expand_end_loop ()
{
rtx start_label = loop_stack->data.loop.start_label;
- rtx insn = get_last_insn ();
- int needs_end_jump = 1;
+ rtx etc_note;
+ int eh_regions, debug_blocks;
/* Mark the continue-point at the top of the loop if none elsewhere. */
if (start_label == loop_stack->data.loop.continue_label)
do_pending_stack_adjust ();
- /* If optimizing, perhaps reorder the loop.
- First, try to use a condjump near the end.
- expand_exit_loop_if_false ends loops with unconditional jumps,
- like this:
-
- if (test) goto label;
- optional: cleanup
- goto loop_stack->data.loop.end_label
- barrier
- label:
-
- If we find such a pattern, we can end the loop earlier. */
-
- if (optimize
- && GET_CODE (insn) == CODE_LABEL
- && LABEL_NAME (insn) == NULL
- && GET_CODE (PREV_INSN (insn)) == BARRIER)
- {
- rtx label = insn;
- rtx jump = PREV_INSN (PREV_INSN (label));
-
- if (GET_CODE (jump) == JUMP_INSN
- && GET_CODE (PATTERN (jump)) == SET
- && SET_DEST (PATTERN (jump)) == pc_rtx
- && GET_CODE (SET_SRC (PATTERN (jump))) == LABEL_REF
- && (XEXP (SET_SRC (PATTERN (jump)), 0)
- == loop_stack->data.loop.end_label))
- {
- rtx prev;
-
- /* The test might be complex and reference LABEL multiple times,
- like the loop in loop_iterations to set vtop. To handle this,
- we move LABEL. */
- insn = PREV_INSN (label);
- reorder_insns (label, label, start_label);
-
- for (prev = PREV_INSN (jump);; prev = PREV_INSN (prev))
- {
- /* We ignore line number notes, but if we see any other note,
- in particular NOTE_INSN_BLOCK_*, NOTE_INSN_EH_REGION_*,
- NOTE_INSN_LOOP_*, we disable this optimization. */
- if (GET_CODE (prev) == NOTE)
- {
- if (NOTE_LINE_NUMBER (prev) < 0)
- break;
- continue;
- }
- if (GET_CODE (prev) == CODE_LABEL)
- break;
- if (GET_CODE (prev) == JUMP_INSN)
- {
- if (GET_CODE (PATTERN (prev)) == SET
- && SET_DEST (PATTERN (prev)) == pc_rtx
- && GET_CODE (SET_SRC (PATTERN (prev))) == IF_THEN_ELSE
- && (GET_CODE (XEXP (SET_SRC (PATTERN (prev)), 1))
- == LABEL_REF)
- && XEXP (XEXP (SET_SRC (PATTERN (prev)), 1), 0) == label)
- {
- XEXP (XEXP (SET_SRC (PATTERN (prev)), 1), 0)
- = start_label;
- emit_note_after (NOTE_INSN_LOOP_END, prev);
- needs_end_jump = 0;
- }
- break;
- }
- }
- }
- }
-
- /* If the loop starts with a loop exit, roll that to the end where
+ /* If the loop starts with a loop exit, roll that to the end where
it will optimize together with the jump back.
- We look for the conditional branch to the exit, except that once
- we find such a branch, we don't look past 30 instructions.
-
- In more detail, if the loop presently looks like this (in pseudo-C):
+ If the loop presently looks like this (in pseudo-C):
- start_label:
- if (test) goto end_label;
- body;
- goto start_label;
- end_label:
+ LOOP_BEG
+ start_label:
+ if (test) goto end_label;
+ LOOP_END_TOP_COND
+ body;
+ goto start_label;
+ end_label:
transform it to look like:
- goto start_label;
- newstart_label:
- body;
- start_label:
- if (test) goto end_label;
- goto newstart_label;
- end_label:
-
- Here, the `test' may actually consist of some reasonably complex
- code, terminating in a test. */
-
- if (optimize
- && needs_end_jump
- &&
- ! (GET_CODE (insn) == JUMP_INSN
- && GET_CODE (PATTERN (insn)) == SET
- && SET_DEST (PATTERN (insn)) == pc_rtx
- && GET_CODE (SET_SRC (PATTERN (insn))) == IF_THEN_ELSE))
- {
- int eh_regions = 0;
- int num_insns = 0;
- rtx last_test_insn = NULL_RTX;
-
- /* Scan insns from the top of the loop looking for a qualified
- conditional exit. */
- for (insn = NEXT_INSN (loop_stack->data.loop.start_label); insn;
- insn = NEXT_INSN (insn))
- {
- if (GET_CODE (insn) == NOTE)
- {
- if (optimize < 2
- && (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG
- || NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END))
- /* The code that actually moves the exit test will
- carefully leave BLOCK notes in their original
- location. That means, however, that we can't debug
- the exit test itself. So, we refuse to move code
- containing BLOCK notes at low optimization levels. */
- break;
-
- if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
- ++eh_regions;
- else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END)
- {
- --eh_regions;
- if (eh_regions < 0)
- /* We've come to the end of an EH region, but
- never saw the beginning of that region. That
- means that an EH region begins before the top
- of the loop, and ends in the middle of it. The
- existence of such a situation violates a basic
- assumption in this code, since that would imply
- that even when EH_REGIONS is zero, we might
- move code out of an exception region. */
- abort ();
- }
-
- /* We must not walk into a nested loop. */
- if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
- break;
-
- /* We already know this INSN is a NOTE, so there's no
- point in looking at it to see if it's a JUMP. */
- continue;
- }
-
- if (GET_CODE (insn) == JUMP_INSN || GET_CODE (insn) == INSN)
- num_insns++;
+ LOOP_BEG
+ goto start_label;
+ top_label:
+ body;
+ start_label:
+ if (test) goto end_label;
+ goto top_label;
+ end_label:
+
+ We rely on the presence of NOTE_INSN_LOOP_END_TOP_COND to mark
+ the end of the entry condtional. Without this, our lexical scan
+ can't tell the difference between an entry conditional and a
+ body conditional that exits the loop. Mistaking the two means
+ that we can misplace the NOTE_INSN_LOOP_CONT note, which can
+ screw up loop unrolling.
+
+ Things will be oh so much better when loop optimization is done
+ off of a proper control flow graph... */
+
+ /* Scan insns from the top of the loop looking for the END_TOP_COND note. */
+
+ eh_regions = debug_blocks = 0;
+ for (etc_note = start_label; etc_note ; etc_note = NEXT_INSN (etc_note))
+ if (GET_CODE (etc_note) == NOTE)
+ {
+ if (NOTE_LINE_NUMBER (etc_note) == NOTE_INSN_LOOP_END_TOP_COND)
+ break;
- if (last_test_insn && num_insns > 30)
+ /* We must not walk into a nested loop. */
+ else if (NOTE_LINE_NUMBER (etc_note) == NOTE_INSN_LOOP_BEG)
+ {
+ etc_note = NULL_RTX;
break;
+ }
- if (eh_regions > 0)
- /* We don't want to move a partial EH region. Consider:
-
- while ( ( { try {
- if (cond ()) 0;
- else {
- bar();
- 1;
- }
- } catch (...) {
- 1;
- } )) {
- body;
- }
-
- This isn't legal C++, but here's what it's supposed to
- mean: if cond() is true, stop looping. Otherwise,
- call bar, and keep looping. In addition, if cond
- throws an exception, catch it and keep looping. Such
- constructs are certainy legal in LISP.
-
- We should not move the `if (cond()) 0' test since then
- the EH-region for the try-block would be broken up.
- (In this case we would the EH_BEG note for the `try'
- and `if cond()' but not the call to bar() or the
- EH_END note.)
-
- So we don't look for tests within an EH region. */
- continue;
-
- if (GET_CODE (insn) == JUMP_INSN
- && GET_CODE (PATTERN (insn)) == SET
- && SET_DEST (PATTERN (insn)) == pc_rtx)
- {
- /* This is indeed a jump. */
- rtx dest1 = NULL_RTX;
- rtx dest2 = NULL_RTX;
- rtx potential_last_test;
- if (GET_CODE (SET_SRC (PATTERN (insn))) == IF_THEN_ELSE)
- {
- /* A conditional jump. */
- dest1 = XEXP (SET_SRC (PATTERN (insn)), 1);
- dest2 = XEXP (SET_SRC (PATTERN (insn)), 2);
- potential_last_test = insn;
- }
- else
- {
- /* An unconditional jump. */
- dest1 = SET_SRC (PATTERN (insn));
- /* Include the BARRIER after the JUMP. */
- potential_last_test = NEXT_INSN (insn);
- }
-
- do {
- if (dest1 && GET_CODE (dest1) == LABEL_REF
- && ((XEXP (dest1, 0)
- == loop_stack->data.loop.alt_end_label)
- || (XEXP (dest1, 0)
- == loop_stack->data.loop.end_label)))
- {
- last_test_insn = potential_last_test;
- break;
- }
+ /* At the same time, scan for EH region notes, as we don't want
+ to scrog region nesting. This shouldn't happen, but... */
+ else if (NOTE_LINE_NUMBER (etc_note) == NOTE_INSN_EH_REGION_BEG)
+ eh_regions++;
+ else if (NOTE_LINE_NUMBER (etc_note) == NOTE_INSN_EH_REGION_END)
+ {
+ if (--eh_regions < 0)
+ /* We've come to the end of an EH region, but never saw the
+ beginning of that region. That means that an EH region
+ begins before the top of the loop, and ends in the middle
+ of it. The existence of such a situation violates a basic
+ assumption in this code, since that would imply that even
+ when EH_REGIONS is zero, we might move code out of an
+ exception region. */
+ abort ();
+ }
- /* If this was a conditional jump, there may be
- another label at which we should look. */
- dest1 = dest2;
- dest2 = NULL_RTX;
- } while (dest1);
- }
- }
+ /* Likewise for debug scopes. In this case we'll either (1) move
+ all of the notes if they are properly nested or (2) leave the
+ notes alone and only rotate the loop at high optimization
+ levels when we expect to scrog debug info. */
+ else if (NOTE_LINE_NUMBER (etc_note) == NOTE_INSN_BLOCK_BEG)
+ debug_blocks++;
+ else if (NOTE_LINE_NUMBER (etc_note) == NOTE_INSN_BLOCK_END)
+ debug_blocks--;
+ }
- if (last_test_insn != 0 && last_test_insn != get_last_insn ())
+ if (etc_note
+ && optimize
+ && eh_regions == 0
+ && (debug_blocks == 0 || optimize >= 2)
+ && NEXT_INSN (etc_note) != NULL_RTX
+ && ! any_condjump_p (get_last_insn ()))
+ {
+ /* We found one. Move everything from START to ETC to the end
+ of the loop, and add a jump from the top of the loop. */
+ rtx top_label = gen_label_rtx ();
+ rtx start_move = start_label;
+
+ /* If the start label is preceded by a NOTE_INSN_LOOP_CONT note,
+ then we want to move this note also. */
+ if (GET_CODE (PREV_INSN (start_move)) == NOTE
+ && NOTE_LINE_NUMBER (PREV_INSN (start_move)) == NOTE_INSN_LOOP_CONT)
+ start_move = PREV_INSN (start_move);
+
+ emit_label_before (top_label, start_move);
+
+ /* Actually move the insns. If the debug scopes are nested, we
+ can move everything at once. Otherwise we have to move them
+ one by one and squeeze out the block notes. */
+ if (debug_blocks == 0)
+ reorder_insns (start_move, etc_note, get_last_insn ());
+ else
{
- /* We found one. Move everything from there up
- to the end of the loop, and add a jump into the loop
- to jump to there. */
- rtx newstart_label = gen_label_rtx ();
- rtx start_move = start_label;
- rtx next_insn;
-
- /* If the start label is preceded by a NOTE_INSN_LOOP_CONT note,
- then we want to move this note also. */
- if (GET_CODE (PREV_INSN (start_move)) == NOTE
- && (NOTE_LINE_NUMBER (PREV_INSN (start_move))
- == NOTE_INSN_LOOP_CONT))
- start_move = PREV_INSN (start_move);
-
- emit_label_after (newstart_label, PREV_INSN (start_move));
-
- /* Actually move the insns. Start at the beginning, and
- keep copying insns until we've copied the
- last_test_insn. */
+ rtx insn, next_insn;
for (insn = start_move; insn; insn = next_insn)
{
/* Figure out which insn comes after this one. We have
to do this before we move INSN. */
- if (insn == last_test_insn)
- /* We've moved all the insns. */
- next_insn = NULL_RTX;
- else
- next_insn = NEXT_INSN (insn);
+ next_insn = (insn == etc_note ? NULL : NEXT_INSN (insn));
if (GET_CODE (insn) == NOTE
&& (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG
|| NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END))
- /* We don't want to move NOTE_INSN_BLOCK_BEGs or
- NOTE_INSN_BLOCK_ENDs because the correct generation
- of debugging information depends on these appearing
- in the same order in the RTL and in the tree
- structure, where they are represented as BLOCKs.
- So, we don't move block notes. Of course, moving
- the code inside the block is likely to make it
- impossible to debug the instructions in the exit
- test, but such is the price of optimization. */
continue;
- /* Move the INSN. */
reorder_insns (insn, insn, get_last_insn ());
}
-
- emit_jump_insn_after (gen_jump (start_label),
- PREV_INSN (newstart_label));
- emit_barrier_after (PREV_INSN (newstart_label));
- start_label = newstart_label;
}
- }
- if (needs_end_jump)
- {
- emit_jump (start_label);
- emit_note (NULL, NOTE_INSN_LOOP_END);
+ /* Add the jump from the top of the loop. */
+ emit_jump_insn_before (gen_jump (start_label), top_label);
+ emit_barrier_before (top_label);
+ start_label = top_label;
}
+
+ emit_jump (start_label);
+ emit_note (NULL, NOTE_INSN_LOOP_END);
emit_label (loop_stack->data.loop.end_label);
POPSTACK (loop_stack);
return 1;
}
+/* Like expand_exit_loop_if_false except also emit a note marking
+ the end of the conditional. Should only be used immediately
+ after expand_loop_start. */
+
+int
+expand_exit_loop_top_cond (whichloop, cond)
+ struct nesting *whichloop;
+ tree cond;
+{
+ if (! expand_exit_loop_if_false (whichloop, cond))
+ return 0;
+
+ emit_note (NULL, NOTE_INSN_LOOP_END_TOP_COND);
+ return 1;
+}
+
/* Return nonzero if the loop nest is empty. Else return zero. */
int
projects / platform / upstream / linaro-gcc.git / commitdiff