diff --git a/compiler/rustc_const_eval/src/interpret/place.rs b/compiler/rustc_const_eval/src/interpret/place.rs
index 08d3165867c..baaee67e787 100644
--- a/compiler/rustc_const_eval/src/interpret/place.rs
+++ b/compiler/rustc_const_eval/src/interpret/place.rs
@@ -441,7 +441,7 @@ pub fn mplace_to_ref(
 
     /// Take an operand, representing a pointer, and dereference it to a place.
     /// Corresponds to the `*` operator in Rust.
-    #[instrument(skip(self), level = "debug")]
+    #[instrument(skip(self), level = "trace")]
     pub fn deref_pointer(
         &self,
         src: &impl Readable<'tcx, M::Provenance>,
@@ -533,7 +533,7 @@ pub fn local_to_place(
 
     /// Computes a place. You should only use this if you intend to write into this
     /// place; for reading, a more efficient alternative is `eval_place_to_op`.
-    #[instrument(skip(self), level = "debug")]
+    #[instrument(skip(self), level = "trace")]
     pub fn eval_place(
         &self,
         mir_place: mir::Place<'tcx>,
@@ -570,7 +570,7 @@ pub fn eval_place(
 
     /// Write an immediate to a place
     #[inline(always)]
-    #[instrument(skip(self), level = "debug")]
+    #[instrument(skip(self), level = "trace")]
     pub fn write_immediate(
         &mut self,
         src: Immediate<M::Provenance>,
@@ -808,7 +808,7 @@ pub fn copy_op(
     /// Copies the data from an operand to a place.
     /// `allow_transmute` indicates whether the layouts may disagree.
     #[inline(always)]
-    #[instrument(skip(self), level = "debug")]
+    #[instrument(skip(self), level = "trace")]
     fn copy_op_inner(
         &mut self,
         src: &impl Readable<'tcx, M::Provenance>,
@@ -837,7 +837,7 @@ fn copy_op_inner(
     /// `allow_transmute` indicates whether the layouts may disagree.
     /// Also, if you use this you are responsible for validating that things get copied at the
     /// right type.
-    #[instrument(skip(self), level = "debug")]
+    #[instrument(skip(self), level = "trace")]
     fn copy_op_no_validate(
         &mut self,
         src: &impl Readable<'tcx, M::Provenance>,
@@ -914,7 +914,7 @@ fn copy_op_no_validate(
     /// If the place currently refers to a local that doesn't yet have a matching allocation,
     /// create such an allocation.
     /// This is essentially `force_to_memplace`.
-    #[instrument(skip(self), level = "debug")]
+    #[instrument(skip(self), level = "trace")]
     pub fn force_allocation(
         &mut self,
         place: &PlaceTy<'tcx, M::Provenance>,
diff --git a/compiler/rustc_mir_transform/src/promote_consts.rs b/compiler/rustc_mir_transform/src/promote_consts.rs
index ecdca8292b4..3f4d2b65ff2 100644
--- a/compiler/rustc_mir_transform/src/promote_consts.rs
+++ b/compiler/rustc_mir_transform/src/promote_consts.rs
@@ -60,7 +60,7 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         let ccx = ConstCx::new(tcx, body);
         let (mut temps, all_candidates) = collect_temps_and_candidates(&ccx);
 
-        let promotable_candidates = validate_candidates(&ccx, &mut temps, &all_candidates);
+        let promotable_candidates = validate_candidates(&ccx, &mut temps, all_candidates);
 
         let promoted = promote_candidates(body, tcx, temps, promotable_candidates);
         self.promoted_fragments.set(promoted);
@@ -98,8 +98,8 @@ struct Collector<'a, 'tcx> {
 }
 
 impl<'tcx> Visitor<'tcx> for Collector<'_, 'tcx> {
+    #[instrument(level = "debug", skip(self))]
     fn visit_local(&mut self, index: Local, context: PlaceContext, location: Location) {
-        debug!("visit_local: index={:?} context={:?} location={:?}", index, context, location);
         // We're only interested in temporaries and the return place
         match self.ccx.body.local_kind(index) {
             LocalKind::Arg => return,
@@ -111,20 +111,15 @@ fn visit_local(&mut self, index: Local, context: PlaceContext, location: Locatio
         // then it's constant and thus drop is noop.
         // Non-uses are also irrelevant.
         if context.is_drop() || !context.is_use() {
-            debug!(
-                "visit_local: context.is_drop={:?} context.is_use={:?}",
-                context.is_drop(),
-                context.is_use(),
-            );
+            debug!(is_drop = context.is_drop(), is_use = context.is_use());
             return;
         }
 
         let temp = &mut self.temps[index];
-        debug!("visit_local: temp={:?}", temp);
+        debug!(?temp);
         *temp = match *temp {
             TempState::Undefined => match context {
-                PlaceContext::MutatingUse(MutatingUseContext::Store)
-                | PlaceContext::MutatingUse(MutatingUseContext::Call) => {
+                PlaceContext::MutatingUse(MutatingUseContext::Store | MutatingUseContext::Call) => {
                     TempState::Defined { location, uses: 0, valid: Err(()) }
                 }
                 _ => TempState::Unpromotable,
@@ -137,7 +132,7 @@ fn visit_local(&mut self, index: Local, context: PlaceContext, location: Locatio
                     | PlaceContext::NonMutatingUse(_) => true,
                     PlaceContext::MutatingUse(_) | PlaceContext::NonUse(_) => false,
                 };
-                debug!("visit_local: allowed_use={:?}", allowed_use);
+                debug!(?allowed_use);
                 if allowed_use {
                     *uses += 1;
                     return;
@@ -146,6 +141,7 @@ fn visit_local(&mut self, index: Local, context: PlaceContext, location: Locatio
             }
             TempState::Unpromotable | TempState::PromotedOut => TempState::Unpromotable,
         };
+        debug!(?temp);
     }
 
     fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
@@ -695,15 +691,12 @@ fn validate_call(
 fn validate_candidates(
     ccx: &ConstCx<'_, '_>,
     temps: &mut IndexSlice<Local, TempState>,
-    candidates: &[Candidate],
+    mut candidates: Vec<Candidate>,
 ) -> Vec<Candidate> {
     let mut validator = Validator { ccx, temps, promotion_safe_blocks: None };
 
+    candidates.retain(|&candidate| validator.validate_candidate(candidate).is_ok());
     candidates
-        .iter()
-        .copied()
-        .filter(|&candidate| validator.validate_candidate(candidate).is_ok())
-        .collect()
 }
 
 struct Promoter<'a, 'tcx> {
@@ -972,7 +965,12 @@ fn promote_candidates<'tcx>(
     candidates: Vec<Candidate>,
 ) -> IndexVec<Promoted, Body<'tcx>> {
     // Visit candidates in reverse, in case they're nested.
-    debug!("promote_candidates({:?})", candidates);
+    debug!(promote_candidates = ?candidates);
+
+    // eagerly fail fast
+    if candidates.is_empty() {
+        return IndexVec::new();
+    }
 
     let mut promotions = IndexVec::new();
 
diff --git a/library/panic_unwind/Cargo.toml b/library/panic_unwind/Cargo.toml
index dce2da31644..f830808d196 100644
--- a/library/panic_unwind/Cargo.toml
+++ b/library/panic_unwind/Cargo.toml
@@ -16,7 +16,7 @@ alloc = { path = "../alloc" }
 core = { path = "../core" }
 unwind = { path = "../unwind" }
 compiler_builtins = "0.1.0"
-cfg-if = "1.0"
+cfg-if = { version = "1.0", features = ['rustc-dep-of-std'] }
 
 [target.'cfg(not(all(windows, target_env = "msvc")))'.dependencies]
 libc = { version = "0.2", default-features = false }