Why Rust compiler (1.77.0 to 1.85.0) reserves 2x extra stack for large enum?

compiler
6

Thanks for the suggestion, didn't know about that tool. The run cargo bisect-rustc --start 1.76.0 --end 1.77.0 --script ./test.sh -vv -- build --release found the regerssion:

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Regression in nightly-2024-01-16
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fetching https://static.rust-lang.org/dist/2024-01-15/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2024-01-15: 40 B / 40 B [======================================================================================================================] 100.00 % 1013.29 KB/s converted 2024-01-15 to 30dfb9e046aeb878db04332c74de76e52fb7db10
fetching https://static.rust-lang.org/dist/2024-01-16/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2024-01-16: 40 B / 40 B [=========================================================================================================================] 100.00 % 1.08 MB/s converted 2024-01-16 to 714b29a17ff5fa727c794bbb60bfd335f8e75d42
looking for regression commit between 2024-01-15 and 2024-01-16
fetching (via remote github) commits from max(30dfb9e046aeb878db04332c74de76e52fb7db10, 2024-01-13) to 714b29a17ff5fa727c794bbb60bfd335f8e75d42
ending github query because we found starting sha: 30dfb9e046aeb878db04332c74de76e52fb7db10
get_commits_between returning commits, len: 7
  commit[0] 2024-01-14: Auto merge of #119970 - GuillaumeGomez:rollup-p53c19o, r=GuillaumeGomez
  commit[1] 2024-01-15: Auto merge of #119581 - Nadrieril:detangle-arena, r=compiler-errors
  commit[2] 2024-01-15: Auto merge of #119508 - Zalathar:graph, r=compiler-errors
  commit[3] 2024-01-15: Auto merge of #119878 - scottmcm:inline-always-unwrap, r=workingjubilee
  commit[4] 2024-01-15: Auto merge of #119987 - matthiaskrgr:rollup-f7lkx4w, r=matthiaskrgr
  commit[5] 2024-01-15: Auto merge of #119988 - lnicola:sync-from-ra, r=lnicola
  commit[6] 2024-01-15: Auto merge of #119610 - Nadrieril:never_pattern_bindings, r=compiler-errors
ERROR: no CI builds available between 30dfb9e046aeb878db04332c74de76e52fb7db10 and 714b29a17ff5fa727c794bbb60bfd335f8e75d42 within last 167 days

Repo with code to find regression, REASY/rust-extra-stack-repro

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