small struct bugs for ppc sysv4

[Aldy Hernandez]

hi david.

here's the small structure bug we had talked about a month ago.
i forgot about the patch and just committed it in a redhat local tree.

alan was nice enough to bootstrap it and test it for regressions while
i was on vacation.

is this ok for branch and trunk?

----- Forwarded message from Aldy Hernandez <aldyh@redhat.com> -----

From: Aldy Hernandez <aldyh@redhat.com>
Subject: small struct problem
To: dje@watson.ibm.com
Date: Sun, 17 Mar 2002 15:32:35 +1100
User-Agent: Mutt/1.3.25i

and the culprit is stmt.c's expand_return():

      /* Structures whose size is not a multiple of a word are aligned
         to the least significant byte (to the right).  On a BYTES_BIG_ENDIAN
         machine, this means we must skip the empty high order bytes when
         calculating the bit offset.  */
      if (BYTES_BIG_ENDIAN
          && !FUNCTION_ARG_REG_LITTLE_ENDIAN
          && bytes % UNITS_PER_WORD)
        big_endian_correction = (BITS_PER_WORD - ((bytes % UNITS_PER_WORD)
                                                  * BITS_PER_UNIT));

that should be aligned to the left for sysv4.  right now, the above
code is eventually generating (for the C code below):

	r3 0x102
	r4 0x03040506

when it should really be:

	r3 0x01020304
	r4 0x0506

...and here's a patch to fix the problem.

2002-04-26  Aldy Hernandez  <aldyh@redhat.com>

	* config/rs6000/rs6000.h (FUNCTION_ARG_REG_LITTLE_ENDIAN): New.


Index: config/rs6000/rs6000.h
===================================================================
RCS file: /cvs/uberbaum/gcc/config/rs6000/rs6000.h,v
retrieving revision 1.199
diff -c -p -r1.199 rs6000.h
*** config/rs6000/rs6000.h	12 Apr 2002 16:57:47 -0000	1.199
--- config/rs6000/rs6000.h	26 Apr 2002 03:02:33 -0000
*************** extern int rs6000_altivec_abi;
*** 519,524 ****
--- 519,530 ----
     instructions for them.  Might as well be consistent with bits and bytes.  */
  #define WORDS_BIG_ENDIAN 1
  
+ /* Define to TRUE on a big-endian system when structure arguments
+    passed (and returned) in registers are passed in a little-endian
+    manner instead of a big-endian manner.  */
+ 
+ #define FUNCTION_ARG_REG_LITTLE_ENDIAN 1
+ 
  #define MAX_BITS_PER_WORD 64
  
  /* Width of a word, in units (bytes).  */