PR rtl-opt/24160
        PR target/24621
        * reload1.c (reg_equiv_invariant): New.
        (reload): Allocate, initialize, and free it.
        (calculate_needs_all_insns): Check it when skipping equivalence
        setting insns.
        (alter_reg): Likewise.
        (eliminate_regs_1): Rename from eliminate_regs.  Add new
        may_use_invariant argument; only use reg_equiv_invariant when true.
        (eliminate_regs): New.
        (eliminate_regs_in_insn): Use eliminate_regs_1; track when we're in
        a context for which may_use_invariant may be true.

Co-Authored-By: J"orn Rennecke <joern.rennecke@st.com>
Co-Authored-By: Ulrich Weigand <uweigand@de.ibm.com>

From-SVN: r107093