ARM AArch64 Pos implementation

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Hello.
I have this function that work with AnsiString:

Code: Pascal  [Select][+][-]

1. function Pos(constref Buf: AnsiChar; C: AnsiChar; Count: SizeUInt): SizeUInt;assembler;nostackframe;
2. asm
3.   mov x8,x0
4.   bic  x3,x0,#15
5.   sub x8,x8,#1
6.   ld1 {v1.16b},[x3]
7.   dup v0.16b,w1
8.   cmeq v2.16b,v1.16b,v0.16b
9.   lsl x6,x0,#2
10.   .byte 67,132,12,15 //shrn v3.8b,v2.8h,#4
11.   fmov x5,d3 //synd,dend
12.   lsr x5,x5,x6 //synd, synd, shift
13.   cbz x5,.LStartLoop
14.   rbit x5,x5
15.   clz x5,x5
16.   cmp x2,x5,lsr #2
17.   add x0,x0,x5,lsr #2
18.   csel x0,x0,xzr,hi
19.   b .LMatch
20.  
21. .LStartLoop:
22.   sub x7,x3,x0 //tmp, src, srcin
23.   add x7,x7,#17 //tmp, tmp, 17
24.   subs x4,x2,x7 //cntrem, cntin, tmp
25.   b.lo .Lnomatch
26.   tbz x4,#4,.Lloop32_2 //cntrem, 4, L(loop32_2)
27.   sub x3,x3,#16 //src, src, 16
28.  
29. .Lloop32:
30.   ldr q1,[x3,#32]! //qdata, [src, 32]!
31.   cmeq v2.16b,v1.16b,v0.16b //vhas_chr.16b, vdata.16b, vrepchr.16b
32.   umaxp v3.16b,v2.16b,v2.16b //vend.16b, vhas_chr.16b, vhas_chr.16b
33.   fmov x5,d3 //synd, dend
34.   cbnz x5,.Lend
35. .Lloop32_2:
36.   ldr q1,[x3,#16] //qdata, [src, 16]
37.   cmeq v2.16b,v1.16b,v0.16b //vhas_chr.16b, vdata.16b, vrepchr.16b
38.   subs x4,x4,#32
39.   b.lo .Lend2
40.   umaxp v3.16b,v2.16b,v2.16b //vend.16b, vhas_chr.16b, vhas_chr.16b
41.   fmov x5,d3 //synd, dend
42.   cbz x5,.Lloop32
43.  
44. .Lend2:
45.   add x3,x3,#16 //src, src, 16
46. .Lend:
47.   .byte 67,132,12,15 //shrn v3.8b,v2.8h,#4
48.   sub x4,x3,x0 //cntrem, src, srcin
49.   fmov x5,d3 //synd, dend
50.   sub x4,x2,x4 //cntrem, cntin, cntrem
51.   clz x5,x5 //synd, synd
52.   cmp x4,x5,lsr #2 //cntrem, synd, lsr 2
53.   add x0,x3,x5,lsr #2 //result, src, synd, lsr 2
54.   csel x0,x0,xzr,hi //result, result, xzr, hi
55.   b .LMatch
56. .Lnomatch:
57.   mov Result,x8
58. .LMatch:
59.   sub Result,Result,x8
60. end;
61.  

(Original code taken from https://codebrowser.dev/glibc/glibc/sysdeps/aarch64/memchr.S.html)
I am looking for way to modify this function to work with WideString.