Bitwise chip: failure to satisfy input_2 byte decomposition constraint

[morganthomas]

On several examples in the Valida LLVM compiler test suite, the trace fails to satisfy a particular constraint of the Bitwise chip, in alu_u32/src/bitwise/stark.rs:

builder.assert_eq(local.input_2[i], byte_2.clone());

For example, the following C file results in the failure in question when compiled by the Valida LLVM compiler:

int main() {
  int v1 = 4;
  int v2 = 5;
  int result = v1 >= v2;
  if (result) {
    while (1) {
    }
  }

  return 0;
}

This file compiles into the following assembly code:

IMM32 -8, 0, 0, 0, 0
JAL -4, 258, 0, 1, 1
IMM32 -8, 0, 0, 0, 14
JAL -10, 90, -14, 1, 1
STOP 0, 0, 0, 0, 0
JALV -4, 4, c, 0, 0
IMM32 -14, 0, 0, 0, 0
ADD32 -4, -14, 0, 0, 1
IMM32 -18, 0, 0, 0, 4
ADD32 -8, -18, 0, 0, 1
IMM32 -1c, 0, 0, 0, 5
ADD32 -c, -1c, 0, 0, 1
ADD32 -20, -8, 0, 0, 1
ADD32 -24, -c, 0, 0, 1
LTE32 -28, -24, -20, 0, 0
AND32 -2c, -28, 1, 0, 1
ADD32 -10, -2c, 0, 0, 1
ADD32 -30, -10, 0, 0, 1
BEQ 210, -30, 0, 0, 1
BEQ 1e0, 4, 4, 0, 0
BEQ 1f8, 4, 4, 0, 0
BEQ 1f8, 4, 4, 0, 0
IMM32 -34, 0, 0, 0, 0
ADD32 8, -34, 0, 0, 1
JALV -4, 4, c, 0, 0
IMM32 4, 0, 0, 0, 0
JALV 0, -4, -8, 0, 0

The following is the result of trying to prove an execution of this program:

Proof successful
thread 'main' panicked at /home/morgan/code/lita/issue/completeness/valida/basic/src/lib.rs:54:10:
Failed to verify constraints on chip 10: OodEvaluationMismatch

When the mentioned constraint is commented out, then proving succeeds and results in a verifiable proof of execution for this example.

Produce a minimal example which exhibits the issue. Fix the issue. Add a regression test to the test suite which verifies the proof of an execution of a minimal example which exhibits the issue.