Swizzle

Swizzle rearranges or copies the destination register words according to the provided four-word swizzle on the given destination register.

Mnemonics

Swizzle has the following synonymous mnemonics:

swi
swizzle

Destination

The swizzle instruction expects a destination register on which the swizzle is performed. The destination must be a general purpose writable register.

Swizzle

The actual swizzle operation to be performed is specified after the destination register's identifier.

This swizzle comes in the form of four letters identifying the source words to be copied into the destination in the order x y z and w.

For example, since this swizzle places the xyzw words into the same order, this is a no-op:

swizzle r0.xyzw

Whereas the following swaps the values of the x and y words:

swizzle r0.yxzw

Swizzling is also not limited to swapping, and you can copy values to multiple destinations. For example, if we instead wanted to place a copy of x into the y word and leave the original x intact:

swizzle r0.xxzw

Swizzling can be useful for building small stack-like structures, for copying data within a vector to be used in another SIMD instruction, or even for rearranging the words to provide access to a register's more significant words to an instruction that can only access the x word of a register.