[Bug tree-optimization/64823] [5 Regression] false "may be used uninitialized", missed jump threading

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64823

--- Comment #6 from Jeffrey A. Law <law at gcc dot gnu.org> ---
Author: law
Date: Fri Feb 13 21:09:58 2015
New Revision: 220696

URL: https://gcc.gnu.org/viewcvs?rev=220696&root=gcc&view=rev
Log:
    PR tree-optimization/64823
    * tree-vrp.c (identify_jump_threads): Handle blocks with no statements.
    * tree-ssa-threadedge.c (potentially_threadable_block): Allow
    threading through blocks with PHIs, but no statements.
    (thread_through_normal_block): Distinguish between blocks where
    we did not process all the statements and blocks with no statements.

    PR tree-optimization/64823
    gcc.dg/uninit-20.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/uninit-20.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-threadedge.c
    trunk/gcc/tree-vrp.c