[RFA] Mips, return_value_location, small structs

[Michael Snyder <msnyder@redhat.com>]

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Re-submitted as a separate patch.

The problem: small structs returned in one (or two) registers
are aligned left in N32/N64 and aligned right in the others
(or vice versa, depending on how you cross your eyes).



There are two code paths here, one for structs of length < MIPS_REGSIZE, 
and one for MIPS_REGSIZE < struct len < 2 * MIPS_REGSIZE.

The first case I've split into two paths: one for N32 &&
TYPE_CODE_STRUCT, 
and a second for everything else (the later being identical to what was
there before).

In the second case, I've simply let the N32/N64 path fall thru.
The next "if" catches it and handles it correctly.

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2002-08-08  Michael Snyder  <msnyder@redhat.com>

	* mips-tdep.c (return_value_location): Structs returned in 
	registers are aligned differently (n32/64 vs. o32/64).

Index: mips-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/mips-tdep.c,v
retrieving revision 1.92
diff -c -3 -p -r1.92 mips-tdep.c
*** mips-tdep.c	8 Aug 2002 00:26:51 -0000	1.92
--- mips-tdep.c	8 Aug 2002 21:48:09 -0000
*************** return_value_location (struct type *valt
*** 3608,3622 ****
        if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG
  	  && len < MIPS_SAVED_REGSIZE)
  	{
! 	  /* "un-left-justify" the value in the low register */
! 	  lo->reg_offset = MIPS_SAVED_REGSIZE - len;
! 	  lo->len = len;
  	  hi->reg_offset = 0;
  	  hi->len = 0;
  	}
        else if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG
  	       && len > MIPS_SAVED_REGSIZE	/* odd-size structs */
  	       && len < MIPS_SAVED_REGSIZE * 2
  	       && (TYPE_CODE (valtype) == TYPE_CODE_STRUCT ||
  		   TYPE_CODE (valtype) == TYPE_CODE_UNION))
  	{
--- 3608,3635 ----
        if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG
  	  && len < MIPS_SAVED_REGSIZE)
  	{
! 	  if ((gdbarch_tdep (current_gdbarch) -> mips_abi == MIPS_ABI_N32 
! 	       || gdbarch_tdep (current_gdbarch) -> mips_abi == MIPS_ABI_N64)
! 	      && (TYPE_CODE (valtype) == TYPE_CODE_STRUCT 
! 		  || TYPE_CODE (valtype) == TYPE_CODE_UNION))
! 	    {
! 	      /* Values are already aligned in the low register.  */
! 	      lo->reg_offset = 0;
! 	    }
! 	  else
! 	    {
! 	      /* "un-left-justify" the value in the low register */
! 	      lo->reg_offset = MIPS_SAVED_REGSIZE - len;
! 	    }
  	  hi->reg_offset = 0;
+ 	  lo->len = len;
  	  hi->len = 0;
  	}
        else if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG
  	       && len > MIPS_SAVED_REGSIZE	/* odd-size structs */
  	       && len < MIPS_SAVED_REGSIZE * 2
+ 	       && gdbarch_tdep (current_gdbarch) -> mips_abi != MIPS_ABI_N32 
+ 	       && gdbarch_tdep (current_gdbarch) -> mips_abi != MIPS_ABI_N64
  	       && (TYPE_CODE (valtype) == TYPE_CODE_STRUCT ||
  		   TYPE_CODE (valtype) == TYPE_CODE_UNION))
  	{