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[PING][PATCH][PR65443] Add transform_to_exit_first_loop_alt
- From: Tom de Vries <Tom_deVries at mentor dot com>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Cc: Richard Biener <rguenther at suse dot de>, Jakub Jelinek <jakub at redhat dot com>
- Date: Wed, 15 Apr 2015 15:38:53 +0200
- Subject: [PING][PATCH][PR65443] Add transform_to_exit_first_loop_alt
- Authentication-results: sourceware.org; auth=none
- References: <551564D0 dot 2090308 at mentor dot com> <551E8A1F dot 5050908 at mentor dot com>
On 03-04-15 14:39, Tom de Vries wrote:
On 27-03-15 15:10, Tom de Vries wrote:
Hi,
this patch fixes PR65443, a todo in the parloops pass for function
transform_to_exit_first_loop:
...
TODO: the common case is that latch of the loop is empty and immediately
follows the loop exit. In this case, it would be better not to copy the
body of the loop, but only move the entry of the loop directly before the
exit check and increase the number of iterations of the loop by one.
This may need some additional preconditioning in case NIT = ~0.
...
The current implementation of transform_to_exit_first_loop transforms the loop
by moving and duplicating the loop body. This patch transforms the loop into the
same normal form, but without the duplication, if that's possible (determined by
try_transform_to_exit_first_loop_alt).
The actual transformation, done by transform_to_exit_first_loop_alt transforms
this loop:
...
bb preheader:
...
goto <bb header>
<bb header>:
...
if (ivtmp < n)
goto <bb latch>;
else
goto <bb exit>;
<bb latch>:
ivtmp = ivtmp + inc;
goto <bb header>
...
into this one:
...
bb preheader:
...
goto <bb newheader>
<bb header>:
...
goto <bb latch>;
<bb newheader>:
if (ivtmp < n + 1)
goto <bb header>;
else
goto <bb exit>;
<bb latch>:
ivtmp = ivtmp + inc;
goto <bb newheader>
...
Updated patch, now using redirect_edge_var_map and flush_pending_stmts.
Bootstrapped and reg-tested on x86_64.
OK for stage1 trunk?
Ping.
Thanks,
- Tom
Add transform_to_exit_first_loop_alt
2015-03-27 Tom de Vries <tom@codesourcery.com>
PR tree-optimization/65443
* tree-parloops.c (replace_imm_uses, replace_uses_in_bb_by)
(replace_uses_in_bbs_by, transform_to_exit_first_loop_alt)
(try_transform_to_exit_first_loop_alt): New function.
(transform_to_exit_first_loop): Use
try_transform_to_exit_first_loop_alt.
* gcc.dg/parloops-exit-first-loop-alt-2.c: New test.
* gcc.dg/parloops-exit-first-loop-alt-3.c: New test.
* gcc.dg/parloops-exit-first-loop-alt.c: New test.
* testsuite/libgomp.c/parloops-exit-first-loop-alt-2.c: New test.
* testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c: New test.
* testsuite/libgomp.c/parloops-exit-first-loop-alt.c: New test.
---
.../gcc.dg/parloops-exit-first-loop-alt-2.c | 27 ++
.../gcc.dg/parloops-exit-first-loop-alt-3.c | 26 ++
.../gcc.dg/parloops-exit-first-loop-alt.c | 27 ++
gcc/tree-parloops.c | 341 ++++++++++++++++++++-
.../libgomp.c/parloops-exit-first-loop-alt-2.c | 48 +++
.../libgomp.c/parloops-exit-first-loop-alt-3.c | 29 ++
.../libgomp.c/parloops-exit-first-loop-alt.c | 48 +++
7 files changed, 534 insertions(+), 12 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-2.c
create mode 100644 gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-3.c
create mode 100644 gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt.c
create mode 100644 libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-2.c
create mode 100644 libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c
create mode 100644 libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt.c
diff --git a/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-2.c b/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-2.c
new file mode 100644
index 0000000..a4d6cb2
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-2.c
@@ -0,0 +1,27 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target pthread } */
+/* { dg-options "-O2 -ftree-parallelize-loops=2 -fdump-tree-parloops" } */
+
+#define N 1000
+
+unsigned int a[N];
+unsigned int b[N];
+unsigned int c[N];
+
+void __attribute__((noclone,noinline))
+f (unsigned int n)
+{
+ int i;
+
+ for (i = 0; i < N; ++i)
+ c[i] = a[i] + b[i];
+}
+
+/* Three times three array accesses:
+ - three in f._loopfn.0
+ - three in the parallel
+ - three in the low iteration count loop
+ Crucially, none for a peeled off last iteration following the parallel. */
+/* { dg-final { scan-tree-dump-times "(?n)\\\[i" 9 "parloops" } } */
+
+/* { dg-final { cleanup-tree-dump "parloops" } } */
diff --git a/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-3.c b/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-3.c
new file mode 100644
index 0000000..c7ab51f88
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt-3.c
@@ -0,0 +1,26 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target pthread } */
+/* { dg-options "-O2 -ftree-parallelize-loops=2 -fdump-tree-parloops" } */
+
+unsigned int *a;
+
+unsigned int __attribute__((noclone,noinline))
+f (unsigned int n)
+{
+ int i;
+ unsigned int sum = 1;
+
+ for (i = 0; i < n; ++i)
+ sum += a[i];
+
+ return sum;
+}
+
+/* Three array accesses:
+ - one in f._loopfn.0
+ - one in the parallel
+ - one in the low iteration count loop
+ Crucially, none for a peeled off last iteration following the parallel. */
+/* { dg-final { scan-tree-dump-times "(?n)\\\* 4" 3 "parloops" } } */
+
+/* { dg-final { cleanup-tree-dump "parloops" } } */
diff --git a/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt.c b/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt.c
new file mode 100644
index 0000000..42ca3ac
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/parloops-exit-first-loop-alt.c
@@ -0,0 +1,27 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target pthread } */
+/* { dg-options "-O2 -ftree-parallelize-loops=2 -fdump-tree-parloops" } */
+
+#define N 1000
+
+unsigned int a[N];
+unsigned int b[N];
+unsigned int c[N];
+
+void __attribute__((noclone,noinline))
+f (unsigned int n)
+{
+ int i;
+
+ for (i = 0; i < n; ++i)
+ c[i] = a[i] + b[i];
+}
+
+/* Three times three array accesses:
+ - three in f._loopfn.0
+ - three in the parallel
+ - three in the low iteration count loop
+ Crucially, none for a peeled off last iteration following the parallel. */
+/* { dg-final { scan-tree-dump-times "(?n)\\\[i" 9 "parloops" } } */
+
+/* { dg-final { cleanup-tree-dump "parloops" } } */
diff --git a/gcc/tree-parloops.c b/gcc/tree-parloops.c
index 62a6444..acb0010 100644
--- a/gcc/tree-parloops.c
+++ b/gcc/tree-parloops.c
@@ -78,6 +78,7 @@ along with GCC; see the file COPYING3. If not see
#include "plugin-api.h"
#include "ipa-ref.h"
#include "cgraph.h"
+#include "tree-ssa.h"
/* This pass tries to distribute iterations of loops into several threads.
The implementation is straightforward -- for each loop we test whether its
@@ -1487,17 +1488,322 @@ create_loop_fn (location_t loc)
return decl;
}
-/* Moves the exit condition of LOOP to the beginning of its header, and
- duplicates the part of the last iteration that gets disabled to the
- exit of the loop. NIT is the number of iterations of the loop
- (used to initialize the variables in the duplicated part).
+/* Replace uses of VAL in iterator IMM_ITER. */
- TODO: the common case is that latch of the loop is empty and immediately
- follows the loop exit. In this case, it would be better not to copy the
- body of the loop, but only move the entry of the loop directly before the
- exit check and increase the number of iterations of the loop by one.
- This may need some additional preconditioning in case NIT = ~0.
- REDUCTION_LIST describes the reductions in LOOP. */
+static void
+replace_imm_uses (tree val, imm_use_iterator *imm_iter)
+{
+ use_operand_p use_p;
+
+ FOR_EACH_IMM_USE_ON_STMT (use_p, *imm_iter)
+ SET_USE (use_p, val);
+}
+
+/* Replace uses of NAME by VAL in block BB. */
+
+static void
+replace_uses_in_bb_by (tree name, tree val, basic_block bb)
+{
+ gimple use_stmt;
+ imm_use_iterator imm_iter;
+
+ FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, name)
+ {
+ if (gimple_bb (use_stmt) != bb)
+ continue;
+
+ replace_imm_uses (val, &imm_iter);
+ }
+}
+
+/* Replace uses of NAME by VAL in blocks BBS. */
+
+static void
+replace_uses_in_bbs_by (tree name, tree val, bitmap bbs)
+{
+ gimple use_stmt;
+ imm_use_iterator imm_iter;
+
+ FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, name)
+ {
+ if (!bitmap_bit_p (bbs, gimple_bb (use_stmt)->index))
+ continue;
+
+ replace_imm_uses (val, &imm_iter);
+ }
+}
+
+/* Do transformation from:
+
+ bb preheader:
+ ...
+ goto <bb header>
+
+ <bb header>:
+ ...
+ if (ivtmp < n)
+ goto <bb latch>;
+ else
+ goto <bb exit>;
+
+ <bb latch>:
+ ivtmp = ivtmp + inc;
+ goto <bb header>
+
+ to:
+
+ bb preheader:
+ ...
+ goto <bb newheader>
+
+ <bb header>:
+ ...
+ goto <bb latch>;
+
+ <bb newheader>:
+ if (ivtmp < n + 1)
+ goto <bb header>;
+ else
+ goto <bb exit>;
+
+ <bb latch>:
+ ivtmp = ivtmp + inc;
+ goto <bb newheader>
+
+ Moves the exit condition of LOOP to the beginning of its header.
+ REDUCTION_LIST describes the reductions in LOOP. BOUND is the new loop
+ bound. */
+
+static void
+transform_to_exit_first_loop_alt (struct loop *loop,
+ reduction_info_table_type *reduction_list,
+ tree bound)
+{
+ basic_block header = loop->header;
+ basic_block latch = loop->latch;
+ edge exit = single_dom_exit (loop);
+ basic_block exit_block = exit->dest;
+ gcond *cond_stmt = as_a <gcond *> (last_stmt (exit->src));
+ tree control = gimple_cond_lhs (cond_stmt);
+ edge e;
+
+ /* Gather the bbs dominated by the exit block. */
+ bitmap exit_dominated = BITMAP_ALLOC (NULL);
+ bitmap_set_bit (exit_dominated, exit_block->index);
+ vec<basic_block> exit_dominated_vec
+ = get_dominated_by (CDI_DOMINATORS, exit_block);
+
+ int i;
+ basic_block dom_bb;
+ FOR_EACH_VEC_ELT (exit_dominated_vec, i, dom_bb)
+ bitmap_set_bit (exit_dominated, dom_bb->index);
+
+ exit_dominated_vec.release ();
+
+ /* Create the new_header block. */
+ basic_block new_header = split_block_before_cond_jump (exit->src);
+ edge split_edge = single_pred_edge (new_header);
+
+ /* Redirect entry edge to new_header. */
+ edge entry = loop_preheader_edge (loop);
+ e = redirect_edge_and_branch (entry, new_header);
+ gcc_assert (e == entry);
+
+ /* Redirect post_inc_edge to new_header. */
+ edge post_inc_edge = single_succ_edge (latch);
+ e = redirect_edge_and_branch (post_inc_edge, new_header);
+ gcc_assert (e == post_inc_edge);
+
+ /* Redirect post_cond_edge to header. */
+ edge post_cond_edge = single_pred_edge (latch);
+ e = redirect_edge_and_branch (post_cond_edge, header);
+ gcc_assert (e == post_cond_edge);
+
+ /* Redirect split_edge to latch. */
+ e = redirect_edge_and_branch (split_edge, latch);
+ gcc_assert (e == split_edge);
+
+ /* Set the new loop bound. */
+ gimple_cond_set_rhs (cond_stmt, bound);
+
+ /* Repair the ssa. */
+ vec<edge_var_map> *v = redirect_edge_var_map_vector (post_inc_edge);
+ edge_var_map *vm;
+ gphi_iterator gsi;
+ for (gsi = gsi_start_phis (header), i = 0;
+ !gsi_end_p (gsi) && v->iterate (i, &vm);
+ gsi_next (&gsi), i++)
+ {
+ gphi *phi = gsi.phi ();
+ tree res = PHI_RESULT (phi);
+
+ /* Create new phi. */
+ tree new_res = copy_ssa_name (res, phi);
+ gphi *nphi = create_phi_node (new_res, new_header);
+
+ replace_uses_in_bb_by (res, new_res, new_header);
+
+ /* Fixup old phi. */
+ add_phi_arg (phi, new_res, post_cond_edge, UNKNOWN_LOCATION);
+
+ /* Loop-closed ssa does not hold for virtuals, so we cannot get away with
+ exit_block only. */
+ tree inc_res = redirect_edge_var_map_def (vm);
+ replace_uses_in_bbs_by (inc_res, new_res, exit_dominated);
+
+ struct reduction_info *red = reduction_phi (reduction_list, phi);
+ gcc_assert (virtual_operand_p (res)
+ || res == control
+ || red != NULL);
+
+ if (red)
+ {
+ /* Register the new reduction phi. */
+ red->reduc_phi = nphi;
+ gimple_set_uid (red->reduc_phi, red->reduc_version);
+ }
+ }
+ gcc_assert (gsi_end_p (gsi) && !v->iterate (i, &vm));
+ BITMAP_FREE (exit_dominated);
+
+ /* Set the entry argument of the new phis. */
+ flush_pending_stmts (entry);
+
+ /* Set the back argument of the new phis. */
+ flush_pending_stmts (post_inc_edge);
+
+ /* Register the reduction exit phis. */
+ for (gphi_iterator gsi = gsi_start_phis (exit_block);
+ !gsi_end_p (gsi);
+ gsi_next (&gsi))
+ {
+ gphi *phi = gsi.phi ();
+ tree res = PHI_RESULT (phi);
+ if (virtual_operand_p (res))
+ continue;
+
+ tree val = PHI_ARG_DEF_FROM_EDGE (phi, exit);
+ gimple reduc_phi = SSA_NAME_DEF_STMT (val);
+ struct reduction_info *red = reduction_phi (reduction_list, reduc_phi);
+ if (red != NULL)
+ red->keep_res = phi;
+ }
+
+ /* Fix up loop structure. TODO: Check whether this is sufficient. */
+ loop->header = new_header;
+
+ /* Recalculate dominance info. */
+ free_dominance_info (CDI_DOMINATORS);
+ calculate_dominance_info (CDI_DOMINATORS);
+}
+
+/* Tries to moves the exit condition of LOOP to the beginning of its header
+ without duplication of the loop body. NIT is the number of iterations of the
+ loop. REDUCTION_LIST describes the reductions in LOOP. Return true if
+ transformation is successful. */
+
+static bool
+try_transform_to_exit_first_loop_alt (struct loop *loop,
+ reduction_info_table_type *reduction_list,
+ tree nit)
+{
+ /* Check whether the latch contains a single statement. */
+ if (!gimple_seq_singleton_p (bb_seq (loop->latch)))
+ return true;
+
+ /* Check whether the latch contains the loop iv increment. */
+ edge back = single_succ_edge (loop->latch);
+ edge exit = single_dom_exit (loop);
+ gcond *cond_stmt = as_a <gcond *> (last_stmt (exit->src));
+ tree control = gimple_cond_lhs (cond_stmt);
+ gphi *phi = as_a <gphi *> (SSA_NAME_DEF_STMT (control));
+ tree inc_res = gimple_phi_arg_def (phi, back->dest_idx);
+ if (gimple_bb (SSA_NAME_DEF_STMT (inc_res)) != loop->latch)
+ return false;
+
+ /* Check whether there's no code between the loop condition and the latch. */
+ if (!single_pred_p (loop->latch)
+ || single_pred (loop->latch) != exit->src)
+ return false;
+
+ tree alt_bound = NULL_TREE;
+ tree nit_type = TREE_TYPE (nit);
+
+ /* Figure out whether nit + 1 overflows. */
+ if (TREE_CODE (nit) == INTEGER_CST)
+ {
+ if (!tree_int_cst_equal (nit, TYPE_MAXVAL (nit_type)))
+ {
+ alt_bound = fold_build2_loc (UNKNOWN_LOCATION, PLUS_EXPR, nit_type,
+ nit, build_one_cst (nit_type));
+
+ gcc_assert (TREE_CODE (alt_bound) == INTEGER_CST);
+ }
+ else
+ {
+ /* Todo: Figure out if we can trigger this, if it's worth to handle
+ optimally, and if we can handle it optimally. */
+ }
+ }
+ else
+ {
+ gcc_assert (TREE_CODE (nit) == SSA_NAME);
+
+ gimple def = SSA_NAME_DEF_STMT (nit);
+
+ if (def
+ && is_gimple_assign (def)
+ && gimple_assign_rhs_code (def) == PLUS_EXPR)
+ {
+ tree op1 = gimple_assign_rhs1 (def);
+ tree op2 = gimple_assign_rhs2 (def);
+ if (integer_minus_onep (op1))
+ alt_bound = op2;
+ else if (integer_minus_onep (op2))
+ alt_bound = op1;
+ }
+
+ /* There is a number of test-cases for which we don't get an alt_bound
+ here: they're listed here, with the lhs of the last stmt as the nit:
+
+ libgomp.graphite/force-parallel-1.c:
+ _21 = (signed long) N_6(D);
+ _19 = _21 + -1;
+ _7 = (unsigned long) _19;
+
+ libgomp.graphite/force-parallel-2.c:
+ _33 = (signed long) N_9(D);
+ _16 = _33 + -1;
+ _37 = (unsigned long) _16;
+
+ libgomp.graphite/force-parallel-5.c:
+ <bb 6>:
+ # graphite_IV.5_46 = PHI <0(5), graphite_IV.5_47(11)>
+ <bb 7>:
+ _33 = (unsigned long) graphite_IV.5_46;
+
+ g++.dg/tree-ssa/pr34355.C:
+ _2 = (unsigned int) i_9;
+ _3 = 4 - _2;
+
+ gcc.dg/pr53849.c:
+ _5 = d.0_11 + -2;
+ _18 = (unsigned int) _5;
+
+ We will be able to handle some of these cases, if we can determine when
+ it's safe to look past casts. */
+ }
+
+ if (alt_bound == NULL_TREE)
+ return false;
+
+ transform_to_exit_first_loop_alt (loop, reduction_list, alt_bound);
+ return true;
+}
+
+/* Moves the exit condition of LOOP to the beginning of its header. NIT is the
+ number of iterations of the loop. REDUCTION_LIST describes the reductions in
+ LOOP. */
static void
transform_to_exit_first_loop (struct loop *loop,
@@ -1882,8 +2188,19 @@ gen_parallel_loop (struct loop *loop,
/* Base all the induction variables in LOOP on a single control one. */
canonicalize_loop_ivs (loop, &nit, true);
- /* Ensure that the exit condition is the first statement in the loop. */
- transform_to_exit_first_loop (loop, reduction_list, nit);
+ /* Ensure that the exit condition is the first statement in the loop.
+ The common case is that latch of the loop is empty (apart from the
+ increment) and immediately follows the loop exit test. Attempt to move the
+ entry of the loop directly before the exit check and increase the number of
+ iterations of the loop by one. */
+ if (!try_transform_to_exit_first_loop_alt (loop, reduction_list, nit))
+ {
+ /* Fall back on the method that handles more cases, but duplicates the
+ loop body: move the exit condition of LOOP to the beginning of its
+ header, and duplicate the part of the last iteration that gets disabled
+ to the exit of the loop. */
+ transform_to_exit_first_loop (loop, reduction_list, nit);
+ }
/* Generate initializations for reductions. */
if (reduction_list->elements () > 0)
diff --git a/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-2.c b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-2.c
new file mode 100644
index 0000000..eb5e11f
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-2.c
@@ -0,0 +1,48 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -ftree-parallelize-loops=2" } */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#define N 1000
+
+unsigned int a[N];
+unsigned int b[N];
+unsigned int c[N];
+
+void __attribute__((noclone,noinline))
+f (void)
+{
+ int i;
+
+ for (i = 0; i < N; ++i)
+ c[i] = a[i] + b[i];
+}
+
+int
+main (void)
+{
+ int i, j;
+
+ /* Complexify loop to inhibit parloops. */
+ for (j = 0; j < 100; ++j)
+ for (i = 0; i < 10; i++)
+ {
+ int k = i + (10 * j);
+ a[k] = k;
+ b[k] = (k * 3) % 7;
+ c[k] = k * 2;
+ }
+
+ f ();
+
+ for (i = 0; i < N; i++)
+ {
+ unsigned int actual = c[i];
+ unsigned int expected = i + ((i * 3) % 7);
+ if (actual != expected)
+ abort ();
+ }
+
+ return 0;
+}
diff --git a/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c
new file mode 100644
index 0000000..b426b3f
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt-3.c
@@ -0,0 +1,29 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -ftree-parallelize-loops=2" } */
+
+unsigned int *a;
+
+unsigned int __attribute__((noclone,noinline))
+f (unsigned int n)
+{
+ int i;
+ unsigned int sum = 1;
+
+ for (i = 0; i < n; ++i)
+ sum += a[i];
+
+ return sum;
+}
+
+int
+main (void)
+{
+ unsigned int res;
+ unsigned int array[4000];
+ int i;
+ for (i = 0; i < 4000; ++i)
+ array[i] = i % 7;
+ a = &array[0];
+ res = f (4000);
+ return !(res == 11995);
+}
diff --git a/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt.c b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt.c
new file mode 100644
index 0000000..d7d4003
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c/parloops-exit-first-loop-alt.c
@@ -0,0 +1,48 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -ftree-parallelize-loops=2" } */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#define N 1000
+
+unsigned int a[N];
+unsigned int b[N];
+unsigned int c[N];
+
+void __attribute__((noclone,noinline))
+f (unsigned int n)
+{
+ int i;
+
+ for (i = 0; i < n; ++i)
+ c[i] = a[i] + b[i];
+}
+
+int
+main (void)
+{
+ int i, j;
+
+ /* Complexify loop to inhibit parloops. */
+ for (j = 0; j < 100; ++j)
+ for (i = 0; i < 10; i++)
+ {
+ int k = i + (10 * j);
+ a[k] = k;
+ b[k] = (k * 3) % 7;
+ c[k] = k * 2;
+ }
+
+ f (N);
+
+ for (i = 0; i < N; i++)
+ {
+ unsigned int actual = c[i];
+ unsigned int expected = i + ((i * 3) % 7);
+ if (actual != expected)
+ abort ();
+ }
+
+ return 0;
+}
--
1.9.1