Mark more assembly outputs as early clobber #1307

1. 
   sipa commented at 9:20 AM on May 12, 2023: contributor

   This fixes #766.

   In the existing code, the compiler is allowed to allocate the RSI register for outputs m0, m1, or m2, which are written to before the input in RSI is read from. Fix this by marking them as early clobber.

   Make a similar change in the field logic, even though not triggerable there.

2. real-or-random added the label bug on May 12, 2023
3. real-or-random added the label assurance on May 12, 2023
4. real-or-random removed the label assurance on May 12, 2023
5. Bugfix: mark outputs as early clobber in scalar x86_64 asm

   In the existing code, the compiler is allowed to allocate the RSI register
   for outputs m0, m1, or m2, which are written to before the input in RSI is
   read from. Fix this by marking them as early clobber.
   
   Reported by ehoffman2 in https://github.com/bitcoin-core/secp256k1/issues/766

   0c729ba70d
6. Mark stack variables as early clobber for technical correctness

   In the field 5x52 asm for x86_64, stack variables are provided as outputs.
   The existing inputs are all forcibly allocated to registers, so cannot
   coincide, but mark them as early clobber anyway to make this clearer.

   350b4bd6e6
7. sipa force-pushed on May 12, 2023
8. real-or-random added the label needs-changelog on May 12, 2023
9. Add release note 8c9ae37a5a
10. sipa added this to the milestone 0.3.2 (or 0.4.0) on May 12, 2023
11. real-or-random approved
12. 
    real-or-random commented at 12:56 PM on May 12, 2023: contributor

    ACK 8c9ae37a5a26cdeb6365624fee43f41b238830e4

13. 
    jonasnick commented at 1:34 PM on May 12, 2023: contributor

    ACK 8c9ae37a5a26cdeb6365624fee43f41b238830e4

    I'm reasonably sure that we with this PR we found all outputs that needed to be marked as early clobbers.

14. jonasnick merged this on May 12, 2023
15. jonasnick closed this on May 12, 2023

    ---

16. hebasto referenced this in commit 49c52ea2b1 on May 13, 2023
17. real-or-random removed the label needs-changelog on May 13, 2023
18. vmta referenced this in commit e1120c94a1 on Jun 4, 2023
19. sipa referenced this in commit 901336eee7 on Jun 21, 2023
20. vmta referenced this in commit 8f03457eed on Jul 1, 2023
21. jonasnick cross-referenced this on Jul 24, 2023 from issue Upstream PRs 1268, 1276, 1267, 1265, 1230, 1279, 1273, 1263, 1231, 1285, 1283, 1205, 1286, 1275, 1234, 1239, 1240, 1284, 1277, 1289, 1270, 1296, 1301, 1299, 1066, 1300, 1292, 1305, 1303, 1133, 1306, 1207, 1304, 1307, 1311, 1309, 1312 by jonasnick

Contributors

sipareal-or-randomjonasnick

Milestone
0.3.3 (or 0.4.0)