Rollup merge of #128688 - RalfJung:custom-mir-tail-calls, r=compiler-errors

custom MIR: add support for tail calls

Cc ``@WaffleLapkin``

2 files changed, 23 insertions, 0 deletions

diff --git a/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs b/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
index 3d4b706aa65..56896d945e5 100644
--- a/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
+++ b/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
@@ -75,6 +75,9 @@ impl<'tcx, 'body> ParseCtxt<'tcx, 'body> {
             @call(mir_call, args) => {
                 self.parse_call(args)
             },
+            @call(mir_tail_call, args) => {
+                self.parse_tail_call(args)
+            },
             ExprKind::Match { scrutinee, arms, .. } => {
                 let discr = self.parse_operand(*scrutinee)?;
                 self.parse_match(arms, expr.span).map(|t| TerminatorKind::SwitchInt { discr, targets: t })
@@ -187,6 +190,25 @@ impl<'tcx, 'body> ParseCtxt<'tcx, 'body> {
         )
     }
 
+    fn parse_tail_call(&self, args: &[ExprId]) -> PResult<TerminatorKind<'tcx>> {
+        parse_by_kind!(self, args[0], _, "tail call",
+            ExprKind::Call { fun, args, fn_span, .. } => {
+                let fun = self.parse_operand(*fun)?;
+                let args = args
+                    .iter()
+                    .map(|arg|
+                        Ok(Spanned { node: self.parse_operand(*arg)?, span: self.thir.exprs[*arg].span  } )
+                    )
+                    .collect::<PResult<Box<[_]>>>()?;
+                Ok(TerminatorKind::TailCall {
+                    func: fun,
+                    args,
+                    fn_span: *fn_span,
+                })
+            },
+        )
+    }
+
     fn parse_rvalue(&self, expr_id: ExprId) -> PResult<Rvalue<'tcx>> {
         parse_by_kind!(self, expr_id, expr, "rvalue",
             @call(mir_discriminant, args) => self.parse_place(args[0]).map(Rvalue::Discriminant),
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 9977fa7425a..94cf21da4ef 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1216,6 +1216,7 @@ symbols! {
         mir_static_mut,
         mir_storage_dead,
         mir_storage_live,
+        mir_tail_call,
         mir_unreachable,
         mir_unwind_cleanup,
         mir_unwind_continue,