-
Notifications
You must be signed in to change notification settings - Fork 13.2k
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
compute union-find of locals flowing into the output of statics
Co-authored-by: lqd <[email protected]> Co-authored-by: nikomatsakis <[email protected]>
- Loading branch information
1 parent
db54765
commit 341a07c
Showing
5 changed files
with
203 additions
and
24 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,161 @@ | ||
| // Copyright 2016 The Rust Project Developers. See the COPYRIGHT | ||
| // file at the top-level directory of this distribution and at | ||
| // http://rust-lang.org/COPYRIGHT. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | ||
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | ||
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | ||
| // option. This file may not be copied, modified, or distributed | ||
| // except according to those terms. | ||
|
|
||
| //! A MIR walk gathering a union-crfind of assigned locals, for the purpose of locating the ones | ||
| //! escaping into the output. | ||
| use rustc::mir::visit::Visitor; | ||
| use rustc::mir::*; | ||
|
|
||
| use rustc_data_structures::indexed_vec::Idx; | ||
| use rustc_data_structures::unify as ut; | ||
|
|
||
| crate struct EscapingLocals { | ||
| unification_table: ut::UnificationTable<ut::InPlace<AssignedLocal>>, | ||
| } | ||
|
|
||
| impl EscapingLocals { | ||
| crate fn compute(mir: &Mir<'_>) -> Self { | ||
| let mut visitor = GatherAssignedLocalsVisitor::new(); | ||
| visitor.visit_mir(mir); | ||
|
|
||
| EscapingLocals { unification_table: visitor.unification_table } | ||
| } | ||
|
|
||
| /// True if `local` is known to escape into static | ||
| /// memory. | ||
| crate fn escapes_into_return(&mut self, local: Local) -> bool { | ||
| let return_place = AssignedLocal::from(RETURN_PLACE); | ||
| let other_place = AssignedLocal::from(local); | ||
| self.unification_table.unioned(return_place, other_place) | ||
| } | ||
| } | ||
|
|
||
| /// The MIR visitor gathering the union-find of the locals used in | ||
| /// assignments. | ||
| struct GatherAssignedLocalsVisitor { | ||
| unification_table: ut::UnificationTable<ut::InPlace<AssignedLocal>>, | ||
| } | ||
|
|
||
| #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)] | ||
| struct AssignedLocal(u32); | ||
|
|
||
| impl ut::UnifyKey for AssignedLocal { | ||
| type Value = (); | ||
|
|
||
| fn index(&self) -> u32 { | ||
| self.0 | ||
| } | ||
|
|
||
| fn from_index(i: u32) -> AssignedLocal { | ||
| AssignedLocal(i) | ||
| } | ||
|
|
||
| fn tag() -> &'static str { | ||
| "AssignedLocal" | ||
| } | ||
| } | ||
|
|
||
| impl From<Local> for AssignedLocal { | ||
| fn from(item: Local) -> Self { | ||
| // newtype_indexes use usize but are u32s. | ||
| assert!(item.index() < ::std::u32::MAX as usize); | ||
| AssignedLocal(item.index() as u32) | ||
| } | ||
| } | ||
|
|
||
| impl GatherAssignedLocalsVisitor { | ||
| fn new() -> Self { | ||
| Self { | ||
| unification_table: ut::UnificationTable::new(), | ||
| } | ||
| } | ||
|
|
||
| fn union_locals_if_needed(&mut self, lvalue: Option<Local>, rvalue: Option<Local>) { | ||
| if let Some(lvalue) = lvalue { | ||
| if let Some(rvalue) = rvalue { | ||
| if lvalue != rvalue { | ||
| self.unification_table | ||
| .union(AssignedLocal::from(lvalue), AssignedLocal::from(rvalue)); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| // Returns the potential `Local` associated to this `Place` or `PlaceProjection` | ||
| fn find_local_in_place(place: &Place) -> Option<Local> { | ||
| match place { | ||
| Place::Local(local) => Some(*local), | ||
|
|
||
| // If you do e.g. `x = a.f` then only *part* of the type of | ||
| // `a` escapes into `x` (the part contained in `f`); if `a`'s | ||
| // type has regions that don't appear in `f`, those might not | ||
| // escape. | ||
| Place::Projection(..) => None, | ||
|
|
||
| Place::Static { .. } | Place::Promoted { .. } => None, | ||
| } | ||
| } | ||
|
|
||
| // Returns the potential `Local` in this `Operand`. | ||
| fn find_local_in_operand(op: &Operand) -> Option<Local> { | ||
| // Conservatively check a subset of `Operand`s we know our | ||
| // benchmarks track, for example `html5ever`. | ||
| match op { | ||
| Operand::Copy(place) | Operand::Move(place) => find_local_in_place(place), | ||
| Operand::Constant(_) => None, | ||
| } | ||
| } | ||
|
|
||
| impl<'tcx> Visitor<'tcx> for GatherAssignedLocalsVisitor { | ||
| fn visit_mir(&mut self, mir: &Mir<'tcx>) { | ||
| // We need as many union-find keys as there are locals | ||
| for _ in 0..mir.local_decls.len() { | ||
| self.unification_table.new_key(()); | ||
| } | ||
|
|
||
| self.super_mir(mir); | ||
| } | ||
|
|
||
| fn visit_assign( | ||
| &mut self, | ||
| block: BasicBlock, | ||
| place: &Place<'tcx>, | ||
| rvalue: &Rvalue<'tcx>, | ||
| location: Location, | ||
| ) { | ||
| let local = find_local_in_place(place); | ||
|
|
||
| // Conservatively check a subset of `Rvalue`s we know our | ||
| // benchmarks track, for example `html5ever`. | ||
| match rvalue { | ||
| Rvalue::Use(op) => self.union_locals_if_needed(local, find_local_in_operand(op)), | ||
| Rvalue::Ref(_, _, place) => { | ||
| self.union_locals_if_needed(local, find_local_in_place(place)) | ||
| } | ||
|
|
||
| Rvalue::Cast(kind, op, _) => match kind { | ||
| CastKind::Unsize => self.union_locals_if_needed(local, find_local_in_operand(op)), | ||
| _ => (), | ||
| }, | ||
|
|
||
| Rvalue::Aggregate(_, ops) => { | ||
| for rvalue in ops.iter().map(find_local_in_operand) { | ||
| self.union_locals_if_needed(local, rvalue); | ||
| } | ||
| } | ||
|
|
||
| _ => (), | ||
| }; | ||
|
|
||
| self.super_assign(block, place, rvalue, location); | ||
| } | ||
| } |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters