[Bug c/47427] [4.6 Regression] ICE in process_constraint, at tree-ssa-structalias.c:2901

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47427

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |hubicka at gcc dot gnu.org,
                   |                            |jakub at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-01-24 12:50:47 UTC ---
I think this is pretty much the same issue as PR47428, except in this case it
is not a PHI in which such a replacement is made, but for y_9 = 0; given that y
is argument declared const the inliner replaces it with 1 = 0;.
So perhaps the PR47428 patch isn't the right fix.

The reason why y_9 is on the LHS of a set is copyrename.  I guess a fix could
be either not doing copyrename if an SSA_NAME of a TREE_READONLY var would be
on the LHS of an assignment or result of a PHI, or drop the TREE_READONLY from
the parameter in such a case (but that would result in us dropping such info in
debug info), or avoid the optimization
  /* If the parameter is never assigned to, has no SSA_NAMEs created,
     we would not need to create a new variable here at all, if it
     weren't for debug info.  Still, we can just use the argument
     value.  */
  if (TREE_READONLY (p)
      ...
in setup_one_parameter.

Richard/Honza, what do you think?