This patch moves the code for recipe implementations to a separate file.
The benefits are:
- Keep VPlan.cpp smaller => faster compile-time during parallel builds.
- Keep code for logical units together
As a follow-up I am also planning on moving all ::execute
implemetnations from LoopVectorize.cpp over to the new file, which
should help to reduce the size of the file a bit.
Hmm, this is not needed at all?