-
Notifications
You must be signed in to change notification settings - Fork 12.7k
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
- Loading branch information
Showing
27 changed files
with
941 additions
and
344 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
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 +1,192 @@ | ||
| use rustc_index::{bit_set::BitSet, IndexVec}; | ||
| use rustc_middle::bug; | ||
| use rustc_middle::mir::visit::{MutVisitor, PlaceContext, Visitor}; | ||
| use rustc_middle::mir::*; | ||
| use rustc_middle::ty::TyCtxt; | ||
|
|
||
| /// Various parts of MIR building introduce temporaries that are commonly not needed. | ||
| /// | ||
| /// Notably, `if CONST` and `match CONST` end up being used-once temporaries, which | ||
| /// obfuscates the structure for other passes and codegen, which would like to always | ||
| /// be able to just see the constant directly. | ||
| /// | ||
| /// At higher optimization levels fancier passes like GVN will take care of this | ||
| /// in a more general fashion, but this handles the easy cases so can run in debug. | ||
| /// | ||
| /// This only removes constants with a single-use because re-evaluating constants | ||
| /// isn't always an improvement, especially for large ones. | ||
| /// | ||
| /// It also removes *never*-used constants, since it had all the information | ||
| /// needed to do that too, including updating the debug info. | ||
| pub struct SingleUseConsts; | ||
|
|
||
| impl<'tcx> MirPass<'tcx> for SingleUseConsts { | ||
| fn is_enabled(&self, sess: &rustc_session::Session) -> bool { | ||
| sess.mir_opt_level() > 0 | ||
| } | ||
|
|
||
| fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { | ||
| let mut finder = SingleUseConstsFinder { | ||
| ineligible_locals: BitSet::new_empty(body.local_decls.len()), | ||
| locations: IndexVec::new(), | ||
| }; | ||
| finder.visit_body(body); | ||
|
|
||
| for (local, locations) in finder.locations.iter_enumerated() { | ||
| if finder.ineligible_locals.contains(local) { | ||
| continue; | ||
| } | ||
|
|
||
| let Some(init_loc) = locations.init_loc else { | ||
| continue; | ||
| }; | ||
|
|
||
| // We're only changing an operand, not the terminator kinds or successors | ||
| let basic_blocks = body.basic_blocks.as_mut_preserves_cfg(); | ||
| let init_statement = | ||
| basic_blocks[init_loc.block].statements[init_loc.statement_index].replace_nop(); | ||
| let StatementKind::Assign(place_and_rvalue) = init_statement.kind else { | ||
| bug!("No longer an assign?"); | ||
| }; | ||
| let (place, rvalue) = *place_and_rvalue; | ||
| debug_assert_eq!(place.as_local(), Some(local)); | ||
| let Rvalue::Use(operand) = rvalue else { bug!("No longer a use?") }; | ||
|
|
||
| let mut replacer = LocalReplacer { tcx, local, operand: Some(operand) }; | ||
|
|
||
| for var_debug_info in &mut body.var_debug_info { | ||
| replacer.visit_var_debug_info(var_debug_info); | ||
| } | ||
|
|
||
| let Some(use_loc) = locations.use_loc else { continue }; | ||
|
|
||
| let use_block = &mut basic_blocks[use_loc.block]; | ||
| if let Some(use_statement) = use_block.statements.get_mut(use_loc.statement_index) { | ||
| replacer.visit_statement(use_statement, use_loc); | ||
| } else { | ||
| replacer.visit_terminator(use_block.terminator_mut(), use_loc); | ||
| } | ||
|
|
||
| if replacer.operand.is_some() { | ||
| bug!( | ||
| "operand wasn't used replacing local {local:?} with locations {locations:?} in body {body:#?}" | ||
| ); | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| #[derive(Copy, Clone, Debug)] | ||
| struct LocationPair { | ||
| init_loc: Option<Location>, | ||
| use_loc: Option<Location>, | ||
| } | ||
|
|
||
| impl LocationPair { | ||
| fn new() -> Self { | ||
| Self { init_loc: None, use_loc: None } | ||
| } | ||
| } | ||
|
|
||
| struct SingleUseConstsFinder { | ||
| ineligible_locals: BitSet<Local>, | ||
| locations: IndexVec<Local, LocationPair>, | ||
| } | ||
|
|
||
| impl<'tcx> Visitor<'tcx> for SingleUseConstsFinder { | ||
| fn visit_assign(&mut self, place: &Place<'tcx>, rvalue: &Rvalue<'tcx>, location: Location) { | ||
| if let Some(local) = place.as_local() | ||
| && let Rvalue::Use(operand) = rvalue | ||
| && let Operand::Constant(_) = operand | ||
| { | ||
| let locations = self.locations.ensure_contains_elem(local, LocationPair::new); | ||
| if locations.init_loc.is_some() { | ||
| self.ineligible_locals.insert(local); | ||
| } else { | ||
| locations.init_loc = Some(location); | ||
| } | ||
| } else { | ||
| self.super_assign(place, rvalue, location); | ||
| } | ||
| } | ||
|
|
||
| fn visit_operand(&mut self, operand: &Operand<'tcx>, location: Location) { | ||
| if let Some(place) = operand.place() | ||
| && let Some(local) = place.as_local() | ||
| { | ||
| let locations = self.locations.ensure_contains_elem(local, LocationPair::new); | ||
| if locations.use_loc.is_some() { | ||
| self.ineligible_locals.insert(local); | ||
| } else { | ||
| locations.use_loc = Some(location); | ||
| } | ||
| } else { | ||
| self.super_operand(operand, location); | ||
| } | ||
| } | ||
|
|
||
| fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) { | ||
| match &statement.kind { | ||
| // Storage markers are irrelevant to this. | ||
| StatementKind::StorageLive(_) | StatementKind::StorageDead(_) => {} | ||
| _ => self.super_statement(statement, location), | ||
| } | ||
| } | ||
|
|
||
| fn visit_var_debug_info(&mut self, var_debug_info: &VarDebugInfo<'tcx>) { | ||
| if let VarDebugInfoContents::Place(place) = &var_debug_info.value | ||
| && let Some(_local) = place.as_local() | ||
| { | ||
| // It's a simple one that we can easily update | ||
| } else { | ||
| self.super_var_debug_info(var_debug_info); | ||
| } | ||
| } | ||
|
|
||
| fn visit_local(&mut self, local: Local, _context: PlaceContext, _location: Location) { | ||
| // If there's any path that gets here, rather than being understood elsewhere, | ||
| // then we'd better not do anything with this local. | ||
| self.ineligible_locals.insert(local); | ||
| } | ||
| } | ||
|
|
||
| struct LocalReplacer<'tcx> { | ||
| tcx: TyCtxt<'tcx>, | ||
| local: Local, | ||
| operand: Option<Operand<'tcx>>, | ||
| } | ||
|
|
||
| impl<'tcx> MutVisitor<'tcx> for LocalReplacer<'tcx> { | ||
| fn tcx(&self) -> TyCtxt<'tcx> { | ||
| self.tcx | ||
| } | ||
|
|
||
| fn visit_operand(&mut self, operand: &mut Operand<'tcx>, _location: Location) { | ||
| if let Operand::Copy(place) | Operand::Move(place) = operand | ||
| && let Some(local) = place.as_local() | ||
| && local == self.local | ||
| { | ||
| *operand = self.operand.take().unwrap_or_else(|| { | ||
| bug!("there was a second use of the operand"); | ||
| }); | ||
| } | ||
| } | ||
|
|
||
| fn visit_var_debug_info(&mut self, var_debug_info: &mut VarDebugInfo<'tcx>) { | ||
| if let VarDebugInfoContents::Place(place) = &var_debug_info.value | ||
| && let Some(local) = place.as_local() | ||
| && local == self.local | ||
| { | ||
| let const_op = self | ||
| .operand | ||
| .as_ref() | ||
| .unwrap_or_else(|| { | ||
| bug!("the operand was already stolen"); | ||
| }) | ||
| .constant() | ||
| .unwrap() | ||
| .clone(); | ||
| var_debug_info.value = VarDebugInfoContents::Const(const_op); | ||
| } | ||
| } | ||
| } |
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
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
Oops, something went wrong.