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re PR tree-optimization/27144 (segfault with -O2 on x86_64 (and powerpc64)) 

PR tree-optimization/27144
	* tree-ssa-loop-niter.c (derive_constant_upper_bound): New function.
	(record_estimate): Only record constant upper bound.
	(infer_loop_bounds_from_undefined): Call
	compute_estimated_nb_iterations just once.
	(proved_non_wrapping_p): Renamed to ...
	(n_of_executions_at_most): ... this.  Expect bound to be a constant.
	(convert_step_widening, scev_probably_wraps_p): Call
	n_of_executions_at_most instead of proved_non_wrapping_p.
	(substitute_in_loop_info): Do not replace values in bounds.
	* cfgloop.h (struct nb_iter_bound): Remove "additional" field.  Update
	comments.

	* gcc.dg/tree-ssa/loop-16.c: New test.

From-SVN: r113425
This commit is contained in:
Zdenek Dvorak 2006-05-01 21:42:01 +02:00 committed by Zdenek Dvorak
parent 2a83cc5254
commit 763f45275b
5 changed files with 101 additions and 77 deletions
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15
gcc/ChangeLog
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@ -1,3 +1,18 @@
2006-05-01 Zdenek Dvorak <dvorakz@suse.cz>
PR tree-optimization/27144
* tree-ssa-loop-niter.c (derive_constant_upper_bound): New function.
(record_estimate): Only record constant upper bound.
(infer_loop_bounds_from_undefined): Call
compute_estimated_nb_iterations just once.
(proved_non_wrapping_p): Renamed to ...
(n_of_executions_at_most): ... this. Expect bound to be a constant.
(convert_step_widening, scev_probably_wraps_p): Call
n_of_executions_at_most instead of proved_non_wrapping_p.
(substitute_in_loop_info): Do not replace values in bounds.
* cfgloop.h (struct nb_iter_bound): Remove "additional" field. Update
comments.
2006-05-01 Richard Henderson <rth@redhat.com>
PR c/27358

10
gcc/cfgloop.h
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@ -47,12 +47,10 @@ struct lpt_decision
struct nb_iter_bound
{
tree bound; /* The expression whose value is an upper bound on the
number of executions of anything after ... */
tree at_stmt; /* ... this statement during one execution of loop. */
tree additional; /* A conjunction of conditions the operands of BOUND
satisfy. The additional information about the value
of the bound may be derived from it. */
tree bound; /* The constant expression whose value is an upper
bound on the number of executions of ... */
tree at_stmt; /* ... this statement during one execution of
a loop. */
struct nb_iter_bound *next;
/* The next bound in a list. */
};

4
gcc/testsuite/ChangeLog
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@ -1,3 +1,7 @@
2006-05-01 Zdenek Dvorak <dvorakz@suse.cz>
* gcc.dg/tree-ssa/loop-16.c: New test.
2006-05-01 Roger Sayle <roger@eyesopen.com>
Joseph S. Myers <joseph@codesourcery.com>

24
gcc/testsuite/gcc.dg/tree-ssa/loop-16.c Normal file
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@ -0,0 +1,24 @@
/* A test for # of iterations estimation. We know that the loop is executed
at most 100 times, thus the (32-bit) induction variables do not overflow,
and we may use 64-bit variable to represent them. */
/* { dg-options "-O2 -fdump-tree-optimized" } */
/* { dg-do compile { target x86_64-*-* } } */
unsigned a[100];
void foo(unsigned n)
{
unsigned i;
for (i = 0; i < n; i++)
a[i] = 4 * i;
}
/* Check that the memory reference was replaced with MEM, and that there is no
multiplication. */
/* { dg-final { scan-tree-dump-times "MEM" 1 "optimized" } } */
/* { dg-final { scan-tree-dump-times "\[^\\n\\r\]*= \\* " 0 "optimized" } } */
/* { dg-final { cleanup-tree-dump "optimized" } } */

125
gcc/tree-ssa-loop-niter.c
View File

@ -1464,6 +1464,24 @@ find_loop_niter_by_eval (struct loop *loop, edge *exit)
*/
/* Returns a constant upper bound on the value of expression VAL. The
condition ADDITIONAL must be satisfied (for example, if VAL is
"(unsigned) n" and ADDITIONAL is "n > 0", then we can derive that
VAL is at most (unsigned) MAX_INT).
TODO -- actually do something nontrivial here. */
static tree
derive_constant_upper_bound (tree val, tree additional ATTRIBUTE_UNUSED)
{
tree type = TREE_TYPE (val);
tree unsigned_type = unsigned_type_for (type);
if (TREE_CODE (val) != INTEGER_CST)
val = upper_bound_in_type (type, type);
return fold_convert (unsigned_type, val);
}
/* Records that AT_STMT is executed at most BOUND times in LOOP. The
additional condition ADDITIONAL is recorded with the bound. */
@ -1471,6 +1489,7 @@ void
record_estimate (struct loop *loop, tree bound, tree additional, tree at_stmt)
{
struct nb_iter_bound *elt = xmalloc (sizeof (struct nb_iter_bound));
tree c_bound = derive_constant_upper_bound (bound, additional);
if (dump_file && (dump_flags & TDF_DETAILS))
{
@ -1478,12 +1497,13 @@ record_estimate (struct loop *loop, tree bound, tree additional, tree at_stmt)
print_generic_expr (dump_file, at_stmt, TDF_SLIM);
fprintf (dump_file, " are executed at most ");
print_generic_expr (dump_file, bound, TDF_SLIM);
fprintf (dump_file, " times in loop %d.\n", loop->num);
fprintf (dump_file, " (bounded by ");
print_generic_expr (dump_file, c_bound, TDF_SLIM);
fprintf (dump_file, ") times in loop %d.\n", loop->num);
}
elt->bound = bound;
elt->bound = c_bound;
elt->at_stmt = at_stmt;
elt->additional = additional;
elt->next = loop->bounds;
loop->bounds = elt;
}
@ -1497,12 +1517,16 @@ compute_estimated_nb_iterations (struct loop *loop)
struct nb_iter_bound *bound;
for (bound = loop->bounds; bound; bound = bound->next)
if (TREE_CODE (bound->bound) == INTEGER_CST
/* Update only when there is no previous estimation. */
&& (chrec_contains_undetermined (loop->estimated_nb_iterations)
/* Or when the current estimation is smaller. */
|| tree_int_cst_lt (bound->bound, loop->estimated_nb_iterations)))
loop->estimated_nb_iterations = bound->bound;
{
if (TREE_CODE (bound->bound) != INTEGER_CST)
continue;
/* Update only when there is no previous estimation, or when the current
estimation is smaller. */
if (chrec_contains_undetermined (loop->estimated_nb_iterations)
|| tree_int_cst_lt (bound->bound, loop->estimated_nb_iterations))
loop->estimated_nb_iterations = bound->bound;
}
}
/* The following analyzers are extracting informations on the bounds
@ -1611,11 +1635,9 @@ infer_loop_bounds_from_undefined (struct loop *loop)
break;
}
}
if (chrec_contains_undetermined (loop->estimated_nb_iterations))
compute_estimated_nb_iterations (loop);
}
compute_estimated_nb_iterations (loop);
free (bbs);
}
@ -1729,73 +1751,41 @@ stmt_dominates_stmt_p (tree s1, tree s2)
return dominated_by_p (CDI_DOMINATORS, bb2, bb1);
}
/* Return true when it is possible to prove that the induction
variable does not wrap: vary outside the type specified bounds.
Checks whether BOUND < VALID_NITER that means in the context of iv
conversion that all the iterations in the loop are safe: not
producing wraps.
The statement NITER_BOUND->AT_STMT is executed at most
NITER_BOUND->BOUND times in the loop.
NITER_BOUND->ADDITIONAL is the additional condition recorded for
operands of the bound. This is useful in the following case,
created by loop header copying:
i = 0;
if (n > 0)
do
{
something;
} while (++i < n)
If the n > 0 condition is taken into account, the number of iterations of the
loop can be expressed as n - 1. If the type of n is signed, the ADDITIONAL
assumption "n > 0" says us that the value of the number of iterations is at
most MAX_TYPE - 1 (without this assumption, it might overflow). */
/* Returns true when we can prove that the number of executions of
STMT in the loop is at most NITER, according to the fact
that the statement NITER_BOUND->at_stmt is executed at most
NITER_BOUND->bound times. */
static bool
proved_non_wrapping_p (tree at_stmt,
struct nb_iter_bound *niter_bound,
tree new_type,
tree valid_niter)
n_of_executions_at_least (tree stmt,
struct nb_iter_bound *niter_bound,
tree niter)
{
tree cond;
tree bound = niter_bound->bound;
tree bound_type = TREE_TYPE (bound);
tree nit_type = TREE_TYPE (niter);
enum tree_code cmp;
if (TYPE_PRECISION (new_type) > TYPE_PRECISION (TREE_TYPE (bound)))
bound = fold_convert (unsigned_type_for (new_type), bound);
gcc_assert (TYPE_UNSIGNED (bound_type)
&& TYPE_UNSIGNED (nit_type)
&& is_gimple_min_invariant (bound));
if (TYPE_PRECISION (nit_type) > TYPE_PRECISION (bound_type))
bound = fold_convert (nit_type, bound);
else
valid_niter = fold_convert (TREE_TYPE (bound), valid_niter);
/* Give up if BOUND was not folded to an INTEGER_CST, as in PR23434. */
if (TREE_CODE (bound) != INTEGER_CST)
return false;
niter = fold_convert (bound_type, niter);
/* After the statement niter_bound->at_stmt we know that anything is
executed at most BOUND times. */
if (at_stmt && stmt_dominates_stmt_p (niter_bound->at_stmt, at_stmt))
if (stmt && stmt_dominates_stmt_p (niter_bound->at_stmt, stmt))
cmp = GE_EXPR;
/* Before the statement niter_bound->at_stmt we know that anything
is executed at most BOUND + 1 times. */
else
cmp = GT_EXPR;
cond = fold_binary (cmp, boolean_type_node, valid_niter, bound);
if (nonzero_p (cond))
return true;
cond = build2 (cmp, boolean_type_node, valid_niter, bound);
/* Try taking additional conditions into account. */
cond = fold_binary (TRUTH_OR_EXPR, boolean_type_node,
invert_truthvalue (niter_bound->additional),
cond);
if (nonzero_p (cond))
return true;
return false;
cond = fold_binary (cmp, boolean_type_node, niter, bound);
return nonzero_p (cond);
}
/* Checks whether it is correct to count the induction variable BASE +
@ -1873,7 +1863,7 @@ convert_step_widening (struct loop *loop, tree new_type, tree base, tree step,
estimate_numbers_of_iterations_loop (loop);
for (bound = loop->bounds; bound; bound = bound->next)
if (proved_non_wrapping_p (at_stmt, bound, new_type, valid_niter))
if (n_of_executions_at_least (at_stmt, bound, valid_niter))
return step_in_new_type;
/* Fail when the loop has no bound estimations, or when no bound can
@ -2077,7 +2067,7 @@ scev_probably_wraps_p (tree type, tree base, tree step,
estimate_numbers_of_iterations_loop (loop);
for (bound = loop->bounds; bound; bound = bound->next)
if (proved_non_wrapping_p (at_stmt, bound, type, valid_niter))
if (n_of_executions_at_least (at_stmt, bound, valid_niter))
return false;
/* At this point we still don't have a proof that the iv does not
@ -2162,14 +2152,7 @@ free_numbers_of_iterations_estimates (struct loops *loops)
void
substitute_in_loop_info (struct loop *loop, tree name, tree val)
{
struct nb_iter_bound *bound;
loop->nb_iterations = simplify_replace_tree (loop->nb_iterations, name, val);
loop->estimated_nb_iterations
= simplify_replace_tree (loop->estimated_nb_iterations, name, val);
for (bound = loop->bounds; bound; bound = bound->next)
{
bound->bound = simplify_replace_tree (bound->bound, name, val);
bound->additional = simplify_replace_tree (bound->additional, name, val);
}
}