Re: [PATCH v3] kernel.h: Skip single-eval logic on literals in min()/max()

[Linus Torvalds]

On Mon, Mar 12, 2018 at 3:55 PM, Andrew Morton
<akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> Replacing the __builtin_choose_expr() with ?: works of course.

Hmm. That sounds like the right thing to do. We were so myopically
staring at the __builtin_choose_expr() problem that we overlooked the
obvious solution.

Using __builtin_constant_p() together with a ?: is in fact our common
pattern, so that should be fine. The only real reason to use
__builtin_choose_expr() is if you want to get the *type* to vary
depending on which side you choose, but that's not an issue for
min/max.

> What will be the runtime effects?

There should be none. Gcc will turn the conditional for the ?: into a
constant, and DTRT.

              Linus