private String getRegisterName(Processor processorIn, int registerIn) {

		// We do not have registers for many of the processors... set the default.
		String registerName = badRegister;
		switch (processorIn) {

			case UNKNOWN:
			case UNK1AB:
			case UNK304:
				break;

			case I8080:
			case I8086:
			case I80286:
			case I80386:
			case I80486:
			case PENTIUM:
			case PENTIUMPRO_PENTIUMII:
			case PENTIUMIII:
				if (registerIn < regX86.length) {
					registerName = regX86[registerIn];
				}
				break;

			case MIPS_MIPSR4000:
			case MIPS16:
			case MIPS32:
			case MIPS64:
			case MIPSI:
			case MIPSII:
			case MIPSIII:
			case MIPSIV:
			case MIPSV:
				if (registerIn < regMips.length) {
					registerName = regMips[registerIn];
				}
				break;

			case M68000:
			case M68010:
			case M68020:
			case M68030:
			case M68040:
				if (registerIn < reg68k.length) {
					registerName = reg68k[registerIn];
				}
				break;

			case ALPHA_21064:
			case ALPHA_21164:
			case ALPHA_21164A:
			case ALPHA_21264:
			case ALPHA_21364:
				if (registerIn < regAlpha.length) {
					registerName = regAlpha[registerIn];
				}
				break;

			case PPC601:
			case PPC603:
			case PPC604:
			case PPC620:
			case PPCFP:
			case PPCBE:
				if (registerIn < regPpc.length) {
					registerName = regPpc[registerIn];
				}
				break;

			case SH3:
			case SH3E:
			case SH3DSP:
			case SH4:
			case SHMEDIA:
				if (registerIn < regSh.length) {
					registerName = regSh[registerIn];
				}
				break;

			case ARM3:
			case ARM4:
			case ARM4T:
			case ARM5:
			case ARM5T:
			case ARM6:
			case ARM_XMAC:
			case ARM_WMMX:
			case ARM7:
				break;

			case OMNI:
				break;

			case IA64_IA64_1:
			case IA64_2:
				if (registerIn < ia64RegistersById.size()) {
					registerName = ia64RegistersById.get(registerIn);
				}
				break;

			case CEE:
				break;

			case AM33:
				break;

			case M32R:
				break;

			case TRICORE:
				break;

			case X64_AMD64:
				if (registerIn < regAmd64.length) {
					registerName = regAmd64[registerIn];
				}
				break;

			case EBC:
				break;

			case THUMB:
			case ARMNT:
			case ARM64:
				break;

			case D3D11_SHADER:
				break;

		}
		return registerName;

	}
Tells if there is no register.
@return True if there is no register.
Ghidra/Features/PDB/src/main/java/ghidra/app/util/bin/format/pdb2/pdbreader/RegisterName.java