diff options
| -rw-r--r-- | src/librustc_trans/trans/expr.rs | 18 |
1 files changed, 11 insertions, 7 deletions
diff --git a/src/librustc_trans/trans/expr.rs b/src/librustc_trans/trans/expr.rs index ecf54cde9f6..85d4876d160 100644 --- a/src/librustc_trans/trans/expr.rs +++ b/src/librustc_trans/trans/expr.rs @@ -2187,15 +2187,19 @@ fn auto_ref<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, let referent_ty = lv_datum.ty; let ptr_ty = bcx.tcx().mk_imm_ref(bcx.tcx().mk_region(ty::ReStatic), referent_ty); + // Construct the resulting datum. The right datum to return here would be an Lvalue datum, + // because there is cleanup scheduled and the datum doesn't own the data, but for thin pointers + // we microoptimize it to be an Rvalue datum to avoid the extra alloca and level of + // indirection and for thin pointers, this has no ill effects. + let kind = if type_is_sized(bcx.tcx(), referent_ty) { + RvalueExpr(Rvalue::new(ByValue)) + } else { + LvalueExpr(lv_datum.kind) + }; + // Get the pointer. let llref = lv_datum.to_llref(); - - // Construct the resulting datum, using what was the "by ref" - // ValueRef of type `referent_ty` to be the "by value" ValueRef - // of type `&referent_ty`. - // Pointers to DST types are non-immediate, and therefore still use ByRef. - let kind = if type_is_sized(bcx.tcx(), referent_ty) { ByValue } else { ByRef }; - DatumBlock::new(bcx, Datum::new(llref, ptr_ty, RvalueExpr(Rvalue::new(kind)))) + DatumBlock::new(bcx, Datum::new(llref, ptr_ty, kind)) } fn deref_multiple<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, |