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/filetests/src/test_run.rs

@@ -0,0 +1,46 @@
+//! Test command for running CLIF files and verifying their results
+//!
+//! The `run` test command compiles each function on the host machine and executes it
+
+use crate::function_runner::FunctionRunner;
+use crate::subtest::{Context, SubTest, SubtestResult};
+use cranelift_codegen;
+use cranelift_codegen::ir;
+use cranelift_reader::TestCommand;
+use std::borrow::Cow;
+
+struct TestRun;
+
+pub fn subtest(parsed: &TestCommand) -> SubtestResult<Box<dyn SubTest>> {
+    assert_eq!(parsed.command, "run");
+    if !parsed.options.is_empty() {
+        Err(format!("No options allowed on {}", parsed))
+    } else {
+        Ok(Box::new(TestRun))
+    }
+}
+
+impl SubTest for TestRun {
+    fn name(&self) -> &'static str {
+        "run"
+    }
+
+    fn is_mutating(&self) -> bool {
+        false
+    }
+
+    fn needs_isa(&self) -> bool {
+        false
+    }
+
+    fn run(&self, func: Cow<ir::Function>, context: &Context) -> SubtestResult<()> {
+        for comment in context.details.comments.iter() {
+            if comment.text.contains("run") {
+                let runner =
+                    FunctionRunner::with_host_isa(func.clone().into_owned(), context.flags.clone());
+                runner.run()?
+            }
+        }
+        Ok(())
+    }
+}