Rollup merge of #71697 - felix91gr:new_prop_into_fn_call, r=wesleywiser
Added MIR constant propagation of Scalars into function call arguments Now for the function call arguments! Caveats: 1. It's only being enabled at `mir-opt-2` or higher, because currently codegen gives performance regressions with this optimization. 2. Only propagates Scalars. Tuples and references (references are `Indirect`, right??) are not being propagated into as of this PR. 3. Maybe more tests would be nice? 4. I need (shamefully) to ask @wesleywiser to write in his words (or explain to me, and then I can write it down) why we want to ignore propagation into `ScalarPairs` and `Indirect` arguments. r? @wesleywiser
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@ -787,6 +787,7 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
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| NonMutatingUse(NonMutatingUseContext::Inspect)
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| NonMutatingUse(NonMutatingUseContext::Projection)
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| NonUse(_) => {}
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// FIXME(felix91gr): explain the reasoning behind this
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MutatingUse(MutatingUseContext::Projection) => {
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if self.local_kinds[local] != LocalKind::Temp {
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self.can_const_prop[local] = ConstPropMode::NoPropagation;
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@ -969,13 +970,58 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
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| TerminatorKind::GeneratorDrop
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| TerminatorKind::FalseEdges { .. }
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| TerminatorKind::FalseUnwind { .. } => {}
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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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// Every argument in our function calls can be const propagated.
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TerminatorKind::Call { ref mut args, .. } => {
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let mir_opt_level = self.tcx.sess.opts.debugging_opts.mir_opt_level;
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// Constant Propagation into function call arguments is gated
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// under mir-opt-level 2, because LLVM codegen gives performance
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// regressions with it.
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if mir_opt_level >= 2 {
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for opr in args {
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/*
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The following code would appear to be incomplete, because
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the function `Operand::place()` returns `None` if the
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`Operand` is of the variant `Operand::Constant`. In this
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context however, that variant will never appear. This is why:
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When constructing the MIR, all function call arguments are
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copied into `Locals` of `LocalKind::Temp`. At least, all arguments
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that are not unsized (Less than 0.1% are unsized. See #71170
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to learn more about those).
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This means that, conversely, all `Operands` found as function call
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arguments are of the variant `Operand::Copy`. This allows us to
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simplify our handling of `Operands` in this case.
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*/
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if let Some(l) = opr.place().and_then(|p| p.as_local()) {
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if let Some(value) = self.get_const(l) {
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if self.should_const_prop(value) {
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// FIXME(felix91gr): this code only handles `Scalar` cases.
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// For now, we're not handling `ScalarPair` cases because
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// doing so here would require a lot of code duplication.
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// We should hopefully generalize `Operand` handling into a fn,
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// and use it to do const-prop here and everywhere else
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// where it makes sense.
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if let interpret::Operand::Immediate(
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interpret::Immediate::Scalar(
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interpret::ScalarMaybeUndef::Scalar(scalar),
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),
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) = *value
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{
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*opr = self.operand_from_scalar(
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scalar,
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value.layout.ty,
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source_info.span,
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);
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}
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}
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}
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}
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}
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}
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}
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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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@ -22,20 +22,27 @@
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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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- _2 = const consume(move _3) -> bb1; // scope 1 at $DIR/scalar_literal_propagation.rs:4:5: 4:15
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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::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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+ _2 = const consume(const 1u32) -> 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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// + val: Value(Scalar(<ZST>))
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// mir::Constant
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// + span: $DIR/scalar_literal_propagation.rs:4:5: 4:12
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// + literal: Const { ty: fn(u32) {consume}, val: Value(Scalar(<ZST>)) }
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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:4:5: 4:15
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+ // + literal: Const { ty: u32, val: Value(Scalar(0x00000001)) }
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}
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bb1: {
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@ -50,6 +50,7 @@
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- StorageDead(_2); // scope 0 at $DIR/simplify-locals-removes-unused-consts.rs:13:27: 13:28
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- StorageDead(_1); // scope 0 at $DIR/simplify-locals-removes-unused-consts.rs:13:28: 13:29
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- StorageLive(_4); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:14:5: 14:22
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- StorageLive(_5); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:14:13: 14:21
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- StorageLive(_6); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:14:14: 14:16
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- _6 = const (); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:14:14: 14:16
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- // ty::Const
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@ -66,6 +67,13 @@
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- // mir::Constant
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- // + span: $DIR/simplify-locals-removes-unused-consts.rs:14:18: 14:20
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- // + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
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- _5 = const ((), ()); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:14:13: 14:21
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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-locals-removes-unused-consts.rs:14:13: 14:21
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- // + literal: Const { ty: ((), ()), val: Value(Scalar(<ZST>)) }
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- StorageDead(_7); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:14:20: 14:21
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- StorageDead(_6); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:14:20: 14:21
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- _4 = const use_zst(const ((), ())) -> bb1; // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:14:5: 14:22
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@ -79,13 +87,15 @@
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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-locals-removes-unused-consts.rs:14:13: 14:21
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// + span: $DIR/simplify-locals-removes-unused-consts.rs:14:5: 14:22
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// + literal: Const { ty: ((), ()), val: Value(Scalar(<ZST>)) }
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}
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bb1: {
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- StorageDead(_5); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:14:21: 14:22
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- StorageDead(_4); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:14:22: 14:23
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- StorageLive(_8); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:5: 16:35
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- StorageLive(_9); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:12: 16:34
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- StorageLive(_10); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:12: 16:30
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- StorageLive(_11); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:12: 16:28
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- _11 = const Temp { x: 40u8 }; // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:12: 16:28
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@ -105,6 +115,13 @@
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- // mir::Constant
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- // + span: $DIR/simplify-locals-removes-unused-consts.rs:16:12: 16:30
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- // + literal: Const { ty: u8, val: Value(Scalar(0x28)) }
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- _9 = const 42u8; // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:12: 16:34
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- // ty::Const
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- // + ty: u8
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- // + val: Value(Scalar(0x2a))
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- // mir::Constant
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- // + span: $DIR/simplify-locals-removes-unused-consts.rs:16:12: 16:34
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- // + literal: Const { ty: u8, val: Value(Scalar(0x2a)) }
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- StorageDead(_10); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:33: 16:34
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- _8 = const use_u8(const 42u8) -> bb2; // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:5: 16:35
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- // ty::Const
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@ -117,11 +134,12 @@
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// + ty: u8
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// + val: Value(Scalar(0x2a))
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// mir::Constant
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// + span: $DIR/simplify-locals-removes-unused-consts.rs:16:12: 16:34
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// + span: $DIR/simplify-locals-removes-unused-consts.rs:16:5: 16:35
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// + literal: Const { ty: u8, val: Value(Scalar(0x2a)) }
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}
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bb2: {
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- StorageDead(_9); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:34: 16:35
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- StorageDead(_11); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:35: 16:36
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- StorageDead(_8); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:35: 16:36
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+ StorageDead(_2); // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:35: 16:36
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