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Diffstat (limited to 'arch/alpha/lib/memchr.S')
| -rw-r--r-- | arch/alpha/lib/memchr.S | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/arch/alpha/lib/memchr.S b/arch/alpha/lib/memchr.S new file mode 100644 index 00000000..14427eeb --- /dev/null +++ b/arch/alpha/lib/memchr.S @@ -0,0 +1,164 @@ +/* Copyright (C) 1996 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 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., 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 +*/ + + .set noreorder + .set noat + + .globl memchr + .ent memchr +memchr: + .frame $30,0,$26,0 + .prologue 0 + + # 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 $18, 0x80, $5 #-e0 : + + beq $18, $not_found # .. e1 : + ldq_u $1, 0($16) # e1 : load first quadword + insbl $17, 1, $2 # .. e0 : $2 = 000000000000ch00 + and $17, 0xff, $17 #-e0 : $17 = 00000000000000ch + cmpult $18, 9, $4 # .. e1 : + or $2, $17, $17 # e0 : $17 = 000000000000chch + lda $3, -1($31) # .. e1 : + sll $17, 16, $2 #-e0 : $2 = 00000000chch0000 + addq $16, $5, $5 # .. e1 : + or $2, $17, $17 # e1 : $17 = 00000000chchchch + unop # : + sll $17, 32, $2 #-e0 : $2 = chchchch00000000 + or $2, $17, $17 # e1 : $17 = chchchchchchchch + extql $1, $16, $7 # e0 : + beq $4, $first_quad # .. e1 : + + ldq_u $6, -1($5) #-e1 : eight or less bytes to search + extqh $6, $16, $6 # .. e0 : + mov $16, $0 # e0 : + or $7, $6, $1 # .. e1 : $1 = quadword starting at $16 + + # Deal with the case where at most 8 bytes remain to be searched + # in $1. E.g.: + # $18 = 6 + # $1 = ????c6c5c4c3c2c1 +$last_quad: + negq $18, $6 #-e0 : + xor $17, $1, $1 # .. e1 : + srl $3, $6, $6 # e0 : $6 = mask of $18 bits set + cmpbge $31, $1, $2 # .. e1 : + and $2, $6, $2 #-e0 : + beq $2, $not_found # .. e1 : + +$found_it: + # Now, determine which byte matched: + negq $2, $3 # e0 : + and $2, $3, $2 # e1 : + + and $2, 0x0f, $1 #-e0 : + addq $0, 4, $3 # .. e1 : + cmoveq $1, $3, $0 # e0 : + + addq $0, 2, $3 # .. e1 : + and $2, 0x33, $1 #-e0 : + cmoveq $1, $3, $0 # .. e1 : + + and $2, 0x55, $1 # e0 : + addq $0, 1, $3 # .. e1 : + cmoveq $1, $3, $0 #-e0 : + +$done: ret # .. e1 : + + # Deal with the case where $18 > 8 bytes remain to be + # searched. $16 may not be aligned. + .align 4 +$first_quad: + andnot $16, 0x7, $0 #-e1 : + insqh $3, $16, $2 # .. e0 : $2 = 0000ffffffffffff ($16<0:2> ff) + xor $1, $17, $1 # e0 : + or $1, $2, $1 # e1 : $1 = ====ffffffffffff + cmpbge $31, $1, $2 #-e0 : + bne $2, $found_it # .. e1 : + + # At least one byte left to process. + + ldq $1, 8($0) # e0 : + subq $5, 1, $18 # .. e1 : + addq $0, 8, $0 #-e0 : + + # Make $18 point to last quad to be accessed (the + # last quad may or may not be partial). + + andnot $18, 0x7, $18 # .. e1 : + cmpult $0, $18, $2 # e0 : + beq $2, $final # .. e1 : + + # At least two quads remain to be accessed. + + subq $18, $0, $4 #-e0 : $4 <- nr quads to be processed + and $4, 8, $4 # e1 : odd number of quads? + bne $4, $odd_quad_count # e1 : + + # At least three quads remain to be accessed + + mov $1, $4 # e0 : move prefetched value to correct reg + + .align 4 +$unrolled_loop: + ldq $1, 8($0) #-e0 : prefetch $1 + xor $17, $4, $2 # .. e1 : + cmpbge $31, $2, $2 # e0 : + bne $2, $found_it # .. e1 : + + addq $0, 8, $0 #-e0 : +$odd_quad_count: + xor $17, $1, $2 # .. e1 : + ldq $4, 8($0) # e0 : prefetch $4 + cmpbge $31, $2, $2 # .. e1 : + addq $0, 8, $6 #-e0 : + bne $2, $found_it # .. e1 : + + cmpult $6, $18, $6 # e0 : + addq $0, 8, $0 # .. e1 : + bne $6, $unrolled_loop #-e1 : + + mov $4, $1 # e0 : move prefetched value into $1 +$final: subq $5, $0, $18 # .. e1 : $18 <- number of bytes left to do + bne $18, $last_quad # e1 : + +$not_found: + mov $31, $0 #-e0 : + ret # .. e1 : + + .end memchr |