# mv.swizzle

Links

* <https://bugs.libre-soc.org/show_bug.cgi?id=139>

TODO: evaluate whether this will fit with [[mv.vec]]

the encoding embeds predication into the swizzle as well as constants 1/1.0 and 0/0.0

# Format

| 0.5 |6.10|11.15|16.20|21.....25|26.....30|31|  name        |
|-----|----|-----|-----|---------|---------|--|--------------|
| 19  | RT | RA  |     | XO[0:4] | XO[5:9] |Rc| XL-Form      |
| 19  | RT | RA  |imm  | imm     | 01 M im |0 | mv.vec.swiz  |
| 19  | RT | RA  |imm  | imm     | 01 M im |1 | fmv.vec.swiz |
| 19  | RT | RA  |imm  | imm     | 11 0 im |0 | mv.swiz      |
| 19  | RT | RA  |imm  | imm     | 11 0 im |1 | fmv.swiz     |

this gives a 12 bit immediate across bits 16 to 25 and 29-30.

* 3 bits X
* 3 bits Y
* 3 bits Z
* 3 bits W

except that the options are:

* 0b0NN index 0 thru 3 to place subelement in pos XYZW
* 0b110 to indicate "skip".  this is equivalent to predicate masking
* 0b100 to indicate "constant 0"
* 0b101 to indicate "constant 1" (or 1.0)
* 0b111 is not needed.

Evaluating efforts to encode 12 bit swizzle into less proved unsuccessful: 7^4 comes out to 2,400 which is larger than 11 bits.

Note that 7 options are needed (not 6) because the 7th option allows predicate masking to be encoded within the swizzle immediate.

Mode M is described in [[mv.vec]] and allows for merge and split of vectors.