mirror of https://github.com/acidanthera/audk.git
141 lines
4.2 KiB
ArmAsm
141 lines
4.2 KiB
ArmAsm
//
|
|
// Copyright (c) 2014, ARM Limited
|
|
// All rights Reserved.
|
|
// SPDX-License-Identifier: BSD-2-Clause-Patent
|
|
//
|
|
|
|
// Assumptions:
|
|
//
|
|
// ARMv8-a, AArch64
|
|
// Neon Available.
|
|
//
|
|
|
|
// Arguments and results.
|
|
#define srcin x0
|
|
#define cntin x1
|
|
#define chrin w2
|
|
|
|
#define result x0
|
|
|
|
#define src x3
|
|
#define tmp x4
|
|
#define wtmp2 w5
|
|
#define synd x6
|
|
#define soff x9
|
|
#define cntrem x10
|
|
|
|
#define vrepchr v0
|
|
#define vdata1 v1
|
|
#define vdata2 v2
|
|
#define vhas_chr1 v3
|
|
#define vhas_chr2 v4
|
|
#define vrepmask v5
|
|
#define vend v6
|
|
|
|
//
|
|
// Core algorithm:
|
|
//
|
|
// For each 32-byte chunk we calculate a 64-bit syndrome value, with two bits
|
|
// per byte. For each tuple, bit 0 is set if the relevant byte matched the
|
|
// requested character and bit 1 is not used (faster than using a 32bit
|
|
// syndrome). Since the bits in the syndrome reflect exactly the order in which
|
|
// things occur in the original string, counting trailing zeros allows to
|
|
// identify exactly which byte has matched.
|
|
//
|
|
|
|
ASM_GLOBAL ASM_PFX(InternalMemScanMem8)
|
|
ASM_PFX(InternalMemScanMem8):
|
|
AARCH64_BTI(c)
|
|
// Do not dereference srcin if no bytes to compare.
|
|
cbz cntin, .Lzero_length
|
|
//
|
|
// Magic constant 0x40100401 allows us to identify which lane matches
|
|
// the requested byte.
|
|
//
|
|
mov wtmp2, #0x0401
|
|
movk wtmp2, #0x4010, lsl #16
|
|
dup vrepchr.16b, chrin
|
|
// Work with aligned 32-byte chunks
|
|
bic src, srcin, #31
|
|
dup vrepmask.4s, wtmp2
|
|
ands soff, srcin, #31
|
|
and cntrem, cntin, #31
|
|
b.eq .Lloop
|
|
|
|
//
|
|
// Input string is not 32-byte aligned. We calculate the syndrome
|
|
// value for the aligned 32 bytes block containing the first bytes
|
|
// and mask the irrelevant part.
|
|
//
|
|
|
|
ld1 {vdata1.16b, vdata2.16b}, [src], #32
|
|
sub tmp, soff, #32
|
|
adds cntin, cntin, tmp
|
|
cmeq vhas_chr1.16b, vdata1.16b, vrepchr.16b
|
|
cmeq vhas_chr2.16b, vdata2.16b, vrepchr.16b
|
|
and vhas_chr1.16b, vhas_chr1.16b, vrepmask.16b
|
|
and vhas_chr2.16b, vhas_chr2.16b, vrepmask.16b
|
|
addp vend.16b, vhas_chr1.16b, vhas_chr2.16b // 256->128
|
|
addp vend.16b, vend.16b, vend.16b // 128->64
|
|
mov synd, vend.d[0]
|
|
// Clear the soff*2 lower bits
|
|
lsl tmp, soff, #1
|
|
lsr synd, synd, tmp
|
|
lsl synd, synd, tmp
|
|
// The first block can also be the last
|
|
b.ls .Lmasklast
|
|
// Have we found something already?
|
|
cbnz synd, .Ltail
|
|
|
|
.Lloop:
|
|
ld1 {vdata1.16b, vdata2.16b}, [src], #32
|
|
subs cntin, cntin, #32
|
|
cmeq vhas_chr1.16b, vdata1.16b, vrepchr.16b
|
|
cmeq vhas_chr2.16b, vdata2.16b, vrepchr.16b
|
|
// If we're out of data we finish regardless of the result
|
|
b.ls .Lend
|
|
// Use a fast check for the termination condition
|
|
orr vend.16b, vhas_chr1.16b, vhas_chr2.16b
|
|
addp vend.2d, vend.2d, vend.2d
|
|
mov synd, vend.d[0]
|
|
// We're not out of data, loop if we haven't found the character
|
|
cbz synd, .Lloop
|
|
|
|
.Lend:
|
|
// Termination condition found, let's calculate the syndrome value
|
|
and vhas_chr1.16b, vhas_chr1.16b, vrepmask.16b
|
|
and vhas_chr2.16b, vhas_chr2.16b, vrepmask.16b
|
|
addp vend.16b, vhas_chr1.16b, vhas_chr2.16b // 256->128
|
|
addp vend.16b, vend.16b, vend.16b // 128->64
|
|
mov synd, vend.d[0]
|
|
// Only do the clear for the last possible block
|
|
b.hi .Ltail
|
|
|
|
.Lmasklast:
|
|
// Clear the (32 - ((cntrem + soff) % 32)) * 2 upper bits
|
|
add tmp, cntrem, soff
|
|
and tmp, tmp, #31
|
|
sub tmp, tmp, #32
|
|
neg tmp, tmp, lsl #1
|
|
lsl synd, synd, tmp
|
|
lsr synd, synd, tmp
|
|
|
|
.Ltail:
|
|
// Count the trailing zeros using bit reversing
|
|
rbit synd, synd
|
|
// Compensate the last post-increment
|
|
sub src, src, #32
|
|
// Check that we have found a character
|
|
cmp synd, #0
|
|
// And count the leading zeros
|
|
clz synd, synd
|
|
// Compute the potential result
|
|
add result, src, synd, lsr #1
|
|
// Select result or NULL
|
|
csel result, xzr, result, eq
|
|
ret
|
|
|
|
.Lzero_length:
|
|
mov result, #0
|
|
ret
|