From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cagney <ac131313@cygnus.com>
To: David B Anderson <davea@quasar.engr.sgi.com>
Cc: drow@mvista.com, gdb-patches@sources.redhat.com
Subject: Re: [rfa] mips argument passing fixes for o32
Date: Mon, 16 Jul 2001 16:44:00 -0000
Message-id: <3B537C4C.1000102@cygnus.com>
References: <200107130003.RAA57770@quasar.engr.sgi.com> <200107160328.UAA42806@quasar.engr.sgi.com>
X-SW-Source: 2001-07/msg00412.html

> |> if (!MIPS_EABI
> |> && MIPS_SAVED_REGSIZE < 8
> |> -		      && TARGET_BYTE_ORDER == BIG_ENDIAN
> |> +		      && (TARGET_BYTE_ORDER == BIG_ENDIAN
> |> +			  || TYPE_LENGTH (arg_type) < MIPS_SAVED_REGSIZE)
> |> && partial_len < MIPS_SAVED_REGSIZE
> |> && (typecode == TYPE_CODE_STRUCT ||
> |> typecode == TYPE_CODE_UNION))
> |
> |I don't know that line being added should be
> 
> 
> ||| TYPE_LENGTH (arg_type) < MIPS_SAVED_REGSIZE
> |
> |
> |it should at least be guarded by ``ABI == o32''.  What does LE n32 do 
> |for instance?
> |If GCC, for o32, always left shifts the structs dregs (PARTIAL_LEN < |MIPS_SAVED_REGSIZE) then is just the ABI test needed?
> |
> |	Andrew
> |
> |PS: That function is the official example of how to _not_ multi-arch an ABI.
> 
> And now I confess I don't quite understand the question.
> Ah. mips_push_arguments().
> The question is whether to shift the contents?
> 
> It's likely I don't really grasp the subtleties of the question
> here at the moment.
> struct mys {
>         int a;
>         char b;
> };
> 
> as a struct argument, with cc -32 -EL, does not seem to do more than
> load b into the second arg reg (r5) and a into r4  if one does
> 	struct mys m
> 	myfunc(m);
> But I don't feel confident that answers anything, really.


The debate os over a possible exception to this rule.  Given a very 
small structure and the code segment:

	struct c1 { char c; } s1;
	foo (struct c1);
	...
	foo (s1);

GCC is always left shifting s1 in a register (regardless of -EL or EB).


> I (and anyone with IRIX cc -32) can do -EL -32.
> (With -n32 and -64,  -EL is ignored by IRIX cc.  )
> If you had a sample you wondered about I could certainly
> compile it -EL, send assembler to anyone. 
> If it would help. As I said,
> any IRIX cc -32 still sort of, unoficially, does try to honor -EL.


gdb/testsuite/gdb.base/structs.c is pretty good but just the above 
segment is :-)

	Andrew