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tree-ssa-loop-niter.c (number_of_iterations_cond): Split into several functions. 

* tree-ssa-loop-niter.c (number_of_iterations_cond): Split into several
	functions.
	(number_of_iterations_ne, number_of_iterations_lt_to_ne,
	assert_no_overflow_lt, assert_loop_rolls_lt, number_of_iterations_lt,
	number_of_iterations_le): New functions.
	(number_of_iterations_special): Removed.
	(number_of_iterations_exit): Do not use number_of_iterations_special.
	* tree.c (unsigned_type_for): Always return integer type.

	* gcc.dg/tree-ssa/pr19210-1.c: Update outcome.  Add new test loop.
	* gcc.dg/tree-ssa/pr19210-2.c: Ditto.

From-SVN: r109702
This commit is contained in:
Zdenek Dvorak 2006-01-14 13:29:06 +01:00 committed by Zdenek Dvorak
parent 26fb114d13
commit 7f17528ab5
6 changed files with 472 additions and 431 deletions
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11
gcc/ChangeLog
View File

@ -1,3 +1,14 @@
2006-01-14 Zdenek Dvorak <dvorakz@suse.cz>
* tree-ssa-loop-niter.c (number_of_iterations_cond): Split into several
functions.
(number_of_iterations_ne, number_of_iterations_lt_to_ne,
assert_no_overflow_lt, assert_loop_rolls_lt, number_of_iterations_lt,
number_of_iterations_le): New functions.
(number_of_iterations_special): Removed.
(number_of_iterations_exit): Do not use number_of_iterations_special.
* tree.c (unsigned_type_for): Always return integer type.
2006-01-14 Steven Bosscher <stevenb.gcc@gmail.com>
Richard Guenther <rguenther@suse.de>

5
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,8 @@
2005-01-14 Zdenek Dvorak <dvorakz@suse.cz>
* gcc.dg/tree-ssa/pr19210-1.c: Update outcome. Add new test loop.
* gcc.dg/tree-ssa/pr19210-2.c: Ditto.
2006-01-14 Steven Bosscher <stevenb.gcc@gmail.com>
Richard Guenther <rguenther@suse.de>

11
gcc/testsuite/gcc.dg/tree-ssa/pr19210-1.c
View File

@ -12,9 +12,18 @@ f (unsigned n)
for(k = 0;k <= n;k += 4) /* { dg-warning "cannot optimize.*overflow" } */
g();
for(k = 5;k <= n;k += 5) /* { dg-warning "cannot optimize.*overflow" } */
/* We used to get warning for this loop. However, since then # of iterations
analysis improved, and we can now prove that this loop does not verflow.
This is because the only case when it would overflow is if n = ~0 (since
~0 is divisible by 5), and this cannot be the case, since when we got
here, the previous loop exited, thus there exists k > n. */
for(k = 5;k <= n;k += 5)
g();
/* So we need the following loop, instead. */
for(k = 4;k <= n;k += 5) /* { dg-warning "cannot optimize.*overflow" } */
g();
for(k = 15;k >= n;k--) /* { dg-warning "cannot optimize.*infinite" } */
g();
}

10
gcc/testsuite/gcc.dg/tree-ssa/pr19210-2.c
View File

@ -12,7 +12,15 @@ f (unsigned n)
for(k = 5;k <= n;k += 4) /* { dg-warning "assuming.*not overflow" } */
g();
for(k = 5;k <= n;k += 5) /* { dg-warning "assuming.*not overflow" } */
/* We used to get warning for this loop. However, since then # of iterations
analysis improved, and we can now prove that this loop does not verflow.
This is because the only case when it would overflow is if n = ~0 (since
~0 is divisible by 5), and this cannot be the case, since when we got
here, the previous loop exited, thus there exists k > n. */
for(k = 5;k <= n;k += 5)
g();
for(k = 4;k <= n;k += 5) /* { dg-warning "assuming.*not overflow" } */
g();
for(k = 15;k >= n;k--) /* { dg-warning "assuming.*not infinite" } */

864
gcc/tree-ssa-loop-niter.c
View File

@ -126,6 +126,395 @@ inverse (tree x, tree mask)
return rslt;
}
/* Determines number of iterations of loop whose ending condition
is IV <> FINAL. TYPE is the type of the iv. The number of
iterations is stored to NITER. NEVER_INFINITE is true if
we know that the loop cannot be infinite (we derived this
earlier, and possibly set NITER->assumptions to make sure this
is the case. */
static bool
number_of_iterations_ne (tree type, affine_iv *iv, tree final,
struct tree_niter_desc *niter, bool never_infinite)
{
tree niter_type = unsigned_type_for (type);
tree s, c, d, bits, assumption, tmp, bound;
/* Rearrange the terms so that we get inequality s * i <> c, with s
positive. Also cast everything to the unsigned type. */
if (tree_int_cst_sign_bit (iv->step))
{
s = fold_convert (niter_type,
fold_build1 (NEGATE_EXPR, type, iv->step));
c = fold_build2 (MINUS_EXPR, niter_type,
fold_convert (niter_type, iv->base),
fold_convert (niter_type, final));
}
else
{
s = fold_convert (niter_type, iv->step);
c = fold_build2 (MINUS_EXPR, niter_type,
fold_convert (niter_type, final),
fold_convert (niter_type, iv->base));
}
/* First the trivial cases -- when the step is 1. */
if (integer_onep (s))
{
niter->niter = c;
return true;
}
/* Let nsd (step, size of mode) = d. If d does not divide c, the loop
is infinite. Otherwise, the number of iterations is
(inverse(s/d) * (c/d)) mod (size of mode/d). */
bits = num_ending_zeros (s);
bound = build_low_bits_mask (niter_type,
(TYPE_PRECISION (niter_type)
- tree_low_cst (bits, 1)));
d = fold_binary_to_constant (LSHIFT_EXPR, niter_type,
build_int_cst_type (niter_type, 1), bits);
s = fold_binary_to_constant (RSHIFT_EXPR, niter_type, s, bits);
if (!never_infinite)
{
/* If we cannot assume that the loop is not infinite, record the
assumptions for divisibility of c. */
assumption = fold_build2 (FLOOR_MOD_EXPR, niter_type, c, d);
assumption = fold_build2 (EQ_EXPR, boolean_type_node,
assumption, build_int_cst (niter_type, 0));
if (!nonzero_p (assumption))
niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
niter->assumptions, assumption);
}
c = fold_build2 (EXACT_DIV_EXPR, niter_type, c, d);
tmp = fold_build2 (MULT_EXPR, niter_type, c, inverse (s, bound));
niter->niter = fold_build2 (BIT_AND_EXPR, niter_type, tmp, bound);
return true;
}
/* Checks whether we can determine the final value of the control variable
of the loop with ending condition IV0 < IV1 (computed in TYPE).
DELTA is the difference IV1->base - IV0->base, STEP is the absolute value
of the step. The assumptions necessary to ensure that the computation
of the final value does not overflow are recorded in NITER. If we
find the final value, we adjust DELTA and return TRUE. Otherwise
we return false. */
static bool
number_of_iterations_lt_to_ne (tree type, affine_iv *iv0, affine_iv *iv1,
struct tree_niter_desc *niter,
tree *delta, tree step)
{
tree niter_type = TREE_TYPE (step);
tree mod = fold_build2 (FLOOR_MOD_EXPR, niter_type, *delta, step);
tree tmod;
tree assumption = boolean_true_node, bound, noloop;
if (TREE_CODE (mod) != INTEGER_CST)
return false;
if (nonzero_p (mod))
mod = fold_build2 (MINUS_EXPR, niter_type, step, mod);
tmod = fold_convert (type, mod);
if (nonzero_p (iv0->step))
{
/* The final value of the iv is iv1->base + MOD, assuming that this
computation does not overflow, and that
iv0->base <= iv1->base + MOD. */
if (!iv1->no_overflow && !zero_p (mod))
{
bound = fold_build2 (MINUS_EXPR, type,
TYPE_MAX_VALUE (type), tmod);
assumption = fold_build2 (LE_EXPR, boolean_type_node,
iv1->base, bound);
if (zero_p (assumption))
return false;
}
noloop = fold_build2 (GT_EXPR, boolean_type_node,
iv0->base,
fold_build2 (PLUS_EXPR, type,
iv1->base, tmod));
}
else
{
/* The final value of the iv is iv0->base - MOD, assuming that this
computation does not overflow, and that
iv0->base - MOD <= iv1->base. */
if (!iv0->no_overflow && !zero_p (mod))
{
bound = fold_build2 (PLUS_EXPR, type,
TYPE_MIN_VALUE (type), tmod);
assumption = fold_build2 (GE_EXPR, boolean_type_node,
iv0->base, bound);
if (zero_p (assumption))
return false;
}
noloop = fold_build2 (GT_EXPR, boolean_type_node,
fold_build2 (MINUS_EXPR, type,
iv0->base, tmod),
iv1->base);
}
if (!nonzero_p (assumption))
niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
niter->assumptions,
assumption);
if (!zero_p (noloop))
niter->may_be_zero = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
niter->may_be_zero,
noloop);
*delta = fold_build2 (PLUS_EXPR, niter_type, *delta, mod);
return true;
}
/* Add assertions to NITER that ensure that the control variable of the loop
with ending condition IV0 < IV1 does not overflow. Types of IV0 and IV1
are TYPE. Returns false if we can prove that there is an overflow, true
otherwise. STEP is the absolute value of the step. */
static bool
assert_no_overflow_lt (tree type, affine_iv *iv0, affine_iv *iv1,
struct tree_niter_desc *niter, tree step)
{
tree bound, d, assumption, diff;
tree niter_type = TREE_TYPE (step);
if (nonzero_p (iv0->step))
{
/* for (i = iv0->base; i < iv1->base; i += iv0->step) */
if (iv0->no_overflow)
return true;
/* If iv0->base is a constant, we can determine the last value before
overflow precisely; otherwise we conservatively assume
MAX - STEP + 1. */
if (TREE_CODE (iv0->base) == INTEGER_CST)
{
d = fold_build2 (MINUS_EXPR, niter_type,
fold_convert (niter_type, TYPE_MAX_VALUE (type)),
fold_convert (niter_type, iv0->base));
diff = fold_build2 (FLOOR_MOD_EXPR, niter_type, d, step);
}
else
diff = fold_build2 (MINUS_EXPR, niter_type, step,
build_int_cst_type (niter_type, 1));
bound = fold_build2 (MINUS_EXPR, type,
TYPE_MAX_VALUE (type), fold_convert (type, diff));
assumption = fold_build2 (LE_EXPR, boolean_type_node,
iv1->base, bound);
}
else
{
/* for (i = iv1->base; i > iv0->base; i += iv1->step) */
if (iv1->no_overflow)
return true;
if (TREE_CODE (iv1->base) == INTEGER_CST)
{
d = fold_build2 (MINUS_EXPR, niter_type,
fold_convert (niter_type, iv1->base),
fold_convert (niter_type, TYPE_MIN_VALUE (type)));
diff = fold_build2 (FLOOR_MOD_EXPR, niter_type, d, step);
}
else
diff = fold_build2 (MINUS_EXPR, niter_type, step,
build_int_cst_type (niter_type, 1));
bound = fold_build2 (PLUS_EXPR, type,
TYPE_MIN_VALUE (type), fold_convert (type, diff));
assumption = fold_build2 (GE_EXPR, boolean_type_node,
iv0->base, bound);
}
if (zero_p (assumption))
return false;
if (!nonzero_p (assumption))
niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
niter->assumptions, assumption);
iv0->no_overflow = true;
iv1->no_overflow = true;
return true;
}
/* Add an assumption to NITER that a loop whose ending condition
is IV0 < IV1 rolls. TYPE is the type of the control iv. */
static void
assert_loop_rolls_lt (tree type, affine_iv *iv0, affine_iv *iv1,
struct tree_niter_desc *niter)
{
tree assumption = boolean_true_node, bound, diff;
tree mbz, mbzl, mbzr;
if (nonzero_p (iv0->step))
{
diff = fold_build2 (MINUS_EXPR, type,
iv0->step, build_int_cst_type (type, 1));
/* We need to know that iv0->base >= MIN + iv0->step - 1. Since
0 address never belongs to any object, we can assume this for
pointers. */
if (!POINTER_TYPE_P (type))
{
bound = fold_build2 (PLUS_EXPR, type,
TYPE_MIN_VALUE (type), diff);
assumption = fold_build2 (GE_EXPR, boolean_type_node,
iv0->base, bound);
}
/* And then we can compute iv0->base - diff, and compare it with
iv1->base. */
mbzl = fold_build2 (MINUS_EXPR, type, iv0->base, diff);
mbzr = iv1->base;
}
else
{
diff = fold_build2 (PLUS_EXPR, type,
iv1->step, build_int_cst_type (type, 1));
if (!POINTER_TYPE_P (type))
{
bound = fold_build2 (PLUS_EXPR, type,
TYPE_MAX_VALUE (type), diff);
assumption = fold_build2 (LE_EXPR, boolean_type_node,
iv1->base, bound);
}
mbzl = iv0->base;
mbzr = fold_build2 (MINUS_EXPR, type, iv1->base, diff);
}
mbz = fold_build2 (GT_EXPR, boolean_type_node, mbzl, mbzr);
if (!nonzero_p (assumption))
niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
niter->assumptions, assumption);
if (!zero_p (mbz))
niter->may_be_zero = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
niter->may_be_zero, mbz);
}
/* Determines number of iterations of loop whose ending condition
is IV0 < IV1. TYPE is the type of the iv. The number of
iterations is stored to NITER. */
static bool
number_of_iterations_lt (tree type, affine_iv *iv0, affine_iv *iv1,
struct tree_niter_desc *niter,
bool never_infinite ATTRIBUTE_UNUSED)
{
tree niter_type = unsigned_type_for (type);
tree delta, step, s;
delta = fold_build2 (MINUS_EXPR, niter_type,
fold_convert (niter_type, iv1->base),
fold_convert (niter_type, iv0->base));
/* First handle the special case that the step is +-1. */
if ((iv0->step && integer_onep (iv0->step)
&& zero_p (iv1->step))
|| (iv1->step && integer_all_onesp (iv1->step)
&& zero_p (iv0->step)))
{
/* for (i = iv0->base; i < iv1->base; i++)
or
for (i = iv1->base; i > iv0->base; i--).
In both cases # of iterations is iv1->base - iv0->base, assuming that
iv1->base >= iv0->base. */
niter->may_be_zero = fold_build2 (LT_EXPR, boolean_type_node,
iv1->base, iv0->base);
niter->niter = delta;
return true;
}
if (nonzero_p (iv0->step))
step = fold_convert (niter_type, iv0->step);
else
step = fold_convert (niter_type,
fold_build1 (NEGATE_EXPR, type, iv1->step));
/* If we can determine the final value of the control iv exactly, we can
transform the condition to != comparison. In particular, this will be
the case if DELTA is constant. */
if (number_of_iterations_lt_to_ne (type, iv0, iv1, niter, &delta, step))
{
affine_iv zps;
zps.base = build_int_cst_type (niter_type, 0);
zps.step = step;
/* number_of_iterations_lt_to_ne will add assumptions that ensure that
zps does not overflow. */
zps.no_overflow = true;
return number_of_iterations_ne (type, &zps, delta, niter, true);
}
/* Make sure that the control iv does not overflow. */
if (!assert_no_overflow_lt (type, iv0, iv1, niter, step))
return false;
/* We determine the number of iterations as (delta + step - 1) / step. For
this to work, we must know that iv1->base >= iv0->base - step + 1,
otherwise the loop does not roll. */
assert_loop_rolls_lt (type, iv0, iv1, niter);
s = fold_build2 (MINUS_EXPR, niter_type,
step, build_int_cst_type (niter_type, 1));
delta = fold_build2 (PLUS_EXPR, niter_type, delta, s);
niter->niter = fold_build2 (FLOOR_DIV_EXPR, niter_type, delta, step);
return true;
}
/* Determines number of iterations of loop whose ending condition
is IV0 <= IV1. TYPE is the type of the iv. The number of
iterations is stored to NITER. NEVER_INFINITE is true if
we know that the loop cannot be infinite (we derived this
earlier, and possibly set NITER->assumptions to make sure this
is the case. */
static bool
number_of_iterations_le (tree type, affine_iv *iv0, affine_iv *iv1,
struct tree_niter_desc *niter, bool never_infinite)
{
tree assumption;
/* Say that IV0 is the control variable. Then IV0 <= IV1 iff
IV0 < IV1 + 1, assuming that IV1 is not equal to the greatest
value of the type. This we must know anyway, since if it is
equal to this value, the loop rolls forever. */
if (!never_infinite)
{
if (nonzero_p (iv0->step))
assumption = fold_build2 (NE_EXPR, boolean_type_node,
iv1->base, TYPE_MAX_VALUE (type));
else
assumption = fold_build2 (NE_EXPR, boolean_type_node,
iv0->base, TYPE_MIN_VALUE (type));
if (zero_p (assumption))
return false;
if (!nonzero_p (assumption))
niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
niter->assumptions, assumption);
}
if (nonzero_p (iv0->step))
iv1->base = fold_build2 (PLUS_EXPR, type,
iv1->base, build_int_cst_type (type, 1));
else
iv0->base = fold_build2 (MINUS_EXPR, type,
iv0->base, build_int_cst_type (type, 1));
return number_of_iterations_lt (type, iv0, iv1, niter, never_infinite);
}
/* Determine the number of iterations according to condition (for staying
inside loop) which compares two induction variables using comparison
operator CODE. The induction variable on left side of the comparison
@ -135,38 +524,45 @@ inverse (tree x, tree mask)
The results (number of iterations and assumptions as described in
comments at struct tree_niter_desc in tree-flow.h) are stored to NITER.
In case we are unable to determine number of iterations, contents of
this structure is unchanged. */
Returns false if it fails to determine number of iterations, true if it
was determined (possibly with some assumptions). */
static void
static bool
number_of_iterations_cond (tree type, affine_iv *iv0, enum tree_code code,
affine_iv *iv1, struct tree_niter_desc *niter)
{
tree step, delta, mmin, mmax;
tree may_xform, bound, s, d, tmp;
bool was_sharp = false, never_infinite;
tree assumption;
tree assumptions = boolean_true_node;
tree noloop_assumptions = boolean_false_node;
tree niter_type, signed_niter_type;
tree bits;
bool never_infinite;
/* The meaning of these assumptions is this:
if !assumptions
then the rest of information does not have to be valid
if noloop_assumptions then the loop does not have to roll
(but it is only conservative approximation, i.e. it only says that
if !noloop_assumptions, then the loop does not end before the computed
number of iterations) */
if may_be_zero then the loop does not roll, even if
niter != 0. */
niter->assumptions = boolean_true_node;
niter->may_be_zero = boolean_false_node;
niter->niter = NULL_TREE;
niter->additional_info = boolean_true_node;
/* Make < comparison from > ones. */
if (code == GE_EXPR
|| code == GT_EXPR)
/* Make < comparison from > ones, and for NE_EXPR comparisons, ensure that
the control variable is on lhs. */
if (code == GE_EXPR || code == GT_EXPR
|| (code == NE_EXPR && zero_p (iv0->step)))
{
SWAP (iv0, iv1);
code = swap_tree_comparison (code);
}
if (POINTER_TYPE_P (type))
{
/* Comparison of pointers is undefined unless both iv0 and iv1 point
to the same object. If they do, the control variable cannot wrap
(as wrap around the bounds of memory will never return a pointer
that would be guaranteed to point to the same object, even if we
avoid undefined behavior by casting to size_t and back). */
iv0->no_overflow = true;
iv1->no_overflow = true;
}
/* If the control induction variable does not overflow, the loop obviously
cannot be infinite. */
if (!zero_p (iv0->step) && iv0->no_overflow)
@ -182,7 +578,7 @@ number_of_iterations_cond (tree type, affine_iv *iv0, enum tree_code code,
if (!zero_p (iv0->step) && !zero_p (iv1->step))
{
if (code != NE_EXPR)
return;
return false;
iv0->step = fold_binary_to_constant (MINUS_EXPR, type,
iv0->step, iv1->step);
@ -191,425 +587,43 @@ number_of_iterations_cond (tree type, affine_iv *iv0, enum tree_code code,
iv1->no_overflow = true;
}
/* If the result is a constant, the loop is weird. More precise handling
would be possible, but the situation is not common enough to waste time
on it. */
/* If the result of the comparison is a constant, the loop is weird. More
precise handling would be possible, but the situation is not common enough
to waste time on it. */
if (zero_p (iv0->step) && zero_p (iv1->step))
return;
return false;
/* Ignore loops of while (i-- < 10) type. */
if (code != NE_EXPR)
{
if (iv0->step && tree_int_cst_sign_bit (iv0->step))
return;
return false;
if (!zero_p (iv1->step) && !tree_int_cst_sign_bit (iv1->step))
return;
return false;
}
if (POINTER_TYPE_P (type))
/* If the loop exits immediatelly, there is nothing to do. */
if (zero_p (fold_build2 (code, boolean_type_node, iv0->base, iv1->base)))
{
/* We assume pointer arithmetic never overflows. */
mmin = mmax = NULL_TREE;
}
else
{
mmin = TYPE_MIN_VALUE (type);
mmax = TYPE_MAX_VALUE (type);
}
/* Some more condition normalization. We must record some assumptions
due to overflows. */
if (code == LT_EXPR)
{
/* We want to take care only of <=; this is easy,
as in cases the overflow would make the transformation unsafe the loop
does not roll. Seemingly it would make more sense to want to take
care of <, as NE is more similar to it, but the problem is that here
the transformation would be more difficult due to possibly infinite
loops. */
if (zero_p (iv0->step))
{
if (mmax)
assumption = fold_build2 (EQ_EXPR, boolean_type_node,
iv0->base, mmax);
else
assumption = boolean_false_node;
if (nonzero_p (assumption))
goto zero_iter;
iv0->base = fold_build2 (PLUS_EXPR, type, iv0->base,
build_int_cst_type (type, 1));
}
else
{
if (mmin)
assumption = fold_build2 (EQ_EXPR, boolean_type_node,
iv1->base, mmin);
else
assumption = boolean_false_node;
if (nonzero_p (assumption))
goto zero_iter;
iv1->base = fold_build2 (MINUS_EXPR, type, iv1->base,
build_int_cst_type (type, 1));
}
noloop_assumptions = assumption;
code = LE_EXPR;
/* It will be useful to be able to tell the difference once more in
<= -> != reduction. */
was_sharp = true;
}
/* Take care of trivially infinite loops. */
if (code != NE_EXPR)
{
if (zero_p (iv0->step)
&& mmin
&& operand_equal_p (iv0->base, mmin, 0))
return;
if (zero_p (iv1->step)
&& mmax
&& operand_equal_p (iv1->base, mmax, 0))
return;
}
/* If we can we want to take care of NE conditions instead of size
comparisons, as they are much more friendly (most importantly
this takes care of special handling of loops with step 1). We can
do it if we first check that upper bound is greater or equal to
lower bound, their difference is constant c modulo step and that
there is not an overflow. */
if (code != NE_EXPR)
{
if (zero_p (iv0->step))
step = fold_unary_to_constant (NEGATE_EXPR, type, iv1->step);
else
step = iv0->step;
delta = fold_build2 (MINUS_EXPR, type, iv1->base, iv0->base);
delta = fold_build2 (FLOOR_MOD_EXPR, type, delta, step);
may_xform = boolean_false_node;
if (TREE_CODE (delta) == INTEGER_CST)
{
tmp = fold_binary_to_constant (MINUS_EXPR, type, step,
build_int_cst_type (type, 1));
if (was_sharp
&& operand_equal_p (delta, tmp, 0))
{
/* A special case. We have transformed condition of type
for (i = 0; i < 4; i += 4)
into
for (i = 0; i <= 3; i += 4)
obviously if the test for overflow during that transformation
passed, we cannot overflow here. Most importantly any
loop with sharp end condition and step 1 falls into this
category, so handling this case specially is definitely
worth the troubles. */
may_xform = boolean_true_node;
}
else if (zero_p (iv0->step))
{
if (!mmin || iv1->no_overflow)
may_xform = boolean_true_node;
else
{
bound = fold_binary_to_constant (PLUS_EXPR, type,
mmin, step);
bound = fold_binary_to_constant (MINUS_EXPR, type,
bound, delta);
may_xform = fold_build2 (LE_EXPR, boolean_type_node,
bound, iv0->base);
}
}
else
{
if (!mmax || iv0->no_overflow)
may_xform = boolean_true_node;
else
{
bound = fold_binary_to_constant (MINUS_EXPR, type,
mmax, step);
bound = fold_binary_to_constant (PLUS_EXPR, type,
bound, delta);
may_xform = fold_build2 (LE_EXPR, boolean_type_node,
iv1->base, bound);
}
}
}
if (!zero_p (may_xform))
{
/* We perform the transformation always provided that it is not
completely senseless. This is OK, as we would need this assumption
to determine the number of iterations anyway. */
if (!nonzero_p (may_xform))
assumptions = may_xform;
if (zero_p (iv0->step))
{
iv0->base = fold_build2 (PLUS_EXPR, type, iv0->base, delta);
iv0->base = fold_build2 (MINUS_EXPR, type, iv0->base, step);
}
else
{
iv1->base = fold_build2 (MINUS_EXPR, type, iv1->base, delta);
iv1->base = fold_build2 (PLUS_EXPR, type, iv1->base, step);
}
assumption = fold_build2 (GT_EXPR, boolean_type_node,
iv0->base, iv1->base);
noloop_assumptions = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
noloop_assumptions, assumption);
code = NE_EXPR;
}
}
/* Count the number of iterations. */
niter_type = unsigned_type_for (type);
signed_niter_type = signed_type_for (type);
if (code == NE_EXPR)
{
/* Everything we do here is just arithmetics modulo size of mode. This
makes us able to do more involved computations of number of iterations
than in other cases. First transform the condition into shape
s * i <> c, with s positive. */
iv1->base = fold_build2 (MINUS_EXPR, type, iv1->base, iv0->base);
iv0->base = NULL_TREE;
if (!zero_p (iv1->step))
iv0->step = fold_unary_to_constant (NEGATE_EXPR, type, iv1->step);
iv1->step = NULL_TREE;
if (tree_int_cst_sign_bit (fold_convert (signed_niter_type, iv0->step)))
{
iv0->step = fold_unary_to_constant (NEGATE_EXPR, type, iv0->step);
iv1->base = fold_build1 (NEGATE_EXPR, type, iv1->base);
}
iv1->base = fold_convert (niter_type, iv1->base);
iv0->step = fold_convert (niter_type, iv0->step);
/* Let nsd (step, size of mode) = d. If d does not divide c, the loop
is infinite. Otherwise, the number of iterations is
(inverse(s/d) * (c/d)) mod (size of mode/d). */
bits = num_ending_zeros (iv0->step);
d = fold_binary_to_constant (LSHIFT_EXPR, niter_type,
build_int_cst_type (niter_type, 1), bits);
s = fold_binary_to_constant (RSHIFT_EXPR, niter_type, iv0->step, bits);
bound = build_low_bits_mask (niter_type,
(TYPE_PRECISION (niter_type)
- tree_low_cst (bits, 1)));
if (!never_infinite)
{
/* If we cannot assume that the loop is not infinite, record the
assumptions for divisibility of c. */
assumption = fold_build2 (FLOOR_MOD_EXPR, niter_type, iv1->base, d);
assumption = fold_build2 (EQ_EXPR, boolean_type_node,
assumption,
build_int_cst (niter_type, 0));
assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
assumptions, assumption);
}
tmp = fold_build2 (EXACT_DIV_EXPR, niter_type, iv1->base, d);
tmp = fold_build2 (MULT_EXPR, niter_type, tmp, inverse (s, bound));
niter->niter = fold_build2 (BIT_AND_EXPR, niter_type, tmp, bound);
}
else
{
if (zero_p (iv1->step))
/* Condition in shape a + s * i <= b
We must know that b + s does not overflow and a <= b + s and then we
can compute number of iterations as (b + s - a) / s. (It might
seem that we in fact could be more clever about testing the b + s
overflow condition using some information about b - a mod s,
but it was already taken into account during LE -> NE transform). */
{
if (mmax && !iv0->no_overflow)
{
bound = fold_binary_to_constant (MINUS_EXPR, type,
mmax, iv0->step);
assumption = fold_build2 (LE_EXPR, boolean_type_node,
iv1->base, bound);
assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
assumptions, assumption);
}
step = iv0->step;
tmp = fold_build2 (PLUS_EXPR, type, iv1->base, iv0->step);
assumption = fold_build2 (GT_EXPR, boolean_type_node,
iv0->base, tmp);
delta = fold_build2 (PLUS_EXPR, type, iv1->base, step);
delta = fold_build2 (MINUS_EXPR, type, delta, iv0->base);
delta = fold_convert (niter_type, delta);
}
else
{
/* Condition in shape a <= b - s * i
We must know that a - s does not overflow and a - s <= b and then
we can again compute number of iterations as (b - (a - s)) / s. */
if (mmin && !iv1->no_overflow)
{
bound = fold_binary_to_constant (MINUS_EXPR, type,
mmin, iv1->step);
assumption = fold_build2 (LE_EXPR, boolean_type_node,
bound, iv0->base);
assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
assumptions, assumption);
}
step = fold_build1 (NEGATE_EXPR, type, iv1->step);
tmp = fold_build2 (PLUS_EXPR, type, iv0->base, iv1->step);
assumption = fold_build2 (GT_EXPR, boolean_type_node, tmp, iv1->base);
delta = fold_build2 (MINUS_EXPR, type, iv0->base, step);
delta = fold_build2 (MINUS_EXPR, type, iv1->base, delta);
delta = fold_convert (niter_type, delta);
}
noloop_assumptions = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
noloop_assumptions, assumption);
delta = fold_build2 (FLOOR_DIV_EXPR, niter_type, delta,
fold_convert (niter_type, step));
niter->niter = delta;
}
niter->assumptions = assumptions;
niter->may_be_zero = noloop_assumptions;
return;
zero_iter:
niter->assumptions = boolean_true_node;
niter->may_be_zero = boolean_true_node;
niter->niter = build_int_cst_type (type, 0);
return;
}
/* Similar to number_of_iterations_cond, but only handles the special
case of loops with step 1 or -1. The meaning of the arguments
is the same as in number_of_iterations_cond. The function
returns true if the special case was recognized, false otherwise. */
static bool
number_of_iterations_special (tree type, affine_iv *iv0, enum tree_code code,
affine_iv *iv1, struct tree_niter_desc *niter)
{
tree niter_type = unsigned_type_for (type), mmax, mmin;
/* Make < comparison from > ones. */
if (code == GE_EXPR
|| code == GT_EXPR)
{
SWAP (iv0, iv1);
code = swap_tree_comparison (code);
niter->niter = build_int_cst_type (unsigned_type_for (type), 0);
return true;
}
/* OK, now we know we have a senseful loop. Handle several cases, depending
on what comparison operator is used. */
switch (code)
{
case NE_EXPR:
if (zero_p (iv0->step))
{
if (zero_p (iv1->step))
return false;
SWAP (iv0, iv1);
}
else if (!zero_p (iv1->step))
return false;
if (integer_onep (iv0->step))
{
/* for (i = iv0->base; i != iv1->base; i++) */
niter->assumptions = boolean_true_node;
niter->may_be_zero = boolean_false_node;
niter->niter = fold_build2 (MINUS_EXPR, type, iv1->base, iv0->base);
niter->additional_info = boolean_true_node;
}
else if (integer_all_onesp (iv0->step))
{
/* for (i = iv0->base; i != iv1->base; i--) */
niter->assumptions = boolean_true_node;
niter->may_be_zero = boolean_false_node;
niter->niter = fold_build2 (MINUS_EXPR, type, iv0->base, iv1->base);
}
else
return false;
break;
gcc_assert (zero_p (iv1->step));
return number_of_iterations_ne (type, iv0, iv1->base, niter, never_infinite);
case LT_EXPR:
if ((iv0->step && integer_onep (iv0->step)
&& zero_p (iv1->step))
|| (iv1->step && integer_all_onesp (iv1->step)
&& zero_p (iv0->step)))
{
/* for (i = iv0->base; i < iv1->base; i++)
or
for (i = iv1->base; i > iv0->base; i--).
In both cases # of iterations is iv1->base - iv0->base. */
niter->assumptions = boolean_true_node;
niter->may_be_zero = fold_build2 (GT_EXPR, boolean_type_node,
iv0->base, iv1->base);
niter->niter = fold_build2 (MINUS_EXPR, type, iv1->base, iv0->base);
}
else
return false;
break;
return number_of_iterations_lt (type, iv0, iv1, niter, never_infinite);
case LE_EXPR:
if (POINTER_TYPE_P (type))
{
/* We assume pointer arithmetic never overflows. */
mmin = mmax = NULL_TREE;
}
else
{
mmin = TYPE_MIN_VALUE (type);
mmax = TYPE_MAX_VALUE (type);
}
if (iv0->step && integer_onep (iv0->step)
&& zero_p (iv1->step))
{
/* for (i = iv0->base; i <= iv1->base; i++) */
if (mmax && !iv0->no_overflow)
niter->assumptions = fold_build2 (NE_EXPR, boolean_type_node,
iv1->base, mmax);
else
niter->assumptions = boolean_true_node;
iv1->base = fold_build2 (PLUS_EXPR, type, iv1->base,
build_int_cst_type (type, 1));
}
else if (iv1->step && integer_all_onesp (iv1->step)
&& zero_p (iv0->step))
{
/* for (i = iv1->base; i >= iv0->base; i--) */
if (mmin && !iv1->no_overflow)
niter->assumptions = fold_build2 (NE_EXPR, boolean_type_node,
iv0->base, mmin);
else
niter->assumptions = boolean_true_node;
iv0->base = fold_build2 (MINUS_EXPR, type, iv0->base,
build_int_cst_type (type, 1));
}
else
return false;
niter->may_be_zero = fold_build2 (GT_EXPR, boolean_type_node,
iv0->base, iv1->base);
niter->niter = fold_build2 (MINUS_EXPR, type, iv1->base, iv0->base);
break;
return number_of_iterations_le (type, iv0, iv1, niter, never_infinite);
default:
gcc_unreachable ();
}
niter->niter = fold_convert (niter_type, niter->niter);
niter->additional_info = boolean_true_node;
return true;
}
/* Substitute NEW for OLD in EXPR and fold the result. */
@ -987,18 +1001,10 @@ number_of_iterations_exit (struct loop *loop, edge exit,
if (!simple_iv (loop, stmt, op1, &iv1, false))
return false;
niter->niter = NULL_TREE;
/* Handle common special cases first, so that we do not need to use
generic (and slow) analysis very often. */
if (!number_of_iterations_special (type, &iv0, code, &iv1, niter))
{
number_of_iterations_cond (type, &iv0, code, &iv1, niter);
if (!niter->niter)
return false;
}
iv0.base = expand_simple_operations (iv0.base);
iv1.base = expand_simple_operations (iv1.base);
if (!number_of_iterations_cond (type, &iv0, code, &iv1, niter))
return false;
if (optimize >= 3)
{

2
gcc/tree.c
View File

@ -6809,6 +6809,8 @@ tree_fold_gcd (tree a, tree b)
tree
unsigned_type_for (tree type)
{
if (POINTER_TYPE_P (type))
return size_type_node;
return lang_hooks.types.unsigned_type (type);
}