From 3783ef6dbe5aa1bb322e11ac33bfc599492d3280 Mon Sep 17 00:00:00 2001 From: Dylan MacKenzie Date: Mon, 28 Oct 2019 12:17:36 -0700 Subject: [PATCH 1/5] Stop returning promotables from `mir_const_qualif` --- src/librustc/query/mod.rs | 2 +- src/librustc/ty/query/mod.rs | 1 - .../rmeta/decoder/cstore_impl.rs | 5 +- src/librustc_metadata/rmeta/encoder.rs | 6 +- .../transform/check_consts/qualifs.rs | 2 +- src/librustc_mir/transform/promote_consts.rs | 2 +- src/librustc_mir/transform/qualify_consts.rs | 64 +++---------------- 7 files changed, 16 insertions(+), 66 deletions(-) diff --git a/src/librustc/query/mod.rs b/src/librustc/query/mod.rs index 12ae2c3201547..bd7b77b0abb17 100644 --- a/src/librustc/query/mod.rs +++ b/src/librustc/query/mod.rs @@ -93,7 +93,7 @@ rustc_queries! { /// Maps DefId's that have an associated `mir::Body` to the result /// of the MIR qualify_consts pass. The actual meaning of /// the value isn't known except to the pass itself. - query mir_const_qualif(key: DefId) -> (u8, &'tcx BitSet) { + query mir_const_qualif(key: DefId) -> u8 { desc { |tcx| "const checking `{}`", tcx.def_path_str(key) } cache_on_disk_if { key.is_local() } } diff --git a/src/librustc/ty/query/mod.rs b/src/librustc/ty/query/mod.rs index 9b15ad560b5d2..0615004125b3c 100644 --- a/src/librustc/ty/query/mod.rs +++ b/src/librustc/ty/query/mod.rs @@ -42,7 +42,6 @@ use crate::util::common::ErrorReported; use crate::util::profiling::ProfileCategory::*; use rustc_data_structures::svh::Svh; -use rustc_index::bit_set::BitSet; use rustc_index::vec::IndexVec; use rustc_data_structures::fx::{FxIndexMap, FxHashMap, FxHashSet}; use rustc_data_structures::stable_hasher::StableVec; diff --git a/src/librustc_metadata/rmeta/decoder/cstore_impl.rs b/src/librustc_metadata/rmeta/decoder/cstore_impl.rs index 6eacfc28de2db..1118162bdeb02 100644 --- a/src/librustc_metadata/rmeta/decoder/cstore_impl.rs +++ b/src/librustc_metadata/rmeta/decoder/cstore_impl.rs @@ -32,7 +32,6 @@ use syntax::parse::parser::emit_unclosed_delims; use syntax::source_map::Spanned; use syntax::symbol::Symbol; use syntax_pos::{Span, FileName}; -use rustc_index::bit_set::BitSet; macro_rules! provide { (<$lt:tt> $tcx:ident, $def_id:ident, $other:ident, $cdata:ident, @@ -122,9 +121,7 @@ provide! { <'tcx> tcx, def_id, other, cdata, } optimized_mir => { tcx.arena.alloc(cdata.get_optimized_mir(tcx, def_id.index)) } promoted_mir => { tcx.arena.alloc(cdata.get_promoted_mir(tcx, def_id.index)) } - mir_const_qualif => { - (cdata.mir_const_qualif(def_id.index), tcx.arena.alloc(BitSet::new_empty(0))) - } + mir_const_qualif => { cdata.mir_const_qualif(def_id.index) } fn_sig => { cdata.fn_sig(def_id.index, tcx) } inherent_impls => { cdata.get_inherent_implementations_for_type(tcx, def_id.index) } is_const_fn_raw => { cdata.is_const_fn_raw(def_id.index) } diff --git a/src/librustc_metadata/rmeta/encoder.rs b/src/librustc_metadata/rmeta/encoder.rs index c6677ea3534d0..ad1ab16a41074 100644 --- a/src/librustc_metadata/rmeta/encoder.rs +++ b/src/librustc_metadata/rmeta/encoder.rs @@ -955,7 +955,7 @@ impl EncodeContext<'tcx> { record!(self.per_def.kind[def_id] <- match impl_item.kind { ty::AssocKind::Const => { if let hir::ImplItemKind::Const(_, body_id) = ast_item.kind { - let mir = self.tcx.at(ast_item.span).mir_const_qualif(def_id).0; + let mir = self.tcx.at(ast_item.span).mir_const_qualif(def_id); EntryKind::AssocConst(container, ConstQualif { mir }, @@ -1089,7 +1089,7 @@ impl EncodeContext<'tcx> { hir::ItemKind::Static(_, hir::MutMutable, _) => EntryKind::MutStatic, hir::ItemKind::Static(_, hir::MutImmutable, _) => EntryKind::ImmStatic, hir::ItemKind::Const(_, body_id) => { - let mir = self.tcx.at(item.span).mir_const_qualif(def_id).0; + let mir = self.tcx.at(item.span).mir_const_qualif(def_id); EntryKind::Const( ConstQualif { mir }, self.encode_rendered_const_for_body(body_id) @@ -1368,7 +1368,7 @@ impl EncodeContext<'tcx> { let id = self.tcx.hir().as_local_hir_id(def_id).unwrap(); let body_id = self.tcx.hir().body_owned_by(id); let const_data = self.encode_rendered_const_for_body(body_id); - let mir = self.tcx.mir_const_qualif(def_id).0; + let mir = self.tcx.mir_const_qualif(def_id); record!(self.per_def.kind[def_id] <- EntryKind::Const(ConstQualif { mir }, const_data)); record!(self.per_def.visibility[def_id] <- ty::Visibility::Public); diff --git a/src/librustc_mir/transform/check_consts/qualifs.rs b/src/librustc_mir/transform/check_consts/qualifs.rs index 840ad30301607..496a56790679b 100644 --- a/src/librustc_mir/transform/check_consts/qualifs.rs +++ b/src/librustc_mir/transform/check_consts/qualifs.rs @@ -123,7 +123,7 @@ pub trait Qualif { if cx.tcx.trait_of_item(def_id).is_some() { Self::in_any_value_of_ty(cx, constant.literal.ty) } else { - let (bits, _) = cx.tcx.at(constant.span).mir_const_qualif(def_id); + let bits = cx.tcx.at(constant.span).mir_const_qualif(def_id); let qualif = QualifSet(bits).contains::(); diff --git a/src/librustc_mir/transform/promote_consts.rs b/src/librustc_mir/transform/promote_consts.rs index f5e49e3283406..bea8b499b914c 100644 --- a/src/librustc_mir/transform/promote_consts.rs +++ b/src/librustc_mir/transform/promote_consts.rs @@ -538,7 +538,7 @@ impl<'tcx> Validator<'_, 'tcx> { // is gone - we can always promote constants even if they // fail to pass const-checking, as compilation would've // errored independently and promotion can't change that. - let (bits, _) = self.tcx.at(constant.span).mir_const_qualif(def_id); + let bits = self.tcx.at(constant.span).mir_const_qualif(def_id); if bits == super::qualify_consts::QUALIF_ERROR_BIT { self.tcx.sess.delay_span_bug( constant.span, diff --git a/src/librustc_mir/transform/qualify_consts.rs b/src/librustc_mir/transform/qualify_consts.rs index 6a7058f193017..2b3ca9e9c5b5a 100644 --- a/src/librustc_mir/transform/qualify_consts.rs +++ b/src/librustc_mir/transform/qualify_consts.rs @@ -258,7 +258,7 @@ trait Qualif { if cx.tcx.trait_of_item(def_id).is_some() { Self::in_any_value_of_ty(cx, constant.literal.ty).unwrap_or(false) } else { - let (bits, _) = cx.tcx.at(constant.span).mir_const_qualif(def_id); + let bits = cx.tcx.at(constant.span).mir_const_qualif(def_id); let qualif = PerQualif::decode_from_bits(bits).0[Self::IDX]; @@ -682,7 +682,7 @@ impl<'a, 'tcx> Checker<'a, 'tcx> { } /// Check a whole const, static initializer or const fn. - fn check_const(&mut self) -> (u8, &'tcx BitSet) { + fn check_const(&mut self) -> u8 { use crate::transform::check_consts as new_checker; debug!("const-checking {} {:?}", self.mode, self.def_id); @@ -704,7 +704,6 @@ impl<'a, 'tcx> Checker<'a, 'tcx> { let mut seen_blocks = BitSet::new_empty(body.basic_blocks().len()); let mut bb = START_BLOCK; - let mut has_controlflow_error = false; loop { seen_blocks.insert(bb.index()); @@ -745,7 +744,6 @@ impl<'a, 'tcx> Checker<'a, 'tcx> { bb = target; } _ => { - has_controlflow_error = true; self.not_const(ops::Loop); validator.check_op(ops::Loop); break; @@ -772,51 +770,7 @@ impl<'a, 'tcx> Checker<'a, 'tcx> { } } - // Collect all the temps we need to promote. - let mut promoted_temps = BitSet::new_empty(self.temp_promotion_state.len()); - - // HACK: if parts of the control-flow graph were skipped due to an error, don't try to - // promote anything, since that can cause errors in a `const` if e.g. rvalue static - // promotion is attempted within a loop body. - let unleash_miri = self.tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you; - let promotion_candidates = if has_controlflow_error && !unleash_miri { - self.tcx.sess.delay_span_bug( - body.span, - "check_const: expected control-flow error(s)", - ); - - vec![] - } else { - promote_consts::validate_candidates( - self.tcx, - self.body, - self.def_id, - &self.temp_promotion_state, - &self.unchecked_promotion_candidates, - ) - }; - - debug!("qualify_const: promotion_candidates={:?}", promotion_candidates); - for candidate in promotion_candidates { - match candidate { - Candidate::Ref(Location { block: bb, statement_index: stmt_idx }) => { - if let StatementKind::Assign(box( _, Rvalue::Ref(_, _, place))) - = &self.body[bb].statements[stmt_idx].kind - { - if let PlaceBase::Local(local) = place.base { - promoted_temps.insert(local); - } - } - } - - // Only rvalue-static promotion requires extending the lifetime of the promoted - // local. - Candidate::Argument { .. } | Candidate::Repeat(_) => {} - } - } - - let qualifs = self.qualifs_in_local(RETURN_PLACE); - (qualifs.encode_to_bits(), self.tcx.arena.alloc(promoted_temps)) + self.qualifs_in_local(RETURN_PLACE).encode_to_bits() } } @@ -1346,7 +1300,7 @@ pub fn provide(providers: &mut Providers<'_>) { // in `promote_consts`, see the comment in `validate_operand`. pub(super) const QUALIF_ERROR_BIT: u8 = 1 << 2; -fn mir_const_qualif(tcx: TyCtxt<'_>, def_id: DefId) -> (u8, &BitSet) { +fn mir_const_qualif(tcx: TyCtxt<'_>, def_id: DefId) -> u8 { // N.B., this `borrow()` is guaranteed to be valid (i.e., the value // cannot yet be stolen), because `mir_validated()`, which steals // from `mir_const(), forces this query to execute before @@ -1355,7 +1309,7 @@ fn mir_const_qualif(tcx: TyCtxt<'_>, def_id: DefId) -> (u8, &BitSet) { if body.return_ty().references_error() { tcx.sess.delay_span_bug(body.span, "mir_const_qualif: MIR had errors"); - return (QUALIF_ERROR_BIT, tcx.arena.alloc(BitSet::new_empty(0))); + return QUALIF_ERROR_BIT; } Checker::new(tcx, def_id, body, Mode::Const).check_const() @@ -1436,11 +1390,11 @@ impl<'tcx> MirPass<'tcx> for QualifyAndPromoteConstants<'tcx> { } else { check_short_circuiting_in_const_local(tcx, body, mode); - let promoted_temps = match mode { - Mode::Const => tcx.mir_const_qualif(def_id).1, - _ => Checker::new(tcx, def_id, body, mode).check_const().1, + match mode { + Mode::Const => tcx.mir_const_qualif(def_id), + _ => Checker::new(tcx, def_id, body, mode).check_const(), }; - remove_drop_and_storage_dead_on_promoted_locals(body, promoted_temps); + remove_drop_and_storage_dead_on_promoted_locals(body, unimplemented!()); } if mode == Mode::Static && !tcx.has_attr(def_id, sym::thread_local) { From 170272b74fdeb1141a23817a4d69b58a084a0cd0 Mon Sep 17 00:00:00 2001 From: Dylan MacKenzie Date: Mon, 28 Oct 2019 15:32:56 -0700 Subject: [PATCH 2/5] Add a `PromoteTemps` pass `remove_storage_dead_and_drop` has been copied to `promote_temps` and now operates on an array of `Candidate`s instead of a bitset. --- src/librustc_mir/transform/promote_consts.rs | 138 ++++++++++++++++++- src/librustc_mir/transform/qualify_consts.rs | 34 ----- 2 files changed, 137 insertions(+), 35 deletions(-) diff --git a/src/librustc_mir/transform/promote_consts.rs b/src/librustc_mir/transform/promote_consts.rs index bea8b499b914c..48a58f1d0ee57 100644 --- a/src/librustc_mir/transform/promote_consts.rs +++ b/src/librustc_mir/transform/promote_consts.rs @@ -17,7 +17,7 @@ use rustc::mir::*; use rustc::mir::interpret::ConstValue; use rustc::mir::visit::{PlaceContext, MutatingUseContext, MutVisitor, Visitor}; use rustc::mir::traversal::ReversePostorder; -use rustc::ty::{self, List, TyCtxt}; +use rustc::ty::{self, List, TyCtxt, TypeFoldable}; use rustc::ty::subst::InternalSubsts; use rustc::ty::cast::CastTy; use syntax::ast::LitKind; @@ -25,12 +25,68 @@ use syntax::symbol::sym; use syntax_pos::{Span, DUMMY_SP}; use rustc_index::vec::{IndexVec, Idx}; +use rustc_index::bit_set::HybridBitSet; use rustc_target::spec::abi::Abi; +use std::cell::Cell; use std::{iter, mem, usize}; +use crate::transform::{MirPass, MirSource}; use crate::transform::check_consts::{qualifs, Item, ConstKind, is_lang_panic_fn}; +/// A `MirPass` for promotion. +/// +/// In this case, "promotion" entails the following: +/// - Extract promotable temps in `fn` and `const fn` into their own MIR bodies. +/// - Extend lifetimes in `const` and `static` by removing `Drop` and `StorageDead`. +/// - Emit errors if the requirements of `#[rustc_args_required_const]` are not met. +/// +/// After this pass is run, `promoted_fragments` will hold the MIR body corresponding to each +/// newly created `StaticKind::Promoted`. +#[derive(Default)] +pub struct PromoteTemps<'tcx> { + pub promoted_fragments: Cell>>, +} + +impl<'tcx> MirPass<'tcx> for PromoteTemps<'tcx> { + fn run_pass(&self, tcx: TyCtxt<'tcx>, src: MirSource<'tcx>, body: &mut Body<'tcx>) { + // There's not really any point in promoting errorful MIR. + // + // This does not include MIR that failed const-checking, which we still try to promote. + if body.return_ty().references_error() { + tcx.sess.delay_span_bug(body.span, "PromoteTemps: MIR had errors"); + return; + } + + if src.promoted.is_some() { + return; + } + + let def_id = src.def_id(); + + let item = Item::new(tcx, def_id, body); + let mut rpo = traversal::reverse_postorder(body); + let (temps, all_candidates) = collect_temps_and_candidates(tcx, body, &mut rpo); + + let promotable_candidates = validate_candidates(tcx, body, def_id, &temps, &all_candidates); + + // For now, lifetime extension is done in `const` and `static`s without creating promoted + // MIR fragments by removing `Drop` and `StorageDead` for each referent. However, this will + // not work inside loops when they are allowed in `const`s. + // + // FIXME: use promoted MIR fragments everywhere? + let promoted_fragments = if should_create_promoted_mir_fragments(item.const_kind) { + promote_candidates(def_id, body, tcx, temps, promotable_candidates) + } else { + // FIXME: promote const array initializers in consts. + remove_drop_and_storage_dead_on_promoted_locals(tcx, body, &promotable_candidates); + IndexVec::new() + }; + + self.promoted_fragments.set(promoted_fragments); + } +} + /// State of a temporary during collection and promotion. #[derive(Copy, Clone, PartialEq, Eq, Debug)] pub enum TempState { @@ -1154,3 +1210,83 @@ crate fn should_suggest_const_in_array_repeat_expressions_attribute<'tcx>( should_promote={:?} feature_flag={:?}", mir_def_id, should_promote, feature_flag); should_promote && !feature_flag } + +fn should_create_promoted_mir_fragments(const_kind: Option) -> bool { + match const_kind { + Some(ConstKind::ConstFn) | None => true, + Some(ConstKind::Const) | Some(ConstKind::Static) | Some(ConstKind::StaticMut) => false, + } +} + +/// In `const` and `static` everything without `StorageDead` +/// is `'static`, we don't have to create promoted MIR fragments, +/// just remove `Drop` and `StorageDead` on "promoted" locals. +fn remove_drop_and_storage_dead_on_promoted_locals( + tcx: TyCtxt<'tcx>, + body: &mut Body<'tcx>, + promotable_candidates: &[Candidate], +) { + debug!("run_pass: promotable_candidates={:?}", promotable_candidates); + + // Removing `StorageDead` will cause errors for temps declared inside a loop body. For now we + // simply skip promotion if a loop exists, since loops are not yet allowed in a `const`. + // + // FIXME: Just create MIR fragments for `const`s instead of using this hackish approach? + if body.is_cfg_cyclic() { + tcx.sess.delay_span_bug(body.span, "Control-flow cycle detected in `const`"); + return; + } + + // The underlying local for promotion contexts like `&temp` and `&(temp.proj)`. + let mut requires_lifetime_extension = HybridBitSet::new_empty(body.local_decls.len()); + + promotable_candidates + .iter() + .filter_map(|c| { + match c { + Candidate::Ref(loc) => Some(loc), + Candidate::Repeat(_) | Candidate::Argument { .. } => None, + } + }) + .map(|&Location { block, statement_index }| { + // FIXME: store the `Local` for each `Candidate` when it is created. + let place = match &body[block].statements[statement_index].kind { + StatementKind::Assign(box ( _, Rvalue::Ref(_, _, place))) => place, + _ => bug!("`Candidate::Ref` without corresponding assignment"), + }; + + match place.base { + PlaceBase::Local(local) => local, + PlaceBase::Static(_) => bug!("`Candidate::Ref` for a non-local"), + } + }) + .for_each(|local| { + requires_lifetime_extension.insert(local); + }); + + // Remove `Drop` terminators and `StorageDead` statements for all promotable temps that require + // lifetime extension. + for block in body.basic_blocks_mut() { + block.statements.retain(|statement| { + match statement.kind { + StatementKind::StorageDead(index) => !requires_lifetime_extension.contains(index), + _ => true + } + }); + let terminator = block.terminator_mut(); + match &terminator.kind { + TerminatorKind::Drop { + location, + target, + .. + } => { + if let Some(index) = location.as_local() { + if requires_lifetime_extension.contains(index) { + terminator.kind = TerminatorKind::Goto { target: *target }; + } + } + } + _ => {} + } + } +} diff --git a/src/librustc_mir/transform/qualify_consts.rs b/src/librustc_mir/transform/qualify_consts.rs index 2b3ca9e9c5b5a..aebc9d23492d7 100644 --- a/src/librustc_mir/transform/qualify_consts.rs +++ b/src/librustc_mir/transform/qualify_consts.rs @@ -1455,40 +1455,6 @@ fn check_short_circuiting_in_const_local(tcx: TyCtxt<'_>, body: &mut Body<'tcx>, } } -/// In `const` and `static` everything without `StorageDead` -/// is `'static`, we don't have to create promoted MIR fragments, -/// just remove `Drop` and `StorageDead` on "promoted" locals. -fn remove_drop_and_storage_dead_on_promoted_locals( - body: &mut Body<'tcx>, - promoted_temps: &BitSet, -) { - debug!("run_pass: promoted_temps={:?}", promoted_temps); - - for block in body.basic_blocks_mut() { - block.statements.retain(|statement| { - match statement.kind { - StatementKind::StorageDead(index) => !promoted_temps.contains(index), - _ => true - } - }); - let terminator = block.terminator_mut(); - match &terminator.kind { - TerminatorKind::Drop { - location, - target, - .. - } => { - if let Some(index) = location.as_local() { - if promoted_temps.contains(index) { - terminator.kind = TerminatorKind::Goto { target: *target }; - } - } - } - _ => {} - } - } -} - fn check_static_is_sync(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>, hir_id: HirId) { let ty = body.return_ty(); tcx.infer_ctxt().enter(|infcx| { From b316384e145d4b21b4e882e7abd29fb41d46e33c Mon Sep 17 00:00:00 2001 From: Dylan MacKenzie Date: Wed, 6 Nov 2019 14:23:35 -0800 Subject: [PATCH 3/5] Use new `PromoteTemps` for promotion --- src/librustc_mir/transform/mod.rs | 7 +-- src/librustc_mir/transform/qualify_consts.rs | 56 ++++++-------------- src/test/mir-opt/match_false_edges.rs | 12 ++--- 3 files changed, 27 insertions(+), 48 deletions(-) diff --git a/src/librustc_mir/transform/mod.rs b/src/librustc_mir/transform/mod.rs index dbe6c7845926d..6d6d6bea2a0ea 100644 --- a/src/librustc_mir/transform/mod.rs +++ b/src/librustc_mir/transform/mod.rs @@ -210,13 +210,14 @@ fn mir_validated( } let mut body = tcx.mir_const(def_id).steal(); - let qualify_and_promote_pass = qualify_consts::QualifyAndPromoteConstants::default(); + let promote_pass = promote_consts::PromoteTemps::default(); run_passes(tcx, &mut body, InstanceDef::Item(def_id), None, MirPhase::Validated, &[ // What we need to run borrowck etc. - &qualify_and_promote_pass, + &qualify_consts::QualifyAndPromoteConstants::default(), + &promote_pass, &simplify::SimplifyCfg::new("qualify-consts"), ]); - let promoted = qualify_and_promote_pass.promoted.into_inner(); + let promoted = promote_pass.promoted_fragments.into_inner(); (tcx.alloc_steal_mir(body), tcx.alloc_steal_promoted(promoted)) } diff --git a/src/librustc_mir/transform/qualify_consts.rs b/src/librustc_mir/transform/qualify_consts.rs index aebc9d23492d7..01111af7c3e03 100644 --- a/src/librustc_mir/transform/qualify_consts.rs +++ b/src/librustc_mir/transform/qualify_consts.rs @@ -1345,48 +1345,27 @@ impl<'tcx> MirPass<'tcx> for QualifyAndPromoteConstants<'tcx> { let mode = determine_mode(tcx, hir_id, def_id); debug!("run_pass: mode={:?}", mode); - if let Mode::NonConstFn | Mode::ConstFn = mode { + if let Mode::NonConstFn = mode { + // No need to const-check a non-const `fn` now that we don't do promotion here. + return; + } else if let Mode::ConstFn = mode { let mut checker = Checker::new(tcx, def_id, body, mode); - if let Mode::ConstFn = mode { - let use_min_const_fn_checks = - !tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you && - tcx.is_min_const_fn(def_id); - if use_min_const_fn_checks { - // Enforce `min_const_fn` for stable `const fn`s. - use super::qualify_min_const_fn::is_min_const_fn; - if let Err((span, err)) = is_min_const_fn(tcx, def_id, body) { - error_min_const_fn_violation(tcx, span, err); - return; - } - - // `check_const` should not produce any errors, but better safe than sorry - // FIXME(#53819) - // NOTE(eddyb) `check_const` is actually needed for promotion inside - // `min_const_fn` functions. - } - - // Enforce a constant-like CFG for `const fn`. - checker.check_const(); - } else { - while let Some((bb, data)) = checker.rpo.next() { - checker.visit_basic_block_data(bb, data); + let use_min_const_fn_checks = + !tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you && + tcx.is_min_const_fn(def_id); + if use_min_const_fn_checks { + // Enforce `min_const_fn` for stable `const fn`s. + use super::qualify_min_const_fn::is_min_const_fn; + if let Err((span, err)) = is_min_const_fn(tcx, def_id, body) { + error_min_const_fn_violation(tcx, span, err); + return; } } - // Promote only the promotable candidates. - let temps = checker.temp_promotion_state; - let candidates = promote_consts::validate_candidates( - tcx, - body, - def_id, - &temps, - &checker.unchecked_promotion_candidates, - ); - - // Do the actual promotion, now that we know what's viable. - self.promoted.set( - promote_consts::promote_candidates(def_id, body, tcx, temps, candidates) - ); + // `check_const` should not produce any errors, but better safe than sorry + // FIXME(#53819) + // Enforce a constant-like CFG for `const fn`. + checker.check_const(); } else { check_short_circuiting_in_const_local(tcx, body, mode); @@ -1394,7 +1373,6 @@ impl<'tcx> MirPass<'tcx> for QualifyAndPromoteConstants<'tcx> { Mode::Const => tcx.mir_const_qualif(def_id), _ => Checker::new(tcx, def_id, body, mode).check_const(), }; - remove_drop_and_storage_dead_on_promoted_locals(body, unimplemented!()); } if mode == Mode::Static && !tcx.has_attr(def_id, sym::thread_local) { diff --git a/src/test/mir-opt/match_false_edges.rs b/src/test/mir-opt/match_false_edges.rs index b275c06e05cd3..648856b5523d3 100644 --- a/src/test/mir-opt/match_false_edges.rs +++ b/src/test/mir-opt/match_false_edges.rs @@ -39,7 +39,7 @@ fn main() { // END RUST SOURCE // -// START rustc.full_tested_match.QualifyAndPromoteConstants.after.mir +// START rustc.full_tested_match.PromoteTemps.after.mir // bb0: { // ... // _2 = std::option::Option::::Some(const 42i32,); @@ -108,9 +108,9 @@ fn main() { // _0 = (); // return; // } -// END rustc.full_tested_match.QualifyAndPromoteConstants.after.mir +// END rustc.full_tested_match.PromoteTemps.after.mir // -// START rustc.full_tested_match2.QualifyAndPromoteConstants.before.mir +// START rustc.full_tested_match2.PromoteTemps.before.mir // bb0: { // ... // _2 = std::option::Option::::Some(const 42i32,); @@ -179,9 +179,9 @@ fn main() { // _0 = (); // return; // } -// END rustc.full_tested_match2.QualifyAndPromoteConstants.before.mir +// END rustc.full_tested_match2.PromoteTemps.before.mir // -// START rustc.main.QualifyAndPromoteConstants.before.mir +// START rustc.main.PromoteTemps.before.mir // bb0: { // ... // _2 = std::option::Option::::Some(const 1i32,); @@ -276,4 +276,4 @@ fn main() { // _0 = (); // return; // } -// END rustc.main.QualifyAndPromoteConstants.before.mir +// END rustc.main.PromoteTemps.before.mir From b13c2c330d623d1254a0c02e6447e3717470728c Mon Sep 17 00:00:00 2001 From: Dylan MacKenzie Date: Mon, 28 Oct 2019 15:21:53 -0700 Subject: [PATCH 4/5] Bless tests now that we do promotion if `min_const_fn` fails We bailed out of `QualifyAndPromoteConsts` immediately if the `min_const_fn` checks failed, which sometimes resulted in additional, spurious errors since promotion was skipped. We now do promotion in a completely separate pass, so this is no longer an issue. --- .../ui/consts/min_const_fn/min_const_fn.rs | 1 - .../consts/min_const_fn/min_const_fn.stderr | 19 +++++-------------- .../consts/min_const_fn/min_const_fn_dyn.rs | 1 - .../min_const_fn/min_const_fn_dyn.stderr | 14 ++------------ 4 files changed, 7 insertions(+), 28 deletions(-) diff --git a/src/test/ui/consts/min_const_fn/min_const_fn.rs b/src/test/ui/consts/min_const_fn/min_const_fn.rs index d0f63b148ff2b..db68a05905a14 100644 --- a/src/test/ui/consts/min_const_fn/min_const_fn.rs +++ b/src/test/ui/consts/min_const_fn/min_const_fn.rs @@ -136,7 +136,6 @@ const fn no_rpit() -> impl std::fmt::Debug {} //~ ERROR `impl Trait` in const fn const fn no_dyn_trait(_x: &dyn std::fmt::Debug) {} //~ ERROR trait bounds other than `Sized` const fn no_dyn_trait_ret() -> &'static dyn std::fmt::Debug { &() } //~^ ERROR trait bounds other than `Sized` -//~| ERROR cannot return reference to temporary value const fn no_unsafe() { unsafe {} } diff --git a/src/test/ui/consts/min_const_fn/min_const_fn.stderr b/src/test/ui/consts/min_const_fn/min_const_fn.stderr index 3158b6284db94..64b2ce83da2f8 100644 --- a/src/test/ui/consts/min_const_fn/min_const_fn.stderr +++ b/src/test/ui/consts/min_const_fn/min_const_fn.stderr @@ -286,17 +286,8 @@ LL | const fn no_dyn_trait_ret() -> &'static dyn std::fmt::Debug { &() } = note: for more information, see issue https://github.com/rust-lang/rust/issues/57563 = help: add `#![feature(const_fn)]` to the crate attributes to enable -error[E0515]: cannot return reference to temporary value - --> $DIR/min_const_fn.rs:137:63 - | -LL | const fn no_dyn_trait_ret() -> &'static dyn std::fmt::Debug { &() } - | ^-- - | || - | |temporary value created here - | returns a reference to data owned by the current function - error[E0723]: trait bounds other than `Sized` on const fn parameters are unstable - --> $DIR/min_const_fn.rs:143:41 + --> $DIR/min_const_fn.rs:142:41 | LL | const fn really_no_traits_i_mean_it() { (&() as &dyn std::fmt::Debug, ()).1 } | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -305,7 +296,7 @@ LL | const fn really_no_traits_i_mean_it() { (&() as &dyn std::fmt::Debug, ()).1 = help: add `#![feature(const_fn)]` to the crate attributes to enable error[E0723]: function pointers in const fn are unstable - --> $DIR/min_const_fn.rs:146:21 + --> $DIR/min_const_fn.rs:145:21 | LL | const fn no_fn_ptrs(_x: fn()) {} | ^^ @@ -314,7 +305,7 @@ LL | const fn no_fn_ptrs(_x: fn()) {} = help: add `#![feature(const_fn)]` to the crate attributes to enable error[E0723]: function pointers in const fn are unstable - --> $DIR/min_const_fn.rs:148:27 + --> $DIR/min_const_fn.rs:147:27 | LL | const fn no_fn_ptrs2() -> fn() { fn foo() {} foo } | ^^^^ @@ -322,7 +313,7 @@ LL | const fn no_fn_ptrs2() -> fn() { fn foo() {} foo } = note: for more information, see issue https://github.com/rust-lang/rust/issues/57563 = help: add `#![feature(const_fn)]` to the crate attributes to enable -error: aborting due to 37 previous errors +error: aborting due to 36 previous errors -Some errors have detailed explanations: E0493, E0515, E0723. +Some errors have detailed explanations: E0493, E0723. For more information about an error, try `rustc --explain E0493`. diff --git a/src/test/ui/consts/min_const_fn/min_const_fn_dyn.rs b/src/test/ui/consts/min_const_fn/min_const_fn_dyn.rs index 3833510c0b3b5..6ca1e59b3af10 100644 --- a/src/test/ui/consts/min_const_fn/min_const_fn_dyn.rs +++ b/src/test/ui/consts/min_const_fn/min_const_fn_dyn.rs @@ -11,6 +11,5 @@ const fn no_inner_dyn_trait2(x: Hide) { } const fn no_inner_dyn_trait_ret() -> Hide { Hide(HasDyn { field: &0 }) } //~^ ERROR trait bounds other than `Sized` -//~| ERROR temporary value dropped while borrowed fn main() {} diff --git a/src/test/ui/consts/min_const_fn/min_const_fn_dyn.stderr b/src/test/ui/consts/min_const_fn/min_const_fn_dyn.stderr index 0ea950d678f87..e20b4f9dcb471 100644 --- a/src/test/ui/consts/min_const_fn/min_const_fn_dyn.stderr +++ b/src/test/ui/consts/min_const_fn/min_const_fn_dyn.stderr @@ -16,16 +16,6 @@ LL | const fn no_inner_dyn_trait_ret() -> Hide { Hide(HasDyn { field: &0 }) } = note: for more information, see issue https://github.com/rust-lang/rust/issues/57563 = help: add `#![feature(const_fn)]` to the crate attributes to enable -error[E0716]: temporary value dropped while borrowed - --> $DIR/min_const_fn_dyn.rs:12:67 - | -LL | const fn no_inner_dyn_trait_ret() -> Hide { Hide(HasDyn { field: &0 }) } - | -^ - temporary value is freed at the end of this statement - | || - | |creates a temporary which is freed while still in use - | cast requires that borrow lasts for `'static` - -error: aborting due to 3 previous errors +error: aborting due to 2 previous errors -Some errors have detailed explanations: E0716, E0723. -For more information about an error, try `rustc --explain E0716`. +For more information about this error, try `rustc --explain E0723`. From a3b03690c07f72ed802e4e77501960482c7c2661 Mon Sep 17 00:00:00 2001 From: Dylan MacKenzie Date: Wed, 6 Nov 2019 15:00:29 -0800 Subject: [PATCH 5/5] Clean up dead code in `qualify_consts` We don't do promotion here anymore, so `Checker` will never even visit the body of a non-const `fn`. --- src/librustc_mir/transform/qualify_consts.rs | 21 -------------------- 1 file changed, 21 deletions(-) diff --git a/src/librustc_mir/transform/qualify_consts.rs b/src/librustc_mir/transform/qualify_consts.rs index 01111af7c3e03..5ad5363768d34 100644 --- a/src/librustc_mir/transform/qualify_consts.rs +++ b/src/librustc_mir/transform/qualify_consts.rs @@ -15,7 +15,6 @@ use rustc::ty::cast::CastTy; use rustc::ty::query::Providers; use rustc::mir::*; use rustc::mir::interpret::ConstValue; -use rustc::mir::traversal::ReversePostorder; use rustc::mir::visit::{PlaceContext, Visitor, MutatingUseContext, NonMutatingUseContext}; use rustc::middle::lang_items; use rustc::session::config::nightly_options; @@ -31,7 +30,6 @@ use std::usize; use rustc::hir::HirId; use crate::transform::{MirPass, MirSource}; -use super::promote_consts::{self, Candidate, TempState}; use crate::transform::check_consts::ops::{self, NonConstOp}; /// What kind of item we are in. @@ -477,10 +475,6 @@ struct Checker<'a, 'tcx> { span: Span, def_id: DefId, - rpo: ReversePostorder<'a, 'tcx>, - - temp_promotion_state: IndexVec, - unchecked_promotion_candidates: Vec, /// If `true`, do not emit errors to the user, merely collect them in `errors`. suppress_errors: bool, @@ -509,10 +503,6 @@ impl Deref for Checker<'a, 'tcx> { impl<'a, 'tcx> Checker<'a, 'tcx> { fn new(tcx: TyCtxt<'tcx>, def_id: DefId, body: &'a Body<'tcx>, mode: Mode) -> Self { assert!(def_id.is_local()); - let mut rpo = traversal::reverse_postorder(body); - let (temps, unchecked_promotion_candidates) = - promote_consts::collect_temps_and_candidates(tcx, body, &mut rpo); - rpo.reset(); let param_env = tcx.param_env(def_id); @@ -539,9 +529,6 @@ impl<'a, 'tcx> Checker<'a, 'tcx> { cx, span: body.span, def_id, - rpo, - temp_promotion_state: temps, - unchecked_promotion_candidates, errors: vec![], suppress_errors: false, } @@ -662,14 +649,6 @@ impl<'a, 'tcx> Checker<'a, 'tcx> { let kind = self.body.local_kind(index); debug!("store to {:?} {:?}", kind, index); - // Only handle promotable temps in non-const functions. - if self.mode == Mode::NonConstFn { - if kind != LocalKind::Temp || - !self.temp_promotion_state[index].is_promotable() { - return; - } - } - // this is overly restrictive, because even full assignments do not clear the qualif // While we could special case full assignments, this would be inconsistent with // aggregates where we overwrite all fields via assignments, which would not get