-
Notifications
You must be signed in to change notification settings - Fork 12.9k
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
fix codegen of drops of fields of packed structs
- Loading branch information
Showing
8 changed files
with
341 additions
and
26 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
141 changes: 141 additions & 0 deletions
141
src/librustc_mir/transform/add_moves_for_packed_drops.rs
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 +1,141 @@ | ||
| // Copyright 2017 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. | ||
|
|
||
| use rustc::hir::def_id::DefId; | ||
| use rustc::mir::*; | ||
| use rustc::ty::TyCtxt; | ||
|
|
||
| use transform::{MirPass, MirSource}; | ||
| use util::patch::MirPatch; | ||
| use util; | ||
|
|
||
| // This pass moves values being dropped that are within a packed | ||
| // struct to a separate local before dropping them, to ensure that | ||
| // they are dropped from an aligned address. | ||
| // | ||
| // For example, if we have something like | ||
| // ```Rust | ||
| // #[repr(packed)] | ||
| // struct Foo { | ||
| // dealign: u8, | ||
| // data: Vec<u8> | ||
| // } | ||
| // | ||
| // let foo = ...; | ||
| // ``` | ||
| // | ||
| // We want to call `drop_in_place::<Vec<u8>>` on `data` from an aligned | ||
| // address. This means we can't simply drop `foo.data` directly, because | ||
| // its address is not aligned. | ||
| // | ||
| // Instead, we move `foo.data` to a local and drop that: | ||
| // ``` | ||
| // storage.live(drop_temp) | ||
| // drop_temp = foo.data; | ||
| // drop(drop_temp) -> next | ||
| // next: | ||
| // storage.dead(drop_temp) | ||
| // ``` | ||
| // | ||
| // The storage instructions are required to avoid stack space | ||
| // blowup. | ||
|
|
||
| pub struct AddMovesForPackedDrops; | ||
|
|
||
| impl MirPass for AddMovesForPackedDrops { | ||
| fn run_pass<'a, 'tcx>(&self, | ||
| tcx: TyCtxt<'a, 'tcx, 'tcx>, | ||
| src: MirSource, | ||
| mir: &mut Mir<'tcx>) | ||
| { | ||
| debug!("add_moves_for_packed_drops({:?} @ {:?})", src, mir.span); | ||
| add_moves_for_packed_drops(tcx, mir, src.def_id); | ||
| } | ||
| } | ||
|
|
||
| pub fn add_moves_for_packed_drops<'a, 'tcx>( | ||
| tcx: TyCtxt<'a, 'tcx, 'tcx>, | ||
| mir: &mut Mir<'tcx>, | ||
| def_id: DefId) | ||
| { | ||
| let patch = add_moves_for_packed_drops_patch(tcx, mir, def_id); | ||
| patch.apply(mir); | ||
| } | ||
|
|
||
| fn add_moves_for_packed_drops_patch<'a, 'tcx>( | ||
| tcx: TyCtxt<'a, 'tcx, 'tcx>, | ||
| mir: &Mir<'tcx>, | ||
| def_id: DefId) | ||
| -> MirPatch<'tcx> | ||
| { | ||
| let mut patch = MirPatch::new(mir); | ||
| let param_env = tcx.param_env(def_id); | ||
|
|
||
| for (bb, data) in mir.basic_blocks().iter_enumerated() { | ||
| let loc = Location { block: bb, statement_index: data.statements.len() }; | ||
| let terminator = data.terminator(); | ||
|
|
||
| match terminator.kind { | ||
| TerminatorKind::Drop { ref location, .. } | ||
| if util::is_disaligned(tcx, mir, param_env, location) => | ||
| { | ||
| add_move_for_packed_drop(tcx, mir, &mut patch, terminator, | ||
| loc, data.is_cleanup); | ||
| } | ||
| TerminatorKind::DropAndReplace { .. } => { | ||
| span_bug!(terminator.source_info.span, | ||
| "replace in AddMovesForPackedDrops"); | ||
| } | ||
| _ => {} | ||
| } | ||
| } | ||
|
|
||
| patch | ||
| } | ||
|
|
||
| fn add_move_for_packed_drop<'a, 'tcx>( | ||
| tcx: TyCtxt<'a, 'tcx, 'tcx>, | ||
| mir: &Mir<'tcx>, | ||
| patch: &mut MirPatch<'tcx>, | ||
| terminator: &Terminator<'tcx>, | ||
| loc: Location, | ||
| is_cleanup: bool) | ||
| { | ||
| debug!("add_move_for_packed_drop({:?} @ {:?})", terminator, loc); | ||
| let (location, target, unwind) = match terminator.kind { | ||
| TerminatorKind::Drop { ref location, target, unwind } => | ||
| (location, target, unwind), | ||
| _ => unreachable!() | ||
| }; | ||
|
|
||
| let source_info = terminator.source_info; | ||
| let ty = location.ty(mir, tcx).to_ty(tcx); | ||
| let temp = patch.new_temp(ty, terminator.source_info.span); | ||
|
|
||
| let storage_dead_block = patch.new_block(BasicBlockData { | ||
| statements: vec![Statement { | ||
| source_info, kind: StatementKind::StorageDead(temp) | ||
| }], | ||
| terminator: Some(Terminator { | ||
| source_info, kind: TerminatorKind::Goto { target } | ||
| }), | ||
| is_cleanup | ||
| }); | ||
|
|
||
| patch.add_statement( | ||
| loc, StatementKind::StorageLive(temp)); | ||
| patch.add_assign(loc, Lvalue::Local(temp), | ||
| Rvalue::Use(Operand::Consume(location.clone()))); | ||
| patch.patch_terminator(loc.block, TerminatorKind::Drop { | ||
| location: Lvalue::Local(temp), | ||
| target: storage_dead_block, | ||
| unwind | ||
| }); | ||
| } |
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
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,74 @@ | ||
| // Copyright 2017 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. | ||
|
|
||
|
|
||
| use rustc::ty::{self, TyCtxt}; | ||
| use rustc::mir::*; | ||
|
|
||
| /// Return `true` if this lvalue is allowed to be less aligned | ||
| /// than its containing struct (because it is within a packed | ||
| /// struct). | ||
| pub fn is_disaligned<'a, 'tcx, L>(tcx: TyCtxt<'a, 'tcx, 'tcx>, | ||
| local_decls: &L, | ||
| param_env: ty::ParamEnv<'tcx>, | ||
| lvalue: &Lvalue<'tcx>) | ||
| -> bool | ||
| where L: HasLocalDecls<'tcx> | ||
| { | ||
| debug!("is_disaligned({:?})", lvalue); | ||
| if !is_within_packed(tcx, local_decls, lvalue) { | ||
| debug!("is_disaligned({:?}) - not within packed", lvalue); | ||
| return false | ||
| } | ||
|
|
||
| let ty = lvalue.ty(local_decls, tcx).to_ty(tcx); | ||
| match tcx.layout_raw(param_env.and(ty)) { | ||
| Ok(layout) if layout.align.abi() == 1 => { | ||
| // if the alignment is 1, the type can't be further | ||
| // disaligned. | ||
| debug!("is_disaligned({:?}) - align = 1", lvalue); | ||
| false | ||
| } | ||
| _ => { | ||
| debug!("is_disaligned({:?}) - true", lvalue); | ||
| true | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn is_within_packed<'a, 'tcx, L>(tcx: TyCtxt<'a, 'tcx, 'tcx>, | ||
| local_decls: &L, | ||
| lvalue: &Lvalue<'tcx>) | ||
| -> bool | ||
| where L: HasLocalDecls<'tcx> | ||
| { | ||
| let mut lvalue = lvalue; | ||
| while let &Lvalue::Projection(box Projection { | ||
| ref base, ref elem | ||
| }) = lvalue { | ||
| match *elem { | ||
| // encountered a Deref, which is ABI-aligned | ||
| ProjectionElem::Deref => break, | ||
| ProjectionElem::Field(..) => { | ||
| let ty = base.ty(local_decls, tcx).to_ty(tcx); | ||
| match ty.sty { | ||
| ty::TyAdt(def, _) if def.repr.packed() => { | ||
| return true | ||
| } | ||
| _ => {} | ||
| } | ||
| } | ||
| _ => {} | ||
| } | ||
| lvalue = base; | ||
| } | ||
|
|
||
| false | ||
| } |
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
Oops, something went wrong.