Allow Locals to be propagated into and from, but restricted to their own block
This commit is contained in:
Félix Fischer
parent
3fd2d4aaa6
commit
86927eddaf
@ -326,6 +326,8 @@ struct ConstPropagator<'mir, 'tcx> {
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// Because we have `MutVisitor` we can't obtain the `SourceInfo` from a `Location`. So we store
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// the last known `SourceInfo` here and just keep revisiting it.
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source_info: Option<SourceInfo>,
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// Locals we need to forget at the end of the current block
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locals_of_current_block: BitSet<Local>,
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}
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impl<'mir, 'tcx> LayoutOf for ConstPropagator<'mir, 'tcx> {
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@ -395,6 +397,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
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//FIXME(wesleywiser) we can't steal this because `Visitor::super_visit_body()` needs it
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local_decls: body.local_decls.clone(),
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source_info: None,
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locals_of_current_block: BitSet::new_empty(body.local_decls.len()),
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}
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}
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@ -409,8 +412,10 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
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}
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}
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fn remove_const(&mut self, local: Local) {
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self.ecx.frame_mut().locals[local] =
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/// Remove `local` from the pool of `Locals`. Allows writing to them,
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/// but not reading from them anymore.
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fn remove_const(ecx: &mut InterpCx<'mir, 'tcx, ConstPropMachine<'mir, 'tcx>>, local: Local) {
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ecx.frame_mut().locals[local] =
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LocalState { value: LocalValue::Uninitialized, layout: Cell::new(None) };
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}
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@ -756,6 +761,8 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
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enum ConstPropMode {
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/// The `Local` can be propagated into and reads of this `Local` can also be propagated.
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FullConstProp,
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/// The `Local` can only be propagated into and from its own block.
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OnlyInsideOwnBlock,
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/// The `Local` can be propagated into but reads cannot be propagated.
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OnlyPropagateInto,
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/// No propagation is allowed at all.
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@ -787,10 +794,18 @@ impl CanConstProp {
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// lint for x != y
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// FIXME(oli-obk): lint variables until they are used in a condition
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// FIXME(oli-obk): lint if return value is constant
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if cpv.local_kinds[local] == LocalKind::Arg || cpv.local_kinds[local] == LocalKind::Var
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{
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if cpv.local_kinds[local] == LocalKind::Arg {
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*val = ConstPropMode::OnlyPropagateInto;
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trace!("local {:?} can't be const propagated because it's not a temporary", local);
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trace!(
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"local {:?} can't be const propagated because it's a function argument",
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local
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);
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} else if cpv.local_kinds[local] == LocalKind::Var {
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*val = ConstPropMode::OnlyInsideOwnBlock;
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trace!(
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"local {:?} will only be propagated inside its block, because it's a user variable",
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local
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);
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}
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}
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cpv.visit_body(&body);
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@ -858,25 +873,35 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
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if let Some(local) = place.as_local() {
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let can_const_prop = self.can_const_prop[local];
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if let Some(()) = self.const_prop(rval, place_layout, source_info, place) {
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if can_const_prop == ConstPropMode::FullConstProp
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|| can_const_prop == ConstPropMode::OnlyPropagateInto
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{
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if can_const_prop != ConstPropMode::NoPropagation {
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// This will return None for Locals that are from other blocks,
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// so it should be okay to propagate from here on down.
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if let Some(value) = self.get_const(local) {
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if self.should_const_prop(value) {
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trace!("replacing {:?} with {:?}", rval, value);
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self.replace_with_const(rval, value, statement.source_info);
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if can_const_prop == ConstPropMode::FullConstProp {
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if can_const_prop == ConstPropMode::FullConstProp
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|| can_const_prop == ConstPropMode::OnlyInsideOwnBlock
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{
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trace!("propagated into {:?}", local);
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}
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}
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if can_const_prop == ConstPropMode::OnlyInsideOwnBlock {
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trace!(
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"found local restricted to its block. Will remove it from const-prop after block is finished. Local: {:?}",
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local
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);
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self.locals_of_current_block.insert(local);
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}
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}
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}
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}
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if self.can_const_prop[local] != ConstPropMode::FullConstProp {
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if self.can_const_prop[local] == ConstPropMode::OnlyPropagateInto
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|| self.can_const_prop[local] == ConstPropMode::NoPropagation
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{
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trace!("can't propagate into {:?}", local);
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if local != RETURN_PLACE {
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self.remove_const(local);
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Self::remove_const(&mut self.ecx, local);
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}
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}
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}
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@ -915,7 +940,7 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
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// doesn't use the invalid value
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match cond {
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Operand::Move(ref place) | Operand::Copy(ref place) => {
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self.remove_const(place.local);
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Self::remove_const(&mut self.ecx, place.local);
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}
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Operand::Constant(_) => {}
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}
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@ -992,5 +1017,13 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
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//FIXME(wesleywiser) Call does have Operands that could be const-propagated
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TerminatorKind::Call { .. } => {}
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}
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// We remove all Locals which are restricted in propagation to their containing blocks.
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// We wouldn't need to clone, but the borrow checker can't see that we're not aliasing
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// the locals_of_current_block field, so we need to clone it first.
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// let ecx = &mut self.ecx;
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for local in self.locals_of_current_block.iter() {
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Self::remove_const(&mut self.ecx, local);
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}
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self.locals_of_current_block.clear();
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}
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}
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@ -21,7 +21,14 @@
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// + literal: Const { ty: u32, val: Value(Scalar(0x00000001)) }
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StorageLive(_2); // scope 1 at $DIR/scalar_literal_propagation.rs:4:5: 4:15
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StorageLive(_3); // scope 1 at $DIR/scalar_literal_propagation.rs:4:13: 4:14
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_3 = _1; // scope 1 at $DIR/scalar_literal_propagation.rs:4:13: 4:14
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- _3 = _1; // scope 1 at $DIR/scalar_literal_propagation.rs:4:13: 4:14
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+ _3 = const 1u32; // scope 1 at $DIR/scalar_literal_propagation.rs:4:13: 4:14
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+ // ty::Const
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+ // + ty: u32
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+ // + val: Value(Scalar(0x00000001))
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+ // mir::Constant
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+ // + span: $DIR/scalar_literal_propagation.rs:4:13: 4:14
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+ // + literal: Const { ty: u32, val: Value(Scalar(0x00000001)) }
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_2 = const consume(move _3) -> bb1; // scope 1 at $DIR/scalar_literal_propagation.rs:4:5: 4:15
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// ty::Const
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// + ty: fn(u32) {consume}
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@ -29,7 +29,20 @@
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// + literal: Const { ty: u32, val: Value(Scalar(0x00000002)) }
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StorageLive(_2); // scope 1 at $DIR/tuple_literal_propagation.rs:5:5: 5:15
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StorageLive(_3); // scope 1 at $DIR/tuple_literal_propagation.rs:5:13: 5:14
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_3 = _1; // scope 1 at $DIR/tuple_literal_propagation.rs:5:13: 5:14
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- _3 = _1; // scope 1 at $DIR/tuple_literal_propagation.rs:5:13: 5:14
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+ _3 = (const 1u32, const 2u32); // scope 1 at $DIR/tuple_literal_propagation.rs:5:13: 5:14
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+ // ty::Const
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+ // + ty: u32
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+ // + val: Value(Scalar(0x00000001))
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+ // mir::Constant
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+ // + span: $DIR/tuple_literal_propagation.rs:5:13: 5:14
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+ // + literal: Const { ty: u32, val: Value(Scalar(0x00000001)) }
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+ // ty::Const
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+ // + ty: u32
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+ // + val: Value(Scalar(0x00000002))
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+ // mir::Constant
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+ // + span: $DIR/tuple_literal_propagation.rs:5:13: 5:14
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+ // + literal: Const { ty: u32, val: Value(Scalar(0x00000002)) }
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_2 = const consume(move _3) -> bb1; // scope 1 at $DIR/tuple_literal_propagation.rs:5:5: 5:15
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// ty::Const
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// + ty: fn((u32, u32)) {consume}
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@ -2,6 +2,7 @@
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// Regression test for issue #66856.
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//
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// compile-flags: -Zmir-opt-level=2
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// EMIT_MIR_FOR_EACH_BIT_WIDTH
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enum Src {
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Foo(u8),
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@ -0,0 +1,53 @@
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- // MIR for `main` before SimplifyArmIdentity
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+ // MIR for `main` after SimplifyArmIdentity
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fn main() -> () {
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let mut _0: (); // return place in scope 0 at $DIR/simplify-arm-identity.rs:17:11: 17:11
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let _1: Src as UserTypeProjection { base: UserType(0), projs: [] }; // in scope 0 at $DIR/simplify-arm-identity.rs:18:9: 18:10
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let mut _2: Dst; // in scope 0 at $DIR/simplify-arm-identity.rs:19:18: 22:6
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let mut _3: isize; // in scope 0 at $DIR/simplify-arm-identity.rs:20:9: 20:20
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let mut _5: u8; // in scope 0 at $DIR/simplify-arm-identity.rs:20:33: 20:34
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scope 1 {
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debug e => _1; // in scope 1 at $DIR/simplify-arm-identity.rs:18:9: 18:10
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let _4: u8; // in scope 1 at $DIR/simplify-arm-identity.rs:20:18: 20:19
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scope 2 {
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}
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scope 3 {
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debug x => _4; // in scope 3 at $DIR/simplify-arm-identity.rs:20:18: 20:19
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}
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}
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bb0: {
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StorageLive(_1); // scope 0 at $DIR/simplify-arm-identity.rs:18:9: 18:10
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((_1 as Foo).0: u8) = const 0u8; // scope 0 at $DIR/simplify-arm-identity.rs:18:18: 18:29
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// ty::Const
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// + ty: u8
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// + val: Value(Scalar(0x00))
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// mir::Constant
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// + span: $DIR/simplify-arm-identity.rs:18:27: 18:28
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// + literal: Const { ty: u8, val: Value(Scalar(0x00)) }
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discriminant(_1) = 0; // scope 0 at $DIR/simplify-arm-identity.rs:18:18: 18:29
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StorageLive(_2); // scope 1 at $DIR/simplify-arm-identity.rs:19:18: 22:6
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_3 = const 0isize; // scope 1 at $DIR/simplify-arm-identity.rs:20:9: 20:20
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// ty::Const
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// + ty: isize
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// + val: Value(Scalar(0x00000000))
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// mir::Constant
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// + span: $DIR/simplify-arm-identity.rs:20:9: 20:20
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// + literal: Const { ty: isize, val: Value(Scalar(0x00000000)) }
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_4 = ((_1 as Foo).0: u8); // scope 1 at $DIR/simplify-arm-identity.rs:20:18: 20:19
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((_2 as Foo).0: u8) = move _4; // scope 3 at $DIR/simplify-arm-identity.rs:20:24: 20:35
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discriminant(_2) = 0; // scope 3 at $DIR/simplify-arm-identity.rs:20:24: 20:35
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StorageDead(_2); // scope 1 at $DIR/simplify-arm-identity.rs:22:6: 22:7
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_0 = const (); // scope 0 at $DIR/simplify-arm-identity.rs:17:11: 23:2
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// ty::Const
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// + ty: ()
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// + val: Value(Scalar(<ZST>))
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// mir::Constant
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// + span: $DIR/simplify-arm-identity.rs:17:11: 23:2
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// + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
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StorageDead(_1); // scope 0 at $DIR/simplify-arm-identity.rs:23:1: 23:2
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return; // scope 0 at $DIR/simplify-arm-identity.rs:23:2: 23:2
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}
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}
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@ -0,0 +1,53 @@
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- // MIR for `main` before SimplifyArmIdentity
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+ // MIR for `main` after SimplifyArmIdentity
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fn main() -> () {
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let mut _0: (); // return place in scope 0 at $DIR/simplify-arm-identity.rs:17:11: 17:11
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let _1: Src as UserTypeProjection { base: UserType(0), projs: [] }; // in scope 0 at $DIR/simplify-arm-identity.rs:18:9: 18:10
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let mut _2: Dst; // in scope 0 at $DIR/simplify-arm-identity.rs:19:18: 22:6
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let mut _3: isize; // in scope 0 at $DIR/simplify-arm-identity.rs:20:9: 20:20
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let mut _5: u8; // in scope 0 at $DIR/simplify-arm-identity.rs:20:33: 20:34
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scope 1 {
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debug e => _1; // in scope 1 at $DIR/simplify-arm-identity.rs:18:9: 18:10
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let _4: u8; // in scope 1 at $DIR/simplify-arm-identity.rs:20:18: 20:19
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scope 2 {
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}
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scope 3 {
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debug x => _4; // in scope 3 at $DIR/simplify-arm-identity.rs:20:18: 20:19
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}
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}
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bb0: {
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StorageLive(_1); // scope 0 at $DIR/simplify-arm-identity.rs:18:9: 18:10
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((_1 as Foo).0: u8) = const 0u8; // scope 0 at $DIR/simplify-arm-identity.rs:18:18: 18:29
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// ty::Const
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// + ty: u8
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// + val: Value(Scalar(0x00))
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// mir::Constant
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// + span: $DIR/simplify-arm-identity.rs:18:27: 18:28
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// + literal: Const { ty: u8, val: Value(Scalar(0x00)) }
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discriminant(_1) = 0; // scope 0 at $DIR/simplify-arm-identity.rs:18:18: 18:29
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StorageLive(_2); // scope 1 at $DIR/simplify-arm-identity.rs:19:18: 22:6
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_3 = const 0isize; // scope 1 at $DIR/simplify-arm-identity.rs:20:9: 20:20
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// ty::Const
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// + ty: isize
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// + val: Value(Scalar(0x0000000000000000))
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// mir::Constant
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// + span: $DIR/simplify-arm-identity.rs:20:9: 20:20
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// + literal: Const { ty: isize, val: Value(Scalar(0x0000000000000000)) }
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_4 = ((_1 as Foo).0: u8); // scope 1 at $DIR/simplify-arm-identity.rs:20:18: 20:19
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((_2 as Foo).0: u8) = move _4; // scope 3 at $DIR/simplify-arm-identity.rs:20:24: 20:35
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discriminant(_2) = 0; // scope 3 at $DIR/simplify-arm-identity.rs:20:24: 20:35
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StorageDead(_2); // scope 1 at $DIR/simplify-arm-identity.rs:22:6: 22:7
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_0 = const (); // scope 0 at $DIR/simplify-arm-identity.rs:17:11: 23:2
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// ty::Const
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// + ty: ()
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// + val: Value(Scalar(<ZST>))
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// mir::Constant
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// + span: $DIR/simplify-arm-identity.rs:17:11: 23:2
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// + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
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StorageDead(_1); // scope 0 at $DIR/simplify-arm-identity.rs:23:1: 23:2
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return; // scope 0 at $DIR/simplify-arm-identity.rs:23:2: 23:2
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}
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}
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@ -10,19 +10,24 @@
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}
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bb0: {
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nop; // scope 0 at $DIR/simplify_match.rs:6:11: 6:31
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nop; // scope 0 at $DIR/simplify_match.rs:6:17: 6:18
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nop; // scope 0 at $DIR/simplify_match.rs:6:21: 6:26
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nop; // scope 1 at $DIR/simplify_match.rs:6:28: 6:29
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nop; // scope 0 at $DIR/simplify_match.rs:6:30: 6:31
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- switchInt(const false) -> [false: bb1, otherwise: bb2]; // scope 0 at $DIR/simplify_match.rs:7:9: 7:13
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- // ty::Const
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- // + ty: bool
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- // + val: Value(Scalar(0x00))
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- // mir::Constant
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- // + span: $DIR/simplify_match.rs:6:21: 6:26
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- // + literal: Const { ty: bool, val: Value(Scalar(0x00)) }
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+ goto -> bb1; // scope 0 at $DIR/simplify_match.rs:7:9: 7:13
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StorageLive(_1); // scope 0 at $DIR/simplify_match.rs:6:11: 6:31
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StorageLive(_2); // scope 0 at $DIR/simplify_match.rs:6:17: 6:18
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_2 = const false; // scope 0 at $DIR/simplify_match.rs:6:21: 6:26
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// ty::Const
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// + ty: bool
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// + val: Value(Scalar(0x00))
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// mir::Constant
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// + span: $DIR/simplify_match.rs:6:21: 6:26
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// + literal: Const { ty: bool, val: Value(Scalar(0x00)) }
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_1 = const false; // scope 1 at $DIR/simplify_match.rs:6:28: 6:29
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// ty::Const
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// + ty: bool
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// + val: Value(Scalar(0x00))
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// mir::Constant
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// + span: $DIR/simplify_match.rs:6:28: 6:29
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// + literal: Const { ty: bool, val: Value(Scalar(0x00)) }
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StorageDead(_2); // scope 0 at $DIR/simplify_match.rs:6:30: 6:31
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goto -> bb1; // scope 0 at $DIR/simplify_match.rs:7:9: 7:13
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}
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bb1: {
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@ -47,7 +52,7 @@
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}
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bb3: {
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nop; // scope 0 at $DIR/simplify_match.rs:10:1: 10:2
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StorageDead(_1); // scope 0 at $DIR/simplify_match.rs:10:1: 10:2
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return; // scope 0 at $DIR/simplify_match.rs:10:2: 10:2
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}
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}
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@ -1,5 +1,5 @@
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// error-pattern:attempt to divide by zero
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#[allow(unconditional_panic)]
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fn main() {
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let y = 0;
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let _z = 1 / y;
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@ -1,6 +1,6 @@
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// Test bounds checking for DST raw slices
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// error-pattern:index out of bounds
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#[allow(unconditional_panic)]
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fn main() {
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let a: *const [_] = &[1, 2, 3];
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unsafe {
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@ -1,5 +1,5 @@
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// error-pattern:attempt to calculate the remainder with a divisor of zero
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#[allow(unconditional_panic)]
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fn main() {
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let y = 0;
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let _z = 1 % y;
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