Bitwise CRC32 kernel¶

Generated workload catalogue · Execution contract

Purpose¶

Exercise integer bit operations and data-dependent branches without a lookup table or special instruction.

Setup¶

Property	Value
Workload ID	`crc32`
Selection	`--workload crc32`
Generator	`buildRV32IBenchmark() in RV32IBenchmarks.cpp`
End condition	EBREAK after the loop and result store

Use the low byte of each of n seeded words as the input stream.

Use the shared address map and parameter bounds. N includes any training iterations; n means size.

Implementation¶

Each iteration starts CRC at 0xffffffff. XOR each byte into the CRC; repeat eight logical right shifts, XORing 0xedb88320 when the old low bit was one. Complement at the end and add to x10.

crc = 0xffffffff;
for (uint8_t b : bytes) {
  crc ^= b;
  for (unsigned bit = 0; bit < 8; ++bit)
    crc = (crc >> 1) ^ ((crc & 1) ? 0xedb88320 : 0);
}
sum += ~crc;

This is a behavioral summary of the generated assembly, not the host program being timed.

Expected result¶

Result=N*CRC32(bytes) modulo 2^32. The host-side generator computes the expected checksum; every iteration processes the same bytes.

The runner checks the generator's expected result in addition to retirement-by-retirement oracle validation. Output-array assertions, where described, check more than a checksum.

Measurement and running¶

This project-owned generated kernel differs from Embench CRC32 in its input, repetition scheme, and verifier. Their instruction counts and scores are not interchangeable.

build/rv32i_experiment --core advanced --workload crc32 \
  --iterations 2 --size 16 --seed 1  \
  --fidelity behavioral --period 4000 \
  --allocation-limit-mib 512 --max-cycles 4096

The explicit period is for a bounded functional check, not a hardware-speed result. For comparisons, use the serial campaign driver, identical case inputs, and a certified per-target clock.

Source and tests¶

src/analysis/RV32IBenchmarks.cpp: emitted instructions and independent expected results.
tests/cpp/RV32IBenchmarkTest.cpp: generator results, parameter bounds, and edge cases.
tests/checks/RV32IBenchmarkCLITest.py and tests/checks/BenchmarkCampaignCLITest.py: shared execution/campaign checks.