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| 1 | +use rustc_middle::mir::visit::Visitor; |
| 2 | +use rustc_middle::mir::{self, Location, MentionedItem, MirPass}; |
| 3 | +use rustc_middle::ty::{self, adjustment::PointerCoercion, TyCtxt}; |
| 4 | +use rustc_session::Session; |
| 5 | +use rustc_span::source_map::Spanned; |
| 6 | + |
| 7 | +pub struct MentionedItems; |
| 8 | + |
| 9 | +struct MentionedItemsVisitor<'a, 'tcx> { |
| 10 | + tcx: TyCtxt<'tcx>, |
| 11 | + body: &'a mir::Body<'tcx>, |
| 12 | + mentioned_items: &'a mut Vec<Spanned<MentionedItem<'tcx>>>, |
| 13 | +} |
| 14 | + |
| 15 | +impl<'tcx> MirPass<'tcx> for MentionedItems { |
| 16 | + fn is_enabled(&self, _sess: &Session) -> bool { |
| 17 | + // If this pass is skipped the collector assume that nothing got mentioned! We could |
| 18 | + // potentially skip it in opt-level 0 if we are sure that opt-level will never *remove* uses |
| 19 | + // of anything, but that still seems fragile. Furthermore, even debug builds use level 1, so |
| 20 | + // special-casing level 0 is just not worth it. |
| 21 | + true |
| 22 | + } |
| 23 | + |
| 24 | + fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut mir::Body<'tcx>) { |
| 25 | + debug_assert!(body.mentioned_items.is_empty()); |
| 26 | + let mut mentioned_items = Vec::new(); |
| 27 | + MentionedItemsVisitor { tcx, body, mentioned_items: &mut mentioned_items }.visit_body(body); |
| 28 | + body.mentioned_items = mentioned_items; |
| 29 | + } |
| 30 | +} |
| 31 | + |
| 32 | +// This visitor is carefully in sync with the one in `rustc_monomorphize::collector`. We are |
| 33 | +// visiting the exact same places but then instead of monomorphizing and creating `MonoItems`, we |
| 34 | +// have to remain generic and just recording the relevant information in `mentioned_items`, where it |
| 35 | +// will then be monomorphized later during "mentioned items" collection. |
| 36 | +impl<'tcx> Visitor<'tcx> for MentionedItemsVisitor<'_, 'tcx> { |
| 37 | + fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, location: Location) { |
| 38 | + self.super_terminator(terminator, location); |
| 39 | + let span = || self.body.source_info(location).span; |
| 40 | + match &terminator.kind { |
| 41 | + mir::TerminatorKind::Call { func, .. } => { |
| 42 | + let callee_ty = func.ty(self.body, self.tcx); |
| 43 | + self.mentioned_items |
| 44 | + .push(Spanned { node: MentionedItem::Fn(callee_ty), span: span() }); |
| 45 | + } |
| 46 | + mir::TerminatorKind::Drop { place, .. } => { |
| 47 | + let ty = place.ty(self.body, self.tcx).ty; |
| 48 | + self.mentioned_items.push(Spanned { node: MentionedItem::Drop(ty), span: span() }); |
| 49 | + } |
| 50 | + mir::TerminatorKind::InlineAsm { ref operands, .. } => { |
| 51 | + for op in operands { |
| 52 | + match *op { |
| 53 | + mir::InlineAsmOperand::SymFn { ref value } => { |
| 54 | + self.mentioned_items.push(Spanned { |
| 55 | + node: MentionedItem::Fn(value.const_.ty()), |
| 56 | + span: span(), |
| 57 | + }); |
| 58 | + } |
| 59 | + _ => {} |
| 60 | + } |
| 61 | + } |
| 62 | + } |
| 63 | + _ => {} |
| 64 | + } |
| 65 | + } |
| 66 | + |
| 67 | + fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'tcx>, location: Location) { |
| 68 | + self.super_rvalue(rvalue, location); |
| 69 | + let span = || self.body.source_info(location).span; |
| 70 | + match *rvalue { |
| 71 | + // We need to detect unsizing casts that required vtables. |
| 72 | + mir::Rvalue::Cast( |
| 73 | + mir::CastKind::PointerCoercion(PointerCoercion::Unsize), |
| 74 | + ref operand, |
| 75 | + target_ty, |
| 76 | + ) |
| 77 | + | mir::Rvalue::Cast(mir::CastKind::DynStar, ref operand, target_ty) => { |
| 78 | + // This isn't monomorphized yet so we can't tell what the actual types are -- just |
| 79 | + // add everything that may involve a vtable. |
| 80 | + let source_ty = operand.ty(self.body, self.tcx); |
| 81 | + let may_involve_vtable = match ( |
| 82 | + source_ty.builtin_deref(true).map(|t| t.ty.kind()), |
| 83 | + target_ty.builtin_deref(true).map(|t| t.ty.kind()), |
| 84 | + ) { |
| 85 | + (Some(ty::Array(..)), Some(ty::Str | ty::Slice(..))) => false, // &str/&[T] unsizing |
| 86 | + _ => true, |
| 87 | + }; |
| 88 | + if may_involve_vtable { |
| 89 | + self.mentioned_items.push(Spanned { |
| 90 | + node: MentionedItem::UnsizeCast { source_ty, target_ty }, |
| 91 | + span: span(), |
| 92 | + }); |
| 93 | + } |
| 94 | + } |
| 95 | + // Similarly, record closures that are turned into function pointers. |
| 96 | + mir::Rvalue::Cast( |
| 97 | + mir::CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_)), |
| 98 | + ref operand, |
| 99 | + _, |
| 100 | + ) => { |
| 101 | + let source_ty = operand.ty(self.body, self.tcx); |
| 102 | + self.mentioned_items |
| 103 | + .push(Spanned { node: MentionedItem::Closure(source_ty), span: span() }); |
| 104 | + } |
| 105 | + // And finally, function pointer reification casts. |
| 106 | + mir::Rvalue::Cast( |
| 107 | + mir::CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer), |
| 108 | + ref operand, |
| 109 | + _, |
| 110 | + ) => { |
| 111 | + let fn_ty = operand.ty(self.body, self.tcx); |
| 112 | + self.mentioned_items.push(Spanned { node: MentionedItem::Fn(fn_ty), span: span() }); |
| 113 | + } |
| 114 | + _ => {} |
| 115 | + } |
| 116 | + } |
| 117 | +} |
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