Auto merge of #147791 - cuviper:beta-next, r=cuviper

[beta] backports

- Change int-to-ptr transmute lowering back to inttoptr rust-lang/rust#147541
- rewrite outlives placeholder constraints to outlives static when handling opaque types rust-lang/rust#147566
- GVN: Invalidate derefs at loop headers rust-lang/rust#147607

r? cuviper

compiler/rustc_borrowck/src/handle_placeholders.rs

@@ -348,7 +348,7 @@ pub(crate) fn compute_sccs_applying_placeholder_outlives_constraints<'tcx>(
     }
 }
 
-fn rewrite_placeholder_outlives<'tcx>(
+pub(crate) fn rewrite_placeholder_outlives<'tcx>(
     sccs: &Sccs<RegionVid, ConstraintSccIndex>,
     annotations: &SccAnnotations<'_, '_, RegionTracker>,
     fr_static: RegionVid,

compiler/rustc_borrowck/src/region_infer/opaque_types/member_constraints.rs

@@ -39,7 +39,7 @@ pub(super) fn apply_member_constraints<'tcx>(
     debug!(?member_constraints);
     for scc_a in rcx.constraint_sccs.all_sccs() {
         debug!(?scc_a);
-        // Start by  adding the region values required by outlives constraints. This
+        // Start by adding the region values required by outlives constraints. This
         // matches how we compute the final region values in `fn compute_regions`.
         //
         // We need to do this here to get a lower bound when applying member constraints.
@@ -64,6 +64,7 @@ fn apply_member_constraint<'tcx>(
     // If the member region lives in a higher universe, we currently choose
     // the most conservative option by leaving it unchanged.
     if !rcx.max_placeholder_universe_reached(member).is_root() {
+        debug!("member region reached non root universe, bailing");
         return;
     }
 

compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs

@@ -254,6 +254,10 @@ fn collect_defining_uses<'tcx>(
                 }
             } else {
                 errors.push(DeferredOpaqueTypeError::InvalidOpaqueTypeArgs(err));
+                debug!(
+                    "collect_defining_uses: InvalidOpaqueTypeArgs for {:?} := {:?}",
+                    non_nll_opaque_type_key, hidden_type
+                );
             }
             continue;
         }
@@ -277,6 +281,7 @@ fn collect_defining_uses<'tcx>(
     defining_uses
 }
 
+#[instrument(level = "debug", skip(rcx, concrete_opaque_types, defining_uses, errors))]
 fn compute_concrete_types_from_defining_uses<'tcx>(
     rcx: &RegionCtxt<'_, 'tcx>,
     concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
@@ -288,6 +293,7 @@ fn compute_concrete_types_from_defining_uses<'tcx>(
     let mut decls_modulo_regions: FxIndexMap<OpaqueTypeKey<'tcx>, (OpaqueTypeKey<'tcx>, Span)> =
         FxIndexMap::default();
     for &DefiningUse { opaque_type_key, ref arg_regions, hidden_type } in defining_uses {
+        debug!(?opaque_type_key, ?arg_regions, ?hidden_type);
         // After applying member constraints, we now map all regions in the hidden type
         // to the `arg_regions` of this defining use. In case a region in the hidden type
         // ended up not being equal to any such region, we error.
@@ -295,6 +301,7 @@ fn compute_concrete_types_from_defining_uses<'tcx>(
             match hidden_type.try_fold_with(&mut ToArgRegionsFolder::new(rcx, arg_regions)) {
                 Ok(hidden_type) => hidden_type,
                 Err(r) => {
+                    debug!("UnexpectedHiddenRegion: {:?}", r);
                     errors.push(DeferredOpaqueTypeError::UnexpectedHiddenRegion {
                         hidden_type,
                         opaque_type_key,

compiler/rustc_borrowck/src/region_infer/opaque_types/region_ctxt.rs

@@ -11,7 +11,9 @@ use crate::constraints::ConstraintSccIndex;
 use crate::handle_placeholders::{SccAnnotations, region_definitions};
 use crate::region_infer::reverse_sccs::ReverseSccGraph;
 use crate::region_infer::values::RegionValues;
-use crate::region_infer::{ConstraintSccs, RegionDefinition, RegionTracker, Representative};
+use crate::region_infer::{
+    ConstraintSccs, OutlivesConstraintSet, RegionDefinition, RegionTracker, Representative,
+};
 use crate::type_check::MirTypeckRegionConstraints;
 use crate::type_check::free_region_relations::UniversalRegionRelations;
 use crate::universal_regions::UniversalRegions;
@@ -39,16 +41,36 @@ impl<'a, 'tcx> RegionCtxt<'a, 'tcx> {
         location_map: Rc<DenseLocationMap>,
         constraints: &MirTypeckRegionConstraints<'tcx>,
     ) -> RegionCtxt<'a, 'tcx> {
+        let mut outlives_constraints = constraints.outlives_constraints.clone();
         let universal_regions = &universal_region_relations.universal_regions;
         let (definitions, _has_placeholders) = region_definitions(infcx, universal_regions);
+
+        let compute_sccs =
+            |outlives_constraints: &OutlivesConstraintSet<'tcx>,
+             annotations: &mut SccAnnotations<'_, 'tcx, RegionTracker>| {
+                ConstraintSccs::new_with_annotation(
+                    &outlives_constraints
+                        .graph(definitions.len())
+                        .region_graph(outlives_constraints, universal_regions.fr_static),
+                    annotations,
+                )
+            };
+
         let mut scc_annotations = SccAnnotations::init(&definitions);
-        let constraint_sccs = ConstraintSccs::new_with_annotation(
-            &constraints
-                .outlives_constraints
-                .graph(definitions.len())
-                .region_graph(&constraints.outlives_constraints, universal_regions.fr_static),
-            &mut scc_annotations,
+        let mut constraint_sccs = compute_sccs(&outlives_constraints, &mut scc_annotations);
+
+        let added_constraints = crate::handle_placeholders::rewrite_placeholder_outlives(
+            &constraint_sccs,
+            &scc_annotations,
+            universal_regions.fr_static,
+            &mut outlives_constraints,
         );
+
+        if added_constraints {
+            scc_annotations = SccAnnotations::init(&definitions);
+            constraint_sccs = compute_sccs(&outlives_constraints, &mut scc_annotations);
+        }
+
         let scc_annotations = scc_annotations.scc_to_annotation;
 
         // Unlike the `RegionInferenceContext`, we only care about free regions

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -1048,14 +1048,14 @@ pub(super) fn transmute_scalar<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     imm = match (from_scalar.primitive(), to_scalar.primitive()) {
         (Int(..) | Float(_), Int(..) | Float(_)) => bx.bitcast(imm, to_backend_ty),
         (Pointer(..), Pointer(..)) => bx.pointercast(imm, to_backend_ty),
-        (Int(..), Pointer(..)) => bx.ptradd(bx.const_null(bx.type_ptr()), imm),
+        (Int(..), Pointer(..)) => bx.inttoptr(imm, to_backend_ty),
         (Pointer(..), Int(..)) => {
             // FIXME: this exposes the provenance, which shouldn't be necessary.
             bx.ptrtoint(imm, to_backend_ty)
         }
         (Float(_), Pointer(..)) => {
             let int_imm = bx.bitcast(imm, bx.cx().type_isize());
-            bx.ptradd(bx.const_null(bx.type_ptr()), int_imm)
+            bx.inttoptr(int_imm, to_backend_ty)
         }
         (Pointer(..), Float(_)) => {
             // FIXME: this exposes the provenance, which shouldn't be necessary.

compiler/rustc_middle/src/mir/loops.rs

@@ -0,0 +1,29 @@
+use rustc_index::bit_set::DenseBitSet;
+
+use super::*;
+
+/// Compute the set of loop headers in the given body. A loop header is usually defined as a block
+/// which dominates one of its predecessors. This definition is only correct for reducible CFGs.
+/// However, computing dominators is expensive, so we approximate according to the post-order
+/// traversal order. A loop header for us is a block which is visited after its predecessor in
+/// post-order. This is ok as we mostly need a heuristic.
+pub fn maybe_loop_headers(body: &Body<'_>) -> DenseBitSet<BasicBlock> {
+    let mut maybe_loop_headers = DenseBitSet::new_empty(body.basic_blocks.len());
+    let mut visited = DenseBitSet::new_empty(body.basic_blocks.len());
+    for (bb, bbdata) in traversal::postorder(body) {
+        // Post-order means we visit successors before the block for acyclic CFGs.
+        // If the successor is not visited yet, consider it a loop header.
+        for succ in bbdata.terminator().successors() {
+            if !visited.contains(succ) {
+                maybe_loop_headers.insert(succ);
+            }
+        }
+
+        // Only mark `bb` as visited after we checked the successors, in case we have a self-loop.
+        //     bb1: goto -> bb1;
+        let _new = visited.insert(bb);
+        debug_assert!(_new);
+    }
+
+    maybe_loop_headers
+}

compiler/rustc_middle/src/mir/mod.rs

@@ -51,6 +51,7 @@ mod statement;
 mod syntax;
 mod terminator;
 
+pub mod loops;
 pub mod traversal;
 pub mod visit;
 

compiler/rustc_mir_transform/src/gvn.rs

@@ -126,6 +126,7 @@ impl<'tcx> crate::MirPass<'tcx> for GVN {
         let ssa = SsaLocals::new(tcx, body, typing_env);
         // Clone dominators because we need them while mutating the body.
         let dominators = body.basic_blocks.dominators().clone();
+        let maybe_loop_headers = loops::maybe_loop_headers(body);
 
         let mut state = VnState::new(tcx, body, typing_env, &ssa, dominators, &body.local_decls);
 
@@ -136,6 +137,11 @@ impl<'tcx> crate::MirPass<'tcx> for GVN {
 
         let reverse_postorder = body.basic_blocks.reverse_postorder().to_vec();
         for bb in reverse_postorder {
+            // N.B. With loops, reverse postorder cannot produce a valid topological order.
+            // A statement or terminator from inside the loop, that is not processed yet, may have performed an indirect write.
+            if maybe_loop_headers.contains(bb) {
+                state.invalidate_derefs();
+            }
             let data = &mut body.basic_blocks.as_mut_preserves_cfg()[bb];
             state.visit_basic_block_data(bb, data);
         }

compiler/rustc_mir_transform/src/jump_threading.rs

@@ -84,7 +84,7 @@ impl<'tcx> crate::MirPass<'tcx> for JumpThreading {
             body,
             arena,
             map: Map::new(tcx, body, Some(MAX_PLACES)),
-            loop_headers: loop_headers(body),
+            loop_headers: loops::maybe_loop_headers(body),
             opportunities: Vec::new(),
         };
 
@@ -832,21 +832,3 @@ enum Update {
     Incr,
     Decr,
 }
-
-/// Compute the set of loop headers in the given body. We define a loop header as a block which has
-/// at least a predecessor which it dominates. This definition is only correct for reducible CFGs.
-/// But if the CFG is already irreducible, there is no point in trying much harder.
-/// is already irreducible.
-fn loop_headers(body: &Body<'_>) -> DenseBitSet<BasicBlock> {
-    let mut loop_headers = DenseBitSet::new_empty(body.basic_blocks.len());
-    let dominators = body.basic_blocks.dominators();
-    // Only visit reachable blocks.
-    for (bb, bbdata) in traversal::preorder(body) {
-        for succ in bbdata.terminator().successors() {
-            if dominators.dominates(succ, bb) {
-                loop_headers.insert(succ);
-            }
-        }
-    }
-    loop_headers
-}

tests/codegen-llvm/common_prim_int_ptr.rs

@@ -11,7 +11,7 @@
 #[no_mangle]
 pub fn insert_int(x: usize) -> Result<usize, Box<()>> {
     // CHECK: start:
-    // CHECK-NEXT: %[[WO_PROV:.+]] = getelementptr i8, ptr null, [[USIZE:i[0-9]+]] %x
+    // CHECK-NEXT: %[[WO_PROV:.+]] = inttoptr [[USIZE:i[0-9]+]] %x to ptr
     // CHECK-NEXT: %[[R:.+]] = insertvalue { [[USIZE]], ptr } { [[USIZE]] 0, ptr poison }, ptr %[[WO_PROV]], 1
     // CHECK-NEXT: ret { [[USIZE]], ptr } %[[R]]
     Ok(x)

tests/codegen-llvm/enum/enum-aggregate.rs

@@ -71,7 +71,7 @@ fn make_ok_ptr(x: NonNull<u16>) -> Result<NonNull<u16>, usize> {
 fn make_ok_int(x: usize) -> Result<usize, NonNull<u16>> {
     // CHECK-LABEL: { i64, ptr } @make_ok_int(i64 %x)
     // CHECK-NEXT: start:
-    // CHECK-NEXT: %[[NOPROV:.+]] = getelementptr i8, ptr null, i64 %x
+    // CHECK-NEXT: %[[NOPROV:.+]] = inttoptr i64 %x to ptr
     // CHECK-NEXT: %[[R:.+]] = insertvalue { i64, ptr } { i64 0, ptr poison }, ptr %[[NOPROV]], 1
     // CHECK-NEXT: ret { i64, ptr } %[[R]]
     Ok(x)

tests/codegen-llvm/int-ptr-int-enum-miscompile.rs

@@ -0,0 +1,22 @@
+// This is a regression test for https://github.com/rust-lang/rust/issues/147265.
+
+//@ compile-flags: -Copt-level=3
+
+#![crate_type = "lib"]
+
+#[no_mangle]
+pub fn mk_result(a: usize) -> Result<u8, *const u8> {
+    // CHECK-LABEL: @mk_result
+    // CHECK-NOT: unreachable
+    // CHECK: load i8,
+    // CHECK-NOT: unreachable
+    match g(a) {
+        Ok(b) => Ok(unsafe { *(b as *const u8) }),
+        Err(c) => Err(c),
+    }
+}
+
+#[cold]
+fn g(a: usize) -> Result<usize, *const u8> {
+    Ok(a)
+}

tests/codegen-llvm/intrinsics/transmute-niched.rs

@@ -249,7 +249,7 @@ pub unsafe fn check_four_or_eight_to_nonnull(x: FourOrEight) -> NonNull<u8> {
     // OPT: call void @llvm.assume(i1 %1)
     // CHECK-NOT: icmp
     // CHECK-NOT: assume
-    // CHECK: %[[RET:.+]] = getelementptr i8, ptr null, i64 %x
+    // CHECK: %[[RET:.+]] = inttoptr i64 %x to ptr
     // CHECK-NEXT: ret ptr %[[RET]]
 
     transmute(x)

tests/codegen-llvm/intrinsics/transmute.rs

@@ -303,7 +303,7 @@ pub unsafe fn check_pair_with_bool(x: (u8, bool)) -> (bool, i8) {
 pub unsafe fn check_float_to_pointer(x: f64) -> *const () {
     // CHECK-NOT: alloca
     // CHECK: %0 = bitcast double %x to i64
-    // CHECK: %_0 = getelementptr i8, ptr null, i64 %0
+    // CHECK: %_0 = inttoptr i64 %0 to ptr
     // CHECK: ret ptr %_0
     transmute(x)
 }
@@ -378,7 +378,7 @@ pub unsafe fn check_issue_110005(x: (usize, bool)) -> Option<Box<[u8]>> {
 // CHECK-LABEL: @check_pair_to_dst_ref(
 #[no_mangle]
 pub unsafe fn check_pair_to_dst_ref<'a>(x: (usize, usize)) -> &'a [u8] {
-    // CHECK: %_0.0 = getelementptr i8, ptr null, i64 %x.0
+    // CHECK: %_0.0 = inttoptr i64 %x.0 to ptr
     // CHECK: %0 = icmp ne ptr %_0.0, null
     // CHECK: call void @llvm.assume(i1 %0)
     // CHECK: %1 = insertvalue { ptr, i64 } poison, ptr %_0.0, 0

tests/codegen-llvm/transmute-scalar.rs

@@ -56,7 +56,7 @@ pub fn ptr_to_int(p: *mut u16) -> usize {
 }
 
 // CHECK: define{{.*}}ptr @int_to_ptr([[USIZE]] %i)
-// CHECK: %_0 = getelementptr i8, ptr null, [[USIZE]] %i
+// CHECK: %_0 = inttoptr [[USIZE]] %i to ptr
 // CHECK-NEXT: ret ptr %_0
 #[no_mangle]
 pub fn int_to_ptr(i: usize) -> *mut u16 {

tests/mir-opt/gvn_loop.loop_deref_mut.GVN.diff

@@ -0,0 +1,115 @@
+- // MIR for `loop_deref_mut` before GVN
++ // MIR for `loop_deref_mut` after GVN
+  
+  fn loop_deref_mut(_1: &mut Value) -> Value {
+      debug val => _1;
+      let mut _0: Value;
+      let _2: &Value;
+      let _3: &Value;
+      let mut _4: &Value;
+      let mut _6: !;
+      let mut _8: isize;
+      let mut _9: !;
+      let mut _10: ();
+      let mut _12: i32;
+      let _13: ();
+      let mut _14: bool;
+      let mut _15: !;
+      let mut _16: Value;
+      scope 1 {
+          debug val_alias => _2;
+          let mut _5: bool;
+          scope 2 {
+              debug stop => _5;
+              let _7: i32;
+              scope 3 {
+                  debug v => _7;
+                  let _11: Value;
+                  scope 4 {
+                      debug v => _11;
+                  }
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_2);
+-         StorageLive(_3);
++         nop;
+          StorageLive(_4);
+          _4 = &(*_1);
+          _3 = get::<Value>(move _4) -> [return: bb1, unwind unreachable];
+      }
+  
+      bb1: {
+          _2 = &(*_3);
+          StorageDead(_4);
+-         StorageDead(_3);
++         nop;
+          StorageLive(_5);
+          _5 = const false;
+-         _8 = discriminant((*_2));
++         _8 = discriminant((*_3));
+          switchInt(move _8) -> [0: bb3, otherwise: bb2];
+      }
+  
+      bb2: {
+          unreachable;
+      }
+  
+      bb3: {
+-         StorageLive(_7);
+-         _7 = copy (((*_2) as V0).0: i32);
++         nop;
++         _7 = copy (((*_3) as V0).0: i32);
+          StorageLive(_9);
+          goto -> bb4;
+      }
+  
+      bb4: {
+          StorageLive(_11);
+          StorageLive(_12);
+          _12 = copy _7;
+-         _11 = Value::V0(move _12);
++         _11 = Value::V0(copy _7);
+          StorageDead(_12);
+          StorageLive(_13);
+          StorageLive(_14);
+          _14 = copy _5;
+          switchInt(move _14) -> [0: bb6, otherwise: bb5];
+      }
+  
+      bb5: {
+          _0 = move _11;
+          StorageDead(_14);
+          StorageDead(_13);
+          StorageDead(_11);
+          StorageDead(_9);
+-         StorageDead(_7);
++         nop;
+          StorageDead(_5);
+          StorageDead(_2);
+          return;
+      }
+  
+      bb6: {
+          _13 = const ();
+          StorageDead(_14);
+          StorageDead(_13);
+          _5 = const true;
+          StorageLive(_16);
+-         _16 = Value::V1;
+-         (*_1) = move _16;
++         _16 = const Value::V1;
++         (*_1) = const Value::V1;
+          StorageDead(_16);
+          _10 = const ();
+          StorageDead(_11);
+          goto -> bb4;
+      }
++ }
++ 
++ ALLOC0 (size: 8, align: 4) {
++     01 00 00 00 __ __ __ __                         │ ....░░░░
+  }
+  

tests/mir-opt/gvn_loop.rs

@@ -0,0 +1,39 @@
+//@ test-mir-pass: GVN
+
+#![crate_type = "lib"]
+#![feature(core_intrinsics, rustc_attrs)]
+
+pub enum Value {
+    V0(i32),
+    V1,
+}
+
+// Check that we do not use the dereferenced value of `val_alias` when returning.
+
+// EMIT_MIR gvn_loop.loop_deref_mut.GVN.diff
+fn loop_deref_mut(val: &mut Value) -> Value {
+    // CHECK-LABEL: fn loop_deref_mut(
+    // CHECK: [[VAL_REF:_.*]] = get::<Value>(
+    // CHECK: [[V:_.*]] = copy (((*[[VAL_REF]]) as V0).0: i32);
+    // CEHCK-NOT: copy (*[[VAL_REF]]);
+    // CHECK: [[RET:_*]] = Value::V0(copy [[V]]);
+    // CEHCK-NOT: copy (*[[VAL_REF]]);
+    // CHECK: _0 = move [[RET]]
+    let val_alias: &Value = get(val);
+    let mut stop = false;
+    let Value::V0(v) = *val_alias else { unsafe { core::intrinsics::unreachable() } };
+    loop {
+        let v = Value::V0(v);
+        if stop {
+            return v;
+        }
+        stop = true;
+        *val = Value::V1;
+    }
+}
+
+#[inline(never)]
+#[rustc_nounwind]
+fn get<T>(v: &T) -> &T {
+    v
+}

tests/ui/impl-trait/member-constraints/placeholders_lift_to_static.rs

@@ -0,0 +1,33 @@
+//@ check-pass
+
+// We have some `RPIT` with an item bound of `for<'a> Outlives<'a>`. We
+// infer a hidden type of `&'?x i32` where `'?x` is required to outlive
+// some placeholder `'!a` due to the `for<'a> Outlives<'a>` item bound.
+//
+// We previously did not write constraints of the form `'?x: '!a` into
+// `'?x: 'static`. This caused member constraints to bail and not consider
+// `'?x` to be constrained to an arg region.
+
+pub trait Outlives<'a> {}
+impl<'a, T: 'a> Outlives<'a> for T {}
+
+pub fn foo() -> impl for<'a> Outlives<'a> {
+    let x: &'static i32 = &1;
+    x
+}
+
+// This *didn't* regress but feels like it's "the same thing" so
+// test it anyway
+pub fn bar() -> impl Sized {
+    let x: &'static i32 = &1;
+    hr_outlives(x)
+}
+
+fn hr_outlives<T>(v: T) -> T
+where
+    for<'a> T: 'a
+{
+    v
+}
+
+fn main() {}

tests/ui/impl-trait/nested-rpit-hrtb.rs

@@ -48,7 +48,6 @@ fn one_hrtb_mention_fn_trait_param_uses<'b>() -> impl for<'a> Bar<'a, Assoc = im
 // This should resolve.
 fn one_hrtb_mention_fn_outlives_uses<'b>() -> impl for<'a> Bar<'a, Assoc = impl Sized + 'b> {}
 //~^ ERROR implementation of `Bar` is not general enough
-//~| ERROR lifetime may not live long enough
 
 // This should resolve.
 fn two_htrb_trait_param() -> impl for<'a> Foo<'a, Assoc = impl for<'b> Qux<'b>> {}

tests/ui/impl-trait/nested-rpit-hrtb.stderr

@@ -1,5 +1,5 @@
 error[E0261]: use of undeclared lifetime name `'b`
-  --> $DIR/nested-rpit-hrtb.rs:57:77
+  --> $DIR/nested-rpit-hrtb.rs:56:77
    |
 LL | fn two_htrb_outlives() -> impl for<'a> Foo<'a, Assoc = impl for<'b> Sized + 'b> {}
    |                                                                             ^^ undeclared lifetime
@@ -15,7 +15,7 @@ LL | fn two_htrb_outlives<'b>() -> impl for<'a> Foo<'a, Assoc = impl for<'b> Siz
    |                     ++++
 
 error[E0261]: use of undeclared lifetime name `'b`
-  --> $DIR/nested-rpit-hrtb.rs:65:82
+  --> $DIR/nested-rpit-hrtb.rs:64:82
    |
 LL | fn two_htrb_outlives_uses() -> impl for<'a> Bar<'a, Assoc = impl for<'b> Sized + 'b> {}
    |                                                                                  ^^ undeclared lifetime
@@ -87,12 +87,6 @@ LL | fn one_hrtb_mention_fn_trait_param_uses<'b>() -> impl for<'a> Bar<'a, Assoc
            but trait `Qux<'_>` is implemented for `()`
    = help: for that trait implementation, expected `()`, found `&'a ()`
 
-error: lifetime may not live long enough
-  --> $DIR/nested-rpit-hrtb.rs:49:93
-   |
-LL | fn one_hrtb_mention_fn_outlives_uses<'b>() -> impl for<'a> Bar<'a, Assoc = impl Sized + 'b> {}
-   |                                      -- lifetime `'b` defined here                          ^^ opaque type requires that `'b` must outlive `'static`
-
 error: implementation of `Bar` is not general enough
   --> $DIR/nested-rpit-hrtb.rs:49:93
    |
@@ -103,7 +97,7 @@ LL | fn one_hrtb_mention_fn_outlives_uses<'b>() -> impl for<'a> Bar<'a, Assoc =
    = note: ...but it actually implements `Bar<'0>`, for some specific lifetime `'0`
 
 error[E0277]: the trait bound `for<'a, 'b> &'a (): Qux<'b>` is not satisfied
-  --> $DIR/nested-rpit-hrtb.rs:61:64
+  --> $DIR/nested-rpit-hrtb.rs:60:64
    |
 LL | fn two_htrb_trait_param_uses() -> impl for<'a> Bar<'a, Assoc = impl for<'b> Qux<'b>> {}
    |                                                                ^^^^^^^^^^^^^^^^^^^^ the trait `for<'a, 'b> Qux<'b>` is not implemented for `&'a ()`
@@ -112,7 +106,7 @@ LL | fn two_htrb_trait_param_uses() -> impl for<'a> Bar<'a, Assoc = impl for<'b>
            but trait `Qux<'_>` is implemented for `()`
    = help: for that trait implementation, expected `()`, found `&'a ()`
 
-error: aborting due to 10 previous errors
+error: aborting due to 9 previous errors
 
 Some errors have detailed explanations: E0261, E0277, E0657.
 For more information about an error, try `rustc --explain E0261`.

tests/ui/mir/gvn-loop-miscompile.rs

@@ -0,0 +1,34 @@
+//@ compile-flags: -O
+//@ run-pass
+
+pub enum Value {
+    V0(i32),
+    V1,
+}
+
+fn set_discriminant(val: &mut Value) -> Value {
+    let val_alias: &Value = get(val);
+    let mut stop = false;
+    let Value::V0(v) = *val_alias else {
+        unreachable!();
+    };
+    loop {
+        let v = Value::V0(v);
+        if stop {
+            return v;
+        }
+        stop = true;
+        *val = Value::V1;
+    }
+}
+
+fn main() {
+    let mut v = Value::V0(1);
+    let v = set_discriminant(&mut v);
+    assert!(matches!(v, Value::V0(1)));
+}
+
+#[inline(never)]
+fn get<T>(v: &T) -> &T {
+    v
+}

tests/ui/nll/ice-106874.stderr

@@ -17,75 +17,77 @@ LL |     A(B(C::new(D::new(move |st| f(st)))))
    = note: ...but it actually implements `FnOnce<(&'1 mut V,)>`, for some specific lifetime `'1`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: implementation of `FnOnce` is not general enough
-  --> $DIR/ice-106874.rs:8:7
+error: higher-ranked subtype error
+  --> $DIR/ice-106874.rs:8:5
    |
 LL |     A(B(C::new(D::new(move |st| f(st)))))
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough
-   |
-   = note: closure with signature `fn(&'2 mut V)` must implement `FnOnce<(&'1 mut V,)>`, for any lifetime `'1`...
-   = note: ...but it actually implements `FnOnce<(&'2 mut V,)>`, for some specific lifetime `'2`
-
-error: implementation of `Fn` is not general enough
-  --> $DIR/ice-106874.rs:8:7
-   |
-LL |     A(B(C::new(D::new(move |st| f(st)))))
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Fn` is not general enough
-   |
-   = note: closure with signature `fn(&'2 mut V)` must implement `Fn<(&'1 mut V,)>`, for any lifetime `'1`...
-   = note: ...but it actually implements `Fn<(&'2 mut V,)>`, for some specific lifetime `'2`
-
-error: implementation of `FnOnce` is not general enough
-  --> $DIR/ice-106874.rs:8:7
-   |
-LL |     A(B(C::new(D::new(move |st| f(st)))))
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough
-   |
-   = note: closure with signature `fn(&'2 mut V)` must implement `FnOnce<(&'1 mut V,)>`, for any lifetime `'1`...
-   = note: ...but it actually implements `FnOnce<(&'2 mut V,)>`, for some specific lifetime `'2`
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error: implementation of `Fn` is not general enough
-  --> $DIR/ice-106874.rs:8:7
-   |
-LL |     A(B(C::new(D::new(move |st| f(st)))))
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Fn` is not general enough
-   |
-   = note: closure with signature `fn(&'2 mut V)` must implement `Fn<(&'1 mut V,)>`, for any lifetime `'1`...
-   = note: ...but it actually implements `Fn<(&'2 mut V,)>`, for some specific lifetime `'2`
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error: implementation of `FnOnce` is not general enough
-  --> $DIR/ice-106874.rs:8:7
-   |
-LL |     A(B(C::new(D::new(move |st| f(st)))))
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough
-   |
-   = note: closure with signature `fn(&'2 mut V)` must implement `FnOnce<(&'1 mut V,)>`, for any lifetime `'1`...
-   = note: ...but it actually implements `FnOnce<(&'2 mut V,)>`, for some specific lifetime `'2`
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error: implementation of `Fn` is not general enough
-  --> $DIR/ice-106874.rs:8:7
-   |
-LL |     A(B(C::new(D::new(move |st| f(st)))))
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Fn` is not general enough
-   |
-   = note: closure with signature `fn(&'2 mut V)` must implement `Fn<(&'1 mut V,)>`, for any lifetime `'1`...
-   = note: ...but it actually implements `Fn<(&'2 mut V,)>`, for some specific lifetime `'2`
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: higher-ranked subtype error
+  --> $DIR/ice-106874.rs:8:5
+   |
+LL |     A(B(C::new(D::new(move |st| f(st)))))
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: implementation of `FnOnce` is not general enough
   --> $DIR/ice-106874.rs:8:7
    |
 LL |     A(B(C::new(D::new(move |st| f(st)))))
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough
+   |
+   = note: closure with signature `fn(&'2 mut V)` must implement `FnOnce<(&'1 mut V,)>`, for any lifetime `'1`...
+   = note: ...but it actually implements `FnOnce<(&'2 mut V,)>`, for some specific lifetime `'2`
 
-error: higher-ranked subtype error
-  --> $DIR/ice-106874.rs:8:41
+error: implementation of `Fn` is not general enough
+  --> $DIR/ice-106874.rs:8:7
    |
 LL |     A(B(C::new(D::new(move |st| f(st)))))
-   |                                         ^
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Fn` is not general enough
+   |
+   = note: closure with signature `fn(&'2 mut V)` must implement `Fn<(&'1 mut V,)>`, for any lifetime `'1`...
+   = note: ...but it actually implements `Fn<(&'2 mut V,)>`, for some specific lifetime `'2`
+
+error: implementation of `FnOnce` is not general enough
+  --> $DIR/ice-106874.rs:8:7
+   |
+LL |     A(B(C::new(D::new(move |st| f(st)))))
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough
+   |
+   = note: closure with signature `fn(&'2 mut V)` must implement `FnOnce<(&'1 mut V,)>`, for any lifetime `'1`...
+   = note: ...but it actually implements `FnOnce<(&'2 mut V,)>`, for some specific lifetime `'2`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: implementation of `Fn` is not general enough
+  --> $DIR/ice-106874.rs:8:7
+   |
+LL |     A(B(C::new(D::new(move |st| f(st)))))
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Fn` is not general enough
+   |
+   = note: closure with signature `fn(&'2 mut V)` must implement `Fn<(&'1 mut V,)>`, for any lifetime `'1`...
+   = note: ...but it actually implements `Fn<(&'2 mut V,)>`, for some specific lifetime `'2`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: implementation of `FnOnce` is not general enough
+  --> $DIR/ice-106874.rs:8:7
+   |
+LL |     A(B(C::new(D::new(move |st| f(st)))))
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough
+   |
+   = note: closure with signature `fn(&'2 mut V)` must implement `FnOnce<(&'1 mut V,)>`, for any lifetime `'1`...
+   = note: ...but it actually implements `FnOnce<(&'2 mut V,)>`, for some specific lifetime `'2`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: implementation of `Fn` is not general enough
+  --> $DIR/ice-106874.rs:8:7
+   |
+LL |     A(B(C::new(D::new(move |st| f(st)))))
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Fn` is not general enough
+   |
+   = note: closure with signature `fn(&'2 mut V)` must implement `Fn<(&'1 mut V,)>`, for any lifetime `'1`...
+   = note: ...but it actually implements `Fn<(&'2 mut V,)>`, for some specific lifetime `'2`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 10 previous errors