| /* Copyright (C) 1996-2016 Free Software Foundation, Inc. |
| Contributed by Richard Henderson (rth@tamu.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 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, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| /* Fill a block of memory with zeros. Optimized for the Alpha architecture: |
| |
| - memory accessed as aligned quadwords only |
| - destination memory not read unless needed for good cache behaviour |
| - basic blocks arranged to optimize branch prediction for full-quadword |
| aligned memory blocks. |
| - partial head and tail quadwords constructed with byte-mask instructions |
| |
| This is generally scheduled for the EV5 (got to look out for my own |
| interests :-), but with EV4 needs in mind. There *should* be no more |
| stalls for the EV4 than there are for the EV5. |
| */ |
| |
| |
| #include <sysdep.h> |
| |
| .set noat |
| .set noreorder |
| |
| .text |
| .type __bzero, @function |
| .globl __bzero |
| .usepv __bzero, USEPV_PROF |
| |
| cfi_startproc |
| |
| /* On entry to this basic block: |
| t3 == loop counter |
| t4 == bytes in partial final word |
| a0 == possibly misaligned destination pointer */ |
| |
| .align 3 |
| bzero_loop: |
| beq t3, $tail # |
| blbc t3, 0f # skip single store if count even |
| |
| stq_u zero, 0(a0) # e0 : store one word |
| subq t3, 1, t3 # .. e1 : |
| addq a0, 8, a0 # e0 : |
| beq t3, $tail # .. e1 : |
| |
| 0: stq_u zero, 0(a0) # e0 : store two words |
| subq t3, 2, t3 # .. e1 : |
| stq_u zero, 8(a0) # e0 : |
| addq a0, 16, a0 # .. e1 : |
| bne t3, 0b # e1 : |
| |
| $tail: bne t4, 1f # is there a tail to do? |
| ret # no |
| |
| 1: ldq_u t0, 0(a0) # yes, load original data |
| mskqh t0, t4, t0 # |
| stq_u t0, 0(a0) # |
| ret # |
| |
| __bzero: |
| #ifdef PROF |
| ldgp gp, 0(pv) |
| lda AT, _mcount |
| jsr AT, (AT), _mcount |
| #endif |
| |
| mov a0, v0 # e0 : move return value in place |
| beq a1, $done # .. e1 : early exit for zero-length store |
| and a0, 7, t1 # e0 : |
| addq a1, t1, a1 # e1 : add dest misalignment to count |
| srl a1, 3, t3 # e0 : loop = count >> 3 |
| and a1, 7, t4 # .. e1 : find number of bytes in tail |
| unop # : |
| beq t1, bzero_loop # e1 : aligned head, jump right in |
| |
| ldq_u t0, 0(a0) # e0 : load original data to mask into |
| cmpult a1, 8, t2 # .. e1 : is this a sub-word set? |
| bne t2, $oneq # e1 : |
| |
| mskql t0, a0, t0 # e0 : we span words. finish this partial |
| subq t3, 1, t3 # e0 : |
| addq a0, 8, a0 # .. e1 : |
| stq_u t0, -8(a0) # e0 : |
| br bzero_loop # .. e1 : |
| |
| .align 3 |
| $oneq: |
| mskql t0, a0, t2 # e0 : |
| mskqh t0, a1, t3 # e0 : |
| or t2, t3, t0 # e1 : |
| stq_u t0, 0(a0) # e0 : |
| |
| $done: ret |
| |
| cfi_endproc |
| weak_alias (__bzero, bzero) |