return rslt;
}
-/* 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
- has base BASE0 and step STEP0. the right-hand side one has base
- BASE1 and step STEP1. Both induction variables must have type TYPE,
- which must be an integer or pointer type. STEP0 and STEP1 must be
- constants (or NULL_TREE, which is interpreted as constant zero).
-
- 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. */
+/* 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 exit must be taken eventually, i.e., that the IV
+ ever reaches the value FINAL (we derived this earlier, and possibly set
+ NITER->assumptions to make sure this is the case). */
-static void
-number_of_iterations_cond (tree type, tree base0, tree step0,
- enum tree_code code, tree base1, tree step1,
- struct tree_niter_desc *niter)
+static bool
+number_of_iterations_ne (tree type, affine_iv *iv, tree final,
+ struct tree_niter_desc *niter, bool never_infinite)
{
- tree step, delta, mmin, mmax;
- tree may_xform, bound, s, d, tmp;
- bool was_sharp = false;
- tree assumption;
- tree assumptions = boolean_true_node;
- tree noloop_assumptions = boolean_false_node;
- tree niter_type, signed_niter_type;
- tree bits;
+ tree niter_type = unsigned_type_for (type);
+ tree s, c, d, bits, assumption, tmp, bound;
- /* 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) */
-
- /* Make < comparison from > ones. */
- if (code == GE_EXPR
- || code == GT_EXPR)
+ niter->control = *iv;
+ niter->bound = final;
+ niter->cmp = NE_EXPR;
+
+ /* 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))
{
- SWAP (base0, base1);
- SWAP (step0, step1);
- code = swap_tree_comparison (code);
+ 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));
}
-
- /* We can handle the case when neither of the sides of the comparison is
- invariant, provided that the test is NE_EXPR. This rarely occurs in
- practice, but it is simple enough to manage. */
- if (!zero_p (step0) && !zero_p (step1))
+ else
{
- if (code != NE_EXPR)
- return;
+ 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));
+ }
- step0 = fold_binary_to_constant (MINUS_EXPR, type, step0, step1);
- step1 = NULL_TREE;
+ /* First the trivial cases -- when the step is 1. */
+ if (integer_onep (s))
+ {
+ niter->niter = c;
+ return 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 (zero_p (step0) && zero_p (step1))
- return;
+ /* 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)));
- /* Ignore loops of while (i-- < 10) type. */
- if (code != NE_EXPR)
- {
- if (step0 && tree_int_cst_sign_bit (step0))
- return;
+ 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 (!zero_p (step1) && !tree_int_cst_sign_bit (step1))
- return;
+ 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;
+}
- if (POINTER_TYPE_P (type))
+/* 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))
{
- /* We assume pointer arithmetic never overflows. */
- mmin = mmax = NULL_TREE;
+ /* 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
{
- mmin = TYPE_MIN_VALUE (type);
- mmax = TYPE_MAX_VALUE (type);
+ /* 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);
}
- /* Some more condition normalization. We must record some assumptions
- due to overflows. */
+ 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 (code == LT_EXPR)
+ if (nonzero_p (iv0->step))
{
- /* 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 (step0))
+ /* 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)
{
- if (mmax)
- assumption = fold_build2 (EQ_EXPR, boolean_type_node, base0, mmax);
- else
- assumption = boolean_false_node;
- if (nonzero_p (assumption))
- goto zero_iter;
- base0 = fold_build2 (PLUS_EXPR, type, base0,
- build_int_cst_type (type, 1));
+ 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)
{
- if (mmin)
- assumption = fold_build2 (EQ_EXPR, boolean_type_node, base1, mmin);
- else
- assumption = boolean_false_node;
- if (nonzero_p (assumption))
- goto zero_iter;
- base1 = fold_build2 (MINUS_EXPR, type, base1,
- build_int_cst_type (type, 1));
+ 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);
}
- noloop_assumptions = assumption;
- code = LE_EXPR;
-
- /* It will be useful to be able to tell the difference once more in
- <= -> != reduction. */
- was_sharp = true;
+ 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);
}
- /* Take care of trivially infinite loops. */
- if (code != NE_EXPR)
- {
- if (zero_p (step0)
- && mmin
- && operand_equal_p (base0, mmin, 0))
- return;
- if (zero_p (step1)
- && mmax
- && operand_equal_p (base1, mmax, 0))
- return;
- }
+ 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;
+}
- /* 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)
+/* 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))
{
- if (zero_p (step0))
- step = fold_unary_to_constant (NEGATE_EXPR, type, step1);
- else
- step = step0;
- delta = fold_build2 (MINUS_EXPR, type, base1, base0);
- delta = fold_build2 (FLOOR_MOD_EXPR, type, delta, step);
- may_xform = boolean_false_node;
+ diff = fold_build2 (MINUS_EXPR, type,
+ iv0->step, build_int_cst_type (type, 1));
- if (TREE_CODE (delta) == INTEGER_CST)
+ /* 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))
{
- 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 (step0))
- {
- if (!mmin)
- 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, base0);
- }
- }
- else
- {
- if (!mmax)
- 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,
- base1, bound);
- }
- }
+ bound = fold_build2 (PLUS_EXPR, type,
+ TYPE_MIN_VALUE (type), diff);
+ assumption = fold_build2 (GE_EXPR, boolean_type_node,
+ iv0->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 (step0))
- {
- base0 = fold_build2 (PLUS_EXPR, type, base0, delta);
- base0 = fold_build2 (MINUS_EXPR, type, base0, step);
- }
- else
- {
- base1 = fold_build2 (MINUS_EXPR, type, base1, delta);
- base1 = fold_build2 (PLUS_EXPR, type, base1, step);
- }
+ /* 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));
- assumption = fold_build2 (GT_EXPR, boolean_type_node, base0, base1);
- noloop_assumptions = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
- noloop_assumptions, assumption);
- code = NE_EXPR;
+ 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);
}
- /* Count the number of iterations. */
- niter_type = unsigned_type_for (type);
- signed_niter_type = signed_type_for (type);
+ mbz = fold_build2 (GT_EXPR, boolean_type_node, mbzl, mbzr);
- if (code == NE_EXPR)
+ 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;
+
+ if (nonzero_p (iv0->step))
{
- /* 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. */
- base1 = fold_build2 (MINUS_EXPR, type, base1, base0);
- base0 = NULL_TREE;
- if (!zero_p (step1))
- step0 = fold_unary_to_constant (NEGATE_EXPR, type, step1);
- step1 = NULL_TREE;
- if (tree_int_cst_sign_bit (fold_convert (signed_niter_type, step0)))
- {
- step0 = fold_unary_to_constant (NEGATE_EXPR, type, step0);
- base1 = fold_build1 (NEGATE_EXPR, type, base1);
- }
+ niter->control = *iv0;
+ niter->cmp = LT_EXPR;
+ niter->bound = iv1->base;
+ }
+ else
+ {
+ niter->control = *iv1;
+ niter->cmp = GT_EXPR;
+ niter->bound = iv0->base;
+ }
- base1 = fold_convert (niter_type, base1);
- step0 = fold_convert (niter_type, step0);
+ delta = fold_build2 (MINUS_EXPR, niter_type,
+ fold_convert (niter_type, iv1->base),
+ fold_convert (niter_type, iv0->base));
- /* 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 (step0);
- 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, step0, bits);
+ /* 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++)
- bound = build_low_bits_mask (niter_type,
- (TYPE_PRECISION (niter_type)
- - tree_low_cst (bits, 1)));
+ or
- assumption = fold_build2 (FLOOR_MOD_EXPR, niter_type, base1, 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, base1, d);
- tmp = fold_build2 (MULT_EXPR, niter_type, tmp, inverse (s, bound));
- niter->niter = fold_build2 (BIT_AND_EXPR, niter_type, tmp, bound);
+ 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))
{
- if (zero_p (step1))
- /* 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)
- {
- bound = fold_binary_to_constant (MINUS_EXPR, type, mmax, step0);
- assumption = fold_build2 (LE_EXPR, boolean_type_node,
- base1, bound);
- assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
- assumptions, assumption);
- }
+ affine_iv zps;
- step = step0;
- tmp = fold_build2 (PLUS_EXPR, type, base1, step0);
- assumption = fold_build2 (GT_EXPR, boolean_type_node, base0, tmp);
- delta = fold_build2 (PLUS_EXPR, type, base1, step);
- delta = fold_build2 (MINUS_EXPR, type, delta, base0);
- 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)
- {
- bound = fold_binary_to_constant (MINUS_EXPR, type, mmin, step1);
- assumption = fold_build2 (LE_EXPR, boolean_type_node,
- bound, base0);
- assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
- assumptions, assumption);
- }
- step = fold_build1 (NEGATE_EXPR, type, step1);
- tmp = fold_build2 (PLUS_EXPR, type, base0, step1);
- assumption = fold_build2 (GT_EXPR, boolean_type_node, tmp, base1);
- delta = fold_build2 (MINUS_EXPR, type, base0, step);
- delta = fold_build2 (MINUS_EXPR, type, base1, 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;
+ 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);
}
- niter->assumptions = assumptions;
- niter->may_be_zero = noloop_assumptions;
- return;
+ /* 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);
-zero_iter:
- niter->assumptions = boolean_true_node;
- niter->may_be_zero = boolean_true_node;
- niter->niter = build_int_cst_type (type, 0);
- return;
+ 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 this condition must eventually become false (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. */
-/* 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. */
+ 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
+ is IV0, the right-hand side is IV1. Both induction variables must have
+ type TYPE, which must be an integer or pointer type. The steps of the
+ ivs must be constants (or NULL_TREE, which is interpreted as constant zero).
+
+ ONLY_EXIT is true if we are sure this is the only way the loop could be
+ exited (including possibly non-returning function calls, exceptions, etc.)
+ -- in this case we can use the information whether the control induction
+ variables can overflow or not in a more efficient way.
+
+ The results (number of iterations and assumptions as described in
+ comments at struct tree_niter_desc in tree-flow.h) are stored to NITER.
+ Returns false if it fails to determine number of iterations, true if it
+ was determined (possibly with some assumptions). */
static bool
-number_of_iterations_special (tree type, tree base0, tree step0,
- enum tree_code code, tree base1, tree step1,
- struct tree_niter_desc *niter)
+number_of_iterations_cond (tree type, affine_iv *iv0, enum tree_code code,
+ affine_iv *iv1, struct tree_niter_desc *niter,
+ bool only_exit)
{
- tree niter_type = unsigned_type_for (type), mmax, mmin;
+ bool never_infinite;
- /* Make < comparison from > ones. */
- if (code == GE_EXPR
- || code == GT_EXPR)
+ /* The meaning of these assumptions is this:
+ if !assumptions
+ then the rest of information does not have to be valid
+ 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;
+
+ niter->bound = NULL_TREE;
+ niter->cmp = ERROR_MARK;
+
+ /* 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 (base0, base1);
- SWAP (step0, step1);
+ SWAP (iv0, iv1);
code = swap_tree_comparison (code);
}
- switch (code)
+ if (!only_exit)
{
- case NE_EXPR:
- if (zero_p (step0))
- {
- if (zero_p (step1))
- return false;
- SWAP (base0, base1);
- SWAP (step0, step1);
- }
- else if (!zero_p (step1))
- return false;
+ /* If this is not the only possible exit from the loop, the information
+ that the induction variables cannot overflow as derived from
+ signedness analysis cannot be relied upon. We use them e.g. in the
+ following way: given loop for (i = 0; i <= n; i++), if i is
+ signed, it cannot overflow, thus this loop is equivalent to
+ for (i = 0; i < n + 1; i++); however, if n == MAX, but the loop
+ is exited in some other way before i overflows, this transformation
+ is incorrect (the new loop exits immediately). */
+ iv0->no_overflow = false;
+ iv1->no_overflow = false;
+ }
- if (integer_onep (step0))
- {
- /* for (i = base0; i != base1; i++) */
- niter->assumptions = boolean_true_node;
- niter->may_be_zero = boolean_false_node;
- niter->niter = fold_build2 (MINUS_EXPR, type, base1, base0);
- niter->additional_info = boolean_true_node;
- }
- else if (integer_all_onesp (step0))
- {
- /* for (i = base0; i != base1; i--) */
- niter->assumptions = boolean_true_node;
- niter->may_be_zero = boolean_false_node;
- niter->niter = fold_build2 (MINUS_EXPR, type, base0, base1);
- }
- else
- return false;
+ 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). The
+ restrictions on pointer arithmetics and comparisons of pointers
+ ensure that using the no-overflow assumptions is correct in this
+ case even if ONLY_EXIT is false. */
+ iv0->no_overflow = true;
+ iv1->no_overflow = true;
+ }
- break;
+ /* If the control induction variable does not overflow, the loop obviously
+ cannot be infinite. */
+ if (!zero_p (iv0->step) && iv0->no_overflow)
+ never_infinite = true;
+ else if (!zero_p (iv1->step) && iv1->no_overflow)
+ never_infinite = true;
+ else
+ never_infinite = false;
- case LT_EXPR:
- if ((step0 && integer_onep (step0) && zero_p (step1))
- || (step1 && integer_all_onesp (step1) && zero_p (step0)))
- {
- /* for (i = base0; i < base1; i++)
-
- or
+ /* We can handle the case when neither of the sides of the comparison is
+ invariant, provided that the test is NE_EXPR. This rarely occurs in
+ practice, but it is simple enough to manage. */
+ if (!zero_p (iv0->step) && !zero_p (iv1->step))
+ {
+ if (code != NE_EXPR)
+ return false;
- for (i = base1; i > base0; i--).
-
- In both cases # of iterations is base1 - base0. */
+ iv0->step = fold_binary_to_constant (MINUS_EXPR, type,
+ iv0->step, iv1->step);
+ iv0->no_overflow = false;
+ iv1->step = NULL_TREE;
+ iv1->no_overflow = true;
+ }
- niter->assumptions = boolean_true_node;
- niter->may_be_zero = fold_build2 (GT_EXPR, boolean_type_node,
- base0, base1);
- niter->niter = fold_build2 (MINUS_EXPR, type, base1, base0);
- }
- else
- return false;
- break;
+ /* 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 false;
- 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);
- }
+ /* Ignore loops of while (i-- < 10) type. */
+ if (code != NE_EXPR)
+ {
+ if (iv0->step && tree_int_cst_sign_bit (iv0->step))
+ return false;
- if (step0 && integer_onep (step0) && zero_p (step1))
- {
- /* for (i = base0; i <= base1; i++) */
- if (mmax)
- niter->assumptions = fold_build2 (NE_EXPR, boolean_type_node,
- base1, mmax);
- else
- niter->assumptions = boolean_true_node;
- base1 = fold_build2 (PLUS_EXPR, type, base1,
- build_int_cst_type (type, 1));
- }
- else if (step1 && integer_all_onesp (step1) && zero_p (step0))
- {
- /* for (i = base1; i >= base0; i--) */
- if (mmin)
- niter->assumptions = fold_build2 (NE_EXPR, boolean_type_node,
- base0, mmin);
- else
- niter->assumptions = boolean_true_node;
- base0 = fold_build2 (MINUS_EXPR, type, base0,
- build_int_cst_type (type, 1));
- }
- else
+ if (!zero_p (iv1->step) && !tree_int_cst_sign_bit (iv1->step))
return false;
+ }
- niter->may_be_zero = fold_build2 (GT_EXPR, boolean_type_node,
- base0, base1);
- niter->niter = fold_build2 (MINUS_EXPR, type, base1, base0);
- break;
+ /* If the loop exits immediately, there is nothing to do. */
+ if (zero_p (fold_build2 (code, boolean_type_node, iv0->base, iv1->base)))
+ {
+ 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:
+ gcc_assert (zero_p (iv1->step));
+ return number_of_iterations_ne (type, iv0, iv1->base, niter, never_infinite);
+ case LT_EXPR:
+ return number_of_iterations_lt (type, iv0, iv1, niter, never_infinite);
+ case LE_EXPR:
+ 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. */
{
unsigned i, n;
tree ret = NULL_TREE, e, ee, stmt;
- enum tree_code code = TREE_CODE (expr);
+ enum tree_code code;
+
+ if (expr == NULL_TREE)
+ return expr;
if (is_gimple_min_invariant (expr))
return expr;
+ code = TREE_CODE (expr);
if (IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (code)))
{
n = TREE_CODE_LENGTH (code);
return expr;
}
+/* Returns true if EXIT is the only possible exit from LOOP. */
+
+static bool
+loop_only_exit_p (struct loop *loop, edge exit)
+{
+ basic_block *body;
+ block_stmt_iterator bsi;
+ unsigned i;
+ tree call;
+
+ if (exit != loop->single_exit)
+ return false;
+
+ body = get_loop_body (loop);
+ for (i = 0; i < loop->num_nodes; i++)
+ {
+ for (bsi = bsi_start (body[0]); !bsi_end_p (bsi); bsi_next (&bsi))
+ {
+ call = get_call_expr_in (bsi_stmt (bsi));
+ if (call && TREE_SIDE_EFFECTS (call))
+ {
+ free (body);
+ return false;
+ }
+ }
+ }
+
+ free (body);
+ return true;
+}
+
/* Stores description of number of iterations of LOOP derived from
EXIT (an exit edge of the LOOP) in NITER. Returns true if some
useful information could be derived (and fields of NITER has
bool warn)
{
tree stmt, cond, type;
- tree op0, base0, step0;
- tree op1, base1, step1;
+ tree op0, op1;
enum tree_code code;
+ affine_iv iv0, iv1;
if (!dominated_by_p (CDI_DOMINATORS, loop->latch, exit->src))
return false;
&& !POINTER_TYPE_P (type))
return false;
- if (!simple_iv (loop, stmt, op0, &base0, &step0, false))
+ if (!simple_iv (loop, stmt, op0, &iv0, false))
return false;
- if (!simple_iv (loop, stmt, op1, &base1, &step1, false))
+ 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, base0, step0, code, base1, step1,
- niter))
- {
-
- number_of_iterations_cond (type, base0, step0, code, base1, step1,
- 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,
+ loop_only_exit_p (loop, exit)))
+ return false;
if (optimize >= 3)
{
/* We can provide a more specific warning if one of the operator is
constant and the other advances by +1 or -1. */
- if (step1 ? !step0 && (integer_onep (step1) || integer_all_onesp (step1))
- : step0 && (integer_onep (step0) || integer_all_onesp (step0)))
+ if (!zero_p (iv1.step)
+ ? (zero_p (iv0.step)
+ && (integer_onep (iv1.step) || integer_all_onesp (iv1.step)))
+ : (iv0.step
+ && (integer_onep (iv0.step) || integer_all_onesp (iv0.step))))
wording =
flag_unsafe_loop_optimizations
? N_("assuming that the loop is not infinite")
/* For each array access, analyze its access function
and record a bound on the loop iteration domain. */
- if (TREE_CODE (op1) == ARRAY_REF)
- analyze_array (stmt, op1, true);
+ if (TREE_CODE (op1) == ARRAY_REF
+ && !array_ref_contains_indirect_ref (op1))
+ estimate_iters_using_array (stmt, op1);
- if (TREE_CODE (op0) == ARRAY_REF)
- analyze_array (stmt, op0, false);
+ if (TREE_CODE (op0) == ARRAY_REF
+ && !array_ref_contains_indirect_ref (op0))
+ estimate_iters_using_array (stmt, op0);
/* For each signed type variable in LOOP, analyze its
scalar evolution and record a bound of the loop
diff = fold_build2 (MINUS_EXPR, utype,
TYPE_MAX_VALUE (type), init);
- estimation = fold_build2 (CEIL_DIV_EXPR, utype, diff,
- step);
- record_estimate (loop, estimation, boolean_true_node, stmt);
+ if (!integer_zerop (step))
+ {
+ estimation = fold_build2 (CEIL_DIV_EXPR, utype, diff,
+ step);
+ record_estimate (loop, estimation, boolean_true_node,
+ stmt);
+ }
}
break;
for (args = TREE_OPERAND (stmt, 1); args;
args = TREE_CHAIN (args))
- if (TREE_CODE (TREE_VALUE (args)) == ARRAY_REF)
- analyze_array (stmt, TREE_VALUE (args), true);
+ if (TREE_CODE (TREE_VALUE (args)) == ARRAY_REF
+ && !array_ref_contains_indirect_ref (TREE_VALUE (args)))
+ estimate_iters_using_array (stmt, TREE_VALUE (args));
break;
}
struct nb_iter_bound *bound;
tree delta, step_abs;
tree unsigned_type, valid_niter;
- tree base_plus_step;
+ tree base_plus_step, bpsps;
+ int cps, cpsps;
/* FIXME: The following code will not be used anymore once
http://gcc.gnu.org/ml/gcc-patches/2005-06/msg02025.html is
}
}
- if (TREE_CODE (base) == REAL_CST
+ if (chrec_contains_undetermined (base)
+ || chrec_contains_undetermined (step)
+ || TREE_CODE (base) == REAL_CST
|| TREE_CODE (step) == REAL_CST)
{
*unknown_max = true;
*unknown_max = false;
base_plus_step = fold_build2 (PLUS_EXPR, type, base, step);
- switch (compare_trees (base_plus_step, base))
+ bpsps = fold_build2 (PLUS_EXPR, type, base_plus_step, step);
+ cps = compare_trees (base_plus_step, base);
+ cpsps = compare_trees (bpsps, base_plus_step);
+
+ /* Check that the sequence is not wrapping in the first step: it
+ should have the same monotonicity for the first two steps. See
+ PR23410. */
+ if (cps != cpsps)
+ return true;
+
+ switch (cps)
{
case -1:
{
convert_step (struct loop *loop, tree new_type, tree base, tree step,
tree at_stmt)
{
- tree base_type = TREE_TYPE (base);
+ tree res, base_type;
+
+ if (chrec_contains_undetermined (base)
+ || chrec_contains_undetermined (step))
+ return NULL_TREE;
+
+ base_type = TREE_TYPE (base);
/* When not using wrapping arithmetic, signed types don't wrap. */
if (!flag_wrapv && !TYPE_UNSIGNED (base_type))
- return fold_convert (new_type, step);
+ goto do_convert_step;
if (TYPE_PRECISION (new_type) > TYPE_PRECISION (base_type))
return convert_step_widening (loop, new_type, base, step, at_stmt);
- return fold_convert (new_type, step);
+ do_convert_step:
+
+ res = fold_convert (new_type, step);
+
+ if (TREE_CODE (res) == INTEGER_CST)
+ {
+ TREE_OVERFLOW (res) = 0;
+ TREE_CONSTANT_OVERFLOW (res) = 0;
+ }
+
+ return res;
}
/* Frees the information on upper bounds on numbers of iterations of LOOP. */
-static void
+void
free_numbers_of_iterations_estimates_loop (struct loop *loop)
{
struct nb_iter_bound *bound, *next;
-
+
+ loop->nb_iterations = NULL;
+ loop->estimated_nb_iterations = NULL;
for (bound = loop->bounds; bound; bound = next)
{
next = bound->next;
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