Refactor unwind; add FDE support. (#1320)

* Refactor unwind

* add FDE support

* use sink directly in emit functions

* pref off all unwinding generation with feature

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

@@ -3,14 +3,19 @@
 mod abi;
 mod binemit;
 mod enc_tables;
+#[cfg(feature = "unwind")]
+mod fde;
 mod registers;
 pub mod settings;
+#[cfg(feature = "unwind")]
 mod unwind;
 
 use super::super::settings as shared_settings;
 #[cfg(feature = "testing_hooks")]
 use crate::binemit::CodeSink;
 use crate::binemit::{emit_function, MemoryCodeSink};
+#[cfg(feature = "unwind")]
+use crate::binemit::{FrameUnwindKind, FrameUnwindSink};
 use crate::ir;
 use crate::isa::enc_tables::{self as shared_enc_tables, lookup_enclist, Encodings};
 use crate::isa::Builder as IsaBuilder;
@@ -20,7 +25,6 @@ use crate::result::CodegenResult;
 use crate::timing;
 use alloc::borrow::Cow;
 use alloc::boxed::Box;
-use alloc::vec::Vec;
 use core::fmt;
 use target_lexicon::{PointerWidth, Triple};
 
@@ -157,8 +161,14 @@ impl TargetIsa for Isa {
     /// Emit unwind information for the given function.
     ///
     /// Only some calling conventions (e.g. Windows fastcall) will have unwind information.
-    fn emit_unwind_info(&self, func: &ir::Function, mem: &mut Vec<u8>) {
-        abi::emit_unwind_info(func, self, mem);
+    #[cfg(feature = "unwind")]
+    fn emit_unwind_info(
+        &self,
+        func: &ir::Function,
+        kind: FrameUnwindKind,
+        sink: &mut dyn FrameUnwindSink,
+    ) {
+        abi::emit_unwind_info(func, self, kind, sink);
     }
 }