[Bug target/39137] [4.4 Regression] -mpreferred-stack-boundary=2 causes lots of dynamic realign

[hjl dot tools at gmail dot com]

------- Comment #16 from hjl dot tools at gmail dot com  2009-02-12 17:01 -------
(In reply to comment #15)
> The DFmode and DImodes are different. Aligning DFmode on stack is very
> performance critical, while DImodes on 32bit machine can quite safely be
> misaligned (if we ignore their possible use in MMX intrincisc).
> I think we ought to be able to handle this case without any extra options: when
> function use DFmode variables trigger stack realign at
> -mpreferred-stack-boundary=2 and -O2, while do not trigger it with DImode. 

That may break Ada or others. See comment #11. I still think
a new command line option to control DImode alignment is better.
It won't be the first command line option which changes ABI.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39137