From mboxrd@z Thu Jan  1 00:00:00 1970
From: hjl@lucon.org (H.J. Lu)
To: law@cygnus.com
Cc: hjl@lucon.org, wilson@cygnus.com, scox@cygnus.com, crux@pool.informatik.rwth-aachen.de, egcs@cygnus.com
Subject: Re: More fp bug in egcs
Date: Tue, 05 May 1998 19:14:00 -0000
Message-id: <m0yWnXo-000268C@ocean.lucon.org>
References: <23041.894353710@hurl.cygnus.com>
X-SW-Source: 1998-05/msg00154.html

> 
> 
>   In message < m0yVnEy-000268C@ocean.lucon.org >you write:
>   > Here is the trimmed down test case. I am not sure if your patch is
>   > correct. If you take look at the stack RTL dump, you will see SF 1 in
> [ ... ]
> BTW, I added the testcase to the testsuite.
> 
> jeff
> 

Here is the stack RTL dump again. As you can see

            (clobber (reg:SF 14 %st(6)))

should be

            (clobber (reg:SF 8 %st(0)))

Should I worry about it? I think the bug is in move_for_stack_reg () in
reg-stack.c:

  else if (STACK_REG_P (src))
    {
      /* Save from a stack reg to MEM, or possibly integer reg.  Since
	 only top of stack may be saved, emit an exchange first if
	 needs be.  */

      emit_swap_insn (insn, regstack, src);

      note = find_regno_note (insn, REG_DEAD, REGNO (src));
      if (note)
	{
	  replace_reg (&XEXP (note, 0), FIRST_STACK_REG);
	  regstack->top--;
	  CLEAR_HARD_REG_BIT (regstack->reg_set, REGNO (src));
	}
      else if (GET_MODE (src) == XFmode && regstack->top < REG_STACK_SIZE - 1)
	{
	  /* A 387 cannot write an XFmode value to a MEM without
	     clobbering the source reg.  The output code can handle
	     this by reading back the value from the MEM.
	     But it is more efficient to use a temp register if one is
	     available.  Push the source value here if the register
	     stack is not full, and then write the value to memory via
	     a pop.  */
	  rtx push_rtx, push_insn;
	  rtx top_stack_reg = FP_MODE_REG (FIRST_STACK_REG, XFmode);

	  push_rtx = gen_movxf (top_stack_reg, top_stack_reg);
	  push_insn = emit_insn_before (push_rtx, insn);
	  PUT_MODE (push_insn, QImode);
	  REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_DEAD, top_stack_reg,
				      REG_NOTES (insn));
	}

      replace_reg (psrc, FIRST_STACK_REG);
    }

The problem is not all notes are updated.

-- 
H.J. Lu (hjl@gnu.org)
----
;; Insn is not within a basic block
(insn:QI 67 163 166 (parallel[ 
            (set (reg:DI 2 %ecx)
                (fix:DI (fix:SF (reg:SF 8 %st(0)))))
            (clobber (reg:SF 14 %st(6)))
            (clobber (mem:SI (plus:SI (reg:SI 6 %ebp)
                        (const_int -20))))
            (clobber (mem:DI (plus:SI (reg:SI 6 %ebp)
                        (const_int -28))))
            (clobber (reg:SI 1 %edx))
        ] ) 120 {fix_truncxfsi2-1} (nil)
    (nil))

;; Insn is not within a basic block
(insn:QI 166 67 68 (set (mem:SF (plus:SI (reg:SI 6 %ebp)
                (const_int -76)))
        (reg:SF 8 %st(0))) -1 (nil)
    (expr_list:REG_DEAD (reg:DF 8 %st(0))
        (nil)))