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Diffstat (limited to 'ports/sysdeps/alpha/memchr.S')
| -rw-r--r-- | ports/sysdeps/alpha/memchr.S | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/ports/sysdeps/alpha/memchr.S b/ports/sysdeps/alpha/memchr.S new file mode 100644 index 000000000..5d713d53b --- /dev/null +++ b/ports/sysdeps/alpha/memchr.S @@ -0,0 +1,176 @@ +/* Copyright (C) 1996, 2000, 2003 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by David Mosberger (davidm@cs.arizona.edu). + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 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 + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +/* Finds characters in a memory area. Optimized for the Alpha: + + - 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> + + .set noreorder + .set noat + +ENTRY(__memchr) +#ifdef PROF + ldgp gp, 0(pv) + lda AT, _mcount + jsr AT, (AT), _mcount + .prologue 1 +#else + .prologue 0 +#endif + + # Hack -- if someone passes in (size_t)-1, hoping to just + # search til the end of the address space, we will overflow + # below when we find the address of the last byte. Given + # that we will never have a 56-bit address space, cropping + # the length is the easiest way to avoid trouble. + zap a2, 0x80, t4 #-e0 : + + beq a2, $not_found # .. e1 : + ldq_u t0, 0(a0) # e1 : load first quadword + insbl a1, 1, t1 # .. e0 : t1 = 000000000000ch00 + and a1, 0xff, a1 #-e0 : a1 = 00000000000000ch + cmpult a2, 9, t3 # .. e1 : + or t1, a1, a1 # e0 : a1 = 000000000000chch + lda t2, -1(zero) # .. e1 : + sll a1, 16, t1 #-e0 : t1 = 00000000chch0000 + addq a0, t4, t4 # .. e1 : + or t1, a1, a1 # e1 : a1 = 00000000chchchch + unop # : + sll a1, 32, t1 #-e0 : t1 = chchchch00000000 + or t1, a1, a1 # e1 : a1 = chchchchchchchch + extql t0, a0, t6 # e0 : + beq t3, $first_quad # .. e1 : + + ldq_u t5, -1(t4) #-e1 : eight or less bytes to search + extqh t5, a0, t5 # .. e0 : + mov a0, v0 # e0 : + or t6, t5, t0 # .. e1 : t0 = quadword starting at a0 + + # Deal with the case where at most 8 bytes remain to be searched + # in t0. E.g.: + # a2 = 6 + # t0 = ????c6c5c4c3c2c1 +$last_quad: + negq a2, t5 #-e0 : + xor a1, t0, t0 # .. e1 : + srl t2, t5, t5 # e0 : t5 = mask of a2 bits set + cmpbge zero, t0, t1 # .. e1 : + and t1, t5, t1 #-e0 : + beq t1, $not_found # .. e1 : + +$found_it: + # Now, determine which byte matched: + negq t1, t2 # e0 : + and t1, t2, t1 # e1 : + + and t1, 0x0f, t0 #-e0 : + addq v0, 4, t2 # .. e1 : + cmoveq t0, t2, v0 # e0 : + + addq v0, 2, t2 # .. e1 : + and t1, 0x33, t0 #-e0 : + cmoveq t0, t2, v0 # .. e1 : + + and t1, 0x55, t0 # e0 : + addq v0, 1, t2 # .. e1 : + cmoveq t0, t2, v0 #-e0 : + +$done: ret # .. e1 : + + # Deal with the case where a2 > 8 bytes remain to be + # searched. a0 may not be aligned. + .align 4 +$first_quad: + andnot a0, 0x7, v0 #-e1 : + insqh t2, a0, t1 # .. e0 : t1 = 0000ffffffffffff (a0<0:2> ff) + xor t0, a1, t0 # e0 : + or t0, t1, t0 # e1 : t0 = ====ffffffffffff + cmpbge zero, t0, t1 #-e0 : + bne t1, $found_it # .. e1 : + + # At least one byte left to process. + + ldq t0, 8(v0) # e0 : + subq t4, 1, a2 # .. e1 : + addq v0, 8, v0 #-e0 : + + # Make a2 point to last quad to be accessed (the + # last quad may or may not be partial). + + andnot a2, 0x7, a2 # .. e1 : + cmpult v0, a2, t1 # e0 : + beq t1, $final # .. e1 : + + # At least two quads remain to be accessed. + + subq a2, v0, t3 #-e0 : t3 <- nr quads to be processed + and t3, 8, t3 # e1 : odd number of quads? + bne t3, $odd_quad_count # e1 : + + # At least three quads remain to be accessed + + mov t0, t3 # e0 : move prefetched value to correct reg + + .align 4 +$unrolled_loop: + ldq t0, 8(v0) #-e0 : prefetch t0 + xor a1, t3, t1 # .. e1 : + cmpbge zero, t1, t1 # e0 : + bne t1, $found_it # .. e1 : + + addq v0, 8, v0 #-e0 : +$odd_quad_count: + xor a1, t0, t1 # .. e1 : + ldq t3, 8(v0) # e0 : prefetch t3 + cmpbge zero, t1, t1 # .. e1 : + addq v0, 8, t5 #-e0 : + bne t1, $found_it # .. e1 : + + cmpult t5, a2, t5 # e0 : + addq v0, 8, v0 # .. e1 : + bne t5, $unrolled_loop #-e1 : + + mov t3, t0 # e0 : move prefetched value into t0 +$final: subq t4, v0, a2 # .. e1 : a2 <- number of bytes left to do + bne a2, $last_quad # e1 : + +$not_found: + mov zero, v0 #-e0 : + ret # .. e1 : + + END(__memchr) + +weak_alias (__memchr, memchr) +#if !__BOUNDED_POINTERS__ +weak_alias (__memchr, __ubp_memchr) +#endif +libc_hidden_builtin_def (memchr) |