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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/strlen.S | |
parent | 199fc19d3aaaf57944ef036e15904febe877fc93 (diff) | |
download | glibc-5046dbb4a7eba5eccfd258f92f4735c9ffc8d069.tar.gz glibc-5046dbb4a7eba5eccfd258f92f4735c9ffc8d069.tar.xz glibc-5046dbb4a7eba5eccfd258f92f4735c9ffc8d069.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/strlen.S')
-rw-r--r-- | REORG.TODO/sysdeps/alpha/strlen.S | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/alpha/strlen.S b/REORG.TODO/sysdeps/alpha/strlen.S new file mode 100644 index 0000000000..72aef91e0e --- /dev/null +++ b/REORG.TODO/sysdeps/alpha/strlen.S @@ -0,0 +1,76 @@ +/* Copyright (C) 1996-2017 Free Software Foundation, Inc. + Contributed by David Mosberger (davidm@cs.arizona.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/>. */ + +/* Finds length of a 0-terminated string. Optimized for the Alpha + architecture: + + - 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 8 instructions + that the binary search needs). +*/ + +#include <sysdep.h> + + .set noreorder + .set noat + +ENTRY(strlen) +#ifdef PROF + ldgp gp, 0(pv) + lda AT, _mcount + jsr AT, (AT), _mcount + .prologue 1 +#else + .prologue 0 +#endif + + ldq_u t0, 0(a0) # load first quadword (a0 may be misaligned) + lda t1, -1(zero) + insqh t1, a0, t1 + andnot a0, 7, v0 + or t1, t0, t0 + nop # dual issue the next two on ev5 + cmpbge zero, t0, t1 # t1 <- bitmask: bit i == 1 <==> i-th byte == 0 + bne t1, $found + +$loop: ldq t0, 8(v0) + addq v0, 8, v0 # addr += 8 + cmpbge zero, t0, t1 + beq t1, $loop + +$found: negq t1, t2 # clear all but least set bit + and t1, t2, t1 + + and t1, 0xf0, t2 # binary search for that set bit + and t1, 0xcc, t3 + and t1, 0xaa, t4 + cmovne t2, 4, t2 + cmovne t3, 2, t3 + cmovne t4, 1, t4 + addq t2, t3, t2 + addq v0, t4, v0 + addq v0, t2, v0 + nop # dual issue next two on ev4 and ev5 + + subq v0, a0, v0 + ret + + END(strlen) +libc_hidden_builtin_def (strlen) |