> Andrew Cagney wrote:
> 
> 
>> Hello,
>> 
>> I'm trying to find a little history on the original ABI used by DEC on 
>> the PMAX (little endian MIPS) machines.
>> 
>> I'm firstly wondering what the abi is correctly called.
> 
> 
> COFF.


I was thinking of something like o32, n32, o64, ....


>> Second, according to the ABI, how should small structs be passed vis:
>> 
>> struct c1 { char c; };
>> void foo (struct c1 c1);
> 
> 
> I don't have an ABI document, but both appear to be passed on the stack.
> Here's the assembly output of the a simple C program (source included in
> the asm- more assemblers should do this :-):


I think it was was passed in A0, might need to look at the function to 
see which value it uses.


>  #   8	
>  #   9		bar1(c1);
> 	lbu	$14, c1
> 	sb	$14, 0($sp)


pick up c1, store it on the stack at 0($sp).


> 	lw	$4, 0($sp)


move it in to A0 as a word.  This means that c1 is sitting in the least 
significant byte of A0 (and the other bytes contain garbage?).


> 	.livereg	0x0800000E,0x00000000
> 	jal	bar1
> 	.loc	2 10
>  #  10		bar2(foo);
> 	lbu	$15, foo
> 	sb	$15, 0($sp)
> 	lw	$4, 0($sp)
> 	.livereg	0x0800000E,0x00000000
> 	jal	bar2
> 	.loc	2 11
>  #  11	}
> 	move	$2, $0


The reason for asking is that I'm looking at a LE o32 bug involving 
small structs and register alignment.  To the best of my knowledge 
nothing ever specified this formally.

Thanks for the info,

	Andrew