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Re: [PATCH] Fix PR 14262 breakage on Darwin


Alan Modra wrote:
> On Thu, Mar 25, 2004 at 12:00:32AM +0100, Ulrich Weigand wrote:
> > unfortunately my patch to fix PR 14262 broke Darwin, as pointed out
> > by Andreas Tobler (in the PR record).
> 
> I suspect that libffi for darwin ought to use the stack copy..
> 
> > happens on Darwin, where 3-byte structs are supposed to be passed
> > left-aligned on the stack *and* left-aligned in a register, and
> > the callee reads them left-aligned from the stack.
> 
> ..because this seems a little weird.  I don't think the function call
> machinery in gcc is intended to support args passed both in regs and
> on the stack, at least not without using PARALLELs to describe the
> reg and stack copies separately.  See the struct arg_data.pass_on_stack
> comment.

Well, passing the same argument in two places seems rather weird to me
in the first place :-/

Anyway, would you agree that gcc should keep its old behaviour in this
case (as implemented by my patch)?  Or do say that this is just a
libffi bug?

> > PS: Alan, I'm not sure what to do if BLOCK_REG_PADDING is defined.
> > Should this also be applied for arguments passed both in registers
> > and on the stack?  It doesn't matter for Darwin right now, which
> > doesn't currently define BLOCK_REG_PADDING ...
> 
> locate.where_pad will be "none" when pass_on_stack is true, so adding
> !args[i].pass_on_stack won't do anything.

OK, so that's fine, thanks.

Bye,
Ulrich

-- 
  Dr. Ulrich Weigand
  weigand@informatik.uni-erlangen.de


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