1 /* 2 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org> 3 * 4 * Permission is hereby granted, free of charge, to any person obtaining 5 * a copy of this software and associated documentation files (the 6 * "Software"), to deal in the Software without restriction, including 7 * without limitation the rights to use, copy, modify, merge, publish, 8 * distribute, sublicense, and/or sell copies of the Software, and to 9 * permit persons to whom the Software is furnished to do so, subject to 10 * the following conditions: 11 * 12 * The above copyright notice and this permission notice shall be 13 * included in all copies or substantial portions of the Software. 14 * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN 20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 22 * SOFTWARE. 23 */ 24 25 #include "inner.h" 26 27 /* see inner.h */ 28 uint32_t 29 br_i32_sub(uint32_t *a, const uint32_t *b, uint32_t ctl) 30 { 31 uint32_t cc; 32 size_t u, m; 33 34 cc = 0; 35 m = (a[0] + 63) >> 5; 36 for (u = 1; u < m; u ++) { 37 uint32_t aw, bw, naw; 38 39 aw = a[u]; 40 bw = b[u]; 41 naw = aw - bw - cc; 42 43 /* 44 * Carry is 1 if naw > aw. Carry is 1 also if naw == aw 45 * AND the carry was already 1. 46 */ 47 cc = (cc & EQ(naw, aw)) | GT(naw, aw); 48 a[u] = MUX(ctl, naw, aw); 49 } 50 return cc; 51 } 52