Tests that pass in the DSLX interpreter, fail with deadline in the IR interpreter

[rw1nkler]

Describe the bug

We noticed that some of the procs from the ZSTD Decoder cannot be correctly translated to the IR. In a few cases the same simulation that works with the DSLX interpreter, hangs when run with the IR interpreter.

This is a case for at least two tests:

• RamDemux3Test (rule)
• ZstdDecoderInternalTest (rule)

To Reproduce

Steps to reproduce the behavior:

1. Checkout to the zstd_ir_problem branch
2. Run bazel run //xls/modules/zstd:ram_demux3_dslx_test to run the test with the IR interpreter
3. Observe the following error:

Executing tests from //xls/modules/zstd:ram_demux3_dslx_test
-----------------------------------------------------------------------------
[ RUN UNITTEST  ] RamDemux3Test
qE0130 14:34:39.920672 1784807 run_routines.cc:110] Internal error: DEADLINE_EXCEEDED: Exceeded limit of 100000 ticks of the proc network before expected output produced
[        FAILED ] RamDemux3Test: internal error: DEADLINE_EXCEEDED: Exceeded limit of 100000 ticks of the proc network before expected output produced

4. Open the BUILD file and remove the evaluator="ir-interpreter" option from the ram_demux3_dslx_test rule.
5. Run the test with DSLX interpreter and see the test passing

Expected behavior

The test should give the same result when run with DSLX and IR interpreters.