[Bug tree-optimization/54565] New: pass_update_address_taken before forwprop1 for vectors

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54565

             Bug #: 54565
           Summary: pass_update_address_taken before forwprop1 for vectors
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: glisse@gcc.gnu.org


Created attachment 28186
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28186
IRC log

Hello,

during forwprop1, some of the optimizations for vectors fail because some
vectors appear as PARM_DECL or such instead of SSA_NAME. An example is
forwprop-22.c where the code does detect that {v[0],v[1]} is just v, but v is a
PARM_DECL so it just gives up. Before forwprop2, something (fre?) changes it to
an SSA_NAME and the optimization then works. Following some advice by pinskia
and stevenb on IRC (log attached), I tried adding pass_update_address_taken
right before forwprop1 and it did allow the optimization to happen in
forwprop1. The log also contains an argument by pinskia that doing
optimizations in forwprop1 can help a bit make better inlining decisions, and
some later comments by richi.