +nightly miri setup --print-sysroot)
+export RUSTLANTIS_MIRI_PATH="$(rustup run nightly miri --print sysroot)/bin/miri"
+export RUSTLANTIS_RUSTC_PATH="$(rustup run nightly rustc --print sysroot)/bin/rustc"
+
+function cleanup {
+    kill $(jobs -p)
+}
+trap cleanup EXIT
+
+proc=$(nproc)
+for job in $(seq 0 $((proc-1))); do
+    nice -n 19 ./job.sh &> $job.out &
+done
+
+wait

job.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+set -eu
+
+while true
+do
+    seed=$(python3 -c "print(int.from_bytes(open('/dev/urandom', 'rb').read(8), 'little'))")
+    code=$(target/release/generate $seed)
+    if ! target/release/difftest - <<< $code
+    then
+        mkdir -p out
+        printf "%s" "$code" > out/$seed.rs
+    fi
+done