Move the filetest harness into its own crate.

This allows us to run the tests via a library call rather than just
as a command execution. And, it's a step toward a broader goal, which
is to keep the code in the top-level src directory minimal, with
important functionality exposed as crates.

lib/filetests/src/runone.rs

@@ -0,0 +1,144 @@
+//! Run the tests in a single test file.
+
+use std::borrow::Cow;
+use std::path::Path;
+use std::time;
+use std::io::{self, Read};
+use std::fs;
+use cretonne::ir::Function;
+use cretonne::isa::TargetIsa;
+use cretonne::settings::Flags;
+use cretonne::timing;
+use cretonne::verify_function;
+use cretonne::print_errors::pretty_verifier_error;
+use cton_reader::parse_test;
+use cton_reader::IsaSpec;
+use {TestResult, new_subtest};
+use subtest::{SubTest, Context, Result};
+
+/// Read an entire file into a string.
+fn read_to_string<P: AsRef<Path>>(path: P) -> io::Result<String> {
+    let mut file = fs::File::open(path)?;
+    let mut buffer = String::new();
+    file.read_to_string(&mut buffer)?;
+    Ok(buffer)
+}
+
+/// Load `path` and run the test in it.
+///
+/// If running this test causes a panic, it will propagate as normal.
+pub fn run(path: &Path) -> TestResult {
+    let _tt = timing::process_file();
+    dbg!("---\nFile: {}", path.to_string_lossy());
+    let started = time::Instant::now();
+    let buffer = read_to_string(path).map_err(|e| e.to_string())?;
+    let testfile = parse_test(&buffer).map_err(|e| e.to_string())?;
+    if testfile.functions.is_empty() {
+        return Err("no functions found".to_string());
+    }
+
+    // Parse the test commands.
+    let mut tests = testfile
+        .commands
+        .iter()
+        .map(new_subtest)
+        .collect::<Result<Vec<_>>>()?;
+
+    // Flags to use for those tests that don't need an ISA.
+    // This is the cumulative effect of all the `set` commands in the file.
+    let flags = match testfile.isa_spec {
+        IsaSpec::None(ref f) => f,
+        IsaSpec::Some(ref v) => v.last().expect("Empty ISA list").flags(),
+    };
+
+    // Sort the tests so the mutators are at the end, and those that don't need the verifier are at
+    // the front.
+    tests.sort_by_key(|st| (st.is_mutating(), st.needs_verifier()));
+
+    // Expand the tests into (test, flags, isa) tuples.
+    let mut tuples = test_tuples(&tests, &testfile.isa_spec, flags)?;
+
+    // Isolate the last test in the hope that this is the only mutating test.
+    // If so, we can completely avoid cloning functions.
+    let last_tuple = match tuples.pop() {
+        None => return Err("no test commands found".to_string()),
+        Some(t) => t,
+    };
+
+    for (func, details) in testfile.functions {
+        let mut context = Context {
+            preamble_comments: &testfile.preamble_comments,
+            details,
+            verified: false,
+            flags,
+            isa: None,
+        };
+
+        for tuple in &tuples {
+            run_one_test(*tuple, Cow::Borrowed(&func), &mut context)?;
+        }
+        // Run the last test with an owned function which means it won't need to clone it before
+        // mutating.
+        run_one_test(last_tuple, Cow::Owned(func), &mut context)?;
+    }
+
+
+    Ok(started.elapsed())
+}
+
+// Given a slice of tests, generate a vector of (test, flags, isa) tuples.
+fn test_tuples<'a>(
+    tests: &'a [Box<SubTest>],
+    isa_spec: &'a IsaSpec,
+    no_isa_flags: &'a Flags,
+) -> Result<Vec<(&'a SubTest, &'a Flags, Option<&'a TargetIsa>)>> {
+    let mut out = Vec::new();
+    for test in tests {
+        if test.needs_isa() {
+            match *isa_spec {
+                IsaSpec::None(_) => {
+                    // TODO: Generate a list of default ISAs.
+                    return Err(format!("test {} requires an ISA", test.name()));
+                }
+                IsaSpec::Some(ref isas) => {
+                    for isa in isas {
+                        out.push((&**test, isa.flags(), Some(&**isa)));
+                    }
+                }
+            }
+        } else {
+            // This test doesn't require an ISA, and we only want to run one instance of it.
+            // Still, give it an ISA ref if we happen to have a unique one.
+            // For example, `test cat` can use this to print encodings and register names.
+            out.push((&**test, no_isa_flags, isa_spec.unique_isa()));
+        }
+    }
+    Ok(out)
+}
+
+fn run_one_test<'a>(
+    tuple: (&'a SubTest, &'a Flags, Option<&'a TargetIsa>),
+    func: Cow<Function>,
+    context: &mut Context<'a>,
+) -> Result<()> {
+    let (test, flags, isa) = tuple;
+    let name = format!("{}({})", test.name(), func.name);
+    dbg!("Test: {} {}", name, isa.map(TargetIsa::name).unwrap_or("-"));
+
+    context.flags = flags;
+    context.isa = isa;
+
+    // Should we run the verifier before this test?
+    if !context.verified && test.needs_verifier() {
+        verify_function(&func, context.flags_or_isa()).map_err(
+            |e| {
+                pretty_verifier_error(&func, isa, e)
+            },
+        )?;
+        context.verified = true;
+    }
+
+    test.run(func, context).map_err(
+        |e| format!("{}: {}", name, e),
+    )
+}