mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-01-31 19:43:32 +00:00
6f7d0cb1c3
This makes breaking changes to add underscores to many non-standard function names provided by the c library. MODE=tiny is now tinier and we now use smaller locks that are better for tiny apps in this mode. Some headers have been renamed to be in the same folder as the build package, so it'll be easier to know which build dependency is needed. Certain old misguided interfaces have been removed. Intel intrinsics headers are now listed in libc/isystem (but not in the amalgamation) to help further improve open source compatibility. Header complexity has also been reduced. Lastly, more shell scripts are now available.
45 lines
2.7 KiB
ArmAsm
45 lines
2.7 KiB
ArmAsm
/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
|
||
│vi: set et ft=asm ts=8 tw=8 fenc=utf-8 :vi│
|
||
╞══════════════════════════════════════════════════════════════════════════════╡
|
||
│ Copyright 2020 Justine Alexandra Roberts Tunney │
|
||
│ │
|
||
│ Permission to use, copy, modify, and/or distribute this software for │
|
||
│ any purpose with or without fee is hereby granted, provided that the │
|
||
│ above copyright notice and this permission notice appear in all copies. │
|
||
│ │
|
||
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
|
||
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
|
||
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
|
||
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
|
||
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
|
||
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
|
||
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
|
||
│ PERFORMANCE OF THIS SOFTWARE. │
|
||
╚─────────────────────────────────────────────────────────────────────────────*/
|
||
#include "libc/macros.internal.h"
|
||
|
||
// Returns binary logarithm of integer 𝑥.
|
||
//
|
||
// uint32 𝑥 _bsf(𝑥) tzcnt(𝑥) ffs(𝑥) bsr(𝑥) lzcnt(𝑥)
|
||
// 0x00000000 wut 32 0 wut 32
|
||
// 0x00000001 0 0 1 0 31
|
||
// 0x80000001 0 0 1 31 0
|
||
// 0x80000000 31 31 32 31 0
|
||
// 0x00000010 4 4 5 4 27
|
||
// 0x08000010 4 4 5 27 4
|
||
// 0x08000000 27 27 28 27 4
|
||
// 0xffffffff 0 0 1 31 0
|
||
//
|
||
// @param rsi:rdi is 128-bit unsigned 𝑥 value
|
||
// @return eax number in range [0,128) or undef if 𝑥 is 0
|
||
// @see also treasure trove of nearly identical functions
|
||
_bsr128:
|
||
.leafprologue
|
||
.profilable
|
||
bsr %rsi,%rax
|
||
jnz 2f
|
||
bsr %rdi,%rax
|
||
1: .leafepilogue
|
||
2: add $64,%eax
|
||
jmp 1b
|
||
.endfn _bsr128,globl
|