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loop.c (check_ext_dependent_givs): Pass const struct loop * instead of struct loop_info * as argument. 

* loop.c (check_ext_dependent_givs): Pass const struct loop *
	instead of struct loop_info * as argument.  Accept BIVs with
	increment +/- 1 provided there is a friendly exit test against
	a loop-invariant value.
	(strength_reduce): Adapt call to check_ext_dependent_givs.

From-SVN: r69489
This commit is contained in:
Ulrich Weigand 2003-07-17 00:59:52 +00:00 committed by Ulrich Weigand
parent 1129e7f414
commit 03988cac58
2 changed files with 46 additions and 8 deletions
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8
gcc/ChangeLog
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@ -1,3 +1,11 @@
2003-07-16 Ulrich Weigand <uweigand@de.ibm.com>
* loop.c (check_ext_dependent_givs): Pass const struct loop *
instead of struct loop_info * as argument. Accept BIVs with
increment +/- 1 provided there is a friendly exit test against
a loop-invariant value.
(strength_reduce): Adapt call to check_ext_dependent_givs.
2003-07-16 J"orn Rennecke <joern.rennecke@superh.com>
Con Bradley <con.bradley@superh.com>

46
gcc/loop.c
View File

@ -293,7 +293,7 @@ static void record_giv (const struct loop *, struct induction *, rtx, rtx,
rtx, rtx, rtx, rtx, int, enum g_types, int, int,
rtx *);
static void update_giv_derive (const struct loop *, rtx);
static void check_ext_dependent_givs (struct iv_class *, struct loop_info *);
static void check_ext_dependent_givs (const struct loop *, struct iv_class *);
static int basic_induction_var (const struct loop *, rtx, enum machine_mode,
rtx, rtx, rtx *, rtx *, rtx **);
static rtx simplify_giv_expr (const struct loop *, rtx, rtx *, int *);
@ -5143,7 +5143,7 @@ strength_reduce (struct loop *loop, int flags)
/* Check each extension dependent giv in this class to see if its
root biv is safe from wrapping in the interior mode. */
check_ext_dependent_givs (bl, loop_info);
check_ext_dependent_givs (loop, bl);
/* Combine all giv's for this iv_class. */
combine_givs (regs, bl);
@ -7286,8 +7286,9 @@ combine_givs_p (struct induction *g1, struct induction *g2)
make the giv illegal. */
static void
check_ext_dependent_givs (struct iv_class *bl, struct loop_info *loop_info)
check_ext_dependent_givs (const struct loop *loop, struct iv_class *bl)
{
struct loop_info *loop_info = LOOP_INFO (loop);
int ze_ok = 0, se_ok = 0, info_ok = 0;
enum machine_mode biv_mode = GET_MODE (bl->biv->src_reg);
HOST_WIDE_INT start_val;
@ -7298,9 +7299,6 @@ check_ext_dependent_givs (struct iv_class *bl, struct loop_info *loop_info)
/* Make sure the iteration data is available. We must have
constants in order to be certain of no overflow. */
/* ??? An unknown iteration count with an increment of +-1
combined with friendly exit tests of against an invariant
value is also amenable to optimization. Not implemented. */
if (loop_info->n_iterations > 0
&& bl->initial_value
&& GET_CODE (bl->initial_value) == CONST_INT
@ -7367,6 +7365,37 @@ check_ext_dependent_givs (struct iv_class *bl, struct loop_info *loop_info)
}
}
/* If we know the BIV is compared at run-time against an
invariant value, and the increment is +/- 1, we may also
be able to prove that the BIV cannot overflow. */
else if (bl->biv->src_reg == loop_info->iteration_var
&& loop_info->comparison_value
&& loop_invariant_p (loop, loop_info->comparison_value)
&& (incr = biv_total_increment (bl))
&& GET_CODE (incr) == CONST_INT)
{
/* If the increment is +1, and the exit test is a <,
the BIV cannot overflow. (For <=, we have the
problematic case that the comparison value might
be the maximum value of the range.) */
if (INTVAL (incr) == 1)
{
if (loop_info->comparison_code == LT)
se_ok = ze_ok = 1;
else if (loop_info->comparison_code == LTU)
ze_ok = 1;
}
/* Likewise for increment -1 and exit test >. */
if (INTVAL (incr) == -1)
{
if (loop_info->comparison_code == GT)
se_ok = ze_ok = 1;
else if (loop_info->comparison_code == GTU)
ze_ok = 1;
}
}
/* Invalidate givs that fail the tests. */
for (v = bl->giv; v; v = v->next_iv)
if (v->ext_dependent)
@ -7388,8 +7417,9 @@ check_ext_dependent_givs (struct iv_class *bl, struct loop_info *loop_info)
signed or unsigned, so to safely truncate we must satisfy
both. The initial check here verifies the BIV itself;
once that is successful we may check its range wrt the
derived GIV. */
if (se_ok && ze_ok)
derived GIV. This works only if we were able to determine
constant start and end values above. */
if (se_ok && ze_ok && info_ok)
{
enum machine_mode outer_mode = GET_MODE (v->ext_dependent);
unsigned HOST_WIDE_INT max = GET_MODE_MASK (outer_mode) >> 1;