- /* Simplify if (...) { x = a; goto l; } x = b; by converting it
- to x = a; if (...) goto l; x = b;
- if A is sufficiently simple, the test doesn't involve X,
- and nothing in the test modifies A or X.
-
- If we have small register classes, we also can't do this if X
- is a hard register.
-
- If the "x = a;" insn has any REG_NOTES, we don't do this because
- of the possibility that we are running after CSE and there is a
- REG_EQUAL note that is only valid if the branch has already been
- taken. If we move the insn with the REG_EQUAL note, we may
- fold the comparison to always be false in a later CSE pass.
- (We could also delete the REG_NOTES when moving the insn, but it
- seems simpler to not move it.) An exception is that we can move
- the insn if the only note is a REG_EQUAL or REG_EQUIV whose
- value is the same as "a".
-
- INSN is the goto.
-
- We set:
-
- TEMP to the jump insn preceding "x = a;"
- TEMP1 to X
- TEMP2 to the insn that sets "x = b;"
- TEMP3 to the insn that sets "x = a;"
- TEMP4 to the set of "x = a"; */
-
- if (this_is_simplejump
- && (temp2 = next_active_insn (insn)) != 0
- && GET_CODE (temp2) == INSN
- && (temp4 = single_set (temp2)) != 0
- && GET_CODE (temp1 = SET_DEST (temp4)) == REG
- && (! SMALL_REGISTER_CLASSES
- || REGNO (temp1) >= FIRST_PSEUDO_REGISTER)
- && (temp3 = prev_active_insn (insn)) != 0
- && GET_CODE (temp3) == INSN
- && (temp4 = single_set (temp3)) != 0
- && rtx_equal_p (SET_DEST (temp4), temp1)
- && ! side_effects_p (SET_SRC (temp4))
- && ! may_trap_p (SET_SRC (temp4))
- && (REG_NOTES (temp3) == 0
- || ((REG_NOTE_KIND (REG_NOTES (temp3)) == REG_EQUAL
- || REG_NOTE_KIND (REG_NOTES (temp3)) == REG_EQUIV)
- && XEXP (REG_NOTES (temp3), 1) == 0
- && rtx_equal_p (XEXP (REG_NOTES (temp3), 0),
- SET_SRC (temp4))))
- && (temp = prev_active_insn (temp3)) != 0
- && condjump_p (temp) && ! simplejump_p (temp)
- /* TEMP must skip over the "x = a;" insn */
- && prev_real_insn (JUMP_LABEL (temp)) == insn
- && no_labels_between_p (temp, insn))
- {
- rtx prev_label = JUMP_LABEL (temp);
- rtx insert_after = prev_nonnote_insn (temp);
-
-#ifdef HAVE_cc0
- /* We cannot insert anything between a set of cc and its use. */
- if (insert_after && GET_RTX_CLASS (GET_CODE (insert_after)) == 'i'
- && sets_cc0_p (PATTERN (insert_after)))
- insert_after = prev_nonnote_insn (insert_after);
-#endif
- ++LABEL_NUSES (prev_label);
-
- if (insert_after
- && no_labels_between_p (insert_after, temp)
- && ! reg_referenced_between_p (temp1, insert_after, temp3)
- && ! reg_referenced_between_p (temp1, temp3,
- NEXT_INSN (temp2))
- && ! reg_set_between_p (temp1, insert_after, temp)
- && ! modified_between_p (SET_SRC (temp4), insert_after, temp)
- /* Verify that registers used by the jump are not clobbered
- by the instruction being moved. */
- && ! regs_set_between_p (PATTERN (temp),
- PREV_INSN (temp3),
- NEXT_INSN (temp3))
- && invert_jump (temp, JUMP_LABEL (insn)))
- {
- emit_insn_after_with_line_notes (PATTERN (temp3),
- insert_after, temp3);
- delete_insn (temp3);
- delete_insn (insn);
- /* Set NEXT to an insn that we know won't go away. */
- next = temp2;
- changed = 1;
- }
- if (prev_label && --LABEL_NUSES (prev_label) == 0)
- delete_insn (prev_label);
- if (changed)
- continue;
- }
-
-#ifndef HAVE_cc0
- /* If we have if (...) x = exp; and branches are expensive,
- EXP is a single insn, does not have any side effects, cannot
- trap, and is not too costly, convert this to
- t = exp; if (...) x = t;
-
- Don't do this when we have CC0 because it is unlikely to help
- and we'd need to worry about where to place the new insn and
- the potential for conflicts. We also can't do this when we have
- notes on the insn for the same reason as above.
-
- We set:
-
- TEMP to the "x = exp;" insn.
- TEMP1 to the single set in the "x = exp;" insn.
- TEMP2 to "x". */
-
- if (! reload_completed
- && this_is_condjump && ! this_is_simplejump
- && BRANCH_COST >= 3
- && (temp = next_nonnote_insn (insn)) != 0
- && GET_CODE (temp) == INSN
- && REG_NOTES (temp) == 0
- && (reallabelprev == temp
- || ((temp2 = next_active_insn (temp)) != 0
- && simplejump_p (temp2)
- && JUMP_LABEL (temp2) == JUMP_LABEL (insn)))
- && (temp1 = single_set (temp)) != 0
- && (temp2 = SET_DEST (temp1), GET_CODE (temp2) == REG)
- && (! SMALL_REGISTER_CLASSES
- || REGNO (temp2) >= FIRST_PSEUDO_REGISTER)
- && GET_CODE (SET_SRC (temp1)) != REG
- && GET_CODE (SET_SRC (temp1)) != SUBREG
- && GET_CODE (SET_SRC (temp1)) != CONST_INT
- && ! side_effects_p (SET_SRC (temp1))
- && ! may_trap_p (SET_SRC (temp1))
- && rtx_cost (SET_SRC (temp1), SET) < 10)
- {
- rtx new = gen_reg_rtx (GET_MODE (temp2));
-
- if ((temp3 = find_insert_position (insn, temp))
- && validate_change (temp, &SET_DEST (temp1), new, 0))
- {
- next = emit_insn_after (gen_move_insn (temp2, new), insn);
- emit_insn_after_with_line_notes (PATTERN (temp),
- PREV_INSN (temp3), temp);
- delete_insn (temp);
- reallabelprev = prev_active_insn (JUMP_LABEL (insn));
-
- if (after_regscan)
- {
- reg_scan_update (temp3, NEXT_INSN (next), old_max_reg);
- old_max_reg = max_reg_num ();
- }
- }
- }
-
- /* Similarly, if it takes two insns to compute EXP but they
- have the same destination. Here TEMP3 will be the second
- insn and TEMP4 the SET from that insn. */
-
- if (! reload_completed
- && this_is_condjump && ! this_is_simplejump
- && BRANCH_COST >= 4
- && (temp = next_nonnote_insn (insn)) != 0
- && GET_CODE (temp) == INSN
- && REG_NOTES (temp) == 0
- && (temp3 = next_nonnote_insn (temp)) != 0
- && GET_CODE (temp3) == INSN
- && REG_NOTES (temp3) == 0
- && (reallabelprev == temp3
- || ((temp2 = next_active_insn (temp3)) != 0
- && simplejump_p (temp2)
- && JUMP_LABEL (temp2) == JUMP_LABEL (insn)))
- && (temp1 = single_set (temp)) != 0
- && (temp2 = SET_DEST (temp1), GET_CODE (temp2) == REG)
- && GET_MODE_CLASS (GET_MODE (temp2)) == MODE_INT
- && (! SMALL_REGISTER_CLASSES
- || REGNO (temp2) >= FIRST_PSEUDO_REGISTER)
- && ! side_effects_p (SET_SRC (temp1))
- && ! may_trap_p (SET_SRC (temp1))
- && rtx_cost (SET_SRC (temp1), SET) < 10
- && (temp4 = single_set (temp3)) != 0
- && rtx_equal_p (SET_DEST (temp4), temp2)
- && ! side_effects_p (SET_SRC (temp4))
- && ! may_trap_p (SET_SRC (temp4))
- && rtx_cost (SET_SRC (temp4), SET) < 10)
- {
- rtx new = gen_reg_rtx (GET_MODE (temp2));
-
- if ((temp5 = find_insert_position (insn, temp))
- && (temp6 = find_insert_position (insn, temp3))
- && validate_change (temp, &SET_DEST (temp1), new, 0))
- {
- /* Use the earliest of temp5 and temp6. */
- if (temp5 != insn)
- temp6 = temp5;
- next = emit_insn_after (gen_move_insn (temp2, new), insn);
- emit_insn_after_with_line_notes (PATTERN (temp),
- PREV_INSN (temp6), temp);
- emit_insn_after_with_line_notes
- (replace_rtx (PATTERN (temp3), temp2, new),
- PREV_INSN (temp6), temp3);
- delete_insn (temp);
- delete_insn (temp3);
- reallabelprev = prev_active_insn (JUMP_LABEL (insn));
-
- if (after_regscan)
- {
- reg_scan_update (temp6, NEXT_INSN (next), old_max_reg);
- old_max_reg = max_reg_num ();
- }
- }
- }
-
- /* Finally, handle the case where two insns are used to
- compute EXP but a temporary register is used. Here we must
- ensure that the temporary register is not used anywhere else. */
-
- if (! reload_completed
- && after_regscan
- && this_is_condjump && ! this_is_simplejump
- && BRANCH_COST >= 4
- && (temp = next_nonnote_insn (insn)) != 0
- && GET_CODE (temp) == INSN
- && REG_NOTES (temp) == 0
- && (temp3 = next_nonnote_insn (temp)) != 0
- && GET_CODE (temp3) == INSN
- && REG_NOTES (temp3) == 0
- && (reallabelprev == temp3
- || ((temp2 = next_active_insn (temp3)) != 0
- && simplejump_p (temp2)
- && JUMP_LABEL (temp2) == JUMP_LABEL (insn)))
- && (temp1 = single_set (temp)) != 0
- && (temp5 = SET_DEST (temp1),
- (GET_CODE (temp5) == REG
- || (GET_CODE (temp5) == SUBREG
- && (temp5 = SUBREG_REG (temp5),
- GET_CODE (temp5) == REG))))
- && REGNO (temp5) >= FIRST_PSEUDO_REGISTER
- && REGNO_FIRST_UID (REGNO (temp5)) == INSN_UID (temp)
- && REGNO_LAST_UID (REGNO (temp5)) == INSN_UID (temp3)
- && ! side_effects_p (SET_SRC (temp1))
- && ! may_trap_p (SET_SRC (temp1))
- && rtx_cost (SET_SRC (temp1), SET) < 10
- && (temp4 = single_set (temp3)) != 0
- && (temp2 = SET_DEST (temp4), GET_CODE (temp2) == REG)
- && GET_MODE_CLASS (GET_MODE (temp2)) == MODE_INT
- && (! SMALL_REGISTER_CLASSES
- || REGNO (temp2) >= FIRST_PSEUDO_REGISTER)
- && rtx_equal_p (SET_DEST (temp4), temp2)
- && ! side_effects_p (SET_SRC (temp4))
- && ! may_trap_p (SET_SRC (temp4))
- && rtx_cost (SET_SRC (temp4), SET) < 10)
- {
- rtx new = gen_reg_rtx (GET_MODE (temp2));
-
- if ((temp5 = find_insert_position (insn, temp))
- && (temp6 = find_insert_position (insn, temp3))
- && validate_change (temp3, &SET_DEST (temp4), new, 0))
- {
- /* Use the earliest of temp5 and temp6. */
- if (temp5 != insn)
- temp6 = temp5;
- next = emit_insn_after (gen_move_insn (temp2, new), insn);
- emit_insn_after_with_line_notes (PATTERN (temp),
- PREV_INSN (temp6), temp);
- emit_insn_after_with_line_notes (PATTERN (temp3),
- PREV_INSN (temp6), temp3);
- delete_insn (temp);
- delete_insn (temp3);
- reallabelprev = prev_active_insn (JUMP_LABEL (insn));
-
- if (after_regscan)
- {
- reg_scan_update (temp6, NEXT_INSN (next), old_max_reg);
- old_max_reg = max_reg_num ();
- }
- }
- }
-#endif /* HAVE_cc0 */
-
- /* Try to use a conditional move (if the target has them), or a
- store-flag insn. The general case is:
-
- 1) x = a; if (...) x = b; and
- 2) if (...) x = b;
-
- If the jump would be faster, the machine should not have defined
- the movcc or scc insns!. These cases are often made by the
- previous optimization.
-
- The second case is treated as x = x; if (...) x = b;.
-
- INSN here is the jump around the store. We set:
-
- TEMP to the "x = b;" insn.
- TEMP1 to X.
- TEMP2 to B.
- TEMP3 to A (X in the second case).
- TEMP4 to the condition being tested.
- TEMP5 to the earliest insn used to find the condition. */
-
- if (/* We can't do this after reload has completed. */
- ! reload_completed
- && this_is_condjump && ! this_is_simplejump
- /* Set TEMP to the "x = b;" insn. */
- && (temp = next_nonnote_insn (insn)) != 0
- && GET_CODE (temp) == INSN
- && GET_CODE (PATTERN (temp)) == SET
- && GET_CODE (temp1 = SET_DEST (PATTERN (temp))) == REG
- && (! SMALL_REGISTER_CLASSES
- || REGNO (temp1) >= FIRST_PSEUDO_REGISTER)
- && ! side_effects_p (temp2 = SET_SRC (PATTERN (temp)))
- && ! may_trap_p (temp2)
- /* Allow either form, but prefer the former if both apply.
- There is no point in using the old value of TEMP1 if
- it is a register, since cse will alias them. It can
- lose if the old value were a hard register since CSE
- won't replace hard registers. Avoid using TEMP3 if
- small register classes and it is a hard register. */
- && (((temp3 = reg_set_last (temp1, insn)) != 0
- && ! (SMALL_REGISTER_CLASSES && GET_CODE (temp3) == REG
- && REGNO (temp3) < FIRST_PSEUDO_REGISTER))
- /* Make the latter case look like x = x; if (...) x = b; */
- || (temp3 = temp1, 1))
- /* INSN must either branch to the insn after TEMP or the insn
- after TEMP must branch to the same place as INSN. */
- && (reallabelprev == temp
- || ((temp4 = next_active_insn (temp)) != 0
- && simplejump_p (temp4)
- && JUMP_LABEL (temp4) == JUMP_LABEL (insn)))
- && (temp4 = get_condition (insn, &temp5)) != 0
- /* We must be comparing objects whose modes imply the size.
- We could handle BLKmode if (1) emit_store_flag could
- and (2) we could find the size reliably. */
- && GET_MODE (XEXP (temp4, 0)) != BLKmode
- /* Even if branches are cheap, the store_flag optimization
- can win when the operation to be performed can be
- expressed directly. */
-#ifdef HAVE_cc0
- /* If the previous insn sets CC0 and something else, we can't
- do this since we are going to delete that insn. */
-
- && ! ((temp6 = prev_nonnote_insn (insn)) != 0
- && GET_CODE (temp6) == INSN
- && (sets_cc0_p (PATTERN (temp6)) == -1
- || (sets_cc0_p (PATTERN (temp6)) == 1
- && FIND_REG_INC_NOTE (temp6, NULL_RTX))))
-#endif
- )
- {
-#ifdef HAVE_conditional_move
- /* First try a conditional move. */
- {
- enum rtx_code code = GET_CODE (temp4);
- rtx var = temp1;
- rtx cond0, cond1, aval, bval;
- rtx target;
-
- /* Copy the compared variables into cond0 and cond1, so that
- any side effects performed in or after the old comparison,
- will not affect our compare which will come later. */
- /* ??? Is it possible to just use the comparison in the jump
- insn? After all, we're going to delete it. We'd have
- to modify emit_conditional_move to take a comparison rtx
- instead or write a new function. */
- cond0 = gen_reg_rtx (GET_MODE (XEXP (temp4, 0)));
- /* We want the target to be able to simplify comparisons with
- zero (and maybe other constants as well), so don't create
- pseudos for them. There's no need to either. */
- if (GET_CODE (XEXP (temp4, 1)) == CONST_INT
- || GET_CODE (XEXP (temp4, 1)) == CONST_DOUBLE)
- cond1 = XEXP (temp4, 1);
- else
- cond1 = gen_reg_rtx (GET_MODE (XEXP (temp4, 1)));
-
- aval = temp3;
- bval = temp2;
-
- start_sequence ();
- target = emit_conditional_move (var, code,
- cond0, cond1, VOIDmode,
- aval, bval, GET_MODE (var),
- (code == LTU || code == GEU
- || code == LEU || code == GTU));
-
- if (target)
- {
- rtx seq1,seq2,last;
-
- /* Save the conditional move sequence but don't emit it
- yet. On some machines, like the alpha, it is possible
- that temp5 == insn, so next generate the sequence that
- saves the compared values and then emit both
- sequences ensuring seq1 occurs before seq2. */
- seq2 = get_insns ();
- end_sequence ();
-
- /* Now that we can't fail, generate the copy insns that
- preserve the compared values. */
- start_sequence ();
- emit_move_insn (cond0, XEXP (temp4, 0));
- if (cond1 != XEXP (temp4, 1))
- emit_move_insn (cond1, XEXP (temp4, 1));
- seq1 = get_insns ();
- end_sequence ();
-
- emit_insns_before (seq1, temp5);
- /* Insert conditional move after insn, to be sure that
- the jump and a possible compare won't be separated */
- last = emit_insns_after (seq2, insn);
-
- /* ??? We can also delete the insn that sets X to A.
- Flow will do it too though. */
- delete_insn (temp);
- next = NEXT_INSN (insn);
- delete_jump (insn);
-
- if (after_regscan)
- {
- reg_scan_update (seq1, NEXT_INSN (last), old_max_reg);
- old_max_reg = max_reg_num ();
- }
-
- changed = 1;
- continue;
- }
- else
- end_sequence ();
- }
-#endif
-
- /* That didn't work, try a store-flag insn.
-
- We further divide the cases into:
-
- 1) x = a; if (...) x = b; and either A or B is zero,
- 2) if (...) x = 0; and jumps are expensive,
- 3) x = a; if (...) x = b; and A and B are constants where all
- the set bits in A are also set in B and jumps are expensive,
- 4) x = a; if (...) x = b; and A and B non-zero, and jumps are
- more expensive, and
- 5) if (...) x = b; if jumps are even more expensive. */
-
- if (GET_MODE_CLASS (GET_MODE (temp1)) == MODE_INT
- && ((GET_CODE (temp3) == CONST_INT)
- /* Make the latter case look like
- x = x; if (...) x = 0; */
- || (temp3 = temp1,
- ((BRANCH_COST >= 2
- && temp2 == const0_rtx)
- || BRANCH_COST >= 3)))
- /* If B is zero, OK; if A is zero, can only do (1) if we
- can reverse the condition. See if (3) applies possibly
- by reversing the condition. Prefer reversing to (4) when
- branches are very expensive. */
- && (((BRANCH_COST >= 2
- || STORE_FLAG_VALUE == -1
- || (STORE_FLAG_VALUE == 1
- /* Check that the mask is a power of two,
- so that it can probably be generated
- with a shift. */
- && GET_CODE (temp3) == CONST_INT
- && exact_log2 (INTVAL (temp3)) >= 0))
- && (reversep = 0, temp2 == const0_rtx))
- || ((BRANCH_COST >= 2
- || STORE_FLAG_VALUE == -1
- || (STORE_FLAG_VALUE == 1
- && GET_CODE (temp2) == CONST_INT
- && exact_log2 (INTVAL (temp2)) >= 0))
- && temp3 == const0_rtx
- && (reversep = can_reverse_comparison_p (temp4, insn)))
- || (BRANCH_COST >= 2
- && GET_CODE (temp2) == CONST_INT
- && GET_CODE (temp3) == CONST_INT
- && ((INTVAL (temp2) & INTVAL (temp3)) == INTVAL (temp2)
- || ((INTVAL (temp2) & INTVAL (temp3)) == INTVAL (temp3)
- && (reversep = can_reverse_comparison_p (temp4,
- insn)))))
- || BRANCH_COST >= 3)
- )
- {
- enum rtx_code code = GET_CODE (temp4);
- rtx uval, cval, var = temp1;
- int normalizep;
- rtx target;
-
- /* If necessary, reverse the condition. */
- if (reversep)
- code = reverse_condition (code), uval = temp2, cval = temp3;
- else
- uval = temp3, cval = temp2;
-
- /* If CVAL is non-zero, normalize to -1. Otherwise, if UVAL
- is the constant 1, it is best to just compute the result
- directly. If UVAL is constant and STORE_FLAG_VALUE
- includes all of its bits, it is best to compute the flag
- value unnormalized and `and' it with UVAL. Otherwise,
- normalize to -1 and `and' with UVAL. */
- normalizep = (cval != const0_rtx ? -1
- : (uval == const1_rtx ? 1
- : (GET_CODE (uval) == CONST_INT
- && (INTVAL (uval) & ~STORE_FLAG_VALUE) == 0)
- ? 0 : -1));
-
- /* We will be putting the store-flag insn immediately in
- front of the comparison that was originally being done,
- so we know all the variables in TEMP4 will be valid.
- However, this might be in front of the assignment of
- A to VAR. If it is, it would clobber the store-flag
- we will be emitting.
-
- Therefore, emit into a temporary which will be copied to
- VAR immediately after TEMP. */
-
- start_sequence ();
- target = emit_store_flag (gen_reg_rtx (GET_MODE (var)), code,
- XEXP (temp4, 0), XEXP (temp4, 1),
- VOIDmode,
- (code == LTU || code == LEU
- || code == GEU || code == GTU),
- normalizep);
- if (target)
- {
- rtx seq;
- rtx before = insn;
-
- seq = get_insns ();
- end_sequence ();
-
- /* Put the store-flag insns in front of the first insn
- used to compute the condition to ensure that we
- use the same values of them as the current
- comparison. However, the remainder of the insns we
- generate will be placed directly in front of the
- jump insn, in case any of the pseudos we use
- are modified earlier. */
-
- emit_insns_before (seq, temp5);
-
- start_sequence ();
-
- /* Both CVAL and UVAL are non-zero. */
- if (cval != const0_rtx && uval != const0_rtx)
- {
- rtx tem1, tem2;
-
- tem1 = expand_and (uval, target, NULL_RTX);
- if (GET_CODE (cval) == CONST_INT
- && GET_CODE (uval) == CONST_INT
- && (INTVAL (cval) & INTVAL (uval)) == INTVAL (cval))
- tem2 = cval;
- else
- {
- tem2 = expand_unop (GET_MODE (var), one_cmpl_optab,
- target, NULL_RTX, 0);
- tem2 = expand_and (cval, tem2,
- (GET_CODE (tem2) == REG
- ? tem2 : 0));
- }
-
- /* If we usually make new pseudos, do so here. This
- turns out to help machines that have conditional
- move insns. */
- /* ??? Conditional moves have already been handled.
- This may be obsolete. */
-
- if (flag_expensive_optimizations)
- target = 0;
-
- target = expand_binop (GET_MODE (var), ior_optab,
- tem1, tem2, target,
- 1, OPTAB_WIDEN);
- }
- else if (normalizep != 1)
- {
- /* We know that either CVAL or UVAL is zero. If
- UVAL is zero, negate TARGET and `and' with CVAL.
- Otherwise, `and' with UVAL. */
- if (uval == const0_rtx)
- {
- target = expand_unop (GET_MODE (var), one_cmpl_optab,
- target, NULL_RTX, 0);
- uval = cval;
- }
-
- target = expand_and (uval, target,
- (GET_CODE (target) == REG
- && ! preserve_subexpressions_p ()
- ? target : NULL_RTX));
- }
-
- emit_move_insn (var, target);
- seq = get_insns ();
- end_sequence ();
-#ifdef HAVE_cc0
- /* If INSN uses CC0, we must not separate it from the
- insn that sets cc0. */
- if (reg_mentioned_p (cc0_rtx, PATTERN (before)))
- before = prev_nonnote_insn (before);
-#endif
- emit_insns_before (seq, before);
-
- delete_insn (temp);
- next = NEXT_INSN (insn);
- delete_jump (insn);
-
- if (after_regscan)
- {
- reg_scan_update (seq, NEXT_INSN (next), old_max_reg);
- old_max_reg = max_reg_num ();
- }
-
- changed = 1;
- continue;
- }
- else
- end_sequence ();
- }
- }
-
- /* If branches are expensive, convert
- if (foo) bar++; to bar += (foo != 0);
- and similarly for "bar--;"
-
- INSN is the conditional branch around the arithmetic. We set:
-
- TEMP is the arithmetic insn.
- TEMP1 is the SET doing the arithmetic.
- TEMP2 is the operand being incremented or decremented.
- TEMP3 to the condition being tested.
- TEMP4 to the earliest insn used to find the condition. */