Re: reducing stack usage in v4l?

Russell King (rmk@arm.linux.org.uk)
Wed, 5 Mar 2003 09:35:34 +0000

On Wed, Mar 05, 2003 at 10:15:52AM +0100, Gerd Knorr wrote:
> But when looking at the disasm output it is obvious that it isn't true
> (at least with gcc 3.2). On the other hand it is common practice in
> many drivers, there must be a reason for that, no? Any chance this
> used to work with older gcc versions?

I don't believe so - I seem to remember looking at gcc 2.95 and finding
the same annoying behaviour.

> Not sure what is the best idea to fix that. Don't like the kmalloc
> idea that much. The individual structs are not huge, the real problem
> is that many of them are allocated and only few are needed. Any
> chance to tell gcc that it should allocate block-local variables at
> the start block not at the start of the function?

Not a particularly clean idea, but maybe creating a union of the
structures and putting that on the stack? (ie, doing what GCC should
be doing in the first place.)

-- 
Russell King (rmk@arm.linux.org.uk)                The developer of ARM Linux
             http://www.arm.linux.org.uk/personal/aboutme.html


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