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/codegen/src/binemit/memorysink.rs

@@ -162,6 +162,16 @@ impl<'a> CodeSink for MemoryCodeSink<'a> {
     }
 }
 
+/// A `RelocSink` implementation that does nothing, which is convenient when
+/// compiling code that does not relocate anything.
+pub struct NullRelocSink {}
+
+impl RelocSink for NullRelocSink {
+    fn reloc_ebb(&mut self, _: u32, _: Reloc, _: u32) {}
+    fn reloc_external(&mut self, _: u32, _: Reloc, _: &ExternalName, _: i64) {}
+    fn reloc_jt(&mut self, _: u32, _: Reloc, _: JumpTable) {}
+}
+
 /// A `TrapSink` implementation that does nothing, which is convenient when
 /// compiling code that does not rely on trapping semantics.
 pub struct NullTrapSink {}

cranelift/codegen/src/binemit/mod.rs

@@ -9,7 +9,8 @@ mod shrink;
 mod stackmap;
 
 pub use self::memorysink::{
-    MemoryCodeSink, NullStackmapSink, NullTrapSink, RelocSink, StackmapSink, TrapSink,
+    MemoryCodeSink, NullRelocSink, NullStackmapSink, NullTrapSink, RelocSink, StackmapSink,
+    TrapSink,
 };
 pub use self::relaxation::relax_branches;
 pub use self::shrink::shrink_instructions;