/* Copyright (C) 1991, 1993 Free Software Foundation, Inc. Contributed by Torbjorn Granlund (tege@sics.se). The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more details. You should have received a copy of the GNU Library General Public License along with the GNU C Library; see the file COPYING.LIB. If not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ #include #include #include #ifdef isbcmp #define memcmp bcmp #define size_t int #endif /* BE VERY CAREFUL IF YOU CHANGE THIS CODE! */ /* The strategy of this memcmp is: 1. Compare bytes until one of the block pointers is aligned. 2. Compare using memcmp_common_alignment or memcmp_not_common_alignment, regarding the alignment of the other block after the initial byte operations. The maximum number of full words (of type op_t) are compared in this way. 3. Compare the few remaining bytes. */ /* memcmp_common_alignment -- Compare blocks at SRCP1 and SRCP2 with LEN `op_t' objects (not LEN bytes!). Both SRCP1 and SRCP2 should be aligned for memory operations on `op_t's. */ #ifdef __GNUC__ __inline #endif static int memcmp_common_alignment (srcp1, srcp2, len) long int srcp1; long int srcp2; size_t len; { op_t a0, a1; op_t b0, b1; op_t res; switch (len % 4) { case 2: a0 = ((op_t *) srcp1)[0]; b0 = ((op_t *) srcp2)[0]; srcp1 -= 2 * OPSIZ; srcp2 -= 2 * OPSIZ; len += 2; goto do1; case 3: a1 = ((op_t *) srcp1)[0]; b1 = ((op_t *) srcp2)[0]; srcp1 -= OPSIZ; srcp2 -= OPSIZ; len += 1; goto do2; case 0: if (OP_T_THRES <= 3 * OPSIZ && len == 0) return 0; a0 = ((op_t *) srcp1)[0]; b0 = ((op_t *) srcp2)[0]; goto do3; case 1: a1 = ((op_t *) srcp1)[0]; b1 = ((op_t *) srcp2)[0]; srcp1 += OPSIZ; srcp2 += OPSIZ; len -= 1; if (OP_T_THRES <= 3 * OPSIZ && len == 0) goto do0; /* Fall through. */ } do { a0 = ((op_t *) srcp1)[0]; b0 = ((op_t *) srcp2)[0]; res = a1 - b1; if (res != 0) return res; do3: a1 = ((op_t *) srcp1)[1]; b1 = ((op_t *) srcp2)[1]; res = a0 - b0; if (res != 0) return res; do2: a0 = ((op_t *) srcp1)[2]; b0 = ((op_t *) srcp2)[2]; res = a1 - b1; if (res != 0) return res; do1: a1 = ((op_t *) srcp1)[3]; b1 = ((op_t *) srcp2)[3]; res = a0 - b0; if (res != 0) return res; srcp1 += 4 * OPSIZ; srcp2 += 4 * OPSIZ; len -= 4; } while (len != 0); /* This is the right position for do0. Please don't move it into the loop. */ do0: return a1 - b1; } /* SRCP2 should be aligned for memory operations on `op_t', but SRCP1 *should be unaligned*. */ #ifdef __GNUC__ __inline #endif static int memcmp_not_common_alignment (srcp1, srcp2, len) long int srcp1; long int srcp2; size_t len; { op_t a0, a1, a2, a3; op_t b0, b1, b2, b3; op_t res; op_t x; int shl, shr; /* Calculate how to shift a word read at the memory operation aligned srcp1 to make it aligned for comparison. */ shl = 8 * (srcp1 % OPSIZ); shr = 8 * OPSIZ - shl; /* Make SRCP1 aligned by rounding it down to the beginning of the `op_t' it points in the middle of. */ srcp1 &= -OPSIZ; switch (len % 4) { case 2: a1 = ((op_t *) srcp1)[0]; a2 = ((op_t *) srcp1)[1]; b2 = ((op_t *) srcp2)[0]; srcp1 -= 1 * OPSIZ; srcp2 -= 2 * OPSIZ; len += 2; goto do1; case 3: a0 = ((op_t *) srcp1)[0]; a1 = ((op_t *) srcp1)[1]; b1 = ((op_t *) srcp2)[0]; srcp2 -= 1 * OPSIZ; len += 1; goto do2; case 0: if (OP_T_THRES <= 3 * OPSIZ && len == 0) return 0; a3 = ((op_t *) srcp1)[0]; a0 = ((op_t *) srcp1)[1]; b0 = ((op_t *) srcp2)[0]; srcp1 += 1 * OPSIZ; goto do3; case 1: a2 = ((op_t *) srcp1)[0]; a3 = ((op_t *) srcp1)[1]; b3 = ((op_t *) srcp2)[0]; srcp1 += 2 * OPSIZ; srcp2 += 1 * OPSIZ; len -= 1; if (OP_T_THRES <= 3 * OPSIZ && len == 0) goto do0; /* Fall through. */ } do { a0 = ((op_t *) srcp1)[0]; b0 = ((op_t *) srcp2)[0]; x = MERGE(a2, shl, a3, shr); res = x - b3; if (res != 0) return res; do3: a1 = ((op_t *) srcp1)[1]; b1 = ((op_t *) srcp2)[1]; x = MERGE(a3, shl, a0, shr); res = x - b0; if (res != 0) return res; do2: a2 = ((op_t *) srcp1)[2]; b2 = ((op_t *) srcp2)[2]; x = MERGE(a0, shl, a1, shr); res = x - b1; if (res != 0) return res; do1: a3 = ((op_t *) srcp1)[3]; b3 = ((op_t *) srcp2)[3]; x = MERGE(a1, shl, a2, shr); res = x - b2; if (res != 0) return res; srcp1 += 4 * OPSIZ; srcp2 += 4 * OPSIZ; len -= 4; } while (len != 0); /* This is the right position for do0. Please don't move it into the loop. */ do0: x = MERGE(a2, shl, a3, shr); return x - b3; } int memcmp (s1, s2, len) const __ptr_t s1; const __ptr_t s2; size_t len; { op_t a0; op_t b0; long int srcp1 = (long int) s1; long int srcp2 = (long int) s2; op_t res; if (len >= OP_T_THRES) { /* There are at least some bytes to compare. No need to test for LEN == 0 in this alignment loop. */ while (srcp2 % OPSIZ != 0) { a0 = ((byte *) srcp1)[0]; b0 = ((byte *) srcp2)[0]; srcp1 += 1; srcp2 += 1; res = a0 - b0; if (res != 0) return res; len -= 1; } /* SRCP2 is now aligned for memory operations on `op_t'. SRCP1 alignment determines if we can do a simple, aligned compare or need to shuffle bits. */ if (srcp1 % OPSIZ == 0) res = memcmp_common_alignment (srcp1, srcp2, len / OPSIZ); else res = memcmp_not_common_alignment (srcp1, srcp2, len / OPSIZ); if (res != 0) return res; /* Number of bytes remaining in the interval [0..OPSIZ-1]. */ srcp1 += len & -OPSIZ; srcp2 += len & -OPSIZ; len %= OPSIZ; } /* There are just a few bytes to compare. Use byte memory operations. */ while (len != 0) { a0 = ((byte *) srcp1)[0]; b0 = ((byte *) srcp2)[0]; srcp1 += 1; srcp2 += 1; res = a0 - b0; if (res != 0) return res; len -= 1; } return 0; }