Re: [rfa] mips argument passing fixes for o32

[David B Anderson <davea@quasar.engr.sgi.com>]

Andrew Cagney:
|> Andrew Cagney:
|> |(A+3, yes, sorry).
|> |
|> |The SGI compilers are big endian (correct?) so who knows what they would 
|> |do in the little endian case.
|> 
|> 
|> Correct. Years ago it was possible to emit little-endian
|> code, but on MIPS/IRIX that was irrelevant and is no longer 
|> supported.
|> davea@sgi.com
|
|
|You wouldn't have access to such a machine by any chance? :-)
|
|I'm getting the feeling I'm wrong with this one - for some strange 
|historical reason LE o32 really does left/right shift small parameters 
|(I'm still mining the archives).
|
|Assuming that is the case ...

Oh boy.  I have to admit I ignored -EL (which 032 (cc -32)
still admits is a real option) back when it was
sort of current.  Big endian bigot :-) Sorry.

Today, the -EL sort of still works, o32, and generates 2LSB elf.
But it's not 'supported' so supported is here a weasel-word.

We don't test it.

But anyone with an IRIX cc -32 can look at the generated code.

Unfortunately, the MIPS disassembler (recent)
kind of barfs on little endian objects (I said we don't test -EL)...

davea

|>  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.

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.

Hmm. Well hope this helps a little....
davea@sgi.com