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tekknolagi / scrapscript

A functional, content-addressable programming language.
https://scrapscript.fly.dev/repl
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Optimize small_string_concat #182

Closed tekknolagi closed 2 months ago

tekknolagi commented 2 months ago

Goes from a assembly mess with SIMD and stuff to:

0000000000002070 <small_string_concat>:
  return (((uword)obj) >> kImmediateTagBits) & kMaxSmallStringLength;
    2070:   89 f8                   mov    eax,edi
    2072:   c1 e8 05                shr    eax,0x5
    2075:   83 e0 07                and    eax,0x7
  uword length = small_string_length(a_obj) + small_string_length(b_obj);
  uword result = ((uword)b_obj) & ~(uword)0xFFULL;
    2078:   48 89 f2                mov    rdx,rsi
    207b:   48 81 e2 00 ff ff ff    and    rdx,0xffffffffffffff00
  result <<= small_string_length(a_obj) * kBitsPerByte;
    2082:   89 c1                   mov    ecx,eax
    2084:   c1 e1 03                shl    ecx,0x3
    2087:   48 d3 e2                shl    rdx,cl
  result |= ((uword)a_obj) & ~(uword)0xFFULL;
    208a:   48 81 e7 00 ff ff ff    and    rdi,0xffffffffffffff00
  result |= length << kImmediateTagBits;
    2091:   48 c1 e0 05             shl    rax,0x5
    2095:   81 e6 e0 00 00 00       and    esi,0xe0
    209b:   48 01 f0                add    rax,rsi
    209e:   48 09 f8                or     rax,rdi
  result |= kSmallStringTag;
    20a1:   48 09 d0                or     rax,rdx
    20a4:   48 83 c8 0d             or     rax,0xd
  struct object* result_obj = (struct object*)result;
  return result_obj;
    20a8:   c3                      ret