diff options
Diffstat (limited to 'compiler/rustc_mir_transform')
| -rw-r--r-- | compiler/rustc_mir_transform/src/inline.rs | 21 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/lib.rs | 5 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/mentioned_items.rs | 117 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/shim.rs | 4 |
4 files changed, 145 insertions, 2 deletions
diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs index f6a0945c222..4ec76eec3a9 100644 --- a/compiler/rustc_mir_transform/src/inline.rs +++ b/compiler/rustc_mir_transform/src/inline.rs @@ -565,7 +565,8 @@ impl<'tcx> Inliner<'tcx> { mut callee_body: Body<'tcx>, ) { let terminator = caller_body[callsite.block].terminator.take().unwrap(); - let TerminatorKind::Call { args, destination, unwind, target, .. } = terminator.kind else { + let TerminatorKind::Call { func, args, destination, unwind, target, .. } = terminator.kind + else { bug!("unexpected terminator kind {:?}", terminator.kind); }; @@ -717,6 +718,24 @@ impl<'tcx> Inliner<'tcx> { Const::Val(..) | Const::Unevaluated(..) => true, }, )); + // Now that we incorporated the callee's `required_consts`, we can remove the callee from + // `mentioned_items` -- but we have to take their `mentioned_items` in return. This does + // some extra work here to save the monomorphization collector work later. It helps a lot, + // since monomorphization can avoid a lot of work when the "mentioned items" are similar to + // the actually used items. By doing this we can entirely avoid visiting the callee! + // We need to reconstruct the `required_item` for the callee so that we can find and + // remove it. + let callee_item = MentionedItem::Fn(func.ty(caller_body, self.tcx)); + if let Some(idx) = + caller_body.mentioned_items.iter().position(|item| item.node == callee_item) + { + // We found the callee, so remove it and add its items instead. + caller_body.mentioned_items.remove(idx); + caller_body.mentioned_items.extend(callee_body.mentioned_items); + } else { + // If we can't find the callee, there's no point in adding its items. + // Probably it already got removed by being inlined elsewhere in the same function. + } } fn make_call_args( diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs index 5d89015d61c..24bc263e5a7 100644 --- a/compiler/rustc_mir_transform/src/lib.rs +++ b/compiler/rustc_mir_transform/src/lib.rs @@ -88,6 +88,7 @@ mod lint; mod lower_intrinsics; mod lower_slice_len; mod match_branches; +mod mentioned_items; mod multiple_return_terminators; mod normalize_array_len; mod nrvo; @@ -565,6 +566,10 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { tcx, body, &[ + // Before doing anything, remember which items are being mentioned so that the set of items + // visited does not depend on the optimization level. + &mentioned_items::MentionedItems, + // Add some UB checks before any UB gets optimized away. &check_alignment::CheckAlignment, // Before inlining: trim down MIR with passes to reduce inlining work. diff --git a/compiler/rustc_mir_transform/src/mentioned_items.rs b/compiler/rustc_mir_transform/src/mentioned_items.rs new file mode 100644 index 00000000000..57b6126dece --- /dev/null +++ b/compiler/rustc_mir_transform/src/mentioned_items.rs @@ -0,0 +1,117 @@ +use rustc_middle::mir::visit::Visitor; +use rustc_middle::mir::{self, Location, MentionedItem, MirPass}; +use rustc_middle::ty::{self, adjustment::PointerCoercion, TyCtxt}; +use rustc_session::Session; +use rustc_span::source_map::Spanned; + +pub struct MentionedItems; + +struct MentionedItemsVisitor<'a, 'tcx> { + tcx: TyCtxt<'tcx>, + body: &'a mir::Body<'tcx>, + mentioned_items: &'a mut Vec<Spanned<MentionedItem<'tcx>>>, +} + +impl<'tcx> MirPass<'tcx> for MentionedItems { + fn is_enabled(&self, _sess: &Session) -> bool { + // If this pass is skipped the collector assume that nothing got mentioned! We could + // potentially skip it in opt-level 0 if we are sure that opt-level will never *remove* uses + // of anything, but that still seems fragile. Furthermore, even debug builds use level 1, so + // special-casing level 0 is just not worth it. + true + } + + fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut mir::Body<'tcx>) { + debug_assert!(body.mentioned_items.is_empty()); + let mut mentioned_items = Vec::new(); + MentionedItemsVisitor { tcx, body, mentioned_items: &mut mentioned_items }.visit_body(body); + body.mentioned_items = mentioned_items; + } +} + +// This visitor is carefully in sync with the one in `rustc_monomorphize::collector`. We are +// visiting the exact same places but then instead of monomorphizing and creating `MonoItems`, we +// have to remain generic and just recording the relevant information in `mentioned_items`, where it +// will then be monomorphized later during "mentioned items" collection. +impl<'tcx> Visitor<'tcx> for MentionedItemsVisitor<'_, 'tcx> { + fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, location: Location) { + self.super_terminator(terminator, location); + let span = || self.body.source_info(location).span; + match &terminator.kind { + mir::TerminatorKind::Call { func, .. } => { + let callee_ty = func.ty(self.body, self.tcx); + self.mentioned_items + .push(Spanned { node: MentionedItem::Fn(callee_ty), span: span() }); + } + mir::TerminatorKind::Drop { place, .. } => { + let ty = place.ty(self.body, self.tcx).ty; + self.mentioned_items.push(Spanned { node: MentionedItem::Drop(ty), span: span() }); + } + mir::TerminatorKind::InlineAsm { ref operands, .. } => { + for op in operands { + match *op { + mir::InlineAsmOperand::SymFn { ref value } => { + self.mentioned_items.push(Spanned { + node: MentionedItem::Fn(value.const_.ty()), + span: span(), + }); + } + _ => {} + } + } + } + _ => {} + } + } + + fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'tcx>, location: Location) { + self.super_rvalue(rvalue, location); + let span = || self.body.source_info(location).span; + match *rvalue { + // We need to detect unsizing casts that required vtables. + mir::Rvalue::Cast( + mir::CastKind::PointerCoercion(PointerCoercion::Unsize), + ref operand, + target_ty, + ) + | mir::Rvalue::Cast(mir::CastKind::DynStar, ref operand, target_ty) => { + // This isn't monomorphized yet so we can't tell what the actual types are -- just + // add everything that may involve a vtable. + let source_ty = operand.ty(self.body, self.tcx); + let may_involve_vtable = match ( + source_ty.builtin_deref(true).map(|t| t.ty.kind()), + target_ty.builtin_deref(true).map(|t| t.ty.kind()), + ) { + (Some(ty::Array(..)), Some(ty::Str | ty::Slice(..))) => false, // &str/&[T] unsizing + _ => true, + }; + if may_involve_vtable { + self.mentioned_items.push(Spanned { + node: MentionedItem::UnsizeCast { source_ty, target_ty }, + span: span(), + }); + } + } + // Similarly, record closures that are turned into function pointers. + mir::Rvalue::Cast( + mir::CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_)), + ref operand, + _, + ) => { + let source_ty = operand.ty(self.body, self.tcx); + self.mentioned_items + .push(Spanned { node: MentionedItem::Closure(source_ty), span: span() }); + } + // And finally, function pointer reification casts. + mir::Rvalue::Cast( + mir::CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer), + ref operand, + _, + ) => { + let fn_ty = operand.ty(self.body, self.tcx); + self.mentioned_items.push(Spanned { node: MentionedItem::Fn(fn_ty), span: span() }); + } + _ => {} + } + } +} diff --git a/compiler/rustc_mir_transform/src/shim.rs b/compiler/rustc_mir_transform/src/shim.rs index 28b502e8cab..71de64c6d26 100644 --- a/compiler/rustc_mir_transform/src/shim.rs +++ b/compiler/rustc_mir_transform/src/shim.rs @@ -17,7 +17,7 @@ use std::iter; use crate::{ abort_unwinding_calls, add_call_guards, add_moves_for_packed_drops, deref_separator, - pass_manager as pm, remove_noop_landing_pads, simplify, + mentioned_items, pass_manager as pm, remove_noop_landing_pads, simplify, }; use rustc_middle::mir::patch::MirPatch; use rustc_mir_dataflow::elaborate_drops::{self, DropElaborator, DropFlagMode, DropStyle}; @@ -112,6 +112,7 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'tcx>) -> Body<' tcx, &mut body, &[ + &mentioned_items::MentionedItems, &abort_unwinding_calls::AbortUnwindingCalls, &add_call_guards::CriticalCallEdges, ], @@ -143,6 +144,7 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'tcx>) -> Body<' tcx, &mut result, &[ + &mentioned_items::MentionedItems, &add_moves_for_packed_drops::AddMovesForPackedDrops, &deref_separator::Derefer, &remove_noop_landing_pads::RemoveNoopLandingPads, |