std/png/decode_filter_sse128.wuffs

// Copyright 2021 The Wuffs Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// --------

// Filter 1: Sub.

pri func decoder.filter_1_distance_4_sse128!(curr: slice base.u8),
	choose cpu_arch >= sse128,
{
	var c   : slice base.u8
	var fa0 : base.u8
	var fa1 : base.u8
	var fa2 : base.u8
	var fa3 : base.u8

	iterate (c = args.curr)(length: 4, advance: 4, unroll: 1) {
		fa0 ~mod+= c[0]
		c[0] = fa0
		fa1 ~mod+= c[1]
		c[1] = fa1
		fa2 ~mod+= c[2]
		c[2] = fa2
		fa3 ~mod+= c[3]
		c[3] = fa3
	}
}