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Diffstat (limited to 'sysdeps/alpha/memchr.S')
| -rw-r--r-- | sysdeps/alpha/memchr.S | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/sysdeps/alpha/memchr.S b/sysdeps/alpha/memchr.S new file mode 100644 index 0000000000..118a1f13d1 --- /dev/null +++ b/sysdeps/alpha/memchr.S @@ -0,0 +1,163 @@ +/* Copyright (C) 1996 Free Software Foundation, Inc. + Contributed by David Mosberger (davidm@cs.arizona.edu). + +This file is part of the GNU C Library. + +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. */ + +/* Finds characters in a memory area. Optimized for the Alpha +architecture: + + - memory accessed as aligned quadwords only + - uses cmpbge to compare 8 bytes in parallel + - does binary search to find 0 byte in last + quadword (HAKMEM needed 12 instructions to + do this instead of the 9 instructions that + binary search needs). + +For correctness consider that: + + - only minimum number of quadwords may be accessed + - the third argument is an unsigned long +*/ + +#include <sysdep.h> +#ifdef __linux__ +# include <alpha/regdef.h> +#else +#include <regdef.h> +#endif + + .set noreorder + .set noat + +ENTRY(memchr) + beq a2, not_found + ldq_u t0, 0(a0) # load first quadword (a0 may be misaligned) + addq a0, a2, t4 + and a1, 0xff, a1 # a1 = 00000000000000ch + ldq_u t5, -1(t4) + sll a1, 8, t1 # t1 = 000000000000ch00 + cmpult a2, 9, t3 + or t1, a1, a1 # a1 = 000000000000chch + sll a1, 16, t1 # t1 = 00000000chch0000 + lda t2, -1(zero) + or t1, a1, a1 # a1 = 00000000chchchch + sll a1, 32, t1 # t1 = chchchch00000000 + extql t0, a0, t6 + or t1, a1, a1 # a1 = chchchchchchchch + + beq t3, first_quad + + extqh t5, a0, t5 + mov a0, v0 + or t6, t5, t0 # t0 = quadword starting at a0 + + # + # Deal with the case where at most 8 bytes remain to be searched + # in t0. E.g.: + # a2 = 6 + # t0 = ????c6c5c4c3c2c1 +last_quad: + negq a2, t5 + srl t2, t5, t5 # t5 = mask of a2 bits set + xor a1, t0, t0 + cmpbge zero, t0, t1 + and t1, t5, t1 + beq t1, not_found + +found_it: + # now, determine which byte matched: + negq t1, t2 + and t1, t2, t1 + + and t1, 0x0f, t0 + addq v0, 4, t2 + cmoveq t0, t2, v0 + + and t1, 0x33, t0 + addq v0, 2, t2 + cmoveq t0, t2, v0 + + and t1, 0x55, t0 + addq v0, 1, t2 + cmoveq t0, t2, v0 + +done: ret + + + # + # Deal with the case where a2 > 8 bytes remain to be + # searched. a0 may not be aligned. + # +first_quad: + andnot a0, 0x7, v0 + insqh t2, a0, t1 # t1 = 0000ffffffffffff (a0<0:2> ff bytes) + xor t0, a1, t0 + or t0, t1, t0 # t0 = ====ffffffffffff + cmpbge zero, t0, t1 + bne t1, found_it + + /* at least one byte left to process */ + + ldq t0, 8(v0) + addq v0, 8, v0 + /* + * Make a2 point to last quad to be accessed (the + * last quad may or may not be partial). + */ + subq t4, 1, a2 + andnot a2, 0x7, a2 + cmpult v0, a2, t1 + beq t1, final + + /* at least two quads remain to be accessed */ + + subq a2, v0, t3 # t3 <- number of quads to be processed in loop + and t3, 8, t3 # odd number of quads? + bne t3, odd_quad_count + + /* at least three quads remain to be accessed */ + + mov t0, t3 # move prefetched value into correct register + + .align 3 +unrolled_loop: + ldq t0, 8(v0) # prefetch t0 + xor a1, t3, t1 + cmpbge zero, t1, t1 + bne t1, found_it + + addq v0, 8, v0 +odd_quad_count: + xor a1, t0, t1 + ldq t3, 8(v0) # prefetch t3 + cmpbge zero, t1, t1 + bne t1, found_it + + addq v0, 8, v0 + cmpult v0, a2, t5 + bne t5, unrolled_loop + + mov t3, t0 # move prefetched value into t0 +final: subq t4, v0, a2 # a2 <- number of bytes left to do + bne a2, last_quad + +not_found: + mov zero, v0 + ret + + .end memchr |