[hexagon] Prevent alignment search beyond a label

[quic-akaryaki]

When searching for packets to .align, don't consider ones which would require padding beyond a label.

There are two problems with padding beyond a label:

the distance between labels may increase for some offsets to become too large;
u/sleb128 values that encode a difference will not be updated because they are computed before the align command is handled.
This is more a short-term fix/hack. The proper solution would be to unify .align and .falign handling and move it to the layout loop.

[llvmbot]

@llvm/issue-subscribers-backend-hexagon

Author: Alexey Karyakin (quic-akaryaki)

When searching for packets to .align, don't consider ones which would require padding beyond a label.

There are two problems with padding beyond a label:

the distance between labels may increase for some offsets to become too large;
u/sleb128 values that encode a difference will not be updated because they are computed before the align command is handled.
This is more a short-term fix/hack. The proper solution would be to unify .align and .falign handling and move it to the layout loop.

[quic-akaryaki]

/cherry-pick 378fa27

[quic-akaryaki]

I created this issue retroactively to port the fix from main to 20.x

[llvmbot]

Failed to cherry-pick: 378fa27

https://github.com/llvm/llvm-project/actions/runs/13981426279

Please manually backport the fix and push it to your github fork. Once this is done, please create a pull request

[androm3da]

/cherry-pick 1fe4631