fix: Simplify defunctionalize return

[aakoshh]

Description

Problem*

Extracted from #7072
Depends on #7100 to fix SSA parsing

Summary*

Skips the creation of unnecessary blocks in the apply functions during defunctionalize, jumping straight to the return block.

Additional Context

At the time I thought it might play a role in the inlining cost calculation, causing the apply to be too expensive to inline because it affects the weight. It turned out the function was too expensive to inline even with this change.

These blocks would be removed by a simplify pass, but I didn't see a reason they should be generated in the first place.

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]

Compilation Report

Program	Compilation Time	%
sha256_regression	1.000s	-3%
regression_4709	0.789s	-1%
ram_blowup_regression	16.200s	0%
rollup-root	3.690s	6%
rollup-merge	2.064s	0%
rollup-block-root-single-tx	141.000s	-3%
rollup-block-root-empty	2.052s	0%
rollup-block-root	137.000s	2%
rollup-block-merge	3.580s	-2%
rollup-base-public	29.400s	6%
rollup-base-private	10.940s	9%
private-kernel-tail	1.002s	6%
private-kernel-reset	6.030s	-4%
private-kernel-inner	1.940s	0%

[github-actions]

Execution Report

Program	Execution Time	%
sha256_regression	0.051s	0%
regression_4709	0.001s	0%
ram_blowup_regression	0.610s	0%
rollup-root	0.106s	1%
rollup-merge	0.006s	0%
rollup-block-root	37.300s	0%
rollup-block-merge	0.105s	0%
rollup-base-public	1.231s	0%
rollup-base-private	0.455s	0%
private-kernel-tail	0.019s	5%
private-kernel-reset	0.311s	-1%
private-kernel-inner	0.067s	-2%

[github-actions]

Compilation Memory Report

Program	Peak Memory
keccak256	77.65M
workspace	123.88M
regression_4709	424.15M
ram_blowup_regression	1.46G
rollup-root	601.26M
rollup-merge	494.24M
rollup-block-root-single-tx	16.06G
rollup-block-root-empty	488.41M
rollup-block-root	16.07G
rollup-block-merge	601.26M
rollup-base-public	2.38G
rollup-base-private	1.14G
private-kernel-tail	207.34M
private-kernel-reset	584.47M
private-kernel-inner	294.71M

[github-actions]

Execution Memory Report

Program	Peak Memory
keccak256	74.71M
workspace	123.33M
regression_4709	316.02M
ram_blowup_regression	512.62M
rollup-root	498.31M
rollup-merge	473.05M
rollup-block-root	1.22G
rollup-block-merge	498.33M
rollup-base-public	734.17M
rollup-base-private	590.51M
private-kernel-tail	180.91M
private-kernel-reset	245.52M
private-kernel-inner	208.92M

[github-actions]

Changes to Brillig bytecode sizes

Generated at commit: e4428361f7ddf0639c70cf9ca1d9ff34fa32d34f, compared to commit: bd4f90b054038e52af56f21be828efebd4c0d005

🧾 Summary (10% most significant diffs)

Program	Brillig opcodes (+/-)	%
higher_order_functions_inliner_zero	-4 ✅	-0.46%
brillig_fns_as_values_inliner_min	-2 ✅	-1.00%
brillig_fns_as_values_inliner_zero	-2 ✅	-1.48%

---

Full diff report 👇

Program	Brillig opcodes (+/-)	%
hashmap_inliner_max	19,770 (-8)	-0.04%
uhashmap_inliner_max	12,703 (-8)	-0.06%
hashmap_inliner_min	12,336 (-12)	-0.10%
uhashmap_inliner_min	9,734 (-12)	-0.12%
hashmap_inliner_zero	8,081 (-12)	-0.15%
sha256_regression_inliner_min	5,355 (-8)	-0.15%
uhashmap_inliner_zero	7,479 (-12)	-0.16%
sha256_regression_inliner_zero	4,861 (-8)	-0.16%
sha256_var_padding_regression_inliner_min	3,300 (-6)	-0.18%
sha256_var_padding_regression_inliner_zero	2,957 (-6)	-0.20%
higher_order_functions_inliner_min	1,319 (-4)	-0.30%
higher_order_functions_inliner_zero	867 (-4)	-0.46%
brillig_fns_as_values_inliner_min	198 (-2)	-1.00%
brillig_fns_as_values_inliner_zero	133 (-2)	-1.48%

[github-actions]

Changes to number of Brillig opcodes executed

Generated at commit: e4428361f7ddf0639c70cf9ca1d9ff34fa32d34f, compared to commit: bd4f90b054038e52af56f21be828efebd4c0d005

🧾 Summary (10% most significant diffs)

Program	Brillig opcodes (+/-)	%
higher_order_functions_inliner_zero	-26 ✅	-1.39%
brillig_fns_as_values_inliner_min	-6 ✅	-1.72%
brillig_fns_as_values_inliner_zero	-6 ✅	-3.26%

---

Full diff report 👇

Program	Brillig opcodes (+/-)	%
sha256_var_padding_regression_inliner_min	271,083 (-24)	-0.01%
sha256_var_padding_regression_inliner_zero	265,671 (-24)	-0.01%
sha256_regression_inliner_min	161,295 (-28)	-0.02%
sha256_regression_inliner_zero	155,415 (-28)	-0.02%
uhashmap_inliner_max	137,636 (-60)	-0.04%
uhashmap_inliner_min	230,214 (-108)	-0.05%
uhashmap_inliner_zero	176,297 (-108)	-0.06%
hashmap_inliner_min	113,917 (-108)	-0.09%
hashmap_inliner_max	48,525 (-60)	-0.12%
hashmap_inliner_zero	76,420 (-108)	-0.14%
higher_order_functions_inliner_min	2,878 (-26)	-0.90%
higher_order_functions_inliner_zero	1,840 (-26)	-1.39%
brillig_fns_as_values_inliner_min	343 (-6)	-1.72%
brillig_fns_as_values_inliner_zero	178 (-6)	-3.26%