impl janky codegen

Author: xacrimon

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -342,14 +342,14 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
 
 /// Codegen implementations for some terminator variants.
 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
-    #[allow(dead_code)]
     fn codegen_tail_call_terminator(
         &mut self,
         bx: &mut Bx,
         func: &mir::Operand<'tcx>,
         args: &[Spanned<mir::Operand<'tcx>>],
         fn_span: Span,
-    ) {
+        mergeable_succ: bool,
+    ) -> MergingSucc {
         // We don't need source_info as we already have fn_span for diagnostics
         let func = self.codegen_operand(bx, func);
         let fn_ty = func.layout.ty;
@@ -433,6 +433,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
         // Return the result - musttail requires ret immediately after the call
         bx.ret(llret);
+
+        assert_eq!(mergeable_succ, false);
+        MergingSucc::False
     }
 
     /// Generates code for a `Resume` terminator.
@@ -1483,12 +1486,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 fn_span,
                 mergeable_succ(),
             ),
-            mir::TerminatorKind::TailCall { .. } => {
-                // FIXME(explicit_tail_calls): implement tail calls in ssa backend
-                span_bug!(
-                    terminator.source_info.span,
-                    "`TailCall` terminator is not yet supported by `rustc_codegen_ssa`"
-                )
+            mir::TerminatorKind::TailCall { ref func, ref args, fn_span } => {
+                self.codegen_tail_call_terminator(bx, func, args, fn_span, mergeable_succ())
             }
             mir::TerminatorKind::CoroutineDrop | mir::TerminatorKind::Yield { .. } => {
                 bug!("coroutine ops in codegen")