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re PR tree-optimization/55079 (false positive -Warray-bounds (also seen at -O3 bootstrap))

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PR middle-end/55079
	* tree-ssa-loop-niter.c (number_of_iterations_exit): Update
	MAX field if NITER was folded to contant.
	(record_estimate): Sanity check.
	* tree-ssa-loop-ivcanon.c (remove_exits_and_undefined_stmts): New
	function.
	(remove_redundant_iv_test): New function.
	(loops_to_unloop, loops_to_unloop_nunroll): New static vars.
	(unloop_loops): Break out from ...
	(try_unroll_loop_completely): ... here; Pass in MAXITER; use
	remove_exits_and_undefined_stmts; do not unloop.
	(canonicalize_loop_induction_variables): Compute MAXITER;
	use remove_redundant_iv_test; remove loop_close_ssa_invalidated
	and irred_invalidated arguments.
	(canonicalize_induction_variables): Compute fresh bound estimates;
	unloop; walk from innermost.
	(tree_unroll_loops_completely): Likewise.

	* gcc.dg/tree-ssa/cunroll-10.c: New testcase.
	* gcc.dg/tree-ssa/cunroll-9.c: New testcase.

From-SVN: r193098
This commit is contained in:
Jan Hubicka 2012-11-02 17:34:52 +01:00 • committed by Jan Hubicka
parent 7ee840b6bf
commit f2a1b46987
6 changed files with 286 additions and 70 deletions
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20
gcc/ChangeLog
View file

@ -1,3 +1,23 @@
2012-11-02 Jan Hubicka <jh@suse.cz>
PR middle-end/55079
* tree-ssa-loop-niter.c (number_of_iterations_exit): Update
MAX field if NITER was folded to contant.
(record_estimate): Sanity check.
* tree-ssa-loop-ivcanon.c (remove_exits_and_undefined_stmts): New
function.
(remove_redundant_iv_test): New function.
(loops_to_unloop, loops_to_unloop_nunroll): New static vars.
(unloop_loops): Break out from ...
(try_unroll_loop_completely): ... here; Pass in MAXITER; use
remove_exits_and_undefined_stmts; do not unloop.
(canonicalize_loop_induction_variables): Compute MAXITER;
use remove_redundant_iv_test; remove loop_close_ssa_invalidated
and irred_invalidated arguments.
(canonicalize_induction_variables): Compute fresh bound estimates;
unloop; walk from innermost.
(tree_unroll_loops_completely): Likewise.
2012-11-02 Vladimir Makarov <vmakarov@redhat.com>
PR middle-end/55130

5
gcc/testsuite/ChangeLog
View file

@ -1,3 +1,8 @@
2012-11-02 Jan Hubicka <jh@suse.cz>
* gcc.dg/tree-ssa/cunroll-10.c: New testcase.
* gcc.dg/tree-ssa/cunroll-9.c: New testcase.
2012-11-02 Vladimir Makarov <vmakarov@redhat.com>
PR middle-end/55130

13
gcc/testsuite/gcc.dg/tree-ssa/cunroll-10.c Normal file
View file

@ -0,0 +1,13 @@
/* { dg-do compile } */
/* { dg-options "-O3 -Warray-bounds -fdump-tree-cunroll-details" } */
int a[3];
int b[4];
main()
{
int i;
for (i=0;i<4;i++)
if (b[i]==2)
a[i]++;
}
/* { dg-final { scan-tree-dump-times "Forced statement unreachable" 2 "cunroll" } } */
/* { dg-final { cleanup-tree-dump "cunroll" } } */

22
gcc/testsuite/gcc.dg/tree-ssa/cunroll-9.c Normal file
View file

@ -0,0 +1,22 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-cunrolli" } */
void abort (void);
int a[10];
int b[11];
t (int n)
{
int i;
int sum = 0;
for (i = 0; i < n; i++)
{
if (i > 1000)
abort ();
if (q ())
sum += a[i];
else
sum += b[i];
}
return sum;
}
/* { dg-final { scan-tree-dump-times 1 "Removed pointless exit:" "cunroli" } } */
/* { dg-final { cleanup-tree-dump "cunroli" } } */

290
gcc/tree-ssa-loop-ivcanon.c
View file

@ -389,33 +389,192 @@ loop_edge_to_cancel (struct loop *loop)
return NULL;
}
/* Tries to unroll LOOP completely, i.e. NITER times.
UL determines which loops we are allowed to unroll.
EXIT is the exit of the loop that should be eliminated.
/* Remove all tests for exits that are known to be taken after LOOP was
peeled NPEELED times. Put gcc_unreachable before every statement
known to not be executed. */
static bool
remove_exits_and_undefined_stmts (struct loop *loop, unsigned int npeeled)
{
struct nb_iter_bound *elt;
bool changed = false;
for (elt = loop->bounds; elt; elt = elt->next)
{
/* If statement is known to be undefined after peeling, turn it
into unreachable (or trap when debugging experience is supposed
to be good). */
if (!elt->is_exit
&& elt->bound.ult (double_int::from_uhwi (npeeled)))
{
gimple_stmt_iterator gsi = gsi_for_stmt (elt->stmt);
gimple stmt = gimple_build_call
(builtin_decl_implicit (BUILT_IN_UNREACHABLE), 0);
gimple_set_location (stmt, gimple_location (elt->stmt));
gsi_insert_before (&gsi, stmt, GSI_NEW_STMT);
changed = true;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Forced statement unreachable: ");
print_gimple_stmt (dump_file, elt->stmt, 0, 0);
}
}
/* If we know the exit will be taken after peeling, update. */
else if (elt->is_exit
&& elt->bound.ule (double_int::from_uhwi (npeeled)))
{
basic_block bb = gimple_bb (elt->stmt);
edge exit_edge = EDGE_SUCC (bb, 0);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Forced exit to be taken: ");
print_gimple_stmt (dump_file, elt->stmt, 0, 0);
}
if (!loop_exit_edge_p (loop, exit_edge))
exit_edge = EDGE_SUCC (bb, 1);
gcc_checking_assert (loop_exit_edge_p (loop, exit_edge));
if (exit_edge->flags & EDGE_TRUE_VALUE)
gimple_cond_make_true (elt->stmt);
else
gimple_cond_make_false (elt->stmt);
update_stmt (elt->stmt);
changed = true;
}
}
return changed;
}
/* Remove all exits that are known to be never taken because of the loop bound
discovered. */
static bool
remove_redundant_iv_tests (struct loop *loop)
{
struct nb_iter_bound *elt;
bool changed = false;
if (!loop->any_upper_bound)
return false;
for (elt = loop->bounds; elt; elt = elt->next)
{
/* Exit is pointless if it won't be taken before loop reaches
upper bound. */
if (elt->is_exit && loop->any_upper_bound
&& loop->nb_iterations_upper_bound.ult (elt->bound))
{
basic_block bb = gimple_bb (elt->stmt);
edge exit_edge = EDGE_SUCC (bb, 0);
struct tree_niter_desc niter;
if (!loop_exit_edge_p (loop, exit_edge))
exit_edge = EDGE_SUCC (bb, 1);
/* Only when we know the actual number of iterations, not
just a bound, we can remove the exit. */
if (!number_of_iterations_exit (loop, exit_edge,
&niter, false, false))
gcc_unreachable ();
if (!integer_onep (niter.assumptions)
|| !integer_zerop (niter.may_be_zero)
|| !niter.niter
|| TREE_CODE (niter.niter) != INTEGER_CST
|| !loop->nb_iterations_upper_bound.ult
(tree_to_double_int (niter.niter)))
continue;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Removed pointless exit: ");
print_gimple_stmt (dump_file, elt->stmt, 0, 0);
}
if (exit_edge->flags & EDGE_TRUE_VALUE)
gimple_cond_make_false (elt->stmt);
else
gimple_cond_make_true (elt->stmt);
update_stmt (elt->stmt);
changed = true;
}
}
return changed;
}
/* Stores loops that will be unlooped after we process whole loop tree. */
static VEC(loop_p, heap) *loops_to_unloop;
static VEC(int, heap) *loops_to_unloop_nunroll;
/* Cancel all fully unrolled loops by putting __builtin_unreachable
on the latch edge.
We do it after all unrolling since unlooping moves basic blocks
across loop boundaries trashing loop closed SSA form as well
as SCEV info needed to be intact during unrolling.
IRRED_INVALIDATED is used to bookkeep if information about
irreducible regions may become invalid as a result
of the transformation.
LOOP_CLOSED_SSA_INVALIDATED is used to bookkepp the case
when we need to go into loop closed SSA form. */
void
unloop_loops (bitmap loop_closed_ssa_invalidated,
bool *irred_invalidated)
{
while (VEC_length (loop_p, loops_to_unloop))
{
struct loop *loop = VEC_pop (loop_p, loops_to_unloop);
int n_unroll = VEC_pop (int, loops_to_unloop_nunroll);
basic_block latch = loop->latch;
edge latch_edge = loop_latch_edge (loop);
int flags = latch_edge->flags;
location_t locus = latch_edge->goto_locus;
gimple stmt;
gimple_stmt_iterator gsi;
remove_exits_and_undefined_stmts (loop, n_unroll);
/* Unloop destroys the latch edge. */
unloop (loop, irred_invalidated, loop_closed_ssa_invalidated);
/* Create new basic block for the latch edge destination and wire
it in. */
stmt = gimple_build_call (builtin_decl_implicit (BUILT_IN_UNREACHABLE), 0);
latch_edge = make_edge (latch, create_basic_block (NULL, NULL, latch), flags);
latch_edge->probability = 0;
latch_edge->count = 0;
latch_edge->flags |= flags;
latch_edge->goto_locus = locus;
latch_edge->dest->loop_father = current_loops->tree_root;
latch_edge->dest->count = 0;
latch_edge->dest->frequency = 0;
set_immediate_dominator (CDI_DOMINATORS, latch_edge->dest, latch_edge->src);
gsi = gsi_start_bb (latch_edge->dest);
gsi_insert_after (&gsi, stmt, GSI_NEW_STMT);
}
VEC_free (loop_p, heap, loops_to_unloop);
loops_to_unloop = NULL;
VEC_free (int, heap, loops_to_unloop_nunroll);
loops_to_unloop_nunroll = NULL;
}
/* Tries to unroll LOOP completely, i.e. NITER times.
UL determines which loops we are allowed to unroll.
EXIT is the exit of the loop that should be eliminated.
MAXITER specfy bound on number of iterations, -1 if it is
not known or too large for HOST_WIDE_INT. */
static bool
try_unroll_loop_completely (struct loop *loop,
edge exit, tree niter,
enum unroll_level ul,
bool *irred_invalidated,
bitmap loop_closed_ssa_invalidated)
HOST_WIDE_INT maxiter)
{
unsigned HOST_WIDE_INT n_unroll, ninsns, max_unroll, unr_insns;
gimple cond;
struct loop_size size;
bool n_unroll_found = false;
HOST_WIDE_INT maxiter;
basic_block latch;
edge latch_edge;
location_t locus;
int flags;
gimple stmt;
gimple_stmt_iterator gsi;
edge edge_to_cancel = NULL;
int num = loop->num;
@ -445,7 +604,6 @@ try_unroll_loop_completely (struct loop *loop,
exit = NULL;
/* See if we can improve our estimate by using recorded loop bounds. */
maxiter = max_loop_iterations_int (loop);
if (maxiter >= 0
&& (!n_unroll_found || (unsigned HOST_WIDE_INT)maxiter < n_unroll))
{
@ -545,6 +703,7 @@ try_unroll_loop_completely (struct loop *loop,
free_original_copy_tables ();
}
/* Remove the conditional from the last copy of the loop. */
if (edge_to_cancel)
{
@ -557,37 +716,10 @@ try_unroll_loop_completely (struct loop *loop,
/* Do not remove the path. Doing so may remove outer loop
and confuse bookkeeping code in tree_unroll_loops_completelly. */
}
/* We did not manage to cancel the loop.
The loop latch remains reachable even if it will never be reached
at runtime. We must redirect it to somewhere, so create basic
block containg __builtin_unreachable call for this reason. */
else
{
latch = loop->latch;
latch_edge = loop_latch_edge (loop);
flags = latch_edge->flags;
locus = latch_edge->goto_locus;
/* Unloop destroys the latch edge. */
unloop (loop, irred_invalidated, loop_closed_ssa_invalidated);
/* Create new basic block for the latch edge destination and wire
it in. */
stmt = gimple_build_call (builtin_decl_implicit (BUILT_IN_UNREACHABLE), 0);
latch_edge = make_edge (latch, create_basic_block (NULL, NULL, latch), flags);
latch_edge->probability = 0;
latch_edge->count = 0;
latch_edge->flags |= flags;
latch_edge->goto_locus = locus;
latch_edge->dest->loop_father = current_loops->tree_root;
latch_edge->dest->count = 0;
latch_edge->dest->frequency = 0;
set_immediate_dominator (CDI_DOMINATORS, latch_edge->dest, latch_edge->src);
gsi = gsi_start_bb (latch_edge->dest);
gsi_insert_after (&gsi, stmt, GSI_NEW_STMT);
}
/* Store the loop for later unlooping and exit removal. */
VEC_safe_push (loop_p, heap, loops_to_unloop, loop);
VEC_safe_push (int, heap, loops_to_unloop_nunroll, n_unroll);
if (dump_file && (dump_flags & TDF_DETAILS))
{
@ -614,19 +746,17 @@ try_unroll_loop_completely (struct loop *loop,
CREATE_IV is true if we may create a new iv. UL determines
which loops we are allowed to completely unroll. If TRY_EVAL is true, we try
to determine the number of iterations of a loop by direct evaluation.
Returns true if cfg is changed.
IRRED_INVALIDATED is used to keep if irreducible reginos needs to be recomputed. */
Returns true if cfg is changed. */
static bool
canonicalize_loop_induction_variables (struct loop *loop,
bool create_iv, enum unroll_level ul,
bool try_eval,
bool *irred_invalidated,
bitmap loop_closed_ssa_invalidated)
bool try_eval)
{
edge exit = NULL;
tree niter;
HOST_WIDE_INT maxiter;
bool modified = false;
niter = number_of_latch_executions (loop);
if (TREE_CODE (niter) == INTEGER_CST)
@ -657,6 +787,9 @@ canonicalize_loop_induction_variables (struct loop *loop,
if (niter && TREE_CODE (niter) == INTEGER_CST)
record_niter_bound (loop, tree_to_double_int (niter), false, true);
/* Force re-computation of loop bounds so we can remove redundant exits. */
maxiter = max_loop_iterations_int (loop);
if (dump_file && (dump_flags & TDF_DETAILS)
&& TREE_CODE (niter) == INTEGER_CST)
{
@ -665,21 +798,25 @@ canonicalize_loop_induction_variables (struct loop *loop,
fprintf (dump_file, " times.\n");
}
if (dump_file && (dump_flags & TDF_DETAILS)
&& max_loop_iterations_int (loop) >= 0)
&& maxiter >= 0)
{
fprintf (dump_file, "Loop %d iterates at most %i times.\n", loop->num,
(int)max_loop_iterations_int (loop));
(int)maxiter);
}
if (try_unroll_loop_completely (loop, exit, niter, ul, irred_invalidated,
loop_closed_ssa_invalidated))
/* Remove exits that are known to be never taken based on loop bound.
Needs to be called after compilation of max_loop_iterations_int that
populates the loop bounds. */
modified |= remove_redundant_iv_tests (loop);
if (try_unroll_loop_completely (loop, exit, niter, ul, maxiter))
return true;
if (create_iv
&& niter && !chrec_contains_undetermined (niter))
create_canonical_iv (loop, exit, niter);
return false;
return modified;
}
/* The main entry point of the pass. Adds canonical induction variables
@ -694,16 +831,18 @@ canonicalize_induction_variables (void)
bool irred_invalidated = false;
bitmap loop_closed_ssa_invalidated = BITMAP_ALLOC (NULL);
FOR_EACH_LOOP (li, loop, 0)
free_numbers_of_iterations_estimates ();
estimate_numbers_of_iterations ();
FOR_EACH_LOOP (li, loop, LI_FROM_INNERMOST)
{
changed |= canonicalize_loop_induction_variables (loop,
true, UL_SINGLE_ITER,
true,
&irred_invalidated,
loop_closed_ssa_invalidated);
true);
}
gcc_assert (!need_ssa_update_p (cfun));
unloop_loops (loop_closed_ssa_invalidated, &irred_invalidated);
if (irred_invalidated
&& loops_state_satisfies_p (LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS))
mark_irreducible_loops ();
@ -822,7 +961,10 @@ tree_unroll_loops_completely (bool may_increase_size, bool unroll_outer)
if (loops_state_satisfies_p (LOOP_CLOSED_SSA))
loop_closed_ssa_invalidated = BITMAP_ALLOC (NULL);
FOR_EACH_LOOP (li, loop, 0)
free_numbers_of_iterations_estimates ();
estimate_numbers_of_iterations ();
FOR_EACH_LOOP (li, loop, LI_FROM_INNERMOST)
{
struct loop *loop_father = loop_outer (loop);
@ -835,8 +977,7 @@ tree_unroll_loops_completely (bool may_increase_size, bool unroll_outer)
ul = UL_NO_GROWTH;
if (canonicalize_loop_induction_variables
(loop, false, ul, !flag_tree_loop_ivcanon,
&irred_invalidated, loop_closed_ssa_invalidated))
(loop, false, ul, !flag_tree_loop_ivcanon))
{
changed = true;
/* If we'll continue unrolling, we need to propagate constants
@ -856,8 +997,16 @@ tree_unroll_loops_completely (bool may_increase_size, bool unroll_outer)
struct loop **iter;
unsigned i;
/* We can not use TODO_update_ssa_no_phi because VOPS gets confused. */
/* Be sure to skip unlooped loops while procesing father_stack
array. */
FOR_EACH_VEC_ELT (loop_p, loops_to_unloop, i, iter)
(*iter)->aux = NULL;
FOR_EACH_VEC_ELT (loop_p, father_stack, i, iter)
if (!(*iter)->aux)
*iter = NULL;
unloop_loops (loop_closed_ssa_invalidated, &irred_invalidated);
/* We can not use TODO_update_ssa_no_phi because VOPS gets confused. */
if (loop_closed_ssa_invalidated
&& !bitmap_empty_p (loop_closed_ssa_invalidated))
rewrite_into_loop_closed_ssa (loop_closed_ssa_invalidated,
@ -867,14 +1016,15 @@ tree_unroll_loops_completely (bool may_increase_size, bool unroll_outer)
/* Propagate the constants within the new basic blocks. */
FOR_EACH_VEC_ELT (loop_p, father_stack, i, iter)
{
unsigned j;
basic_block *body = get_loop_body_in_dom_order (*iter);
for (j = 0; j < (*iter)->num_nodes; j++)
propagate_constants_for_unrolling (body[j]);
free (body);
(*iter)->aux = NULL;
}
if (*iter)
{
unsigned j;
basic_block *body = get_loop_body_in_dom_order (*iter);
for (j = 0; j < (*iter)->num_nodes; j++)
propagate_constants_for_unrolling (body[j]);
free (body);
(*iter)->aux = NULL;
}
VEC_truncate (loop_p, father_stack, 0);
/* This will take care of removing completely unrolled loops

6
gcc/tree-ssa-loop-niter.c
View file

@ -1880,6 +1880,10 @@ number_of_iterations_exit (struct loop *loop, edge exit,
fold_undefer_and_ignore_overflow_warnings ();
/* If NITER has simplified into a constant, update MAX. */
if (TREE_CODE (niter->niter) == INTEGER_CST)
niter->max = tree_to_double_int (niter->niter);
if (integer_onep (niter->assumptions))
return true;
@ -2556,6 +2560,8 @@ record_estimate (struct loop *loop, tree bound, double_int i_bound,
real number of iterations. */
if (TREE_CODE (bound) != INTEGER_CST)
realistic = false;
else
gcc_checking_assert (i_bound == tree_to_double_int (bound));
if (!upper && !realistic)
return;