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<'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                 if let StatementKind::Assign(box(_, ref rhs)) = stmt.kind {
  16                     if let Rvalue::Aggregate(ref kind, _) = *rhs {
  17                         // FIXME(#48193) Deaggregate arrays when it's cheaper to do so.
  18                         if let AggregateKind::Array(_) = **kind {
  19                             return None;
  20                         }
  21                     } else {
  22                         return None;
  23                     }
  24                 } else {
  25                     return None;
  26                 }
  27
  28                 let stmt = stmt.replace_nop();
  29                 let source_info = stmt.source_info;
  30                 let (lhs, kind, operands) = match stmt.kind {
  31                     StatementKind::Assign(box(lhs, rvalue)) => {
  32                         match rvalue {
  33                             Rvalue::Aggregate(kind, operands) => (lhs, kind, operands),
  34                             _ => bug!()
  35                         }
  36                     }
  37                     _ => bug!()
  38                 };
  39
  40                 Some(expand_aggregate(
  41                     lhs,
  42                     operands.into_iter().map(|op| {
  43                         let ty = op.ty(local_decls, tcx);
  44                         (op, ty)
  45                     }),
  46                     *kind,
  47                     source_info,
  48                 ))
  49             });
  50         }
  51     }
  52 }