Make get_mach_backend non-optional

cranelift/codegen/src/context.rs

@@ -167,8 +167,7 @@ impl Context {
 
         self.remove_constant_phis(isa)?;
 
-        // FIXME: make this non optional
-        let backend = isa.get_mach_backend().expect("only mach backends nowadays");
+        let backend = isa.get_mach_backend();
         let result = backend.compile_function(&self.func, self.want_disasm)?;
         let info = result.code_info();
         self.mach_compile_result = Some(result);
@@ -243,12 +242,10 @@ impl Context {
         &self,
         isa: &dyn TargetIsa,
     ) -> CodegenResult<Option<crate::isa::unwind::UnwindInfo>> {
-        if let Some(backend) = isa.get_mach_backend() {
-            let unwind_info_kind = isa.unwind_info_kind();
-            let result = self.mach_compile_result.as_ref().unwrap();
-            return backend.emit_unwind_info(result, unwind_info_kind);
-        }
-        isa.create_unwind_info(&self.func)
+        let backend = isa.get_mach_backend();
+        let unwind_info_kind = isa.unwind_info_kind();
+        let result = self.mach_compile_result.as_ref().unwrap();
+        backend.emit_unwind_info(result, unwind_info_kind)
     }
 
     /// Run the verifier on the function.

cranelift/codegen/src/isa/mod.rs

@@ -258,10 +258,8 @@ pub trait TargetIsa: fmt::Display + Send + Sync {
         None
     }
 
-    /// Get the new-style MachBackend, if this is an adapter around one.
-    fn get_mach_backend(&self) -> Option<&dyn MachBackend> {
-        None
-    }
+    /// Get the new-style MachBackend.
+    fn get_mach_backend(&self) -> &dyn MachBackend;
 }
 
 /// Methods implemented for free for target ISA!

cranelift/codegen/src/machinst/adapter.rs

@@ -55,8 +55,8 @@ impl TargetIsa for TargetIsaAdapter {
         self.backend.isa_flags()
     }
 
-    fn get_mach_backend(&self) -> Option<&dyn MachBackend> {
-        Some(&*self.backend)
+    fn get_mach_backend(&self) -> &dyn MachBackend {
+        &*self.backend
     }
 
     fn unsigned_add_overflow_condition(&self) -> ir::condcodes::IntCC {