Use the return value of memset to avoid using an additional register

Author: zsparal

contents/huffman_encoding/code/asm-x64/huffman.s

@@ -226,23 +226,20 @@ decode_done:
 # rsi - Huffman-tree root (ptr)
 generate_codebook:
  push r12
- push r13
- sub rsp, bitstr_size + 8 # 8 extra bytes for alignment
- mov r12, rdi
- mov r13, rsi
+ sub rsp, bitstr_size + 16 # 16 extra bytes for alignment
+ mov r12, rsi
  xorps xmm0, xmm0 # Create a 0-initialized bitstring. This will be
  movaps XMMWORD PTR [rsp], xmm0 # used in the recursive function calls
  movaps XMMWORD PTR [rsp + 16], xmm0
  mov QWORD PTR [rsp + 32], 0
  xor rsi, rsi
  mov rdx, codebook_size
  call memset
- mov rdi, r12
- mov rsi, r13
+ mov rdi, rax
+ mov rsi, r12
  mov rdx, rsp
  call generate_codebook_recurse
- add rsp, bitstr_size + 8
- pop r13
+ add rsp, bitstr_size + 16
  pop r12
  ret