middle-end/6180: Infinite loop in cc1 during dbr pass

[John David Anglin]

> Infinite loop occurs compiling nm.c (binutils 2.12.90
> 20020404).  The final loop in dbr_sequence loops forever
> because of a loop in the insn chain that occurs compiling
> the function filter_symbols.  The insn chain appears ok
> when dbr_sequence is called.

This is what is causing the problem.  There is a millicode call
insn in the function "return" just before the epilogue begin note.
dbr_schedule puts the first insn in the epilogue into the delay
slot of the call.  This insn restores %r2 from the stack.  It's
probably ok to put it into the delay slot of the millicode call
since it doesn't use %r2, but the start of the epilogue is now
in an indeterminate position.  reposition_prologue_and_epilogue_notes
moves the epilogue begin note before the sequence.  However, in
fixing the insn chain, it apparently doesn't check for a sequence
and the chain is left in a corrupt state.  In particular, it doesn't
touch the numbering inside the sequence.

I probably can fix this by adding a blockage at the beginning
of the epilogue.  However, this seems like overkill and simply
avoids the problem.

Suggestions?

Dave
-- 
J. David Anglin                                  dave.anglin@nrc.ca
National Research Council of Canada              (613) 990-0752 (FAX: 952-6605)