[Bug middle-end/71654] [6/7 Regression] missing VRP optimization on c++ unsigned char and short expressions

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71654

--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Author: ppalka
Date: Fri Aug 12 16:07:40 2016
New Revision: 239421

URL: https://gcc.gnu.org/viewcvs?rev=239421&root=gcc&view=rev
Log:
Fix PR middle-end/71654 (missed shortening of a compare)

gcc/ChangeLog:

        PR middle-end/71654
        * match.pd ((T)A CMP (T)B -> A CMP B): Allow (T)A to be a
        sign-changing cast from a shorter unsigned type to a wider
        signed type.

gcc/testsuite/ChangeLog:

        PR middle-end/71654
        * gcc.dg/c-c++-common/pr71654.c: New test.
        * gcc.dg/tree-ssa/vrp23: Add -fno-tree-forwprop to
        dg-options.
        * gcc.dg/tree-ssa/vrp24: Likewise.


Added:
    trunk/gcc/testsuite/c-c++-common/pr71654.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/match.pd
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.dg/tree-ssa/vrp23.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/vrp24.c