[Bug tree-optimization/87859] [8/9 Regression] store-merging miscompilation of mesa

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87859

--- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Author: jakub
Date: Mon Nov  5 14:12:15 2018
New Revision: 265807

URL: https://gcc.gnu.org/viewcvs?rev=265807&root=gcc&view=rev
Log:
        PR tree-optimization/87859
        * gimple-ssa-store-merging.c (struct merged_store_group): Add
        first_nonmergeable_order member.
        (merged_store_group::merged_store_group): Initialize them.
        (imm_store_chain_info::coalesce_immediate_stores): Don't merge
        stores with order >= first_nonmergeable_order.
        Set merged_store->first_nonmergeable_order if we've skipped any
        stores.  Attempt to merge overlapping INTEGER_CST stores that
        we would otherwise skip.

        * gcc.dg/store_merging_24.c: New test.
        * gcc.dg/store_merging_25.c: New test.

Added:
    branches/gcc-8-branch/gcc/testsuite/gcc.dg/store_merging_24.c
    branches/gcc-8-branch/gcc/testsuite/gcc.dg/store_merging_25.c
Modified:
    branches/gcc-8-branch/gcc/ChangeLog
    branches/gcc-8-branch/gcc/gimple-ssa-store-merging.c
    branches/gcc-8-branch/gcc/testsuite/ChangeLog