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Run combine_duplicate_switch_targets after the simplification that pr…
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…oduces them
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saethlin committed Apr 21, 2023
1 parent b658050 commit 8ec49ad
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Showing 4 changed files with 19 additions and 20 deletions.
21 changes: 3 additions & 18 deletions compiler/rustc_mir_transform/src/instcombine.rs
Original file line number Diff line number Diff line change
@@ -1,11 +1,9 @@
//! Performs various peephole optimizations.
use crate::simplify::combine_duplicate_switch_targets;
use crate::MirPass;
use rustc_hir::Mutability;
use rustc_middle::mir::{
BinOp, Body, CastKind, Constant, ConstantKind, LocalDecls, Operand, Place, ProjectionElem,
Rvalue, SourceInfo, Statement, StatementKind, SwitchTargets, Terminator, TerminatorKind, UnOp,
};
use rustc_middle::mir::*;
use rustc_middle::ty::layout::ValidityRequirement;
use rustc_middle::ty::util::IntTypeExt;
use rustc_middle::ty::{self, ParamEnv, SubstsRef, Ty, TyCtxt};
Expand Down Expand Up @@ -46,7 +44,7 @@ impl<'tcx> MirPass<'tcx> for InstCombine {
&mut block.terminator.as_mut().unwrap(),
&mut block.statements,
);
ctx.combine_duplicate_switch_targets(&mut block.terminator.as_mut().unwrap());
combine_duplicate_switch_targets(block.terminator.as_mut().unwrap());
}
}
}
Expand Down Expand Up @@ -264,19 +262,6 @@ impl<'tcx> InstCombineContext<'tcx, '_> {
terminator.kind = TerminatorKind::Goto { target: destination_block };
}

fn combine_duplicate_switch_targets(&self, terminator: &mut Terminator<'tcx>) {
let TerminatorKind::SwitchInt { targets, .. } = &mut terminator.kind
else { return };

let otherwise = targets.otherwise();
if targets.iter().any(|t| t.1 == otherwise) {
*targets = SwitchTargets::new(
targets.iter().filter(|t| t.1 != otherwise),
targets.otherwise(),
);
}
}

fn combine_intrinsic_assert(
&self,
terminator: &mut Terminator<'tcx>,
Expand Down
14 changes: 14 additions & 0 deletions compiler/rustc_mir_transform/src/simplify.rs
Original file line number Diff line number Diff line change
Expand Up @@ -278,6 +278,18 @@ impl<'a, 'tcx> CfgSimplifier<'a, 'tcx> {
}
}

pub fn combine_duplicate_switch_targets(terminator: &mut Terminator<'_>) {
if let TerminatorKind::SwitchInt { targets, .. } = &mut terminator.kind {
let otherwise = targets.otherwise();
if targets.iter().any(|t| t.1 == otherwise) {
*targets = SwitchTargets::new(
targets.iter().filter(|t| t.1 != otherwise),
targets.otherwise(),
);
}
}
}

pub fn remove_duplicate_unreachable_blocks<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
struct OptApplier<'tcx> {
tcx: TyCtxt<'tcx>,
Expand All @@ -298,6 +310,8 @@ pub fn remove_duplicate_unreachable_blocks<'tcx>(tcx: TyCtxt<'tcx>, body: &mut B
}
}

combine_duplicate_switch_targets(terminator);

self.super_terminator(terminator, location);
}
}
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@
- // + literal: Const { ty: unsafe fn(Option<T>) -> T {Option::<T>::unwrap_unchecked}, val: Value(<ZST>) }
+ StorageLive(_3); // scope 0 at $DIR/unwrap_unchecked.rs:+1:9: +1:27
+ _4 = discriminant(_2); // scope 1 at $SRC_DIR/core/src/option.rs:LL:COL
+ switchInt(move _4) -> [0: bb1, 1: bb2, otherwise: bb1]; // scope 1 at $SRC_DIR/core/src/option.rs:LL:COL
+ switchInt(move _4) -> [1: bb2, otherwise: bb1]; // scope 1 at $SRC_DIR/core/src/option.rs:LL:COL
}

bb1: {
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@ fn ub_if_b(_1: Thing) -> Thing {

bb0: {
_2 = discriminant(_1); // scope 0 at $DIR/instcombine_duplicate_switch_targets_e2e.rs:+1:11: +1:12
switchInt(move _2) -> [0: bb2, 1: bb1, otherwise: bb1]; // scope 0 at $DIR/instcombine_duplicate_switch_targets_e2e.rs:+1:5: +1:12
switchInt(move _2) -> [0: bb2, otherwise: bb1]; // scope 0 at $DIR/instcombine_duplicate_switch_targets_e2e.rs:+1:5: +1:12
}

bb1: {
Expand Down

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