How to get bitwise negation of values in XMM register? As far as I know there is no such instruction. The only instruction with negation is pandn, but to use it to simply negate values in one XMM register, I would have to have another XMM register padded filled with 1.
Is there another way to negate bits in XMM register? Or is there a clever way to fill XMM register with 1 without accessing memory?
To load a register with all 1s, use
pcmpeqd xmm0, xmm0
After that you can simply subtract xmmX from xmm0 to get ~xmmX, or use pandn
You can also load other constants to xmm registers easily
pcmpeqd xmm0, xmm0
psrld xmm0, 30 ; 3 (32-bit)
pcmpeqd xmm0, xmm0 ; -1
pcmpeqw xmm0, xmm0 ; 1.5f
pslld xmm0, 24
psrld xmm0, 2
pcmpeqw xmm0, xmm0 ; -2.0f
pslld xmm0, 30
Read Agner Fog's optimization guide, 13.4 Generating constants - Making constants for integer vectors in XMM registers