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To: "John David Anglin" <dave@hiauly1.hia.nrc.ca>
cc: rth@redhat.com, alan@linuxcare.com.au, rhirst@linuxcare.com,
        parisc-linux@thepuffingroup.com, gcc-bugs@gcc.gnu.org
Subject: Re: pa reload problem 
Reply-To: law@redhat.com
In-reply-to: Your message of Wed, 13 Dec 2000 19:48:21 EST.
             <200012140048.TAA02603@hiauly1.hia.nrc.ca>
From: Jeffrey A Law <law@redhat.com>
Date: Wed, 13 Dec 2000 20:43:32 -0700
Message-ID: <20289.976765412@upchuck>
Sender: law@cygnus.com
List-ID: <linux-parisc.vger.kernel.org>


  In message <200012140048.TAA02603@hiauly1.hia.nrc.ca>you write:
  > I have made some progress in locating this bug but still don't have a
  > complete understanding of the problem.  The problem is that a code_label
  > insn is "incorrectly" deleted in the loop pass.  Here is the rtl from
  > the gcse pass:
  > 
  > [snip]
  > 
  > (code_label 1158 1268 1439 124 "" "" [3 uses])
  > 
  > (note 1439 1158 262 [bb 12] NOTE_INSN_BASIC_BLOCK -1347440721)
  > 
  > (note 262 1439 1159 85 NOTE_INSN_EH_REGION_END -1347440721)
  > 
  > [snip]
  > 
  > (insn 788 787 789 (set (reg/f:SI 209)
  >         (high:SI (label_ref:SI 1158))) 87 {*pa.md:2435} (nil)
  >     (expr_list:REG_EQUAL (high:SI (label_ref:SI 1158))
  >         (insn_list:REG_LABEL 1158 (nil))))
  > 
  > (insn 789 788 791 (set (reg/f:SI 208)
  >         (lo_sum:SI (reg/f:SI 209)
  >             (label_ref:SI 1158))) 90 {*pa.md:2467} (nil)
  >     (insn_list:REG_LABEL 1158 (expr_list:REG_EQUAL (label_ref:SI 1158)
  >             (nil))))
  > 
  > Here is the rtl after loop:
  > 
  > Loop from 576 to 1288: 105 real insns.
  > Continue at insn 1278.
  > 
  > [snip]
  > 
  > Insn 788: regno 209 (life 2), move-insn savings 2  moved to 1530
  > Insn 789: regno 208 (life 1), move-insn forces 788 savings 1  moved to 1532
  > 
  > [snip]
  > 
  > (insn 1531 1528 1532 (set (reg/f:SI 337)
  >         (high:SI (label_ref:SI 1158))) -1 (nil)
  >     (expr_list:REG_LABEL (code_label/v 1158 1268 1439 124 "" "" [0 uses])
  >         (nil)))
  > 
  > (insn 1532 1531 1535 (set (reg/f:SI 208)
  >         (lo_sum:SI (reg/f:SI 337)
  >             (label_ref:SI 1158))) -1 (nil)
  >     (expr_list:REG_EQUAL (label_ref:SI 1158)
  >         (expr_list:REG_LABEL (code_label/v 1158 1268 1439 124 "" "" [0 uses
  > ])
  >             (nil))))
  > 
  > The code_label 1158 is deleted by delete_trivially_dead_insns apparently 
  > because the preceding call to loop_optimize in toplev.c has reduced the
  > number of uses to 1.  Maybe somebody can see how this occurs.
Seems to me we have a reference counting problem.  There is clearly 
a reference to label 1158 (insn 1531/1532), but it's reference count
is zero.

Seems to me that if you find that reference counting bug that you'll
fix this problem.

jeff