* dse.c (group_info.base_mem, get_group_info): Use BLKmode to
        cover all the possible offsets from this base.
        (scan_reads_nospill): Pass base_mem's mode to canon_true_dependence.

        testsuite/
        * gnat.dg/dse_step.ads, dse_step.adb, test_dse_step.adb: New test.


Co-Authored-By: Eric Botcazou <ebotcazou@adacore.com>

From-SVN: r163582