[Bug middle-end/51982] New: Shrink-wrapping opportunity

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51982

             Bug #: 51982
           Summary: Shrink-wrapping opportunity
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: dje@gcc.gnu.org


Created attachment 26444
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26444
lookdict_string manually split equivalent to shrink-wrapping

I realize that the shrink-wrapping implementation in GCC is preliminary and
conservative. I tested it on an example that presents a good opportunity for
shrink-wrapping and a large perforamnce improvement, but the current
implementation was not able to apply the optimization.

The attached file manually splits the CPython lookdict_string() into two
functions where most of the prologue can be avoided on the slow path.