}
}
\f
+/* Return the label before INSN, or put a new label there. */
+
+static rtx
+get_label_before (rtx insn)
+{
+ rtx label;
+
+ /* Find an existing label at this point
+ or make a new one if there is none. */
+ label = prev_nonnote_insn (insn);
+
+ if (label == 0 || !LABEL_P (label))
+ {
+ rtx prev = PREV_INSN (insn);
+
+ label = gen_label_rtx ();
+ emit_label_after (label, prev);
+ LABEL_NUSES (label) = 0;
+ }
+ return label;
+}
+
/* Scan a function looking for insns that need a delay slot and find insns to
put into the delay slot.
#endif
}
\f
+/* Follow any unconditional jump at LABEL;
+ return the ultimate label reached by any such chain of jumps.
+ Return null if the chain ultimately leads to a return instruction.
+ If LABEL is not followed by a jump, return LABEL.
+ If the chain loops or we can't find end, return LABEL,
+ since that tells caller to avoid changing the insn. */
+
+static rtx
+follow_jumps (rtx label)
+{
+ rtx insn;
+ rtx next;
+ rtx value = label;
+ int depth;
+
+ for (depth = 0;
+ (depth < 10
+ && (insn = next_active_insn (value)) != 0
+ && JUMP_P (insn)
+ && ((JUMP_LABEL (insn) != 0 && any_uncondjump_p (insn)
+ && onlyjump_p (insn))
+ || GET_CODE (PATTERN (insn)) == RETURN)
+ && (next = NEXT_INSN (insn))
+ && BARRIER_P (next));
+ depth++)
+ {
+ rtx tem;
+
+ /* If we have found a cycle, make the insn jump to itself. */
+ if (JUMP_LABEL (insn) == label)
+ return label;
+
+ tem = next_active_insn (JUMP_LABEL (insn));
+ if (tem && (GET_CODE (PATTERN (tem)) == ADDR_VEC
+ || GET_CODE (PATTERN (tem)) == ADDR_DIFF_VEC))
+ break;
+
+ value = JUMP_LABEL (insn);
+ }
+ if (depth == 10)
+ return label;
+ return value;
+}
+
/* Try to find insns to place in delay slots.
INSN is the jump needing SLOTS_TO_FILL delay slots. It tests CONDITION
}
}
\f
+static void delete_computation (rtx insn);
+
+/* Recursively delete prior insns that compute the value (used only by INSN
+ which the caller is deleting) stored in the register mentioned by NOTE
+ which is a REG_DEAD note associated with INSN. */
+
+static void
+delete_prior_computation (rtx note, rtx insn)
+{
+ rtx our_prev;
+ rtx reg = XEXP (note, 0);
+
+ for (our_prev = prev_nonnote_insn (insn);
+ our_prev && (NONJUMP_INSN_P (our_prev)
+ || CALL_P (our_prev));
+ our_prev = prev_nonnote_insn (our_prev))
+ {
+ rtx pat = PATTERN (our_prev);
+
+ /* If we reach a CALL which is not calling a const function
+ or the callee pops the arguments, then give up. */
+ if (CALL_P (our_prev)
+ && (! CONST_OR_PURE_CALL_P (our_prev)
+ || GET_CODE (pat) != SET || GET_CODE (SET_SRC (pat)) != CALL))
+ break;
+
+ /* If we reach a SEQUENCE, it is too complex to try to
+ do anything with it, so give up. We can be run during
+ and after reorg, so SEQUENCE rtl can legitimately show
+ up here. */
+ if (GET_CODE (pat) == SEQUENCE)
+ break;
+
+ if (GET_CODE (pat) == USE
+ && NONJUMP_INSN_P (XEXP (pat, 0)))
+ /* reorg creates USEs that look like this. We leave them
+ alone because reorg needs them for its own purposes. */
+ break;
+
+ if (reg_set_p (reg, pat))
+ {
+ if (side_effects_p (pat) && !CALL_P (our_prev))
+ break;
+
+ if (GET_CODE (pat) == PARALLEL)
+ {
+ /* If we find a SET of something else, we can't
+ delete the insn. */
+
+ int i;
+
+ for (i = 0; i < XVECLEN (pat, 0); i++)
+ {
+ rtx part = XVECEXP (pat, 0, i);
+
+ if (GET_CODE (part) == SET
+ && SET_DEST (part) != reg)
+ break;
+ }
+
+ if (i == XVECLEN (pat, 0))
+ delete_computation (our_prev);
+ }
+ else if (GET_CODE (pat) == SET
+ && REG_P (SET_DEST (pat)))
+ {
+ int dest_regno = REGNO (SET_DEST (pat));
+ int dest_endregno
+ = (dest_regno
+ + (dest_regno < FIRST_PSEUDO_REGISTER
+ ? hard_regno_nregs[dest_regno]
+ [GET_MODE (SET_DEST (pat))] : 1));
+ int regno = REGNO (reg);
+ int endregno
+ = (regno
+ + (regno < FIRST_PSEUDO_REGISTER
+ ? hard_regno_nregs[regno][GET_MODE (reg)] : 1));
+
+ if (dest_regno >= regno
+ && dest_endregno <= endregno)
+ delete_computation (our_prev);
+
+ /* We may have a multi-word hard register and some, but not
+ all, of the words of the register are needed in subsequent
+ insns. Write REG_UNUSED notes for those parts that were not
+ needed. */
+ else if (dest_regno <= regno
+ && dest_endregno >= endregno)
+ {
+ int i;
+
+ REG_NOTES (our_prev)
+ = gen_rtx_EXPR_LIST (REG_UNUSED, reg,
+ REG_NOTES (our_prev));
+
+ for (i = dest_regno; i < dest_endregno; i++)
+ if (! find_regno_note (our_prev, REG_UNUSED, i))
+ break;
+
+ if (i == dest_endregno)
+ delete_computation (our_prev);
+ }
+ }
+
+ break;
+ }
+
+ /* If PAT references the register that dies here, it is an
+ additional use. Hence any prior SET isn't dead. However, this
+ insn becomes the new place for the REG_DEAD note. */
+ if (reg_overlap_mentioned_p (reg, pat))
+ {
+ XEXP (note, 1) = REG_NOTES (our_prev);
+ REG_NOTES (our_prev) = note;
+ break;
+ }
+ }
+}
+
+/* Delete INSN and recursively delete insns that compute values used only
+ by INSN. This uses the REG_DEAD notes computed during flow analysis.
+ If we are running before flow.c, we need do nothing since flow.c will
+ delete dead code. We also can't know if the registers being used are
+ dead or not at this point.
+
+ Otherwise, look at all our REG_DEAD notes. If a previous insn does
+ nothing other than set a register that dies in this insn, we can delete
+ that insn as well.
+
+ On machines with CC0, if CC0 is used in this insn, we may be able to
+ delete the insn that set it. */
+
+static void
+delete_computation (rtx insn)
+{
+ rtx note, next;
+
+#ifdef HAVE_cc0
+ if (reg_referenced_p (cc0_rtx, PATTERN (insn)))
+ {
+ rtx prev = prev_nonnote_insn (insn);
+ /* We assume that at this stage
+ CC's are always set explicitly
+ and always immediately before the jump that
+ will use them. So if the previous insn
+ exists to set the CC's, delete it
+ (unless it performs auto-increments, etc.). */
+ if (prev && NONJUMP_INSN_P (prev)
+ && sets_cc0_p (PATTERN (prev)))
+ {
+ if (sets_cc0_p (PATTERN (prev)) > 0
+ && ! side_effects_p (PATTERN (prev)))
+ delete_computation (prev);
+ else
+ /* Otherwise, show that cc0 won't be used. */
+ REG_NOTES (prev) = gen_rtx_EXPR_LIST (REG_UNUSED,
+ cc0_rtx, REG_NOTES (prev));
+ }
+ }
+#endif
+
+ for (note = REG_NOTES (insn); note; note = next)
+ {
+ next = XEXP (note, 1);
+
+ if (REG_NOTE_KIND (note) != REG_DEAD
+ /* Verify that the REG_NOTE is legitimate. */
+ || !REG_P (XEXP (note, 0)))
+ continue;
+
+ delete_prior_computation (note, insn);
+ }
+
+ delete_related_insns (insn);
+}
+
+/* If all INSN does is set the pc, delete it,
+ and delete the insn that set the condition codes for it
+ if that's what the previous thing was. */
+
+static void
+delete_jump (rtx insn)
+{
+ rtx set = single_set (insn);
+
+ if (set && GET_CODE (SET_DEST (set)) == PC)
+ delete_computation (insn);
+}
+
+\f
/* Once we have tried two ways to fill a delay slot, make a pass over the
code to try to improve the results and to do such things as more jump
threading. */
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