Rollup merge of #142047 - cuviper:s390x-stack, r=oli-obk

Ensure stack in two places that affect s390x

In our Fedora s390x test results, we found two tests that started hitting stack
overflows in the 1.87.0 update. It seems to be related in some part to our use
of PGO as well, probably inlining more into stack frames that were already
recursive. The main points of recursion that I identified were:

- `ui/parser/survive-peano-lesson-queue.rs` in `ThirBuildCx::mirror_exprs`
- `ui/associated-consts/issue-93775.rs` in `Parser::parse_ty`

A couple new `ensure_sufficient_stack` calls will solve these tests.

2 files changed, 16 insertions, 9 deletions

diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index 03448933fa9..3baeccf6409 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -38,7 +38,10 @@ impl<'tcx> ThirBuildCx<'tcx> {
     }
 
     pub(crate) fn mirror_exprs(&mut self, exprs: &'tcx [hir::Expr<'tcx>]) -> Box<[ExprId]> {
-        exprs.iter().map(|expr| self.mirror_expr_inner(expr)).collect()
+        // `mirror_exprs` may also recurse deeply, so it needs protection from stack overflow.
+        // Note that we *could* forward to `mirror_expr` for that, but we can consolidate the
+        // overhead of stack growth by doing it outside the iteration.
+        ensure_sufficient_stack(|| exprs.iter().map(|expr| self.mirror_expr_inner(expr)).collect())
     }
 
     #[instrument(level = "trace", skip(self, hir_expr))]
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index 17481731b11..6eaec2e29ad 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -7,6 +7,7 @@ use rustc_ast::{
     Pinnedness, PolyTraitRef, PreciseCapturingArg, TraitBoundModifiers, TraitObjectSyntax, Ty,
     TyKind, UnsafeBinderTy,
 };
+use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_errors::{Applicability, Diag, PResult};
 use rustc_span::{ErrorGuaranteed, Ident, Span, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
@@ -104,14 +105,17 @@ fn can_begin_dyn_bound_in_edition_2015(t: &Token) -> bool {
 impl<'a> Parser<'a> {
     /// Parses a type.
     pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
-        self.parse_ty_common(
-            AllowPlus::Yes,
-            AllowCVariadic::No,
-            RecoverQPath::Yes,
-            RecoverReturnSign::Yes,
-            None,
-            RecoverQuestionMark::Yes,
-        )
+        // Make sure deeply nested types don't overflow the stack.
+        ensure_sufficient_stack(|| {
+            self.parse_ty_common(
+                AllowPlus::Yes,
+                AllowCVariadic::No,
+                RecoverQPath::Yes,
+                RecoverReturnSign::Yes,
+                None,
+                RecoverQuestionMark::Yes,
+            )
+        })
     }
 
     pub(super) fn parse_ty_with_generics_recovery(