public boolean setBitAt(Instruction instr, int bit) {
		if (isBitRegister || value != null) {
			setAddr = instr.getFallThrough();
			if (setAddr != null) {
				if (value == null) {
					value = BigInteger.valueOf(0);
				}
				value = value.setBit(bit);
				if (mask != null) {
					value = value.and(mask);
				}
				return true;
			}
		}
		value = null;
		return false;
	}
The specified instr has set the specified bit for this context reg.
If setting fails the value will be left in an unknown state.
@param instr instruction which has made the bit modification
@param bit the bit to be set.
@return false if setting not possible (caused by instr not having a fall-through or
this is a multi-bit register without a previous value setting, or bit is null).
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/analysis/RegisterContextBuilder.java