return 0;
/* If the value was set in a later insn than the ones we are processing,
- we can't use it even if the register was only set once, but make a quick
- check to see if the previous insn set it to something. This is commonly
- the case when the same pseudo is used by repeated insns.
-
- This does not work if there exists an instruction which is temporarily
- not on the insn chain. */
-
+ we can't use it even if the register was only set once. */
if (INSN_CUID (reg_last_set[regno]) >= subst_low_cuid)
- {
- rtx insn, set;
-
- /* We can't do anything if the value is set in between the insns we are
- processing. */
- if (INSN_CUID (reg_last_set[regno]) <= INSN_CUID (subst_insn))
- return 0;
-
- /* We can not do anything useful in this case, because there is
- an instruction which is not on the insn chain. */
- if (subst_prev_insn)
- return 0;
-
- /* Skip over USE insns. They are not useful here, and they may have
- been made by combine, in which case they do not have a INSN_CUID
- value. We can't use prev_real_insn, because that would incorrectly
- take us backwards across labels. Skip over BARRIERs also, since
- they could have been made by combine. If we see one, we must be
- optimizing dead code, so it doesn't matter what we do. */
- for (insn = prev_nonnote_insn (subst_insn);
- insn && ((GET_CODE (insn) == INSN
- && GET_CODE (PATTERN (insn)) == USE)
- || GET_CODE (insn) == BARRIER
- || INSN_CUID (insn) >= subst_low_cuid);
- insn = prev_nonnote_insn (insn))
- ;
-
- if (insn
- && (set = single_set (insn)) != 0
- && rtx_equal_p (SET_DEST (set), x))
- {
- value = SET_SRC (set);
-
- /* Make sure that VALUE doesn't reference X. Replace any
- explicit references with a CLOBBER. If there are any remaining
- references (rare), don't use the value. */
-
- if (reg_mentioned_p (x, value))
- value = replace_rtx (copy_rtx (value), x,
- gen_rtx_CLOBBER (GET_MODE (x), const0_rtx));
-
- if (reg_overlap_mentioned_p (x, value))
- return 0;
- }
- else
- return 0;
- }
+ return 0;
/* If the value has all its registers valid, return it. */
if (get_last_value_validate (&value, reg_last_set[regno],