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 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)
+        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 {

crates/cranelift/src/obj.rs

@@ -16,7 +16,7 @@
 use crate::debug::{DwarfSection, DwarfSectionRelocTarget};
 use crate::{CompiledFunction, Relocation, RelocationTarget};
 use anyhow::Result;
-use cranelift_codegen::binemit::{Addend, Reloc};
+use cranelift_codegen::binemit::Reloc;
 use cranelift_codegen::ir::LibCall;
 use cranelift_codegen::isa::{
     unwind::{systemv, UnwindInfo},
@@ -204,12 +204,9 @@ impl<'a> ObjectBuilder<'a> {
             systemv_unwind_info_id: None,
             systemv_unwind_info: Vec::new(),
             relocations: Vec::new(),
-            text: match isa.get_mach_backend() {
-                Some(backend) => backend.text_section_builder(
-                    (module.functions.len() - module.num_imported_funcs) as u32,
-                ),
-                None => Box::new(DummyBuilder::default()),
-            },
+            text: isa
+                .get_mach_backend()
+                .text_section_builder((module.functions.len() - module.num_imported_funcs) as u32),
             added_unwind_info: false,
         }
     }
@@ -627,37 +624,3 @@ impl<'a> ObjectBuilder<'a> {
         }
     }
 }
-
-#[derive(Default)]
-struct DummyBuilder {
-    data: Vec<u8>,
-}
-
-impl TextSectionBuilder for DummyBuilder {
-    fn append(&mut self, _named: bool, func: &[u8], align: u32) -> u64 {
-        while self.data.len() % align as usize != 0 {
-            self.data.push(0);
-        }
-        let pos = self.data.len() as u64;
-        self.data.extend_from_slice(func);
-        pos
-    }
-
-    fn resolve_reloc(
-        &mut self,
-        _offset: u64,
-        _reloc: Reloc,
-        _addend: Addend,
-        _target: u32,
-    ) -> bool {
-        false
-    }
-
-    fn force_veneers(&mut self) {
-        // not implemented
-    }
-
-    fn finish(&mut self) -> Vec<u8> {
-        mem::take(&mut self.data)
-    }
-}