* expr.c (expand_expr): Mind EXPAND_INITIALIZER for truncation also.
        * final.c (output_addr_const): Accept and discard SUBREG.
        * varasm.c (decode_addr_const): Don't abort on unknown expressions --
        mark them unknown instead.
        (simplify_subtraction): Handle RTX_UNKNOWN.
        (initializer_constant_valid_p): Strip NOP_EXPRs that narrow the mode.

        * gcc.c-torture/compile/labels-3.c: New.

From-SVN: r49622