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doloop.c (doloop_valid_p): Correct comment.

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* doloop.c (doloop_valid_p): Correct comment.
	(doloop_modify_runtime <abs_inc != 1>): Simplify.
	(doloop_modify_runtime <do-while>): Don't emit code when NE.

From-SVN: r54938
This commit is contained in:
Alan Modra 2002-06-24 02:16:42 +00:00 committed by Alan Modra
parent 17ba19fe45
commit 0228d06bca
2 changed files with 29 additions and 44 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2002-06-24 Alan Modra <amodra@bigpond.net.au>
* doloop.c (doloop_valid_p): Correct comment.
(doloop_modify_runtime <abs_inc != 1>): Simplify.
(doloop_modify_runtime <do-while>): Don't emit code when NE.
Thu Jun 20 00:26:53 2002 Denis Chertykov <denisc@overta.ru>
* config.gcc: Add support for ip2k.

67
gcc/doloop.c
View File

@ -361,8 +361,8 @@ doloop_valid_p (loop, jump_insn)
{
/* If the comparison is LEU and the comparison value is UINT_MAX
then the loop will not terminate. Similarly, if the
comparison code is GEU and the initial value is 0, the loop
will not terminate.
comparison code is GEU and the comparison value is 0, the
loop will not terminate.
If the absolute increment is not 1, the loop can be infinite
even with LTU/GTU, e.g. for (i = 3; i > 0; i -= 2)
@ -591,6 +591,10 @@ doloop_modify_runtime (loop, iterations_max,
n = abs (final - initial) / abs_inc;
n += (abs (final - initial) % abs_inc) != 0;
But when abs_inc is a power of two, the summation won't overflow
except in cases where the loop never terminates. So we don't
need to use this more costly calculation.
If the loop has been unrolled, then the loop body has been
preconditioned to iterate a multiple of unroll_number times. If
abs_inc is != 1, the full calculation is
@ -666,50 +670,22 @@ doloop_modify_runtime (loop, iterations_max,
if (abs_inc * loop_info->unroll_number != 1)
{
int shift_count;
rtx extra;
rtx label;
unsigned HOST_WIDE_INT limit;
shift_count = exact_log2 (abs_inc * loop_info->unroll_number);
if (shift_count < 0)
abort ();
/* abs (final - initial) / (abs_inc * unroll_number) */
iterations = expand_simple_binop (GET_MODE (diff), LSHIFTRT,
diff, GEN_INT (shift_count),
NULL_RTX, 1,
OPTAB_LIB_WIDEN);
if (abs_inc != 1)
{
/* abs (final - initial) % (abs_inc * unroll_number) */
rtx count = GEN_INT (abs_inc * loop_info->unroll_number - 1);
extra = expand_simple_binop (GET_MODE (iterations), AND,
diff, count, NULL_RTX, 1,
OPTAB_LIB_WIDEN);
diff = expand_simple_binop (GET_MODE (diff), PLUS,
diff, GEN_INT (abs_inc - 1),
diff, 1, OPTAB_LIB_WIDEN);
/* If (abs (final - initial) % (abs_inc * unroll_number)
<= abs_inc * (unroll - 1)),
jump past following increment instruction. */
label = gen_label_rtx ();
limit = abs_inc * (loop_info->unroll_number - 1);
emit_cmp_and_jump_insns (extra, GEN_INT (limit),
limit == 0 ? EQ : LEU, NULL_RTX,
GET_MODE (extra), 0, label);
JUMP_LABEL (get_last_insn ()) = label;
LABEL_NUSES (label)++;
/* Increment the iteration count by one. */
iterations = expand_simple_binop (GET_MODE (iterations), PLUS,
iterations, GEN_INT (1),
iterations, 1,
OPTAB_LIB_WIDEN);
emit_label (label);
}
/* (abs (final - initial) + abs_inc - 1) / (abs_inc * unroll_number) */
diff = expand_simple_binop (GET_MODE (diff), LSHIFTRT,
diff, GEN_INT (shift_count),
diff, 1, OPTAB_LIB_WIDEN);
}
else
iterations = diff;
iterations = diff;
/* If there is a NOTE_INSN_LOOP_VTOP, we have a `for' or `while'
style loop, with a loop exit test at the start. Thus, we can
@ -722,17 +698,20 @@ doloop_modify_runtime (loop, iterations_max,
iteration count to one if necessary. */
if (! loop->vtop)
{
rtx label;
if (loop_dump_stream)
fprintf (loop_dump_stream, "Doloop: Do-while loop.\n");
/* A `do-while' loop must iterate at least once. If the
iteration count is bogus, we set the iteration count to 1.
/* A `do-while' loop must iterate at least once. For code like
i = initial; do { ... } while (++i < final);
we will calculate a bogus iteration count if initial > final.
So detect this and set the iteration count to 1.
Note that if the loop has been unrolled, then the loop body
is guaranteed to execute at least once. */
if (loop_info->unroll_number == 1)
is guaranteed to execute at least once. Also, when the
comparison is NE, our calculated count will be OK. */
if (loop_info->unroll_number == 1 && comparison_code != NE)
{
rtx label;
/* Emit insns to test if the loop will immediately
terminate and to set the iteration count to 1 if true. */
label = gen_label_rtx();