From 8f08b16c030d89049e0633ced8665c317db83f03 Mon Sep 17 00:00:00 2001 From: Nadrieril Date: Sat, 9 May 2020 13:49:04 +0100 Subject: [PATCH] Small allocation improvement --- src/librustc_mir_build/hair/pattern/_match.rs | 29 ++++++++++--------- 1 file changed, 16 insertions(+), 13 deletions(-) diff --git a/src/librustc_mir_build/hair/pattern/_match.rs b/src/librustc_mir_build/hair/pattern/_match.rs index f8c2e7a4ae3..c2dbe303be9 100644 --- a/src/librustc_mir_build/hair/pattern/_match.rs +++ b/src/librustc_mir_build/hair/pattern/_match.rs @@ -990,8 +990,8 @@ fn from_single_pattern(pat: &'p Pat<'tcx>) -> Self { /// Construct a new `Fields` from the given patterns. You must be sure those patterns can't /// contain fields that need to be filtered out. When in doubt, prefer `replace_fields`. - fn from_vec_unfiltered(pats: SmallVec<[&'p Pat<'tcx>; 2]>) -> Self { - Fields::Vec(pats) + fn from_slice_unfiltered(pats: &'p [Pat<'tcx>]) -> Self { + Fields::Slice(pats) } /// Convenience; internal use. @@ -2537,20 +2537,23 @@ fn specialize_one_pattern<'p, 'tcx>( if ctor_wild_subpatterns.len() as u64 != n { return None; } + // Convert a constant slice/array pattern to a list of patterns. let layout = cx.tcx.layout_of(cx.param_env.and(ty)).ok()?; let ptr = Pointer::new(AllocId(0), offset); - let pats = (0..n) - .map(|i| { - let ptr = ptr.offset(layout.size * i, &cx.tcx).ok()?; - let scalar = alloc.read_scalar(&cx.tcx, ptr, layout.size).ok()?; - let scalar = scalar.not_undef().ok()?; - let value = ty::Const::from_scalar(cx.tcx, scalar, ty); - let pattern = Pat { ty, span: pat.span, kind: box PatKind::Constant { value } }; - Some(&*cx.pattern_arena.alloc(pattern)) - }) - .collect::>()?; - Some(Fields::from_vec_unfiltered(pats)) + let pats = cx.pattern_arena.alloc_from_iter((0..n).filter_map(|i| { + let ptr = ptr.offset(layout.size * i, &cx.tcx).ok()?; + let scalar = alloc.read_scalar(&cx.tcx, ptr, layout.size).ok()?; + let scalar = scalar.not_undef().ok()?; + let value = ty::Const::from_scalar(cx.tcx, scalar, ty); + let pattern = Pat { ty, span: pat.span, kind: box PatKind::Constant { value } }; + Some(pattern) + })); + // Ensure none of the dereferences failed. + if pats.len() as u64 != n { + return None; + } + Some(Fields::from_slice_unfiltered(pats)) } PatKind::Constant { .. } | PatKind::Range { .. } => { -- 2.44.0