Rotating a bitmap 90 degrees

Question

I have a one 64-bit integer, which I need to rotate 90 degrees in 8 x 8 area (preferably with straight bit-manipulation). I cannot figure out any handy algorith

Answer 1

This is quite easy using IA32 SIMD, there's a handy opcode to extract every eighth bit from a 64 bit value (this was written using DevStudio 2005):

char
  source [8] = {0, 0, 0, 0, 0, 0, 0, 0xd0},
  dest [8];

__asm
{
  mov ch,3
  movq xmm0,qword ptr [source]
Rotate2:
  lea edi,dest
  mov cl,8
Rotate1:
  pmovmskb eax,xmm0
  psllq xmm0,1
  stosb
  dec cl
  jnz Rotate1
  movq xmm0,qword ptr [dest]
  dec ch
  jnz Rotate2
}

It rotates the data three times (-270 degrees) since +90 is a bit trickier (needs a bit more thought)