src/librustc_mir/transform/deaggregator.rs

   1 use rustc::mir::*;
   2 use rustc::ty::TyCtxt;
   3 use crate::transform::{MirPass, MirSource};
   4 use crate::util::expand_aggregate;
   5
   6 pub struct Deaggregator;
   7
   8 impl MirPass for Deaggregator {
   9     fn run_pass<'a, 'tcx>(&self,
  10                           tcx: TyCtxt<'a, 'tcx, 'tcx>,
  11                           _source: MirSource<'tcx>,
  12                           body: &mut Body<'tcx>) {
  13         let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut();
  14         let local_decls = &*local_decls;
  15         for bb in basic_blocks {
  16             bb.expand_statements(|stmt| {
  17                 // FIXME(eddyb) don't match twice on `stmt.kind` (post-NLL).
  18                 if let StatementKind::Assign(_, ref rhs) = stmt.kind {
  19                     if let Rvalue::Aggregate(ref kind, _) = **rhs {
  20                         // FIXME(#48193) Deaggregate arrays when it's cheaper to do so.
  21                         if let AggregateKind::Array(_) = **kind {
  22                             return None;
  23                         }
  24                     } else {
  25                         return None;
  26                     }
  27                 } else {
  28                     return None;
  29                 }
  30
  31                 let stmt = stmt.replace_nop();
  32                 let source_info = stmt.source_info;
  33                 let (lhs, kind, operands) = match stmt.kind {
  34                     StatementKind::Assign(lhs, box rvalue) => {
  35                         match rvalue {
  36                             Rvalue::Aggregate(kind, operands) => (lhs, kind, operands),
  37                             _ => bug!()
  38                         }
  39                     }
  40                     _ => bug!()
  41                 };
  42
  43                 Some(expand_aggregate(
  44                     lhs,
  45                     operands.into_iter().map(|op| {
  46                         let ty = op.ty(local_decls, tcx);
  47                         (op, ty)
  48                     }),
  49                     *kind,
  50                     source_info,
  51                 ))
  52             });
  53         }
  54     }
  55 }