gen_ipbus_addr_decode does not return non-zero exit code when node address errors are detected

[tswilliams]

If the gen_ipbus_addr_decode script detects either of the following errors:

• overlaps between nodes
• 'endpoint' nodes whose base address does not align with their address mask (i.e. 2^width)

... it will print corresponding error messages, but it currently still produces an exit code of 0.

Instead, if these errors are detected, the script should finish with an non-zero exit code, before writing the VHDL output file.

[tswilliams]

Example address table that leads to 'non-aligned address' errors (for 2 nodes, id and csr:

<node description="Example slaves file">
	<node id="id" address="0x0" description="ID register" fwinfo="endpoint;width=0"/>
	<node id="csr" address="0x43" description="ctrl/stat register" fwinfo="endpoint;width=1">
		<node id="ctrl" address="0x0"/>
		<node id="stat" address="0x1"/>
	</node>
	<node id="xpoint" address="0x57" size="0x4" fwinfo="endpoint;width=2"/>
</node>

Current output of gen_ipbus_addr_decode script for this address table:

main ERROR: Non-aligned base address detected: csr 0x43 0x1
main ERROR: Non-aligned base address detected: xpoint 0x57 0x2
main ERROR: ERROR: Non Aligned address 0b00000000000000000000000001000011 with respect to address bit mask 0b00000000000000000000000000000001
main ERROR: ERROR: Non Aligned address 0b00000000000000000000000001010111 with respect to address bit mask 0b00000000000000000000000000000011
VHDL decode file saved:  ipbus_decode_addr_table.vhd

[tswilliams]

Bug is now fixed (in pull request #37); for an example problematic address table with 'non-aligned address' errors in 2 nodes - csr and xpoint:

<node description="Example slaves file">
	<node id="id" address="0x0" description="ID register" fwinfo="endpoint;width=0"/>
	<node id="csr" address="0x43" description="ctrl/stat register" fwinfo="endpoint;width=1">
		<node id="ctrl" address="0x0"/>
		<node id="stat" address="0x1"/>
	</node>
	<node id="xpoint" address="0x57" size="0x4" fwinfo="endpoint;width=2"/>
</node>

... gen_ipbus_addr_decode now returns with exit code 3 before writing the VHDL file, and produces the following output:

[developer@e4f2df29fc74 build]$ gen_ipbus_addr_decode addr_table_bad3.xml 
main ERROR: Node 'csr' at 0x43: Width, 0x1, produces address mask 0x2 that is not aligned with node's base address
main ERROR: Node 'xpoint' at 0x57: Width, 0x2, produces address mask 0x4 that is not aligned with node's base address
main ERROR: Node errors detected (e.g. non-aligned addresses, or address overlaps); exiting early before writing output