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<'tcx>(
  10         &self,
  11         tcx: TyCtxt<'tcx, 'tcx>,
  12         _source: MirSource<'tcx>,
  13         body: &mut Body<'tcx>,
  14     ) {
  15         let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut();
  16         let local_decls = &*local_decls;
  17         for bb in basic_blocks {
  18             bb.expand_statements(|stmt| {
  19                 // FIXME(eddyb) don't match twice on `stmt.kind` (post-NLL).
  20                 if let StatementKind::Assign(_, ref rhs) = stmt.kind {
  21                     if let Rvalue::Aggregate(ref kind, _) = **rhs {
  22                         // FIXME(#48193) Deaggregate arrays when it's cheaper to do so.
  23                         if let AggregateKind::Array(_) = **kind {
  24                             return None;
  25                         }
  26                     } else {
  27                         return None;
  28                     }
  29                 } else {
  30                     return None;
  31                 }
  32
  33                 let stmt = stmt.replace_nop();
  34                 let source_info = stmt.source_info;
  35                 let (lhs, kind, operands) = match stmt.kind {
  36                     StatementKind::Assign(lhs, box rvalue) => {
  37                         match rvalue {
  38                             Rvalue::Aggregate(kind, operands) => (lhs, kind, operands),
  39                             _ => bug!()
  40                         }
  41                     }
  42                     _ => bug!()
  43                 };
  44
  45                 Some(expand_aggregate(
  46                     lhs,
  47                     operands.into_iter().map(|op| {
  48                         let ty = op.ty(local_decls, tcx);
  49                         (op, ty)
  50                     }),
  51                     *kind,
  52                     source_info,
  53                 ))
  54             });
  55         }
  56     }
  57 }