From 9978261a6e38ca3583cdf3eb2956cb4d14cd5a6f Mon Sep 17 00:00:00 2001
From: Maybe Waffle <waffle.lapkin@gmail.com>
Date: Thu, 15 Feb 2024 19:54:37 +0000
Subject: [PATCH] Support tail calls in mir via `TerminatorKind::TailCall`

---
 src/base.rs     | 5 +++++
 src/constant.rs | 1 +
 2 files changed, 6 insertions(+)

diff --git a/src/base.rs b/src/base.rs
index c5b4277015a..5adbbb09ac8 100644
--- a/src/base.rs
+++ b/src/base.rs
@@ -491,6 +491,11 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
                     )
                 });
             }
+            // FIXME(explicit_tail_calls): add support for tail calls to the cranelift backend, once cranelift supports tail calls
+            TerminatorKind::TailCall { fn_span, .. } => span_bug!(
+                *fn_span,
+                "tail calls are not yet supported in `rustc_codegen_cranelift` backend"
+            ),
             TerminatorKind::InlineAsm {
                 template,
                 operands,
diff --git a/src/constant.rs b/src/constant.rs
index 87c5da3b7c3..fc12f0ff738 100644
--- a/src/constant.rs
+++ b/src/constant.rs
@@ -565,6 +565,7 @@ pub(crate) fn mir_operand_get_const_val<'tcx>(
                     {
                         return None;
                     }
+                    TerminatorKind::TailCall { .. } => return None,
                     TerminatorKind::Call { .. } => {}
                 }
             }