Inlining (was: GCC 3.3 release criteria)

[Matt Austern <austern at apple dot com>]

On Monday, February 24, 2003, at 12:28 PM, Andi Kleen wrote:

> "Kaveh R. Ghazi" <ghazi at caip dot rutgers dot edu> writes:
>
> > <tr><td><a href="http://www.kernel.org";>Linux kernel</a></td>
>
> gcc 3.3 doesn't compile the linux kernels (2.4 and 2.5) very well
> currently because the inlining algorithm is too broken. The Linux
> kernel often assumes that functions marked "inline" get inlined and
> when they aren't it results in linking errors. In a few rare cases
> you also get silent miscompilation (this happened in the x86-64 port,
> now fixed)

As it happens, Apple may be able to contribute a patch that does what
you're looking for.  We've got a local patch that adds a new command
line switch, -fobey-inline.   The switch does exactly what you think: 
the
compiler will inline every function that's marked 'inline' whenever it's
possible.  (There are still cases where it's not possible, of course, 
e.g.
if you mark a recursive function inline.)

We definitely don't want -fobey-inline to be the default: usually it's
better for the compiler to treat the inline keyword as a hint, and to
use its own heuristics to decide when to accept the hint.  But there are
cases, as you've found, when a flag like this is useful.

If Apple contributed the -fobey-inline patch, would people here be
interested in it?

			--Matt