[Bug tree-optimization/18046] Missed jump threading optimization

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=18046

--- Comment #20 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Author: ppalka
Date: Fri Aug  5 23:29:53 2016
New Revision: 239181

URL: https://gcc.gnu.org/viewcvs?rev=239181&root=gcc&view=rev
Log:
Improve forward jump threading of switch statements (PR18046)

gcc/ChangeLog:

        PR tree-optimization/18046
        * tree-ssa-threadedge.c: Include cfganal.h.
        (simplify_control_statement_condition): If simplifying a
        GIMPLE_SWITCH, replace the index operand of the GIMPLE_SWITCH
        with the dominating ASSERT_EXPR before handing it off to VRP.
        Mention that a CASE_LABEL_EXPR may be returned.
        (thread_around_empty_blocks): Adjust to handle
        simplify_control_statement_condition() returning a
        CASE_LABEL_EXPR.
        (thread_through_normal_block): Likewise.
        * tree-vrp.c (simplify_stmt_for_jump_threading): Simplify
        a switch statement by trying to determine which case label
        will be taken.

gcc/testsuite/ChangeLog:

        PR tree-optimization/18046
        * gcc.dg/tree-ssa/vrp105.c: New test.
        * gcc.dg/tree-ssa/vrp106.c: New test.


Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/vrp105.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/vrp106.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-threadedge.c
    trunk/gcc/tree-vrp.c