private void initContextBitMasks(Register reg) {
		byte[] subMask = reg.getBaseMask();
		if (!reg.followsFlow()) {
			hasNonFlowingContext = true;
			for (int i = 0; i < flowingContextRegisterMask.length; i++) {
				flowingContextRegisterMask[i] &= ~subMask[i];
			}
		}
		else {
			for (int i = 0; i < flowingContextRegisterMask.length; i++) {
				flowingContextRegisterMask[i] |= subMask[i];
			}
			if (reg.hasChildren()) {
				for (Register childReg : reg.getChildRegisters()) {
					initContextBitMasks(childReg);
				}
			}
		}
	}
Set those bits in the nonFlowingContextRegisterMask which should not 
flow with context.
@param reg context register piece
Ghidra/Framework/Emulation/src/main/java/ghidra/pcode/emulate/EmulateDisassemblerContext.java