if len(b.Succs) == 1 {
			if s.f.Config.hasGReg && s.regs[s.GReg].v != nil {
				s.freeReg(s.GReg) // Spill value in G register before any merge.
			}
			// For this to be worthwhile, the loop must have no calls in it.
			top := b.Succs[0].b
			loop := s.loopnest.b2l[top.ID]
			if loop == nil || loop.header != top || loop.containsUnavoidableCall {
				goto badloop
			}

	brev_arch := []sys.ArchFamily{sys.AMD64, sys.I386, sys.ARM64, sys.ARM, sys.S390X}
	if buildcfg.GOPPC64 >= 10 {
		// Use only on Power10 as the new byte reverse instructions that Power10 provide
		// make it worthwhile as an intrinsic
		brev_arch = append(brev_arch, sys.PPC64)
	}
	/******** runtime/internal/sys ********/
	addF("runtime/internal/sys", "Bswap32",
		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {