chore: pull value merger code from sync

[TomAFrench]

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Changes to circuit sizes

Generated at commit: 73881ee2ce957b233b1217d63543b0f1a4db7b18, compared to commit: 10df7c552456062e9a71257c2649f8a4d6237b90

🧾 Summary (100% most significant diffs)

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
private_kernel_reset_4_4_4_4_4_4_4_4_1	+4,719 ❌	+14.57%	+19,236 ❌	+22.24%
private_kernel_reset	+5,633 ❌	+6.70%	+19,440 ❌	+3.15%
rollup_block_root	-168 ✅	-3.74%	-144 ✅	-0.01%
parity_root	-252 ✅	-5.01%	-216 ✅	-0.01%
rollup_merge	-168 ✅	-4.91%	-144 ✅	-0.01%
rollup_block_merge	-465 ✅	-3.87%	-451 ✅	-0.02%
rollup_root	-465 ✅	-3.88%	-451 ✅	-0.02%
private_kernel_tail	-6 ✅	-0.15%	-6 ✅	-0.05%
parity_base	-252 ✅	-5.86%	-216 ✅	-0.70%
rollup_base_private	-28,501 ✅	-14.42%	-41,353 ✅	-1.56%
private_kernel_inner	-785 ✅	-2.09%	-1,034 ✅	-1.82%
private_kernel_init	-741 ✅	-3.46%	-986 ✅	-2.86%
rollup_base_public	-91,453 ✅	-20.45%	-129,514 ✅	-3.24%
private_kernel_tail_to_public	-2,133 ✅	-12.27%	-3,044 ✅	-10.32%

---

Full diff report 👇

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
private_kernel_reset_4_4_4_4_4_4_4_4_1	37,104 (+4,719)	+14.57%	105,727 (+19,236)	+22.24%
private_kernel_reset	89,660 (+5,633)	+6.70%	637,477 (+19,440)	+3.15%
rollup_block_root	4,321 (-168)	-3.74%	2,739,508 (-144)	-0.01%
parity_root	4,782 (-252)	-5.01%	3,636,536 (-216)	-0.01%
rollup_merge	3,251 (-168)	-4.91%	1,826,902 (-144)	-0.01%
rollup_block_merge	11,544 (-465)	-3.87%	1,858,073 (-451)	-0.02%
rollup_root	11,528 (-465)	-3.88%	1,858,059 (-451)	-0.02%
private_kernel_tail	4,125 (-6)	-0.15%	12,508 (-6)	-0.05%
parity_base	4,049 (-252)	-5.86%	30,482 (-216)	-0.70%
rollup_base_private	169,172 (-28,501)	-14.42%	2,617,226 (-41,353)	-1.56%
private_kernel_inner	36,764 (-785)	-2.09%	55,845 (-1,034)	-1.82%
private_kernel_init	20,666 (-741)	-3.46%	33,517 (-986)	-2.86%
rollup_base_public	355,672 (-91,453)	-20.45%	3,867,929 (-129,514)	-3.24%
private_kernel_tail_to_public	15,251 (-2,133)	-12.27%	26,460 (-3,044)	-10.32%

[TomAFrench]

@asterite can you pull this branch and run the unconditional_recursion test locally? This passes locally for me but fails in CI.

[asterite]

It passes too.

That said, I can make it fail locally if I change RUST_MIN_STACK:

RUST_MIN_STACK=100000 cargo test unconditional_recursion

Maybe that value is different in CI, compared to our machines?

[asterite]

It seems the value is platform-dependent:

https://doc.rust-lang.org/std/thread/#stack-size

But I don't know if this is running in a non-main thread.

That said, maybe we should set that value to a fixed constant somewhere so code runs the same way everywhere.

(I think, for example, the Rust compiler sets it to a higher-than-normal value to support deeply nested code structures, so we could do the same)