mirror of https://github.com/rust-lang/rust.git
mir-opt: Replace clone on primitives with copy
We can't do it for everything, but it would be nice to at least stop making calls to clone methods in debug from things like derived-clones.
This commit is contained in:
Scott McMurray
parent
d7b282b886
commit
0d4a3f11e2
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@ -1915,6 +1915,27 @@ impl<'tcx> Place<'tcx> {
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(base, proj)
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})
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}
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/// Generates a new place by appending `more_projections` to the existing ones
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/// and interning the result.
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pub fn project_deeper(self, more_projections: &[PlaceElem<'tcx>], tcx: TyCtxt<'tcx>) -> Self {
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if more_projections.is_empty() {
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return self;
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}
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let mut v: Vec<PlaceElem<'tcx>>;
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let new_projections = if self.projection.is_empty() {
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more_projections
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} else {
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v = Vec::with_capacity(self.projection.len() + more_projections.len());
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v.extend(self.projection);
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v.extend(more_projections);
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&v
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};
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Place { local: self.local, projection: tcx.intern_place_elems(new_projections) }
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}
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}
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impl From<Local> for Place<'_> {
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@ -2187,6 +2208,15 @@ impl<'tcx> Operand<'tcx> {
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Operand::Copy(_) | Operand::Move(_) => None,
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}
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}
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/// Gets the `ty::FnDef` from an operand if it's a constant function item.
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///
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/// While this is unlikely in general, it's the normal case of what you'll
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/// find as the `func` in a [`TerminatorKind::Call`].
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pub fn const_fn_def(&self) -> Option<(DefId, SubstsRef<'tcx>)> {
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let const_ty = self.constant()?.literal.const_for_ty()?.ty();
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if let ty::FnDef(def_id, substs) = *const_ty.kind() { Some((def_id, substs)) } else { None }
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}
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}
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///////////////////////////////////////////////////////////////////////////
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@ -4,9 +4,9 @@ use crate::MirPass;
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use rustc_hir::Mutability;
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use rustc_middle::mir::{
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BinOp, Body, Constant, LocalDecls, Operand, Place, ProjectionElem, Rvalue, SourceInfo,
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StatementKind, UnOp,
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Statement, StatementKind, Terminator, TerminatorKind, UnOp,
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};
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use rustc_middle::ty::{self, TyCtxt};
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use rustc_middle::ty::{self, Ty, TyCtxt, TyKind};
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pub struct InstCombine;
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@ -29,6 +29,11 @@ impl<'tcx> MirPass<'tcx> for InstCombine {
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_ => {}
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}
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}
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ctx.combine_primitive_clone(
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&mut block.terminator.as_mut().unwrap(),
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&mut block.statements,
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);
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}
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}
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}
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@ -130,4 +135,80 @@ impl<'tcx> InstCombineContext<'tcx, '_> {
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}
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}
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}
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fn combine_primitive_clone(
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&self,
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terminator: &mut Terminator<'tcx>,
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statements: &mut Vec<Statement<'tcx>>,
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) {
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let TerminatorKind::Call { func, args, destination, .. } = &mut terminator.kind
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else { return };
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// It's definitely not a clone if there are multiple arguments
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if args.len() != 1 {
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return;
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}
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let Some((destination_place, destination_block)) = *destination
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else { return };
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// Only bother looking more if it's easy to know what we're calling
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let Some((fn_def_id, fn_substs)) = func.const_fn_def()
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else { return };
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// Clone needs one subst, so we can cheaply rule out other stuff
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if fn_substs.len() != 1 {
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return;
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}
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// These types are easily available from locals, so check that before
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// doing DefId lookups to figure out what we're actually calling.
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let arg_ty = args[0].ty(self.local_decls, self.tcx);
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let ty::Ref(_region, inner_ty, Mutability::Not) = *arg_ty.kind()
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else { return };
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if !is_trivially_pure_copy(self.tcx, inner_ty) {
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return;
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}
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let trait_def_id = self.tcx.trait_of_item(fn_def_id);
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if trait_def_id.is_none() || trait_def_id != self.tcx.lang_items().clone_trait() {
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return;
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}
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if !self.tcx.consider_optimizing(|| {
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format!(
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"InstCombine - Call: {:?} SourceInfo: {:?}",
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(fn_def_id, fn_substs),
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terminator.source_info
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)
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}) {
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return;
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}
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let Some(arg_place) = args.pop().unwrap().place()
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else { return };
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statements.push(Statement {
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source_info: terminator.source_info,
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kind: StatementKind::Assign(box (
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destination_place,
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Rvalue::Use(Operand::Copy(
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arg_place.project_deeper(&[ProjectionElem::Deref], self.tcx),
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)),
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)),
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});
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terminator.kind = TerminatorKind::Goto { target: destination_block };
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}
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}
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fn is_trivially_pure_copy<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool {
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use TyKind::*;
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match *ty.kind() {
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Bool | Char | Int(..) | Uint(..) | Float(..) => true,
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Array(element_ty, _len) => is_trivially_pure_copy(tcx, element_ty),
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Tuple(field_tys) => field_tys.iter().all(|x| is_trivially_pure_copy(tcx, x)),
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_ => false,
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}
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}
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@ -6,7 +6,7 @@
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pub fn f() {
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let a = A;
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let b = (0i32, 1i32, 2i32, 3i32);
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let b = (0i32, 1i32, 2i32, 3 as *const i32);
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let c = || {};
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a(String::new(), String::new());
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@ -21,7 +21,7 @@ struct A(String, String);
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// CHECK-NOT: inlinehint
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// CHECK-SAME: {{$}}
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// CHECK: ; <(i32, i32, i32, i32) as core::clone::Clone>::clone
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// CHECK: ; <(i32, i32, i32, *const i{{16|32|64}}) as core::clone::Clone>::clone
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// CHECK-NEXT: ; Function Attrs: inlinehint
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// CHECK: ; inline_hint::f::{closure#0}
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@ -0,0 +1,19 @@
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// compile-flags: -C opt-level=0 -Z inline_mir=no
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// EMIT_MIR combine_clone_of_primitives.{impl#0}-clone.InstCombine.diff
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#[derive(Clone)]
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struct MyThing<T> {
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v: T,
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i: u64,
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a: [f32; 3],
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}
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fn main() {
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let x = MyThing::<i16> { v: 2, i: 3, a: [0.0; 3] };
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let y = x.clone();
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assert_eq!(y.v, 2);
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assert_eq!(y.i, 3);
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assert_eq!(y.a, [0.0; 3]);
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}
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@ -0,0 +1,80 @@
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- // MIR for `<impl at $DIR/combine_clone_of_primitives.rs:5:10: 5:15>::clone` before InstCombine
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+ // MIR for `<impl at $DIR/combine_clone_of_primitives.rs:5:10: 5:15>::clone` after InstCombine
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fn <impl at $DIR/combine_clone_of_primitives.rs:5:10: 5:15>::clone(_1: &MyThing<T>) -> MyThing<T> {
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debug self => _1; // in scope 0 at $DIR/combine_clone_of_primitives.rs:5:10: 5:15
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let mut _0: MyThing<T>; // return place in scope 0 at $DIR/combine_clone_of_primitives.rs:5:10: 5:15
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let _2: &T; // in scope 0 at $DIR/combine_clone_of_primitives.rs:7:5: 7:9
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let _3: &u64; // in scope 0 at $DIR/combine_clone_of_primitives.rs:8:5: 8:11
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let _4: &[f32; 3]; // in scope 0 at $DIR/combine_clone_of_primitives.rs:9:5: 9:16
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let mut _5: T; // in scope 0 at $DIR/combine_clone_of_primitives.rs:7:5: 7:9
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let mut _6: &T; // in scope 0 at $DIR/combine_clone_of_primitives.rs:7:5: 7:9
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let _7: &T; // in scope 0 at $DIR/combine_clone_of_primitives.rs:7:5: 7:9
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let mut _8: u64; // in scope 0 at $DIR/combine_clone_of_primitives.rs:8:5: 8:11
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let mut _9: &u64; // in scope 0 at $DIR/combine_clone_of_primitives.rs:8:5: 8:11
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let _10: &u64; // in scope 0 at $DIR/combine_clone_of_primitives.rs:8:5: 8:11
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let mut _11: [f32; 3]; // in scope 0 at $DIR/combine_clone_of_primitives.rs:9:5: 9:16
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let mut _12: &[f32; 3]; // in scope 0 at $DIR/combine_clone_of_primitives.rs:9:5: 9:16
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let _13: &[f32; 3]; // in scope 0 at $DIR/combine_clone_of_primitives.rs:9:5: 9:16
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scope 1 {
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debug __self_0_0 => _2; // in scope 1 at $DIR/combine_clone_of_primitives.rs:7:5: 7:9
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debug __self_0_1 => _3; // in scope 1 at $DIR/combine_clone_of_primitives.rs:8:5: 8:11
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debug __self_0_2 => _4; // in scope 1 at $DIR/combine_clone_of_primitives.rs:9:5: 9:16
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}
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bb0: {
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_2 = &((*_1).0: T); // scope 0 at $DIR/combine_clone_of_primitives.rs:7:5: 7:9
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_3 = &((*_1).1: u64); // scope 0 at $DIR/combine_clone_of_primitives.rs:8:5: 8:11
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_4 = &((*_1).2: [f32; 3]); // scope 0 at $DIR/combine_clone_of_primitives.rs:9:5: 9:16
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- _7 = &(*_2); // scope 1 at $DIR/combine_clone_of_primitives.rs:7:5: 7:9
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- _6 = &(*_7); // scope 1 at $DIR/combine_clone_of_primitives.rs:7:5: 7:9
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+ _7 = _2; // scope 1 at $DIR/combine_clone_of_primitives.rs:7:5: 7:9
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+ _6 = _7; // scope 1 at $DIR/combine_clone_of_primitives.rs:7:5: 7:9
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_5 = <T as Clone>::clone(move _6) -> bb1; // scope 1 at $DIR/combine_clone_of_primitives.rs:7:5: 7:9
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// mir::Constant
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// + span: $DIR/combine_clone_of_primitives.rs:7:5: 7:9
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// + literal: Const { ty: for<'r> fn(&'r T) -> T {<T as Clone>::clone}, val: Value(Scalar(<ZST>)) }
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}
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bb1: {
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- _10 = &(*_3); // scope 1 at $DIR/combine_clone_of_primitives.rs:8:5: 8:11
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- _9 = &(*_10); // scope 1 at $DIR/combine_clone_of_primitives.rs:8:5: 8:11
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- _8 = <u64 as Clone>::clone(move _9) -> [return: bb2, unwind: bb4]; // scope 1 at $DIR/combine_clone_of_primitives.rs:8:5: 8:11
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- // mir::Constant
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- // + span: $DIR/combine_clone_of_primitives.rs:8:5: 8:11
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- // + literal: Const { ty: for<'r> fn(&'r u64) -> u64 {<u64 as Clone>::clone}, val: Value(Scalar(<ZST>)) }
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+ _10 = _3; // scope 1 at $DIR/combine_clone_of_primitives.rs:8:5: 8:11
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+ _9 = _10; // scope 1 at $DIR/combine_clone_of_primitives.rs:8:5: 8:11
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+ _8 = (*_9); // scope 1 at $DIR/combine_clone_of_primitives.rs:8:5: 8:11
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+ goto -> bb2; // scope 1 at $DIR/combine_clone_of_primitives.rs:8:5: 8:11
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}
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bb2: {
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- _13 = &(*_4); // scope 1 at $DIR/combine_clone_of_primitives.rs:9:5: 9:16
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- _12 = &(*_13); // scope 1 at $DIR/combine_clone_of_primitives.rs:9:5: 9:16
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- _11 = <[f32; 3] as Clone>::clone(move _12) -> [return: bb3, unwind: bb4]; // scope 1 at $DIR/combine_clone_of_primitives.rs:9:5: 9:16
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- // mir::Constant
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- // + span: $DIR/combine_clone_of_primitives.rs:9:5: 9:16
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- // + literal: Const { ty: for<'r> fn(&'r [f32; 3]) -> [f32; 3] {<[f32; 3] as Clone>::clone}, val: Value(Scalar(<ZST>)) }
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+ _13 = _4; // scope 1 at $DIR/combine_clone_of_primitives.rs:9:5: 9:16
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+ _12 = _13; // scope 1 at $DIR/combine_clone_of_primitives.rs:9:5: 9:16
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+ _11 = (*_12); // scope 1 at $DIR/combine_clone_of_primitives.rs:9:5: 9:16
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+ goto -> bb3; // scope 1 at $DIR/combine_clone_of_primitives.rs:9:5: 9:16
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}
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bb3: {
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(_0.0: T) = move _5; // scope 1 at $DIR/combine_clone_of_primitives.rs:5:10: 5:15
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(_0.1: u64) = move _8; // scope 1 at $DIR/combine_clone_of_primitives.rs:5:10: 5:15
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(_0.2: [f32; 3]) = move _11; // scope 1 at $DIR/combine_clone_of_primitives.rs:5:10: 5:15
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return; // scope 0 at $DIR/combine_clone_of_primitives.rs:5:15: 5:15
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}
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bb4 (cleanup): {
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drop(_5) -> bb5; // scope 1 at $DIR/combine_clone_of_primitives.rs:5:14: 5:15
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}
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bb5 (cleanup): {
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resume; // scope 0 at $DIR/combine_clone_of_primitives.rs:5:10: 5:15
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}
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}
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