fix rtl-opt/15289, part 2

[Richard Henderson]

A small patchlet after I noticed that we were generating 
(subreg:SF (reg:SC 0 ax) 0) when setting up the return value
instead of (reg:SF 0 ax) as expected.

This was bootstrapped and tested with several other patches
on i686, alpha, and ia64 linux.


r~


        * expmed.c (store_bit_field): Use simplify_gen_subreg instead
        of gen_rtx_SUBREG directly.

Index: expmed.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/expmed.c,v
retrieving revision 1.209
diff -c -p -d -r1.209 expmed.c
*** expmed.c	27 Nov 2004 01:01:12 -0000	1.209
--- expmed.c	1 Dec 2004 17:33:11 -0000
*************** store_bit_field (rtx str_rtx, unsigned H
*** 431,451 ****
      {
        if (GET_MODE (op0) != fieldmode)
  	{
! 	  if (GET_CODE (op0) == SUBREG)
! 	    {
! 	      /* Else we've got some float mode source being extracted
! 		 into a different float mode destination -- this
! 		 combination of subregs results in Severe Tire
! 		 Damage.  */
! 	      gcc_assert (GET_MODE (SUBREG_REG (op0)) == fieldmode
! 			  || GET_MODE_CLASS (fieldmode) == MODE_INT
! 			  || GET_MODE_CLASS (fieldmode) == MODE_PARTIAL_INT);
! 	      op0 = SUBREG_REG (op0);
! 	    }
! 	  if (REG_P (op0))
! 	    op0 = gen_rtx_SUBREG (fieldmode, op0, byte_offset);
! 	  else
  	    op0 = adjust_address (op0, fieldmode, offset);
  	}
        emit_move_insn (op0, value);
        return value;
--- 431,441 ----
      {
        if (GET_MODE (op0) != fieldmode)
  	{
! 	  if (MEM_P (op0))
  	    op0 = adjust_address (op0, fieldmode, offset);
+ 	  else
+ 	    op0 = simplify_gen_subreg (fieldmode, op0, GET_MODE (op0),
+ 				       byte_offset);
  	}
        emit_move_insn (op0, value);
        return value;