peepmatic: Introduce the peepmatic-fuzzing crate

This crate contains oracles, generators, and fuzz targets for use with fuzzing
engines (e.g. libFuzzer). This doesn't contain the actual
`libfuzzer_sys::fuzz_target!` definitions (those are in the `peepmatic-fuzz`
crate) but does those definitions are one liners calling out to functions
defined in this crate.

cranelift/peepmatic/crates/fuzzing/src/parser.rs

@@ -0,0 +1,29 @@
+//! Utilities for fuzzing our DSL's parser.
+
+use peepmatic::Optimizations;
+use std::str;
+
+/// Attempt to parse the given string as if it were a snippet of our DSL.
+pub fn parse(data: &[u8]) {
+    let source = match str::from_utf8(data) {
+        Ok(s) => s,
+        Err(_) => return,
+    };
+
+    let buf = match wast::parser::ParseBuffer::new(&source) {
+        Ok(buf) => buf,
+        Err(_) => return,
+    };
+
+    let _ = wast::parser::parse::<Optimizations>(&buf);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn check_parse() {
+        crate::check(|s: String| parse(s.as_bytes()));
+    }
+}