Low Level Bit Hacks You Absolutely Must Know

Re:Low Level Bit Hacks You Absolutely Must Know by BearOso on Friday May 11, 2018 @01:33PM (#17049257)

I highly doubt it. That’s 1:1

  test eax, 1
  ; use result

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Re:Low Level Bit Hacks You Absolutely Must Know by Hello71 on Friday May 11, 2018 @06:33PM (#17051203)

gcc -O2, clang, and icc all produce the sequence:

    is_even(int):
      mov eax, edi
      not eax
      and eax, 1
      ret

I am far from a x86 expert, but I assume this version avoids contention on the flags registers and increases pipelining.

edit: my mistake, icc and clang produce the equivalent sequence "not edi; and edi, 1; mov eax, edi; ret".

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