Always use a normal segment for first SegmentArena segment

[notlesh]

Problem: Starknet OS expects SegmentArena segments to all be temporary except the first segment, which must be normal. This is so that relocation rules for all segments can chain back into the first.

Solution: Use temporary segments only if it's not the first.

Description

The Starknet OS verifies the continuity of the segments in SegmentArenas here, which requires relocation rules to be properly set up.

The requirements for this to work are that each src_ptr is a temporary segment and each dest_ptr is a non-temporary segment (or a temporary segment with an existing rule mapping it to a non-temporary segment).

cairo-vm uses a number of hints to accomplish this, and these are injected by the sierra-to-casm compiler. However, it relies on one additional hint which is not injected anywhere in the case of SNOS.

This hint seems to ensure the same condition needed in SNOS: that the initial segment is a normal segment and that all other segments are temporary segments with relocation rules pointing back to the initial one.

SNOS handles this by simply allocating the initial segment as a normal one as explained here. This seems to alleviate the need to later recreate the segment in relocate_all_segments(), allowing the implementation to work in SNOS without the hint mentioned above.

Checklist

• Linked to Github Issue
• Unit tests added
• Integration tests added.
• This change requires new documentation.
  • Documentation has been added/updated.
  • CHANGELOG has been updated.

[github-actions]

Benchmark Results for unmodified programs 🚀

Command	Mean [s]	Min [s]	Max [s]	Relative
base big_factorial	2.078 ± 0.047	2.036	2.205	1.01 ± 0.03
head big_factorial	2.067 ± 0.023	2.039	2.104	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base big_fibonacci	2.026 ± 0.045	1.983	2.149	1.01 ± 0.02
head big_fibonacci	2.008 ± 0.013	1.993	2.032	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base blake2s_integration_benchmark	7.608 ± 0.050	7.526	7.689	1.00
head blake2s_integration_benchmark	7.663 ± 0.162	7.550	8.092	1.01 ± 0.02

Command	Mean [s]	Min [s]	Max [s]	Relative
base compare_arrays_200000	2.133 ± 0.012	2.110	2.148	1.00 ± 0.01
head compare_arrays_200000	2.123 ± 0.020	2.108	2.155	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base dict_integration_benchmark	1.408 ± 0.011	1.396	1.429	1.00
head dict_integration_benchmark	1.446 ± 0.009	1.433	1.469	1.03 ± 0.01

Command	Mean [s]	Min [s]	Max [s]	Relative
base field_arithmetic_get_square_benchmark	1.217 ± 0.021	1.201	1.275	1.00 ± 0.02
head field_arithmetic_get_square_benchmark	1.216 ± 0.007	1.207	1.229	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base integration_builtins	7.672 ± 0.056	7.606	7.776	1.00
head integration_builtins	7.907 ± 0.586	7.619	9.527	1.03 ± 0.08

Command	Mean [s]	Min [s]	Max [s]	Relative
base keccak_integration_benchmark	7.958 ± 0.300	7.820	8.805	1.00 ± 0.05
head keccak_integration_benchmark	7.942 ± 0.205	7.807	8.373	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base linear_search	2.121 ± 0.034	2.087	2.213	1.00
head linear_search	2.146 ± 0.062	2.101	2.304	1.01 ± 0.03

Command	Mean [s]	Min [s]	Max [s]	Relative
base math_cmp_and_pow_integration_benchmark	1.483 ± 0.011	1.465	1.500	1.00
head math_cmp_and_pow_integration_benchmark	1.485 ± 0.010	1.469	1.504	1.00 ± 0.01

Command	Mean [s]	Min [s]	Max [s]	Relative
base math_integration_benchmark	1.436 ± 0.011	1.422	1.452	1.00
head math_integration_benchmark	1.440 ± 0.012	1.425	1.461	1.00 ± 0.01

Command	Mean [s]	Min [s]	Max [s]	Relative
base memory_integration_benchmark	1.183 ± 0.012	1.166	1.199	1.00
head memory_integration_benchmark	1.200 ± 0.010	1.184	1.215	1.01 ± 0.01

Command	Mean [s]	Min [s]	Max [s]	Relative
base operations_with_data_structures_benchmarks	1.561 ± 0.040	1.537	1.672	1.00 ± 0.03
head operations_with_data_structures_benchmarks	1.558 ± 0.009	1.543	1.570	1.00

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
base pedersen	521.8 ± 8.4	516.5	545.4	1.00
head pedersen	525.4 ± 5.1	521.0	537.0	1.01 ± 0.02

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
base poseidon_integration_benchmark	754.9 ± 3.6	748.1	758.8	1.01 ± 0.01
head poseidon_integration_benchmark	750.0 ± 6.5	735.9	756.7	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
base secp_integration_benchmark	1.787 ± 0.029	1.760	1.864	1.00 ± 0.02
head secp_integration_benchmark	1.779 ± 0.016	1.760	1.808	1.00

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
base set_integration_benchmark	630.5 ± 2.3	627.8	634.8	1.00
head set_integration_benchmark	633.7 ± 4.9	628.7	644.8	1.00 ± 0.01

Command	Mean [s]	Min [s]	Max [s]	Relative
base uint256_integration_benchmark	4.269 ± 0.154	4.173	4.693	1.00
head uint256_integration_benchmark	4.292 ± 0.198	4.161	4.828	1.01 ± 0.06

[github-actions]

Benchmark Results for modified programs 🚀

Command	Mean [s]	Min [s]	Max [s]	Relative
head big_factorial	2.307 ± 0.024	2.282	2.362	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
head big_fibonacci	2.241 ± 0.026	2.211	2.302	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
head blake2s_integration_benchmark	8.172 ± 0.179	7.971	8.630	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
head compare_arrays_200000	2.374 ± 0.038	2.338	2.470	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
head dict_integration_benchmark	1.566 ± 0.006	1.559	1.576	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
head field_arithmetic_get_square_benchmark	1.319 ± 0.011	1.301	1.337	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
head integration_builtins	8.306 ± 0.229	8.130	8.947	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
head keccak_integration_benchmark	8.608 ± 0.500	8.281	9.808	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
head linear_search	2.368 ± 0.031	2.329	2.434	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
head math_cmp_and_pow_integration_benchmark	1.661 ± 0.045	1.633	1.778	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
head math_integration_benchmark	1.594 ± 0.010	1.579	1.609	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
head memory_integration_benchmark	1.329 ± 0.026	1.309	1.398	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
head operations_with_data_structures_benchmarks	1.718 ± 0.006	1.704	1.725	1.00

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
head pedersen	556.4 ± 2.8	553.5	560.3	1.00

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
head poseidon_integration_benchmark	656.8 ± 6.1	650.3	672.0	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
head secp_integration_benchmark	1.934 ± 0.009	1.923	1.946	1.00

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
head set_integration_benchmark	685.2 ± 4.2	677.5	692.7	1.00

Command	Mean [s]	Min [s]	Max [s]	Relative
head uint256_integration_benchmark	4.646 ± 0.241	4.515	5.327	1.00