src/librustc_mir/transform/deaggregator.rs

   1 use crate::transform::{MirPass, MirSource};
   2 use crate::util::expand_aggregate;
   3 use rustc_middle::mir::*;
   4 use rustc_middle::ty::TyCtxt;
   5
   6 pub struct Deaggregator;
   7
   8 impl<'tcx> MirPass<'tcx> for Deaggregator {
   9     fn run_pass(&self, tcx: TyCtxt<'tcx>, _source: MirSource<'tcx>, body: &mut Body<'tcx>) {
  10         let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut();
  11         let local_decls = &*local_decls;
  12         for bb in basic_blocks {
  13             bb.expand_statements(|stmt| {
  14                 // FIXME(eddyb) don't match twice on `stmt.kind` (post-NLL).
  15                 match stmt.kind {
  16                     // FIXME(#48193) Deaggregate arrays when it's cheaper to do so.
  17                     StatementKind::Assign(box (
  18                         _,
  19                         Rvalue::Aggregate(box AggregateKind::Array(_), _),
  20                     )) => {
  21                         return None;
  22                     }
  23                     StatementKind::Assign(box (_, Rvalue::Aggregate(_, _))) => {}
  24                     _ => return None,
  25                 }
  26
  27                 let stmt = stmt.replace_nop();
  28                 let source_info = stmt.source_info;
  29                 let (lhs, kind, operands) = match stmt.kind {
  30                     StatementKind::Assign(box (lhs, Rvalue::Aggregate(kind, operands))) => {
  31                         (lhs, kind, operands)
  32                     }
  33                     _ => bug!(),
  34                 };
  35
  36                 Some(expand_aggregate(
  37                     lhs,
  38                     operands.into_iter().map(|op| {
  39                         let ty = op.ty(local_decls, tcx);
  40                         (op, ty)
  41                     }),
  42                     *kind,
  43                     source_info,
  44                     tcx,
  45                 ))
  46             });
  47         }
  48     }
  49 }