-/* Generate RTL for the start of a loop. EXIT_FLAG is nonzero if this
- loop should be exited by `exit_something'. This is a loop for which
- `expand_continue' will jump to the top of the loop.
-
- Make an entry on loop_stack to record the labels associated with
- this loop. */
-
-struct nesting *
-expand_start_loop (exit_flag)
- int exit_flag;
-{
- struct nesting *thisloop = ALLOC_NESTING ();
-
- /* Make an entry on loop_stack for the loop we are entering. */
-
- thisloop->desc = LOOP_NESTING;
- thisloop->next = loop_stack;
- thisloop->all = nesting_stack;
- thisloop->depth = ++nesting_depth;
- thisloop->data.loop.start_label = gen_label_rtx ();
- thisloop->data.loop.end_label = gen_label_rtx ();
- thisloop->data.loop.continue_label = thisloop->data.loop.start_label;
- thisloop->exit_label = exit_flag ? thisloop->data.loop.end_label : 0;
- loop_stack = thisloop;
- nesting_stack = thisloop;
-
- do_pending_stack_adjust ();
- emit_queue ();
- emit_note (NULL, NOTE_INSN_LOOP_BEG);
- emit_label (thisloop->data.loop.start_label);
-
- return thisloop;
-}
-
-/* Like expand_start_loop but for a loop where the continuation point
- (for expand_continue_loop) will be specified explicitly. */
-
-struct nesting *
-expand_start_loop_continue_elsewhere (exit_flag)
- int exit_flag;
-{
- struct nesting *thisloop = expand_start_loop (exit_flag);
- loop_stack->data.loop.continue_label = gen_label_rtx ();
- return thisloop;
-}
-
-/* Begin a null, aka do { } while (0) "loop". But since the contents
- of said loop can still contain a break, we must frob the loop nest. */
-
-struct nesting *
-expand_start_null_loop ()
-{
- struct nesting *thisloop = ALLOC_NESTING ();
-
- /* Make an entry on loop_stack for the loop we are entering. */
-
- thisloop->desc = LOOP_NESTING;
- thisloop->next = loop_stack;
- thisloop->all = nesting_stack;
- thisloop->depth = ++nesting_depth;
- thisloop->data.loop.start_label = emit_note (NULL, NOTE_INSN_DELETED);
- thisloop->data.loop.end_label = gen_label_rtx ();
- thisloop->data.loop.continue_label = thisloop->data.loop.end_label;
- thisloop->exit_label = thisloop->data.loop.end_label;
- loop_stack = thisloop;
- nesting_stack = thisloop;
-
- return thisloop;
-}
-
-/* Specify the continuation point for a loop started with
- expand_start_loop_continue_elsewhere.
- Use this at the point in the code to which a continue statement
- should jump. */
-
-void
-expand_loop_continue_here ()
-{
- do_pending_stack_adjust ();
- emit_note (NULL, NOTE_INSN_LOOP_CONT);
- emit_label (loop_stack->data.loop.continue_label);
-}
-
-/* Finish a loop. Generate a jump back to the top and the loop-exit label.
- Pop the block off of loop_stack. */
-
-void
-expand_end_loop ()
-{
- rtx start_label = loop_stack->data.loop.start_label;
- rtx etc_note;
- int eh_regions, debug_blocks;
- bool empty_test;
-
- /* Mark the continue-point at the top of the loop if none elsewhere. */
- if (start_label == loop_stack->data.loop.continue_label)
- emit_note_before (NOTE_INSN_LOOP_CONT, start_label);
-
- do_pending_stack_adjust ();
-
- /* If the loop starts with a loop exit, roll that to the end where
- it will optimize together with the jump back.
-
- If the loop presently looks like this (in pseudo-C):
-
- LOOP_BEG
- start_label:
- if (test) goto end_label;
- LOOP_END_TOP_COND
- body;
- goto start_label;
- end_label:
-
- transform it to look like:
-
- 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 conditional. 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. */
-
- empty_test = true;
- 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;
-
- /* We must not walk into a nested loop. */
- else if (NOTE_LINE_NUMBER (etc_note) == NOTE_INSN_LOOP_BEG)
- {
- etc_note = NULL_RTX;
- 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 ();
- }
-
- /* 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--;
- }
- else if (INSN_P (etc_note))
- empty_test = false;
-
- if (etc_note
- && optimize
- && ! empty_test
- && 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
- {
- 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. */
- 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))
- continue;
-
- reorder_insns (insn, insn, get_last_insn ());
- }
- }
-
- /* 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);
-
- clear_last_expr ();
-}
-
-/* Finish a null loop, aka do { } while (0). */
-
-void
-expand_end_null_loop ()
-{
- do_pending_stack_adjust ();
- emit_label (loop_stack->data.loop.end_label);
-
- POPSTACK (loop_stack);
-
- clear_last_expr ();
-}
-
-/* Generate a jump to the current loop's continue-point.
- This is usually the top of the loop, but may be specified
- explicitly elsewhere. If not currently inside a loop,
- return 0 and do nothing; caller will print an error message. */
-
-int
-expand_continue_loop (whichloop)
- struct nesting *whichloop;
-{
- /* Emit information for branch prediction. */
- rtx note;
-
- note = emit_note (NULL, NOTE_INSN_PREDICTION);
- NOTE_PREDICTION (note) = NOTE_PREDICT (PRED_CONTINUE, IS_TAKEN);
- clear_last_expr ();
- if (whichloop == 0)
- whichloop = loop_stack;
- if (whichloop == 0)
- return 0;
- expand_goto_internal (NULL_TREE, whichloop->data.loop.continue_label,
- NULL_RTX);
- return 1;
-}
-
-/* Generate a jump to exit the current loop. If not currently inside a loop,
- return 0 and do nothing; caller will print an error message. */
-
-int
-expand_exit_loop (whichloop)
- struct nesting *whichloop;
-{
- clear_last_expr ();
- if (whichloop == 0)
- whichloop = loop_stack;
- if (whichloop == 0)
- return 0;
- expand_goto_internal (NULL_TREE, whichloop->data.loop.end_label, NULL_RTX);
- return 1;
-}
-
-/* Generate a conditional jump to exit the current loop if COND
- evaluates to zero. If not currently inside a loop,
- return 0 and do nothing; caller will print an error message. */
-
-int
-expand_exit_loop_if_false (whichloop, cond)
- struct nesting *whichloop;
- tree cond;
-{
- rtx label;
- clear_last_expr ();
-
- if (whichloop == 0)
- whichloop = loop_stack;
- if (whichloop == 0)
- return 0;
-
- if (integer_nonzerop (cond))
- return 1;
- if (integer_zerop (cond))
- return expand_exit_loop (whichloop);
-
- /* Check if we definitely won't need a fixup. */
- if (whichloop == nesting_stack)
- {
- jumpifnot (cond, whichloop->data.loop.end_label);
- return 1;
- }
-
- /* In order to handle fixups, we actually create a conditional jump
- around an unconditional branch to exit the loop. If fixups are
- necessary, they go before the unconditional branch. */
-
- label = gen_label_rtx ();
- jumpif (cond, label);
- expand_goto_internal (NULL_TREE, whichloop->data.loop.end_label,
- NULL_RTX);
- emit_label (label);
-
- 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;
-}
-
OSDN Git Service
