Add test run to cranelift-filetests to allow executing CLIF (#890)

* Add ability to run CLIF IR using `clif-util run [-v] {file}` and add `test run` to cranelift-filetests to allow executing CLIF

This re-factors the compile/execute parts to a FunctionRunner that is shared between cranelift-filetests and clif-util. CLIF can be now be run using `clif-util run` as well as during `clif-util test` for files with a `test run` header. As before, only functions suffixed with a `run` comment are executed. The `run: fn(...) == ...` expression syntax is left for a subsequent change.

cranelift/src/run.rs

@@ -0,0 +1,118 @@
+//! CLI tool to compile Cranelift IR files to native code in memory and execute them.
+
+use crate::utils::read_to_string;
+use cranelift_codegen::isa::TargetIsa;
+use cranelift_filetests::FunctionRunner;
+use cranelift_native::builder as host_isa_builder;
+use cranelift_reader::{parse_test, Details, IsaSpec};
+use std::path::PathBuf;
+use walkdir::WalkDir;
+
+pub fn run(files: Vec<String>, flag_print: bool) -> Result<(), String> {
+    let mut total = 0;
+    let mut errors = 0;
+    for file in iterate_files(files) {
+        total += 1;
+        match run_single_file(&file) {
+            Ok(_) => {
+                if flag_print {
+                    println!("{}", file.to_string_lossy());
+                }
+            }
+            Err(e) => {
+                if flag_print {
+                    println!("{}: {}", file.to_string_lossy(), e);
+                }
+                errors += 1;
+            }
+        }
+    }
+
+    if flag_print {
+        match total {
+            0 => println!("0 files"),
+            1 => println!("1 file"),
+            n => println!("{} files", n),
+        }
+    }
+
+    match errors {
+        0 => Ok(()),
+        1 => Err(String::from("1 failure")),
+        n => Err(format!("{} failures", n)),
+    }
+}
+
+/// Iterate over all of the files passed as arguments, recursively iterating through directories
+fn iterate_files(files: Vec<String>) -> impl Iterator<Item = PathBuf> {
+    files
+        .into_iter()
+        .flat_map(WalkDir::new)
+        .filter(|f| match f {
+            Ok(d) => {
+                // filter out hidden files (starting with .)
+                !d.file_name().to_str().map_or(false, |s| s.starts_with("."))
+                    // filter out directories
+                    && !d.file_type().is_dir()
+            }
+            Err(e) => {
+                println!("Unable to read file: {}", e);
+                false
+            }
+        })
+        .map(|f| {
+            f.expect("This should not happen: we have already filtered out the errors")
+                .into_path()
+        })
+}
+
+/// Run all functions in a file that are succeeded by "run:" comments
+fn run_single_file(path: &PathBuf) -> Result<(), String> {
+    let file_contents = read_to_string(&path).map_err(|e| e.to_string())?;
+    run_file_contents(file_contents)
+}
+
+/// Main body of `run_single_file` separated for testing
+fn run_file_contents(file_contents: String) -> Result<(), String> {
+    let test_file = parse_test(&file_contents, None, None).map_err(|e| e.to_string())?;
+    for (func, Details { comments, .. }) in test_file.functions {
+        if comments.iter().any(|c| c.text.contains("run")) {
+            let isa = create_target_isa(&test_file.isa_spec)?;
+            FunctionRunner::new(func, isa).run()?
+        }
+    }
+    Ok(())
+}
+
+/// Build an ISA based on the current machine running this code (the host)
+fn create_target_isa(isa_spec: &IsaSpec) -> Result<Box<dyn TargetIsa>, String> {
+    if let IsaSpec::None(flags) = isa_spec {
+        // build an ISA for the current machine
+        let builder = host_isa_builder()?;
+        Ok(builder.finish(flags.clone()))
+    } else {
+        Err(String::from("A target ISA was specified in the file but should not have been--only the host ISA can be used for running CLIF files"))?
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn nop() {
+        let code = String::from(
+            "
+            function %test() -> b8 system_v {
+            ebb0:
+                nop
+                v1 = bconst.b8 true
+                return v1
+            }
+            
+            ; run
+            ",
+        );
+        run_file_contents(code).unwrap()
+    }
+}