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stmt.c (expand_end_loop): Grok code emitted by expand_exit_loop_if_false.

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* stmt.c (expand_end_loop): Grok code emitted by
	expand_exit_loop_if_false.

From-SVN: r25433
This commit is contained in:
J"orn Rennecke 1999-02-25 10:46:06 +00:00 • committed by Joern Rennecke
parent 9f6ce99046
commit a7d308f7c4
2 changed files with 83 additions and 5 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
Thu Feb 25 18:40:06 1999 J"orn Rennecke <amylaar@cygnus.co.uk>
* stmt.c (expand_end_loop): Grok code emitted by
expand_exit_loop_if_false.
Thu Feb 25 10:17:32 1999 Nick Clifton <nickc@cygnus.com>
* config/arm/arm.c (return_in_memory): Float fields in unions

83
gcc/stmt.c
View file

@ -2069,6 +2069,7 @@ expand_end_loop ()
{
rtx start_label = loop_stack->data.loop.start_label;
rtx insn = get_last_insn ();
int needs_end_jump = 1;
/* Mark the continue-point at the top of the loop if none elsewhere. */
if (start_label == loop_stack->data.loop.continue_label)
@ -2076,9 +2077,77 @@ expand_end_loop ()
do_pending_stack_adjust ();
/* If optimizing, perhaps reorder the loop. If the loop starts with
a loop exit, roll that to the end where it will optimize together
with the jump back.
/* 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
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.
@ -2105,6 +2174,7 @@ expand_end_loop ()
code, terminating in a test. */
if (optimize
&& needs_end_jump
&&
! (GET_CODE (insn) == JUMP_INSN
&& GET_CODE (PATTERN (insn)) == SET
@ -2288,8 +2358,11 @@ expand_end_loop ()
}
}
emit_jump (start_label);
emit_note (NULL_PTR, NOTE_INSN_LOOP_END);
if (needs_end_jump)
{
emit_jump (start_label);
emit_note (NULL_PTR, NOTE_INSN_LOOP_END);
}
emit_label (loop_stack->data.loop.end_label);
POPSTACK (loop_stack);