Move rustc_mir::transform to rustc_mir_transform.

compiler/rustc_mir_transform/src/deaggregator.rs

@@ -0,0 +1,49 @@
+use crate::util::expand_aggregate;
+use crate::MirPass;
+use rustc_middle::mir::*;
+use rustc_middle::ty::TyCtxt;
+
+pub struct Deaggregator;
+
+impl<'tcx> MirPass<'tcx> for Deaggregator {
+    fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
+        let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut();
+        let local_decls = &*local_decls;
+        for bb in basic_blocks {
+            bb.expand_statements(|stmt| {
+                // FIXME(eddyb) don't match twice on `stmt.kind` (post-NLL).
+                match stmt.kind {
+                    // FIXME(#48193) Deaggregate arrays when it's cheaper to do so.
+                    StatementKind::Assign(box (
+                        _,
+                        Rvalue::Aggregate(box AggregateKind::Array(_), _),
+                    )) => {
+                        return None;
+                    }
+                    StatementKind::Assign(box (_, Rvalue::Aggregate(_, _))) => {}
+                    _ => return None,
+                }
+
+                let stmt = stmt.replace_nop();
+                let source_info = stmt.source_info;
+                let (lhs, kind, operands) = match stmt.kind {
+                    StatementKind::Assign(box (lhs, Rvalue::Aggregate(kind, operands))) => {
+                        (lhs, kind, operands)
+                    }
+                    _ => bug!(),
+                };
+
+                Some(expand_aggregate(
+                    lhs,
+                    operands.into_iter().map(|op| {
+                        let ty = op.ty(local_decls, tcx);
+                        (op, ty)
+                    }),
+                    *kind,
+                    source_info,
+                    tcx,
+                ))
+            });
+        }
+    }
+}