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/function_runner.rs

@@ -0,0 +1,118 @@
+use core::mem;
+use cranelift_codegen::binemit::{NullRelocSink, NullStackmapSink, NullTrapSink};
+use cranelift_codegen::ir::Function;
+use cranelift_codegen::isa::{CallConv, TargetIsa};
+use cranelift_codegen::{settings, Context};
+use cranelift_native::builder as host_isa_builder;
+use mmap::{MapOption, MemoryMap};
+use region;
+use region::Protection;
+
+/// Run a function on a host
+pub struct FunctionRunner {
+    function: Function,
+    isa: Box<dyn TargetIsa>,
+}
+
+impl FunctionRunner {
+    /// Build a function runner from a function and the ISA to run on (must be the host machine's ISA)
+    pub fn new(function: Function, isa: Box<dyn TargetIsa>) -> Self {
+        FunctionRunner { function, isa }
+    }
+
+    /// Build a function runner using the host machine's ISA and the passed flags
+    pub fn with_host_isa(function: Function, flags: settings::Flags) -> Self {
+        let builder = host_isa_builder().expect("Unable to build a TargetIsa for the current host");
+        let isa = builder.finish(flags);
+        FunctionRunner::new(function, isa)
+    }
+
+    /// Build a function runner using the host machine's ISA and the default flags for this ISA
+    pub fn with_default_host_isa(function: Function) -> Self {
+        let flags = settings::Flags::new(settings::builder());
+        FunctionRunner::with_host_isa(function, flags)
+    }
+
+    /// Compile and execute a single function, expecting a boolean to be returned; a 'true' value is
+    /// interpreted as a successful test execution and mapped to Ok whereas a 'false' value is
+    /// interpreted as a failed test and mapped to Err.
+    pub fn run(&self) -> Result<(), String> {
+        let func = self.function.clone();
+        if !(func.signature.params.is_empty()
+            && func.signature.returns.len() == 1
+            && func.signature.returns.first().unwrap().value_type.is_bool())
+        {
+            return Err(String::from(
+                "Functions must have a signature like: () -> boolean",
+            ));
+        }
+
+        if func.signature.call_conv != self.isa.default_call_conv()
+            && func.signature.call_conv != CallConv::Fast
+        {
+            // ideally we wouldn't have to also check for Fast here but currently there is no way to inform the filetest parser that we would like to use a default other than Fast
+            return Err(String::from(
+                "Functions only run on the host's default calling convention; remove the specified calling convention in the function signature to use the host's default.",
+            ));
+        }
+
+        // set up the context
+        let mut context = Context::new();
+        context.func = func;
+
+        // compile and encode the result to machine code
+        let relocs = &mut NullRelocSink {};
+        let traps = &mut NullTrapSink {};
+        let stackmaps = &mut NullStackmapSink {};
+        let code_info = context
+            .compile(self.isa.as_ref())
+            .map_err(|e| e.to_string())?;
+        let code_page = MemoryMap::new(code_info.total_size as usize, &[MapOption::MapWritable])
+            .map_err(|e| e.to_string())?;
+        let callable_fn: fn() -> bool = unsafe {
+            context.emit_to_memory(
+                self.isa.as_ref(),
+                code_page.data(),
+                relocs,
+                traps,
+                stackmaps,
+            );
+            region::protect(code_page.data(), code_page.len(), Protection::ReadExecute)
+                .map_err(|e| e.to_string())?;
+            mem::transmute(code_page.data())
+        };
+
+        // execute
+        match callable_fn() {
+            true => Ok(()),
+            false => Err(format!("Failed: {}", context.func.name.to_string())),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use cranelift_reader::parse_test;
+
+    #[test]
+    fn nop() {
+        let code = String::from(
+            "function %test() -> b8 system_v {
+            ebb0:
+                nop
+                v1 = bconst.b8 true
+                return v1
+            }",
+        );
+
+        // extract function
+        let test_file = parse_test(code.as_str(), None, None).unwrap();
+        assert_eq!(1, test_file.functions.len());
+        let function = test_file.functions[0].0.clone();
+
+        // execute function
+        let runner = FunctionRunner::with_default_host_isa(function);
+        runner.run().unwrap() // will panic if execution fails
+    }
+}