| lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame] | 1 | /* Copyright (C) 1996-2015 Free Software Foundation, Inc. |
| 2 | Contributed by Richard Henderson (rth@tamu.edu) |
| 3 | This file is part of the GNU C Library. |
| 4 | |
| 5 | The GNU C Library is free software; you can redistribute it and/or |
| 6 | modify it under the terms of the GNU Lesser General Public |
| 7 | License as published by the Free Software Foundation; either |
| 8 | version 2.1 of the License, or (at your option) any later version. |
| 9 | |
| 10 | The GNU C Library is distributed in the hope that it will be useful, |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 13 | Lesser General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU Lesser General Public |
| 16 | License along with the GNU C Library. If not, see |
| 17 | <http://www.gnu.org/licenses/>. */ |
| 18 | |
| 19 | /* Fill a block of memory with zeros. Optimized for the Alpha architecture: |
| 20 | |
| 21 | - memory accessed as aligned quadwords only |
| 22 | - destination memory not read unless needed for good cache behaviour |
| 23 | - basic blocks arranged to optimize branch prediction for full-quadword |
| 24 | aligned memory blocks. |
| 25 | - partial head and tail quadwords constructed with byte-mask instructions |
| 26 | |
| 27 | This is generally scheduled for the EV5 (got to look out for my own |
| 28 | interests :-), but with EV4 needs in mind. There *should* be no more |
| 29 | stalls for the EV4 than there are for the EV5. |
| 30 | */ |
| 31 | |
| 32 | |
| 33 | #include <sysdep.h> |
| 34 | |
| 35 | .set noat |
| 36 | .set noreorder |
| 37 | |
| 38 | .text |
| 39 | .type __bzero, @function |
| 40 | .globl __bzero |
| 41 | .usepv __bzero, USEPV_PROF |
| 42 | |
| 43 | cfi_startproc |
| 44 | |
| 45 | /* On entry to this basic block: |
| 46 | t3 == loop counter |
| 47 | t4 == bytes in partial final word |
| 48 | a0 == possibly misaligned destination pointer */ |
| 49 | |
| 50 | .align 3 |
| 51 | bzero_loop: |
| 52 | beq t3, $tail # |
| 53 | blbc t3, 0f # skip single store if count even |
| 54 | |
| 55 | stq_u zero, 0(a0) # e0 : store one word |
| 56 | subq t3, 1, t3 # .. e1 : |
| 57 | addq a0, 8, a0 # e0 : |
| 58 | beq t3, $tail # .. e1 : |
| 59 | |
| 60 | 0: stq_u zero, 0(a0) # e0 : store two words |
| 61 | subq t3, 2, t3 # .. e1 : |
| 62 | stq_u zero, 8(a0) # e0 : |
| 63 | addq a0, 16, a0 # .. e1 : |
| 64 | bne t3, 0b # e1 : |
| 65 | |
| 66 | $tail: bne t4, 1f # is there a tail to do? |
| 67 | ret # no |
| 68 | |
| 69 | 1: ldq_u t0, 0(a0) # yes, load original data |
| 70 | mskqh t0, t4, t0 # |
| 71 | stq_u t0, 0(a0) # |
| 72 | ret # |
| 73 | |
| 74 | __bzero: |
| 75 | #ifdef PROF |
| 76 | ldgp gp, 0(pv) |
| 77 | lda AT, _mcount |
| 78 | jsr AT, (AT), _mcount |
| 79 | #endif |
| 80 | |
| 81 | mov a0, v0 # e0 : move return value in place |
| 82 | beq a1, $done # .. e1 : early exit for zero-length store |
| 83 | and a0, 7, t1 # e0 : |
| 84 | addq a1, t1, a1 # e1 : add dest misalignment to count |
| 85 | srl a1, 3, t3 # e0 : loop = count >> 3 |
| 86 | and a1, 7, t4 # .. e1 : find number of bytes in tail |
| 87 | unop # : |
| 88 | beq t1, bzero_loop # e1 : aligned head, jump right in |
| 89 | |
| 90 | ldq_u t0, 0(a0) # e0 : load original data to mask into |
| 91 | cmpult a1, 8, t2 # .. e1 : is this a sub-word set? |
| 92 | bne t2, $oneq # e1 : |
| 93 | |
| 94 | mskql t0, a0, t0 # e0 : we span words. finish this partial |
| 95 | subq t3, 1, t3 # e0 : |
| 96 | addq a0, 8, a0 # .. e1 : |
| 97 | stq_u t0, -8(a0) # e0 : |
| 98 | br bzero_loop # .. e1 : |
| 99 | |
| 100 | .align 3 |
| 101 | $oneq: |
| 102 | mskql t0, a0, t2 # e0 : |
| 103 | mskqh t0, a1, t3 # e0 : |
| 104 | or t2, t3, t0 # e1 : |
| 105 | stq_u t0, 0(a0) # e0 : |
| 106 | |
| 107 | $done: ret |
| 108 | |
| 109 | cfi_endproc |
| 110 | weak_alias (__bzero, bzero) |