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loop.c (strength_reduce): Do not clear NOT_EVERY_ITERATION at the last CODE_LABEL in a loop if... 

* loop.c (strength_reduce): Do not clear NOT_EVERY_ITERATION at the
	last CODE_LABEL in a loop if we have previously passed a jump
	to the top of the loop.

From-SVN: r27125
This commit is contained in:
Jeffrey A Law 1999-05-24 13:43:22 +00:00 committed by Jeff Law
parent 79d6c91640
commit ae188a870e
2 changed files with 26 additions and 3 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
Mon May 24 14:35:24 1999 Jeffrey A Law (law@cygnus.com)
* loop.c (strength_reduce): Do not clear NOT_EVERY_ITERATION at the
last CODE_LABEL in a loop if we have previously passed a jump
to the top of the loop.
Mon May 24 07:56:29 1999 Nick Clifton <nickc@cygnus.com>
* config/arm/arm.h (OUTPUT_INT_ADDR_CONST): Fix blunder made when

23
gcc/loop.c
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@ -3669,6 +3669,9 @@ strength_reduce (scan_start, end, loop_top, insn_count,
/* This is 1 if current insn may be executed more than once for every
loop iteration. */
int maybe_multiple = 0;
/* This is 1 if we have past a branch back to the top of the loop
(aka a loop latch). */
int past_loop_latch = 0;
/* Temporary list pointers for traversing loop_iv_list. */
struct iv_class *bl, **backbl;
/* Ratio of extra register life span we can justify
@ -3836,16 +3839,30 @@ strength_reduce (scan_start, end, loop_top, insn_count,
loop_depth--;
}
/* Note if we pass a loop latch. If we do, then we can not clear
NOT_EVERY_ITERATION below when we pass the last CODE_LABEL in
a loop since a jump before the last CODE_LABEL may have started
a new loop iteration.
Note that LOOP_TOP is only set for rotated loops and we need
this check for all loops, so compare against the CODE_LABEL
which immediately follows LOOP_START. */
if (GET_CODE (p) == JUMP_INSN && JUMP_LABEL (p) == NEXT_INSN (loop_start))
past_loop_latch = 1;
/* Unlike in the code motion pass where MAYBE_NEVER indicates that
an insn may never be executed, NOT_EVERY_ITERATION indicates whether
or not an insn is known to be executed each iteration of the
loop, whether or not any iterations are known to occur.
Therefore, if we have just passed a label and have no more labels
between here and the test insn of the loop, we know these insns
will be executed each iteration. */
between here and the test insn of the loop, and we have not passed
a jump to the top of the loop, then we know these insns will be
executed each iteration. */
if (not_every_iteration && GET_CODE (p) == CODE_LABEL
if (not_every_iteration
&& ! past_loop_latch
&& GET_CODE (p) == CODE_LABEL
&& no_labels_between_p (p, loop_end)
&& loop_insn_first_p (p, loop_cont))
not_every_iteration = 0;