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author | Zack Weinberg <zackw@panix.com> | 2017-06-08 15:39:03 -0400 |
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committer | Zack Weinberg <zackw@panix.com> | 2017-06-08 15:39:03 -0400 |
commit | 5046dbb4a7eba5eccfd258f92f4735c9ffc8d069 (patch) | |
tree | 4470480d904b65cf14ca524f96f79eca818c3eaf /REORG.TODO/sysdeps/alpha/bzero.S | |
parent | 199fc19d3aaaf57944ef036e15904febe877fc93 (diff) | |
download | glibc-zack/build-layout-experiment.tar.gz glibc-zack/build-layout-experiment.tar.xz glibc-zack/build-layout-experiment.zip |
Prepare for radical source tree reorganization. zack/build-layout-experiment
All top-level files and directories are moved into a temporary storage directory, REORG.TODO, except for files that will certainly still exist in their current form at top level when we're done (COPYING, COPYING.LIB, LICENSES, NEWS, README), all old ChangeLog files (which are moved to the new directory OldChangeLogs, instead), and the generated file INSTALL (which is just deleted; in the new order, there will be no generated files checked into version control).
Diffstat (limited to 'REORG.TODO/sysdeps/alpha/bzero.S')
-rw-r--r-- | REORG.TODO/sysdeps/alpha/bzero.S | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/alpha/bzero.S b/REORG.TODO/sysdeps/alpha/bzero.S new file mode 100644 index 0000000000..9cea9fb59d --- /dev/null +++ b/REORG.TODO/sysdeps/alpha/bzero.S @@ -0,0 +1,110 @@ +/* Copyright (C) 1996-2017 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) |