Patchwork Fix var tracking ICE due to reorg.

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Submitter David Miller
Date May 16, 2012, 1:15 a.m.
Message ID <20120515.211500.40143465924601627.davem@davemloft.net>
Download mbox | patch
Permalink /patch/159484/
State New
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Comments

David Miller - May 16, 2012, 1:15 a.m.
How bugs like this were not hit earlier, I'll never understand :-)

If during reorg we delete a code label, and as a result we decide to
delete all the code following that label, we hit this condition in
jump.c:delete_related_insns():

  if (was_code_label && prev && BARRIER_P (prev))                                

which passes and then we proceed to delete insns until we hit a
non-deleted code label.

During this traversal, we can end up deleting a CALL, but in doing so
we will leave the var tracking note for the call arguments around.

Later in dwarf2_var_location() we will ICE, because we can't find the
CALL when we search backwards for it.

The note searching scheme in the fix below is cribbed from code in
try_split() which has to handle a similar problem.

I fully understand that delete_related_insns() is a deprecated
interface, and the "right" way to do this is to use delete_insn() and
perform cfg cleanups afterwards.  But fixing reorg to no longer use
delete_related_insns() is a rather large task, and certainly outside
the scope of fixing this bug in 4.7.

Ok for mainline and 4.7 branch?

	* jump.c (delete_related_insns): If we remove a CALL, make sure
	we delete it's NOTE_INSN_CALL_ARG_LOCATION note too.
Richard Sandiford - May 16, 2012, 9:23 a.m.
David Miller <davem@davemloft.net> writes:
> Ok for mainline and 4.7 branch?

OK for both, thanks.

> 	* jump.c (delete_related_insns): If we remove a CALL, make sure
> 	we delete it's NOTE_INSN_CALL_ARG_LOCATION note too.

Patch

diff --git a/gcc/jump.c b/gcc/jump.c
index 52cbbca..d49b58e 100644
--- a/gcc/jump.c
+++ b/gcc/jump.c
@@ -1252,6 +1252,26 @@  delete_related_insns (rtx insn)
   if (next != 0 && BARRIER_P (next))
     delete_insn (next);
 
+  /* If this is a call, then we have to remove the var tracking note
+     for the call arguments.  */
+
+  if (CALL_P (insn)
+      || (NONJUMP_INSN_P (insn)
+	  && GET_CODE (PATTERN (insn)) == SEQUENCE
+	  && CALL_P (XVECEXP (PATTERN (insn), 0, 0))))
+    {
+      rtx p = insn;
+
+      for (p = NEXT_INSN (p);
+	   p && NOTE_P (p);
+	   p = NEXT_INSN (p))
+	if (NOTE_KIND (p) == NOTE_INSN_CALL_ARG_LOCATION)
+	  {
+	    remove_insn (p);
+	    break;
+	  }
+    }
+
   /* If deleting a jump, decrement the count of the label,
      and delete the label if it is now unused.  */