[ ... ]

Subject: Re: [PATCH] ARM: Do not allow unaligned accesses when
	CONFIG_ALIGNMENT_TRAP
Message-ID: [ref]
Content-Type: text/plain; charset="UTF-8"

Hi Andi,

On Thu, 2011-05-26 at 22:10 +0100, Andi Kleen wrote:

quoted

quoted

It is possible that -fconserve-stack is still valuable on ARM given that
it is also used with -mno-unaligned-access for other things than
structure packing on the stack, and therefore its merits can be debated
independently from the alignment issue at hand.

The big advantage of -fconserve-stack is that it throttles the inliner
if the inlining
would cause too much stack growth. This is something you likely want
on ARM too, especially as code gets more and more complex.

Do you have any concrete examples of -fconserve-stack giving an overall
win that isn't in the noise? The fact that the GCC documentation
explicitly states that enabling the option can lead to `making the
program slower' does make me question why we're enabling it in the first
place.

quoted

From private conversation, the GCC guys don't seem to think this is a

bug so I'm reluctant to open a bugzilla ticket.

Will

Isn't this again one of those orthogonalities ? If what is desirable is to 
curb the inlining, then achieving that as one but not the only side effect 
of limiting stack space usage is kind of missing the point.

The GCC manual says -finline-limit does this based on function size; 
haven't experimented, though.

FrankH.