Fix warnings (causing CI failures) with new Rust beta.

- Panic messages must now be string literals (we used `format!()` in
  many places; `panic!()` can take format strings directly).
- Some dead enum options with EVEX encoding stuff in old x86 backend.
  This will go away soon and/or be moved to the new backend anyway, so
  let's silence the warning for now.
- A few other misc warnings.

cranelift/codegen/src/isa/x86/binemit.rs

@@ -277,6 +277,7 @@ impl EvexContext {
 }
 
 /// The EVEX format allows choosing a vector length in the `L'` and `L` bits; see `EvexContext`.
+#[allow(dead_code)]
 enum EvexVectorLength {
     V128,
     V256,
@@ -296,6 +297,7 @@ impl EvexVectorLength {
 }
 
 /// The EVEX format allows defining rounding control in the `L'` and `L` bits; see `EvexContext`.
+#[allow(dead_code)]
 enum EvexRoundingControl {
     RNE,
     RD,

cranelift/codegen/src/verifier/mod.rs

@@ -2064,10 +2064,7 @@ mod tests {
                 Some(&VerifierError { ref message, .. }) => {
                     if !message.contains($msg) {
                         #[cfg(feature = "std")]
-                        panic!(format!(
-                            "'{}' did not contain the substring '{}'",
-                            message, $msg
-                        ));
+                        panic!("'{}' did not contain the substring '{}'", message, $msg);
                         #[cfg(not(feature = "std"))]
                         panic!("error message did not contain the expected substring");
                     }

cranelift/filetests/src/test_binemit.rs

@@ -31,7 +31,6 @@ pub fn subtest(parsed: &TestCommand) -> anyhow::Result<Box<dyn SubTest>> {
 
 /// Code sink that generates text.
 struct TextSink {
-    code_size: binemit::CodeOffset,
     offset: binemit::CodeOffset,
     text: String,
 }
@@ -40,7 +39,6 @@ impl TextSink {
     /// Create a new empty TextSink.
     pub fn new() -> Self {
         Self {
-            code_size: 0,
             offset: 0,
             text: String::new(),
         }
@@ -98,9 +96,7 @@ impl binemit::CodeSink for TextSink {
         write!(self.text, "{} ", code).unwrap();
     }
 
-    fn begin_jumptables(&mut self) {
-        self.code_size = self.offset
-    }
+    fn begin_jumptables(&mut self) {}
     fn begin_rodata(&mut self) {}
     fn end_codegen(&mut self) {}
     fn add_stack_map(

cranelift/frontend/src/ssa.rs

@@ -1098,7 +1098,7 @@ mod tests {
             Ok(()) => {}
             Err(_errors) => {
                 #[cfg(feature = "std")]
-                panic!(_errors);
+                panic!("{}", _errors);
                 #[cfg(not(feature = "std"))]
                 panic!("function failed to verify");
             }
@@ -1291,7 +1291,7 @@ mod tests {
             Ok(()) => {}
             Err(_errors) => {
                 #[cfg(feature = "std")]
-                panic!(_errors);
+                panic!("{}", _errors);
                 #[cfg(not(feature = "std"))]
                 panic!("function failed to verify");
             }
@@ -1357,7 +1357,7 @@ mod tests {
             Ok(()) => {}
             Err(_errors) => {
                 #[cfg(feature = "std")]
-                panic!(_errors);
+                panic!("{}", _errors);
                 #[cfg(not(feature = "std"))]
                 panic!("function failed to verify");
             }

cranelift/wasm/tests/wasm_testsuite.rs

@@ -90,7 +90,7 @@ fn handle_module(data: Vec<u8>, flags: &Flags, return_mode: ReturnMode) {
 
     for func in dummy_environ.info.function_bodies.values() {
         verifier::verify_function(func, &*isa)
-            .map_err(|errors| panic!(pretty_verifier_error(func, Some(&*isa), None, errors)))
+            .map_err(|errors| panic!("{}", pretty_verifier_error(func, Some(&*isa), None, errors)))
             .unwrap();
     }
 }