lib/59231: assert.h: missing branch prediction

[campbell+netbsd%mumble.net@localhost]

>Number:         59231
>Category:       lib
>Synopsis:       assert.h: missing branch prediction
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    lib-bug-people
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Sat Mar 29 01:40:00 +0000 2025
>Originator:     Taylor R Campbell
>Release:        current, 10, 9, ...
>Organization:
The NetBSD Assertion
>Environment:
>Description:
The assert() macro, and its cousin _DIAGASSERT for NetBSD-internal library use, gives no hints to the compiler that the condition being asserted is expected to be true.

As a result, the compiler is left to guess which way to prioritize branches, and will often create suboptimal decisions under the premise that the condition has just as good a chance of being false.  For example, the compiler is apt to allocate a stack frame in what is otherwise a leaf routine just because it has a subroutine call to __assert13.
>How-To-Repeat:
code inspection
>Fix:
__predict_true