The llvm.reloc.none intrinsic (introduced in 5f08fb4d72f6) causes an
infinite loop when compiling for Hexagon target. The Hexagon scheduler's
hazard recognizer enters an infinite loop because RELOC_NONE
RELOC_NONE is a pseudo-instruction that doesn't correspond to real
hardware, but the Hexagon hazard recognizer was treating it as a regular
instruction requiring hardware resource allocation.
Mark RELOC_NONE as a meta-instruction and update Hexagon's hazard
recognizer to skip resource checks for meta-instructions, similar to how
it handles zero-cost instructions.
3d96b36964