From 434226256d3dad92065354897ba13196797b020c Mon Sep 17 00:00:00 2001
From: Camille GILLOT <gillot.camille@gmail.com>
Date: Sun, 5 Mar 2023 14:58:31 +0000
Subject: [PATCH] Fetch the value of has_ffi_unwind_calls before stealing
 mir_built.

---
 compiler/rustc_mir_transform/src/ffi_unwind_calls.rs | 5 ++---
 compiler/rustc_mir_transform/src/lib.rs              | 8 ++++++--
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs b/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs
index e6546911a2d0d..ffa1743b4efe5 100644
--- a/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs
+++ b/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs
@@ -47,14 +47,12 @@ fn has_ffi_unwind_calls(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> bool {
         return false;
     }
 
-    let body = &*tcx.mir_built(ty::WithOptConstParam::unknown(local_def_id)).borrow();
-
     let body_ty = tcx.type_of(def_id).skip_binder();
     let body_abi = match body_ty.kind() {
         ty::FnDef(..) => body_ty.fn_sig(tcx).abi(),
         ty::Closure(..) => Abi::RustCall,
         ty::Generator(..) => Abi::Rust,
-        _ => span_bug!(body.span, "unexpected body ty: {:?}", body_ty),
+        _ => span_bug!(tcx.def_span(def_id), "unexpected body ty: {:?}", body_ty),
     };
     let body_can_unwind = layout::fn_can_unwind(tcx, Some(def_id), body_abi);
 
@@ -65,6 +63,7 @@ fn has_ffi_unwind_calls(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> bool {
 
     let mut tainted = false;
 
+    let body = &*tcx.mir_built(ty::WithOptConstParam::unknown(local_def_id)).borrow();
     for block in body.basic_blocks.iter() {
         if block.is_cleanup {
             continue;
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index cdd28ae0c0197..128c5e2a05739 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -284,8 +284,12 @@ fn mir_const(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> &Steal<
         }
     }
 
-    // has_ffi_unwind_calls query uses the raw mir, so make sure it is run.
-    tcx.ensure().has_ffi_unwind_calls(def.did);
+    // has_ffi_unwind_calls query uses `mir_built(WithOptConstParam::unknown(def.did))`,
+    // so make sure it is run.
+    if def.const_param_did.is_none() {
+        // Actually fetch the value, to avoid having to compute the query later.
+        let _ = tcx.has_ffi_unwind_calls(def.did);
+    }
 
     let mut body = tcx.mir_built(def).steal();