We don't have very many compressible FP instructions, just load and store.
These instruction require the FP register to be f8-f15.
This patch changes the FP allocation order to prioritize f10-f15 first.
These are also the FP argument registers. So I allocated them in reverse
order starting at f15 to avoid taking the first argument registers.
This appears to match gcc allocation order.
Reviewed By: asb
Differential Revision: https://reviews.llvm.org/D146488
The Zfhmin subset only has FLH, FSH, FMV.X.H, FMV.H.X, FCVT.S.H, and FCVT.H.S.
If the D extension is present, the FCVT.D.H and FCVT.H.D instructions are also included.
Since most instructions are not included for Zfhmin, so most operations are promoted.
The patch primarily about making f16 a legal type.
RISC-V ISA info:
https://wiki.riscv.org/display/HOME/Recently+Ratified+Extensions
Reviewed By: craig.topper
Differential Revision: https://reviews.llvm.org/D139391
