diff options
Diffstat (limited to 'compiler/rustc_mir_transform/src/lib.rs')
| -rw-r--r-- | compiler/rustc_mir_transform/src/lib.rs | 49 |
1 files changed, 3 insertions, 46 deletions
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs index 350929ffaa5..9459ef99445 100644 --- a/compiler/rustc_mir_transform/src/lib.rs +++ b/compiler/rustc_mir_transform/src/lib.rs @@ -34,8 +34,7 @@ use rustc_middle::util::Providers; use rustc_middle::{bug, query, span_bug}; use rustc_span::source_map::Spanned; use rustc_span::{DUMMY_SP, sym}; -use rustc_trait_selection::traits; -use tracing::{debug, trace}; +use tracing::debug; #[macro_use] mod pass_manager; @@ -142,6 +141,7 @@ declare_passes! { // Made public so that `mir_drops_elaborated_and_const_checked` can be overridden // by custom rustc drivers, running all the steps by themselves. See #114628. pub mod inline : Inline, ForceInline; + mod impossible_predicates : ImpossiblePredicates; mod instsimplify : InstSimplify { BeforeInline, AfterSimplifyCfg }; mod jump_threading : JumpThreading; mod known_panics_lint : KnownPanicsLint; @@ -502,50 +502,6 @@ fn mir_drops_elaborated_and_const_checked(tcx: TyCtxt<'_>, def: LocalDefId) -> & body.tainted_by_errors = Some(error_reported); } - // Check if it's even possible to satisfy the 'where' clauses - // for this item. - // - // This branch will never be taken for any normal function. - // However, it's possible to `#!feature(trivial_bounds)]` to write - // a function with impossible to satisfy clauses, e.g.: - // `fn foo() where String: Copy {}` - // - // We don't usually need to worry about this kind of case, - // since we would get a compilation error if the user tried - // to call it. However, since we optimize even without any - // calls to the function, we need to make sure that it even - // makes sense to try to evaluate the body. - // - // If there are unsatisfiable where clauses, then all bets are - // off, and we just give up. - // - // We manually filter the predicates, skipping anything that's not - // "global". We are in a potentially generic context - // (e.g. we are evaluating a function without instantiating generic - // parameters, so this filtering serves two purposes: - // - // 1. We skip evaluating any predicates that we would - // never be able prove are unsatisfiable (e.g. `<T as Foo>` - // 2. We avoid trying to normalize predicates involving generic - // parameters (e.g. `<T as Foo>::MyItem`). This can confuse - // the normalization code (leading to cycle errors), since - // it's usually never invoked in this way. - let predicates = tcx - .predicates_of(body.source.def_id()) - .predicates - .iter() - .filter_map(|(p, _)| if p.is_global() { Some(*p) } else { None }); - if traits::impossible_predicates(tcx, traits::elaborate(tcx, predicates).collect()) { - trace!("found unsatisfiable predicates for {:?}", body.source); - // Clear the body to only contain a single `unreachable` statement. - let bbs = body.basic_blocks.as_mut(); - bbs.raw.truncate(1); - bbs[START_BLOCK].statements.clear(); - bbs[START_BLOCK].terminator_mut().kind = TerminatorKind::Unreachable; - body.var_debug_info.clear(); - body.local_decls.raw.truncate(body.arg_count + 1); - } - run_analysis_to_runtime_passes(tcx, &mut body); // Now that drop elaboration has been performed, we can check for @@ -593,6 +549,7 @@ pub fn run_analysis_to_runtime_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<' /// After this series of passes, no lifetime analysis based on borrowing can be done. fn run_analysis_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { let passes: &[&dyn MirPass<'tcx>] = &[ + &impossible_predicates::ImpossiblePredicates, &cleanup_post_borrowck::CleanupPostBorrowck, &remove_noop_landing_pads::RemoveNoopLandingPads, &simplify::SimplifyCfg::PostAnalysis, |