simplify_subreg fix take 2

[Jan Hubicka]

Hi,
bootstrapping with -fomit-frame-pointer has found another problem in the same
simplification.  If we eliminate frame_pointer, after reload the subregs of
frame pointer can be simplified, as it is normal register.

In the testcase I have, gen_lowpart was called by add to lea splitter and
it resulted in (subreg:SI (reg:QI bpl)), that got refused by
address_operand, as we prohibit SUBREGs in addresses.

bootstrapped -fomit-frame-pointer and without, regression tested
on the i386 together with my previous patches.

Honza

Thu May 24 15:01:13 CEST 2001  Jan Hubicka  <jh@suse.cz>

	* simplify_rtx.c (simplify_subreg): Keep subregs on return values,
	check CLASS_CANNOT_CHANGE_MODE before avoiding subreg on hard reg,
	in case register wasn't OK previously, accept it now; allow
	subregs of frame pointer if reload completed and frame pointer
	is not needed.

Index: simplify-rtx.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/simplify-rtx.c,v
retrieving revision 1.54
diff -c -3 -p -r1.54 simplify-rtx.c
*** simplify-rtx.c	2001/05/22 07:40:26	1.54
--- simplify-rtx.c	2001/05/24 14:57:32
*************** simplify_subreg (outermode, op, innermod
*** 2346,2357 ****
       suppress this simplification.  If the hard register is the stack,
       frame, or argument pointer, leave this as a SUBREG.  */
  
!   if (REG_P (op) == REG
        && REGNO (op) < FIRST_PSEUDO_REGISTER
!       && REGNO (op) != FRAME_POINTER_REGNUM
  #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
!       && REGNO (op) != HARD_FRAME_POINTER_REGNUM
  #endif
  #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
        && REGNO (op) != ARG_POINTER_REGNUM
  #endif
--- 2346,2369 ----
       suppress this simplification.  If the hard register is the stack,
       frame, or argument pointer, leave this as a SUBREG.  */
  
!   if (REG_P (op)
!       && (! REG_FUNCTION_VALUE_P (op)
! 	  || ! rtx_equal_function_value_matters)
! #ifdef CLASS_CANNOT_CHANGE_MODE
!       && ! (CLASS_CANNOT_CHANGE_MODE_P (outermode, innermode)
! 	    && GET_MODE_CLASS (innermode) != MODE_COMPLEX_INT
! 	    && GET_MODE_CLASS (innermode) != MODE_COMPLEX_FLOAT
! 	    && (TEST_HARD_REG_BIT
! 		(reg_class_contents[(int) CLASS_CANNOT_CHANGE_MODE],
! 		 REGNO (op))))
! #endif
        && REGNO (op) < FIRST_PSEUDO_REGISTER
!       && ((reload_completed && !frame_pointer_needed)
! 	  || (REGNO (op) != FRAME_POINTER_REGNUM
  #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
! 	      && REGNO (op) != HARD_FRAME_POINTER_REGNUM
  #endif
+ 	     ))
  #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
        && REGNO (op) != ARG_POINTER_REGNUM
  #endif
*************** simplify_subreg (outermode, op, innermod
*** 2360,2366 ****
        int final_regno = subreg_hard_regno (gen_rtx_SUBREG (outermode, op, byte),
  					   0);
  
!       if (HARD_REGNO_MODE_OK (final_regno, outermode))
  	return gen_rtx_REG (outermode, final_regno);
      }
  
--- 2372,2382 ----
        int final_regno = subreg_hard_regno (gen_rtx_SUBREG (outermode, op, byte),
  					   0);
  
!       /* ??? We do allow it if the current REG is not valid for
! 	 it's mode.  It is a kludge to work around how float/complex
! 	 arguments are passed on 32-bit Sparc and should be fixed.  */
!       if (HARD_REGNO_MODE_OK (final_regno, outermode)
! 	  || ! HARD_REGNO_MODE_OK (REGNO (op), innermode))
  	return gen_rtx_REG (outermode, final_regno);
      }