For simplicity, punt order > field or width mismatches. Analogous
optimizations are possible, but the generic path works fine and no
commonly-used curve looks hits those cases.
Before:
Did 5888 ECDSA P-384 verify operations in 3094535us (1902.7 ops/sec)
After [+6.7%]:
Did 6107 ECDSA P-384 verify operations in 3007515us (2030.6 ops/sec)
Also we can fill in p - order generically and avoid extra copies of some
constants.
Change-Id: I38e1b6d51b28ed4f8cb74697b00a4f0fbc5efc3c
Reviewed-on: https://boringssl-review.googlesource.com/c/33068
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>
8618f2bfe0