[Bug rtl-optimization/59461] missed zero-extension elimination in the combiner

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59461

--- Comment #4 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Author: ebotcazou
Date: Fri Nov 11 22:38:33 2016
New Revision: 242326

URL: https://gcc.gnu.org/viewcvs?rev=242326&root=gcc&view=rev
Log:
        PR rtl-optimization/59461
        * doc/rtl.texi (paradoxical subregs): Add missing word.
        * combine.c (reg_nonzero_bits_for_combine): Do not discard results
        in modes with precision larger than that of last_set_mode.
        * rtlanal.c (nonzero_bits1) <SUBREG>: If WORD_REGISTER_OPERATIONS is
        set and LOAD_EXTEND_OP is appropriate, propagate results from inner
        REGs to paradoxical SUBREGs.
        (num_sign_bit_copies1) <SUBREG>: Likewise.  Check that the mode is not
        larger than a word before invoking LOAD_EXTEND_OP on it.

Added:
    trunk/gcc/testsuite/gcc.target/sparc/20161111-1.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/combine.c
    trunk/gcc/doc/rtl.texi
    trunk/gcc/rtlanal.c
    trunk/gcc/testsuite/ChangeLog