[llvm] [LV][NFC] Add option to control debug printing of cost per lane (PR #201824)

[Luke Lau via llvm-commits]

lukel97 wrote:

> If it is possible to generate stable output without too much extra work that would be great. Alternatively, not sure if the update scripts support only generating checks for parts of a matched line? At least update_test_checks.py supports excluding parts of a line I think

If we really want to avoid the flag maybe the easiest thing to do is just print the cost per lane on a new line. I presume UTC will just skip that line.

https://github.com/llvm/llvm-project/pull/201824