+
+ /* Now that we have completed handling INSN, check and see if it is
+ a CLOBBER beginning a libcall block. If it is, record the
+ end of the libcall sequence.
+
+ We want to schedule libcall blocks as a unit before reload. While
+ this restricts scheduling, it preserves the meaning of a libcall
+ block.
+
+ As a side effect, we may get better code due to decreased register
+ pressure as well as less chance of a foreign insn appearing in
+ a libcall block. */
+ if (!reload_completed
+ /* Note we may have nested libcall sequences. We only care about
+ the outermost libcall sequence. */
+ && deps->libcall_block_tail_insn == 0
+ /* The sequence must start with a clobber of a register. */
+ && NONJUMP_INSN_P (insn)
+ && GET_CODE (PATTERN (insn)) == CLOBBER
+ && (r0 = XEXP (PATTERN (insn), 0), REG_P (r0))
+ && REG_P (XEXP (PATTERN (insn), 0))
+ /* The CLOBBER must also have a REG_LIBCALL note attached. */
+ && (link = find_reg_note (insn, REG_LIBCALL, NULL_RTX)) != 0
+ && (end_seq = XEXP (link, 0)) != 0
+ /* The insn referenced by the REG_LIBCALL note must be a
+ simple nop copy with the same destination as the register
+ mentioned in the clobber. */
+ && (set = single_set (end_seq)) != 0
+ && SET_DEST (set) == r0 && SET_SRC (set) == r0
+ /* And finally the insn referenced by the REG_LIBCALL must
+ also contain a REG_EQUAL note and a REG_RETVAL note. */
+ && find_reg_note (end_seq, REG_EQUAL, NULL_RTX) != 0
+ && find_reg_note (end_seq, REG_RETVAL, NULL_RTX) != 0)
+ deps->libcall_block_tail_insn = XEXP (link, 0);
+
+ /* If we have reached the end of a libcall block, then close the
+ block. */
+ if (deps->libcall_block_tail_insn == insn)
+ deps->libcall_block_tail_insn = 0;
+