[Bug target/94452] I386 ABI: How to determine the alignment arguments on the stack of struct or union for argument passing

hjl.tools at gmail dot com gcc-bugzilla@gcc.gnu.org
Thu Apr 2 11:56:55 GMT 2020


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94452

H.J. Lu <hjl.tools at gmail dot com> changed:

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--- Comment #6 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to ChenLiu from comment #5)
> (In reply to Richard Biener from comment #4)
> > (In reply to ChenLiu from comment #2)
> > > (In reply to Richard Biener from comment #1)
> > > > I see gx aligned to 64 bytes (as I expected).  Can you be more specific as
> > > > to what target you tested?
> > > 
> > > I tested on i386 target. I think you may misunderstand what I mean. The gx
> > > will align to 4 byte when passing it on stack. I think this should belong to
> > > calling conventions.
> > 
> > Ah, OK.  IIRC the psABI does not factor in over/under alignment but only
> > size and kind of (sub-)objects so eventually extra copy-in/out is required
> > to have the callee see arguments of the desired alignment.
> > 
> > HJ can probably clarify.
> > 
> > Note bugzilla isn't really for this kind of questions, there's a psABI
> > mailing list somewhere.
> 
> Thanks for your help.

Please raise this question at

https://groups.google.com/forum/#!forum/ia32-abi


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