re PR rtl-optimization/23098 (store of 0.0 to float)

        PR rtl-optimization/23098
        * config/rs6000/predicates.md (easy_fp_constant): SFmode constant
        0.0f is easy.
        * config/rs6000/rs6000.md (movdf splitter): Use
        const_double_operand predicate for TARGET_POWERPC64.
        * config/rs6000/rs6000.c (rs6000_legitimize_reload_address): Expand
        SYMBOL_REF method to ABI_V4.

        * config/rs6000/altivec.md (build_vector_mask_for_load): Use
        replace_equiv_address.
        * config/rs6000/rs6000.c (rs6000_emit_eh_reg_restore): Mark MEM as
        rs6000_sr_alias_set and MEM_NOTRAP.
        (rs6000_aix_emit_builtin_unwind_init): Use gen_frame_mem().

From-SVN: r104145