-
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.
Auto merge of #107009 - cjgillot:jump-threading, r=pnkfelix
Implement jump threading MIR opt This pass is an attempt to generalize `ConstGoto` and `SeparateConstSwitch` passes into a more complete jump threading pass. This pass is rather heavy, as it performs a truncated backwards DFS on MIR starting from each `SwitchInt` terminator. This backwards DFS remains very limited, as it only walks through `Goto` terminators. It is build to support constants and discriminants, and a propagating through a very limited set of operations. The pass successfully manages to disentangle the `Some(x?)` use case and the DFA use case. It still needs a few tests before being ready.
- Loading branch information
Showing
31 changed files
with
2,797 additions
and
137 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
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 +1,98 @@ | ||
| use rustc_middle::mir::visit::*; | ||
| use rustc_middle::mir::*; | ||
| use rustc_middle::ty::{self, ParamEnv, Ty, TyCtxt}; | ||
|
|
||
| const INSTR_COST: usize = 5; | ||
| const CALL_PENALTY: usize = 25; | ||
| const LANDINGPAD_PENALTY: usize = 50; | ||
| const RESUME_PENALTY: usize = 45; | ||
|
|
||
| /// Verify that the callee body is compatible with the caller. | ||
| #[derive(Clone)] | ||
| pub(crate) struct CostChecker<'b, 'tcx> { | ||
| tcx: TyCtxt<'tcx>, | ||
| param_env: ParamEnv<'tcx>, | ||
| cost: usize, | ||
| callee_body: &'b Body<'tcx>, | ||
| instance: Option<ty::Instance<'tcx>>, | ||
| } | ||
|
|
||
| impl<'b, 'tcx> CostChecker<'b, 'tcx> { | ||
| pub fn new( | ||
| tcx: TyCtxt<'tcx>, | ||
| param_env: ParamEnv<'tcx>, | ||
| instance: Option<ty::Instance<'tcx>>, | ||
| callee_body: &'b Body<'tcx>, | ||
| ) -> CostChecker<'b, 'tcx> { | ||
| CostChecker { tcx, param_env, callee_body, instance, cost: 0 } | ||
| } | ||
|
|
||
| pub fn cost(&self) -> usize { | ||
| self.cost | ||
| } | ||
|
|
||
| fn instantiate_ty(&self, v: Ty<'tcx>) -> Ty<'tcx> { | ||
| if let Some(instance) = self.instance { | ||
| instance.instantiate_mir(self.tcx, ty::EarlyBinder::bind(&v)) | ||
| } else { | ||
| v | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> { | ||
| fn visit_statement(&mut self, statement: &Statement<'tcx>, _: Location) { | ||
| // Don't count StorageLive/StorageDead in the inlining cost. | ||
| match statement.kind { | ||
| StatementKind::StorageLive(_) | ||
| | StatementKind::StorageDead(_) | ||
| | StatementKind::Deinit(_) | ||
| | StatementKind::Nop => {} | ||
| _ => self.cost += INSTR_COST, | ||
| } | ||
| } | ||
|
|
||
| fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, _: Location) { | ||
| let tcx = self.tcx; | ||
| match terminator.kind { | ||
| TerminatorKind::Drop { ref place, unwind, .. } => { | ||
| // If the place doesn't actually need dropping, treat it like a regular goto. | ||
| let ty = self.instantiate_ty(place.ty(self.callee_body, tcx).ty); | ||
| if ty.needs_drop(tcx, self.param_env) { | ||
| self.cost += CALL_PENALTY; | ||
| if let UnwindAction::Cleanup(_) = unwind { | ||
| self.cost += LANDINGPAD_PENALTY; | ||
| } | ||
| } else { | ||
| self.cost += INSTR_COST; | ||
| } | ||
| } | ||
| TerminatorKind::Call { func: Operand::Constant(ref f), unwind, .. } => { | ||
| let fn_ty = self.instantiate_ty(f.const_.ty()); | ||
| self.cost += if let ty::FnDef(def_id, _) = *fn_ty.kind() && tcx.is_intrinsic(def_id) { | ||
| // Don't give intrinsics the extra penalty for calls | ||
| INSTR_COST | ||
| } else { | ||
| CALL_PENALTY | ||
| }; | ||
| if let UnwindAction::Cleanup(_) = unwind { | ||
| self.cost += LANDINGPAD_PENALTY; | ||
| } | ||
| } | ||
| TerminatorKind::Assert { unwind, .. } => { | ||
| self.cost += CALL_PENALTY; | ||
| if let UnwindAction::Cleanup(_) = unwind { | ||
| self.cost += LANDINGPAD_PENALTY; | ||
| } | ||
| } | ||
| TerminatorKind::UnwindResume => self.cost += RESUME_PENALTY, | ||
| TerminatorKind::InlineAsm { unwind, .. } => { | ||
| self.cost += INSTR_COST; | ||
| if let UnwindAction::Cleanup(_) = unwind { | ||
| self.cost += LANDINGPAD_PENALTY; | ||
| } | ||
| } | ||
| _ => self.cost += INSTR_COST, | ||
| } | ||
| } | ||
| } |
Oops, something went wrong.