I'm not qualified to review, but LGTM besides a couple nit picks.

@cem got this pushed upstream [1] and we pulled it back down with v1.3.8 in r342598.

Equivalent patch was done in r343672 by @vangyzen .

Silence warnings in code instead of disabling the warning.

@cem pointed out to me r340842 & r340843. @kib would you prefer we just
did the same to i386 as was done to amd64?

@cem is direct commit to sys/contrib/zstd okay for this?

dim feedback: use CWARNFLAGS.gcc for warning suppression

Always nice to have minus diffs, assuming it still compiles :)

Most of these changes look to be in the right direction. I don't think evaluating if a bool == true or == false is necessary. In some places parentheses have been added which are not strictly needed, I don't feel strongly about those either way. I did not evaluate for completeness.

My opinion is generally that branch predictions should be sparse. Is it really going to make any difference in setup/teardown functions, which many of the functions edited here appear to be?

Review feedback: avoid touching "superfluous" macro parens for now

mjoras feedback: parenthesization fixes

In D12753#264690, @mjoras wrote:

The superfluous parentheses stuff is sort of nitpicky, but I do feel that at least in the case where the expansion is surrounded by commas then it should be dropped since comma operators / separators have the lowest possible precedence.

In D12683#263679, @pfg wrote:

Upstream indeed seems to have disappeared but Benno Rice may know better.

In D12675#263212, @hselasky wrote:

Just give this patch a spin with clang aswell before committing. I'll handle this issue towards Mellanox.
Thank you!
--HPS

hselasky feedback: replace const vars with enum constants

In D12675#263187, @hselasky wrote:

What is the purpose of this change?

Padlock fix-up LGTM.

The change looks fine to me.

Just dropping some nitpicks, I haven't reached a deep enough understanding for a real review yet.

The change itself seems fine to me. I'll defer to others with respect to whether this is the right direction and whether the documentation needs to be in this revision.

@emaste suggested out of band to verify with a universe build. I did a make tinderbox and it succeeded.