-
-/* LOOP_START is a NOTE_INSN_LOOP_BEG note that is followed by an unconditional
- jump. Assume that this unconditional jump is to the exit test code. If
- the code is sufficiently simple, make a copy of it before INSN,
- followed by a jump to the exit of the loop. Then delete the unconditional
- jump after INSN.
-
- Return 1 if we made the change, else 0.
-
- This is only safe immediately after a regscan pass because it uses the
- values of regno_first_uid and regno_last_uid. */
-
-static int
-duplicate_loop_exit_test (loop_start)
- rtx loop_start;
-{
- rtx insn, set, reg, p, link;
- rtx copy = 0, first_copy = 0;
- int num_insns = 0;
- rtx exitcode
- = NEXT_INSN (JUMP_LABEL (next_nonnote_insn_in_loop (loop_start)));
- rtx lastexit;
- int max_reg = max_reg_num ();
- rtx *reg_map = 0;
- rtx loop_pre_header_label;
-
- /* Scan the exit code. We do not perform this optimization if any insn:
-
- is a CALL_INSN
- is a CODE_LABEL
- has a REG_RETVAL or REG_LIBCALL note (hard to adjust)
- is a NOTE_INSN_LOOP_BEG because this means we have a nested loop
-
- We also do not do this if we find an insn with ASM_OPERANDS. While
- this restriction should not be necessary, copying an insn with
- ASM_OPERANDS can confuse asm_noperands in some cases.
-
- Also, don't do this if the exit code is more than 20 insns. */
-
- for (insn = exitcode;
- insn
- && ! (GET_CODE (insn) == NOTE
- && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END);
- insn = NEXT_INSN (insn))
- {
- switch (GET_CODE (insn))
- {
- case CODE_LABEL:
- case CALL_INSN:
- return 0;
- case NOTE:
-
- if (optimize < 2
- && (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG
- || NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END))
- /* If we were to duplicate this code, we would not move
- the BLOCK notes, and so debugging the moved code would
- be difficult. Thus, we only move the code with -O2 or
- higher. */
- return 0;
-
- break;
- case JUMP_INSN:
- case INSN:
- if (++num_insns > 20
- || find_reg_note (insn, REG_RETVAL, NULL_RTX)
- || find_reg_note (insn, REG_LIBCALL, NULL_RTX))
- return 0;
- break;
- default:
- break;
- }
- }
-
- /* Unless INSN is zero, we can do the optimization. */
- if (insn == 0)
- return 0;
-
- lastexit = insn;
-
- /* See if any insn sets a register only used in the loop exit code and
- not a user variable. If so, replace it with a new register. */
- for (insn = exitcode; insn != lastexit; insn = NEXT_INSN (insn))
- if (GET_CODE (insn) == INSN
- && (set = single_set (insn)) != 0
- && ((reg = SET_DEST (set), GET_CODE (reg) == REG)
- || (GET_CODE (reg) == SUBREG
- && (reg = SUBREG_REG (reg), GET_CODE (reg) == REG)))
- && REGNO (reg) >= FIRST_PSEUDO_REGISTER
- && REGNO_FIRST_UID (REGNO (reg)) == INSN_UID (insn))
- {
- for (p = NEXT_INSN (insn); p != lastexit; p = NEXT_INSN (p))
- if (REGNO_LAST_UID (REGNO (reg)) == INSN_UID (p))
- break;
-
- if (p != lastexit)
- {
- /* We can do the replacement. Allocate reg_map if this is the
- first replacement we found. */
- if (reg_map == 0)
- reg_map = (rtx *) xcalloc (max_reg, sizeof (rtx));
-
- REG_LOOP_TEST_P (reg) = 1;
-
- reg_map[REGNO (reg)] = gen_reg_rtx (GET_MODE (reg));
- }
- }
- loop_pre_header_label = gen_label_rtx ();
-
- /* Now copy each insn. */
- for (insn = exitcode; insn != lastexit; insn = NEXT_INSN (insn))
- {
- switch (GET_CODE (insn))
- {
- case BARRIER:
- copy = emit_barrier_before (loop_start);
- break;
- case NOTE:
- /* Only copy line-number notes. */
- if (NOTE_LINE_NUMBER (insn) >= 0)
- {
- copy = emit_note_before (NOTE_LINE_NUMBER (insn), loop_start);
- NOTE_SOURCE_FILE (copy) = NOTE_SOURCE_FILE (insn);
- }
- break;
-
- case INSN:
- copy = emit_insn_before (copy_insn (PATTERN (insn)), loop_start);
- if (reg_map)
- replace_regs (PATTERN (copy), reg_map, max_reg, 1);
-
- mark_jump_label (PATTERN (copy), copy, 0);
- INSN_LOCATOR (copy) = INSN_LOCATOR (insn);
-
- /* Copy all REG_NOTES except REG_LABEL since mark_jump_label will
- make them. */
- for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
- if (REG_NOTE_KIND (link) != REG_LABEL)
- {
- if (GET_CODE (link) == EXPR_LIST)
- REG_NOTES (copy)
- = copy_insn_1 (gen_rtx_EXPR_LIST (REG_NOTE_KIND (link),
- XEXP (link, 0),
- REG_NOTES (copy)));
- else
- REG_NOTES (copy)
- = copy_insn_1 (gen_rtx_INSN_LIST (REG_NOTE_KIND (link),
- XEXP (link, 0),
- REG_NOTES (copy)));
- }
-
- if (reg_map && REG_NOTES (copy))
- replace_regs (REG_NOTES (copy), reg_map, max_reg, 1);
- break;
-
- case JUMP_INSN:
- copy = emit_jump_insn_before (copy_insn (PATTERN (insn)),
- loop_start);
- INSN_LOCATOR (copy) = INSN_LOCATOR (insn);
- if (reg_map)
- replace_regs (PATTERN (copy), reg_map, max_reg, 1);
- mark_jump_label (PATTERN (copy), copy, 0);
- if (REG_NOTES (insn))
- {
- REG_NOTES (copy) = copy_insn_1 (REG_NOTES (insn));
- if (reg_map)
- replace_regs (REG_NOTES (copy), reg_map, max_reg, 1);
- }
-
- /* Predict conditional jump that do make loop looping as taken.
- Other jumps are probably exit conditions, so predict
- them as untaken. */
- if (any_condjump_p (copy))
- {
- rtx label = JUMP_LABEL (copy);
- if (label)
- {
- /* The jump_insn after loop_start should be followed
- by barrier and loopback label. */
- if (prev_nonnote_insn (label)
- && (prev_nonnote_insn (prev_nonnote_insn (label))
- == next_nonnote_insn (loop_start)))
- {
- predict_insn_def (copy, PRED_LOOP_HEADER, TAKEN);
- /* To keep pre-header, we need to redirect all loop
- entrances before the LOOP_BEG note. */
- redirect_jump (copy, loop_pre_header_label, 0);
- }
- else
- predict_insn_def (copy, PRED_LOOP_HEADER, NOT_TAKEN);
- }
- }
- break;
-
- default:
- abort ();
- }
-
- /* Record the first insn we copied. We need it so that we can
- scan the copied insns for new pseudo registers. */
- if (! first_copy)
- first_copy = copy;
- }
-
- /* Now clean up by emitting a jump to the end label and deleting the jump
- at the start of the loop. */
- if (! copy || GET_CODE (copy) != BARRIER)
- {
- copy = emit_jump_insn_before (gen_jump (get_label_after (insn)),
- loop_start);
-
- /* Record the first insn we copied. We need it so that we can
- scan the copied insns for new pseudo registers. This may not
- be strictly necessary since we should have copied at least one
- insn above. But I am going to be safe. */
- if (! first_copy)
- first_copy = copy;
-
- mark_jump_label (PATTERN (copy), copy, 0);
- emit_barrier_before (loop_start);
- }
-
- emit_label_before (loop_pre_header_label, loop_start);
-
- /* Now scan from the first insn we copied to the last insn we copied
- (copy) for new pseudo registers. Do this after the code to jump to
- the end label since that might create a new pseudo too. */
- reg_scan_update (first_copy, copy, max_reg);
-
- /* Mark the exit code as the virtual top of the converted loop. */
- emit_note_before (NOTE_INSN_LOOP_VTOP, exitcode);
-
- delete_related_insns (next_nonnote_insn (loop_start));
-
- /* Clean up. */
- if (reg_map)
- free (reg_map);
-
- return 1;
-}