- Let targets specify their own conversion for EVTs.
- Use this to map (almost all) vector EVTs to vector register for the VE target. Also use this across function calls in the 'fastcc'.
Without this patch, isel scalarizes "weird" vector types such as <17 x i16>. This is not really an option for long-vector architectures such as SX-Aurora. This patch adds a custom callback to let the target decide to map also those EVTs to vector registers.