ROM >= 8k fails to build

[urish]

Describe the bug A clear and concise description of what the bug is.

Version 1.2.48 (b6a6f12642df6b84facc24a77f9a6f67a0d62dab)

To Reproduce Generate a 8kbyte ROM binary file, e.g.:

dd if=/dev/zero bs=1 count=8192 | tr '\000' 'U' > rom_configs/rom_8k.bin

Use the following configuration:

word_size = 1
check_lvsdrc = True
rom_data = "rom_configs/rom_8k.bin"
data_type = "bin"
output_name = "sky130_rom_8k
output_path = "macro/{output_name}".format(**locals())

import os
exec(open(os.path.join(os.path.dirname(__file__), 'sky130_rom_common.py')).read())

Expected behavior Should build without any errors

Logs

[openram.router.signal_escape_router/route]: Running signal escape router...
Traceback (most recent call last):
  File "/home/runner/work/sky130-rom-experiments/sky130-rom-experiments/OpenRAM/rom_compiler.py", line 65, in <module>
    r = rom()
  File "/home/runner/work/sky130-rom-experiments/sky130-rom-experiments/OpenRAM/compiler/rom.py", line 54, in __init__
    self.r.create_layout()
  File "/home/runner/work/sky130-rom-experiments/sky130-rom-experiments/OpenRAM/compiler/modules/rom_bank.py", line [86](https://github.com/TinyTapeout/sky130-rom-experiments/actions/runs/8441697713/job/23121431113#step:4:87), in create_layout
    self.route_layout()
  File "/home/runner/work/sky130-rom-experiments/sky130-rom-experiments/OpenRAM/compiler/modules/rom_bank.py", line 124, in route_layout
    self.route_escape_pins(init_bbox)
  File "/home/runner/work/sky130-rom-experiments/sky130-rom-experiments/OpenRAM/compiler/modules/rom_bank.py", line 534, in route_escape_pins
    rtr.route(pins_to_route)
  File "/home/runner/work/sky130-rom-experiments/sky130-rom-experiments/OpenRAM/compiler/router/signal_escape_router.py", line 73, in route
    self.new_pins[source.name] = new_wires[-1]
IndexError: list index out of range
make[1]: *** [Makefile:[90](https://github.com/TinyTapeout/sky130-rom-experiments/actions/runs/8441697713/job/23121431113#step:4:91): sky130_rom_8192.ok] Error 1
make: *** [Makefile:95: sky130_rom_8192] Error 2

(You can see the complete logs here)

Additional context Also happens on larger sizes (tried 12k, 16k, 24k, 32k), and even with smaller sizes if we increase the value of words_per_row, e.g., for a 128 bytes ROM:

dd if=/dev/zero bs=1 count=128 | tr '\000' 'U' > rom_configs/rom_128.bin

word_size = 1
words_per_row = 32

check_lvsdrc = True

rom_data = "rom_configs/rom_128.bin"
data_type = "bin"

output_name = "rom_128"
output_path = "macro/{output_name}".format(**locals())

import os
exec(open(os.path.join(os.path.dirname(__file__), 'sky130_rom_common.py')).read())

[mguthaus]

A 1-bit ROM seems very odd and I'm not surprised that doesn't work. Why would you only need 1-bit output?

It would probably be better to have a 8 or even 32-bit output and then select which bit of the output is needed.

[urish]

Thanks for responding! word_size = 1 generates a 8-bit ROM. It's the same word size as defined in the 1K example ROM:

https://github.com/VLSIDA/OpenRAM/blob/b6a6f12642df6b84facc24a77f9a6f67a0d62dab/macros/rom_configs/sky130_rom_1kbyte.py#L9

[mguthaus]

I see. This is actually a mistake as it should be in bits, not bytes like the SRAMs:

https://github.com/VLSIDA/OpenRAM/blob/b6a6f12642df6b84facc24a77f9a6f67a0d62dab/compiler/rom_config.py#L21