chore: optimise older opcodes in reverse order

[guipublic]

Description

Problem*

Related to #6451 and #6461

Summary*

Handle the case where we can optimise an older opcode

Additional Context

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[github-actions]

Changes to circuit sizes

Generated at commit: 8694821c0149848b8251e5bfd208c85e0fe40d73, compared to commit: 78e784879716e1a8372fea06cdf7dc6df3b04339

🧾 Summary (10% most significant diffs)

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
to_bytes_consistent	+45 ❌	+2250.00%	+45 ❌	+264.71%
poseidon_bn254_hash_width_3	+596 ❌	+66.82%	+467 ❌	+45.03%
simple_radix	+3 ❌	+150.00%	+3 ❌	+17.65%
hashmap	+32,337 ❌	+50.40%	+16,216 ❌	+11.75%
to_bytes_integration	+143 ❌	+50.00%	+50 ❌	+11.19%
eddsa	+5,665 ❌	+8.77%	+4,601 ❌	+6.99%
to_be_bytes	+14 ❌	+20.00%	+8 ❌	+6.84%
array_dynamic_main_output	-11 ✅	-25.00%	-42 ✅	-19.00%

---

Full diff report 👇

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
to_bytes_consistent	47 (+45)	+2250.00%	62 (+45)	+264.71%
poseidon_bn254_hash_width_3	1,488 (+596)	+66.82%	1,504 (+467)	+45.03%
simple_radix	5 (+3)	+150.00%	20 (+3)	+17.65%
hashmap	96,492 (+32,337)	+50.40%	154,175 (+16,216)	+11.75%
to_bytes_integration	429 (+143)	+50.00%	497 (+50)	+11.19%
eddsa	70,294 (+5,665)	+8.77%	70,416 (+4,601)	+6.99%
to_be_bytes	84 (+14)	+20.00%	125 (+8)	+6.84%
bench_eddsa_poseidon	17,922 (+1,483)	+9.02%	20,762 (+1,176)	+6.00%
poseidonsponge_x5_254	1,302 (+262)	+25.19%	1,318 (+63)	+5.02%
regression_5252	43,422 (+8,826)	+25.51%	50,165 (+2,202)	+4.59%
regression_6451	17 (+1)	+6.25%	29 (+1)	+3.57%
bit_shifts_runtime	1,212 (+326)	+36.79%	4,849 (+151)	+3.21%
poseidon_bn254_hash	1,053 (+161)	+18.05%	1,069 (+32)	+3.09%
to_le_bytes	83 (+10)	+13.70%	121 (+3)	+2.54%
nested_array_dynamic	3,822 (+627)	+19.62%	13,258 (+317)	+2.45%
slice_dynamic_index	1,199 (+212)	+21.48%	6,564 (+106)	+1.64%
nested_array_in_slice	1,041 (+148)	+16.57%	5,587 (+74)	+1.34%
7_function	234 (+78)	+50.00%	3,007 (+37)	+1.25%
array_len	17 (+3)	+21.43%	82 (+1)	+1.23%
conditional_1	4,403 (+247)	+5.94%	12,062 (+136)	+1.14%
binary_operator_overloading	383 (+101)	+35.82%	4,512 (+49)	+1.10%
sha256_var_size_regression	17,789 (+1,628)	+10.07%	71,739 (+778)	+1.10%
slices	919 (+78)	+9.27%	3,994 (+41)	+1.04%
u128	782 (+101)	+14.83%	4,734 (+44)	+0.94%
u16_support	203 (+54)	+36.24%	3,016 (+25)	+0.84%
sha256_regression	36,275 (+1,182)	+3.37%	198,509 (+1,046)	+0.53%
hash_to_field	613 (+31)	+5.33%	3,629 (+11)	+0.30%
regression	158 (+16)	+11.27%	3,694 (+10)	+0.27%
bench_poseidon_hash_100	40,700 (+3,100)	+8.24%	40,716 (+100)	+0.25%
bench_poseidon_hash_30	12,210 (+930)	+8.24%	12,226 (+30)	+0.25%
bench_poseidon_hash	407 (+31)	+8.24%	423 (+1)	+0.24%
ram_blowup_regression	177,643 (+4,119)	+2.37%	678,406 (+1,541)	+0.23%
schnorr	1,639 (+120)	+7.90%	23,981 (+49)	+0.20%
sha256_var_witness_const_regression	1,770 (+93)	+5.55%	17,251 (+33)	+0.19%
sha256	1,984 (+102)	+5.42%	21,345 (+34)	+0.16%
bigint	1,185 (+19)	+1.63%	8,124 (+7)	+0.09%
6_array	415 (+2)	+0.48%	4,055 (+3)	+0.07%
regression_3607	43 (+4)	+10.26%	2,804 (+2)	+0.07%
regression_4709	72 (+2)	+2.86%	2,919 (+2)	+0.07%
array_if_cond_simple	111 (+3)	+2.78%	3,134 (+2)	+0.06%
conditional_2	22 (+1)	+4.76%	2,782 (+1)	+0.04%
arithmetic_binary_operations	18 (+2)	+12.50%	2,789 (+1)	+0.04%
regression_struct_array_conditional	72 (+1)	+1.41%	3,204 (+1)	+0.03%
regression_mem_op_predicate	58 (+2)	+3.57%	3,587 (+1)	+0.03%
regression_capacity_tracker	115 (+2)	+1.77%	3,965 (+1)	+0.03%
regression_4449	9,177 (+630)	+7.37%	285,354 (+70)	+0.02%
bench_sha256_100	18,409 (+900)	+5.14%	408,699 (+100)	+0.02%
bench_sha256_30	5,529 (+270)	+5.13%	124,711 (+30)	+0.02%
keccak256	137 (+12)	+9.60%	20,151 (+4)	+0.02%
6	364 (+18)	+5.20%	11,132 (+2)	+0.02%
conditional_regression_short_circuit	392 (+18)	+4.81%	11,161 (+2)	+0.02%
bench_sha256	193 (+9)	+4.89%	7,056 (+1)	+0.01%
sha2_byte	15,973 (+33)	+0.21%	82,690 (+9)	+0.01%
array_dynamic_blackbox_input	1,380 (+18)	+1.32%	21,408 (+2)	+0.01%
bench_sha256_long	882 (+9)	+1.03%	19,467 (+1)	+0.01%
sha256_var_padding_regression	3,872 (+54)	+1.41%	193,947 (+6)	+0.00%
ecdsa_secp256k1	499 (+9)	+1.84%	43,519 (+1)	+0.00%
integer_array_indexing	3 (+1)	+50.00%	2,762 (0)	0.00%
merkle_insert	66 (+12)	+22.22%	3,684 (0)	0.00%
pedersen_check	24 (+1)	+4.35%	3,176 (0)	0.00%
signed_arithmetic	189 (+1)	+0.53%	2,937 (0)	0.00%
signed_div	510 (+15)	+3.03%	538 (0)	0.00%
signed_division	207 (+4)	+1.97%	3,678 (0)	0.00%
simple_shield	53 (+6)	+12.77%	4,872 (0)	0.00%
slice_loop	2 (+1)	+100.00%	18 (0)	0.00%
nested_dyn_array_regression_5782	32 (-3)	-8.57%	2,859 (-4)	-0.14%
array_dynamic	107 (-1)	-0.93%	3,716 (-15)	-0.40%
aes128_encrypt	143 (+16)	+12.60%	1,623 (-20)	-1.22%
array_dynamic_nested_blackbox_input	256 (-19)	-6.91%	7,316 (-91)	-1.23%
array_dynamic_main_output	33 (-11)	-25.00%	179 (-42)	-19.00%

[guipublic]

The increase in circuit size is not expected. This is worrying and we should not merge the PR which is supposed to improve (only a little bit but still) this number.

[github-actions]

Changes to Brillig bytecode sizes

Generated at commit: 8694821c0149848b8251e5bfd208c85e0fe40d73, compared to commit: 78e784879716e1a8372fea06cdf7dc6df3b04339

🧾 Summary (10% most significant diffs)

Program	Brillig opcodes (+/-)	%
brillig_array_to_slice	+24 ❌	+26.67%
reference_only_used_as_alias	+33 ❌	+13.31%
pedersen_hash	+24 ❌	+6.70%
regression_struct_array_conditional	+30 ❌	+5.73%
merkle_insert	+36 ❌	+4.63%
brillig_pedersen	+27 ❌	+3.62%
pedersen_check	+27 ❌	+3.62%

---

Full diff report 👇

Program	Brillig opcodes (+/-)	%
brillig_array_to_slice	114 (+24)	+26.67%
reference_only_used_as_alias	281 (+33)	+13.31%
pedersen_hash	382 (+24)	+6.70%
regression_struct_array_conditional	554 (+30)	+5.73%
merkle_insert	814 (+36)	+4.63%
brillig_pedersen	772 (+27)	+3.62%
pedersen_check	772 (+27)	+3.62%
simple_shield	897 (+27)	+3.10%
array_to_slice	1,043 (+30)	+2.96%
schnorr	1,492 (+36)	+2.47%
fold_complex_outputs	573 (+12)	+2.14%
import	149 (+3)	+2.05%
array_sort	302 (+6)	+2.03%
sha2_byte	3,388 (+66)	+1.99%
brillig_rc_regression_6123	175 (+3)	+1.74%
hashmap	26,656 (+411)	+1.57%
nested_array_dynamic	2,181 (+33)	+1.54%
pedersen_commitment	200 (+3)	+1.52%
brillig_cow_regression	2,410 (+30)	+1.26%
databus_two_calldata	270 (+3)	+1.12%
nested_array_in_slice	1,202 (+12)	+1.01%
array_dynamic	320 (+3)	+0.95%
conditional_1	1,337 (+12)	+0.91%
regression_capacity_tracker	231 (+2)	+0.87%
regression	729 (+6)	+0.83%
slice_dynamic_index	2,736 (+22)	+0.81%
keccak256	1,778 (+12)	+0.68%
brillig_keccak	1,778 (+12)	+0.68%
uhashmap	16,310 (+102)	+0.63%
array_dynamic_nested_blackbox_input	994 (+6)	+0.61%
array_dynamic_blackbox_input	1,176 (+6)	+0.51%
6	1,367 (+6)	+0.44%
sha256	2,053 (+9)	+0.44%
sha256_var_witness_const_regression	1,403 (+6)	+0.43%
conditional_regression_short_circuit	1,437 (+6)	+0.42%
no_predicates_numeric_generic_poseidon	770 (+3)	+0.39%
fold_numeric_generic_poseidon	770 (+3)	+0.39%
brillig_sha256	796 (+3)	+0.38%
regression_4449	859 (+3)	+0.35%
sha256_var_padding_regression	5,248 (+18)	+0.34%
ram_blowup_regression	1,009 (+3)	+0.30%
ecdsa_secp256k1	1,013 (+3)	+0.30%
sha256_var_size_regression	2,046 (+6)	+0.29%
strings	1,042 (+3)	+0.29%
sha256_regression	7,272 (+18)	+0.25%
poseidonsponge_x5_254	4,502 (+6)	+0.13%
regression_5252	4,879 (+6)	+0.12%
poseidon_bn254_hash_width_3	5,692 (+6)	+0.11%
poseidon_bn254_hash	5,692 (+6)	+0.11%
u128	2,911 (+3)	+0.10%
eddsa	10,894 (+9)	+0.08%

[github-actions]

Changes to number of Brillig opcodes executed

Generated at commit: 8694821c0149848b8251e5bfd208c85e0fe40d73, compared to commit: 78e784879716e1a8372fea06cdf7dc6df3b04339

🧾 Summary (10% most significant diffs)

Program	Brillig opcodes (+/-)	%
reference_only_used_as_alias	+163 ❌	+66.53%
regression_capacity_tracker	+336 ❌	+58.95%
brillig_array_to_slice	+31 ❌	+37.80%
regression_struct_array_conditional	+270 ❌	+20.87%
pedersen_hash	+99 ❌	+17.22%
merkle_insert	+486 ❌	+14.48%

---

Full diff report 👇

Program	Brillig opcodes (+/-)	%
reference_only_used_as_alias	408 (+163)	+66.53%
regression_capacity_tracker	906 (+336)	+58.95%
brillig_array_to_slice	113 (+31)	+37.80%
regression_struct_array_conditional	1,564 (+270)	+20.87%
pedersen_hash	674 (+99)	+17.22%
merkle_insert	3,842 (+486)	+14.48%
simple_shield	2,885 (+306)	+11.87%
sha2_byte	52,231 (+5,049)	+10.70%
brillig_pedersen	1,252 (+117)	+10.31%
pedersen_check	1,252 (+117)	+10.31%
array_sort	538 (+36)	+7.17%
pedersen_commitment	296 (+18)	+6.47%
import	153 (+9)	+6.25%
array_to_slice	2,475 (+133)	+5.68%
fold_complex_outputs	889 (+36)	+4.22%
hashmap	58,421 (+2,079)	+3.69%
brillig_rc_regression_6123	289 (+9)	+3.21%
slice_dynamic_index	4,355 (+132)	+3.13%
array_dynamic_blackbox_input	19,955 (+594)	+3.07%
schnorr	10,396 (+216)	+2.12%
uhashmap	153,618 (+2,796)	+1.85%
databus_two_calldata	500 (+9)	+1.83%
nested_array_dynamic	3,116 (+54)	+1.76%
nested_array_in_slice	1,469 (+24)	+1.66%
array_dynamic_nested_blackbox_input	4,629 (+45)	+0.98%
regression	2,703 (+18)	+0.67%
poseidon_bn254_hash	169,552 (+1,053)	+0.62%
poseidon_bn254_hash_width_3	169,552 (+1,053)	+0.62%
conditional_1	5,860 (+36)	+0.62%
regression_5252	951,206 (+5,400)	+0.57%
poseidonsponge_x5_254	190,917 (+1,080)	+0.57%
strings	1,897 (+9)	+0.48%
regression_4449	219,762 (+630)	+0.29%
u128	25,428 (+72)	+0.28%
sha256_var_witness_const_regression	7,036 (+18)	+0.26%
sha256	10,844 (+27)	+0.25%
6	7,357 (+18)	+0.25%
conditional_regression_short_circuit	7,432 (+18)	+0.24%
eddsa	737,279 (+1,620)	+0.22%
brillig_sha256	4,200 (+9)	+0.21%
fold_numeric_generic_poseidon	5,239 (+9)	+0.17%
no_predicates_numeric_generic_poseidon	5,239 (+9)	+0.17%
ecdsa_secp256k1	7,075 (+9)	+0.13%
sha256_var_size_regression	18,331 (+18)	+0.10%
brillig_keccak	37,099 (+36)	+0.10%
keccak256	37,099 (+36)	+0.10%
brillig_cow_regression	583,839 (+252)	+0.04%
sha256_regression	126,254 (+45)	+0.04%
sha256_var_padding_regression	234,837 (+54)	+0.02%
ram_blowup_regression	877,404 (+9)	+0.00%