From 73ddf95bf187bda7f85cac64974c843328a0832d Mon Sep 17 00:00:00 2001
From: Jan Hubicka <jh@suse.cz>
Date: Fri, 2 Nov 2012 20:35:44 +0100
Subject: [PATCH] tree-ssa-loop-niter.c (double_int_cmp, [...]): New functions.
* tree-ssa-loop-niter.c (double_int_cmp, bound_index,
discover_iteration_bound_by_body_walk): New functions.
(discover_iteration_bound_by_body_walk): Use it.
* gcc.dg/tree-ssa/loop-38.c: New testcase.
From-SVN: r193104
---
gcc/ChangeLog | 6 +
gcc/testsuite/ChangeLog | 4 +
gcc/testsuite/gcc.dg/tree-ssa/loop-38.c | 18 ++
gcc/tree-ssa-loop-niter.c | 220 ++++++++++++++++++++++++
4 files changed, 248 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/loop-38.c
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 29c8147ac77c..284dd8a15203 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2012-11-02 Jan Hubicka <jh@suse.cz>
+
+ * tree-ssa-loop-niter.c (double_int_cmp, bound_index,
+ discover_iteration_bound_by_body_walk): New functions.
+ (discover_iteration_bound_by_body_walk): Use it.
+
2012-11-02 Jan Hubicka <jh@suse.cz>
* predict.c (predict_loops): Predict also exits not dominating
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 2a2f86d43b47..7bf85b0c714c 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -11,6 +11,10 @@
* gcc.target/powerpc/pr46728-8.c: Likewise.
* gcc/testsuite/gcc.dg/pr46728-6.c: Likewise.
+2012-11-02 Jan Hubicka <jh@suse.cz>
+
+ * gcc.dg/tree-ssa/loop-38.c: New testcase.
+
2012-11-02 Jan Hubicka <jh@suse.cz>
* gcc.dg/tree-ssa/cunroll-10.c: New testcase.
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/loop-38.c b/gcc/testsuite/gcc.dg/tree-ssa/loop-38.c
new file mode 100644
index 000000000000..d5568d64624a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/loop-38.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-cunrolli-details" } */
+int a[10];
+int b[11];
+t(int n)
+{
+ int i;
+ int sum = 0;
+ for (i=0;i<n;i++)
+ if (q())
+ sum+=a[i];
+ else
+ sum+=b[i];
+ return sum;
+}
+/* { dg-final { scan-tree-dump "Found better loop bound 10" "cunrolli" } } */
+/* { dg-final { scan-tree-dump "Loop 1 iterates at most 10 times" "cunrolli" } } */
+/* { dg-final { cleanup-tree-dump "cunrolli" } } */
diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
index b77bcbbe5bad..b769f849d0e9 100644
--- a/gcc/tree-ssa-loop-niter.c
+++ b/gcc/tree-ssa-loop-niter.c
@@ -2961,6 +2961,224 @@ gcov_type_to_double_int (gcov_type val)
return ret;
}
+/* Compare double ints, callback for qsort. */
+
+int
+double_int_cmp (const void *p1, const void *p2)
+{
+ const double_int *d1 = (const double_int *)p1;
+ const double_int *d2 = (const double_int *)p2;
+ if (*d1 == *d2)
+ return 0;
+ if (d1->ult (*d2))
+ return -1;
+ return 1;
+}
+
+/* Return index of BOUND in BOUNDS array sorted in increasing order.
+ Lookup by binary search. */
+
+int
+bound_index (VEC (double_int, heap) *bounds, double_int bound)
+{
+ unsigned int end = VEC_length (double_int, bounds);
+ unsigned int begin = 0;
+
+ /* Find a matching index by means of a binary search. */
+ while (begin != end)
+ {
+ unsigned int middle = (begin + end) / 2;
+ double_int index = VEC_index (double_int, bounds, middle);
+
+ if (index == bound)
+ return middle;
+ else if (index.ult (bound))
+ begin = middle + 1;
+ else
+ end = middle;
+ }
+ gcc_unreachable ();
+}
+
+/* Used to hold vector of queues of basic blocks bellow. */
+typedef VEC (basic_block, heap) *bb_queue;
+DEF_VEC_P(bb_queue);
+DEF_VEC_ALLOC_P(bb_queue,heap);
+
+/* We recorded loop bounds only for statements dominating loop latch (and thus
+ executed each loop iteration). If there are any bounds on statements not
+ dominating the loop latch we can improve the estimate by walking the loop
+ body and seeing if every path from loop header to loop latch contains
+ some bounded statement. */
+
+static void
+discover_iteration_bound_by_body_walk (struct loop *loop)
+{
+ pointer_map_t *bb_bounds;
+ struct nb_iter_bound *elt;
+ VEC (double_int, heap) *bounds = NULL;
+ VEC (bb_queue, heap) *queues = NULL;
+ bb_queue queue = NULL;
+ ptrdiff_t queue_index;
+ ptrdiff_t latch_index = 0;
+ pointer_map_t *block_priority;
+
+ /* Discover what bounds may interest us. */
+ for (elt = loop->bounds; elt; elt = elt->next)
+ {
+ double_int bound = elt->bound;
+
+ /* Exit terminates loop at given iteration, while non-exits produce undefined
+ effect on the next iteration. */
+ if (!elt->is_exit)
+ bound += double_int_one;
+
+ if (!loop->any_upper_bound
+ || bound.ult (loop->nb_iterations_upper_bound))
+ VEC_safe_push (double_int, heap, bounds, bound);
+ }
+
+ /* Exit early if there is nothing to do. */
+ if (!bounds)
+ return;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " Trying to walk loop body to reduce the bound.\n");
+
+ /* Sort the bounds in decreasing order. */
+ qsort (VEC_address (double_int, bounds), VEC_length (double_int, bounds),
+ sizeof (double_int), double_int_cmp);
+
+ /* For every basic block record the lowest bound that is guaranteed to
+ terminate the loop. */
+
+ bb_bounds = pointer_map_create ();
+ for (elt = loop->bounds; elt; elt = elt->next)
+ {
+ double_int bound = elt->bound;
+ if (!elt->is_exit)
+ bound += double_int_one;
+
+ if (!loop->any_upper_bound
+ || bound.ult (loop->nb_iterations_upper_bound))
+ {
+ ptrdiff_t index = bound_index (bounds, bound);
+ void **entry = pointer_map_contains (bb_bounds,
+ gimple_bb (elt->stmt));
+ if (!entry)
+ *pointer_map_insert (bb_bounds,
+ gimple_bb (elt->stmt)) = (void *)index;
+ else if ((ptrdiff_t)*entry > index)
+ *entry = (void *)index;
+ }
+ }
+
+ block_priority = pointer_map_create ();
+
+ /* Perform shortest path discovery loop->header ... loop->latch.
+
+ The "distance" is given by the smallest loop bound of basic block
+ present in the path and we look for path with largest smallest bound
+ on it.
+
+ To avoid the need for fibonaci heap on double ints we simply compress
+ double ints into indexes to BOUNDS array and then represent the queue
+ as arrays of queues for every index.
+ Index of VEC_length (BOUNDS) means that the execution of given BB has
+ no bounds determined.
+
+ VISITED is a pointer map translating basic block into smallest index
+ it was inserted into the priority queue with. */
+ latch_index = -1;
+
+ /* Start walk in loop header with index set to infinite bound. */
+ queue_index = VEC_length (double_int, bounds);
+ VEC_safe_grow_cleared (bb_queue, heap, queues, queue_index + 1);
+ VEC_safe_push (basic_block, heap, queue, loop->header);
+ VEC_replace (bb_queue, queues, queue_index, queue);
+ *pointer_map_insert (block_priority, loop->header) = (void *)queue_index;
+
+ for (; queue_index >= 0; queue_index--)
+ {
+ if (latch_index < queue_index)
+ {
+ while (VEC_length (basic_block,
+ VEC_index (bb_queue, queues, queue_index)))
+ {
+ basic_block bb;
+ ptrdiff_t bound_index = queue_index;
+ void **entry;
+ edge e;
+ edge_iterator ei;
+
+ queue = VEC_index (bb_queue, queues, queue_index);
+ bb = VEC_pop (basic_block, queue);
+
+ /* OK, we later inserted the BB with lower priority, skip it. */
+ if ((ptrdiff_t)*pointer_map_contains (block_priority, bb) > queue_index)
+ continue;
+
+ /* See if we can improve the bound. */
+ entry = pointer_map_contains (bb_bounds, bb);
+ if (entry && (ptrdiff_t)*entry < bound_index)
+ bound_index = (ptrdiff_t)*entry;
+
+ /* Insert succesors into the queue, watch for latch edge
+ and record greatest index we saw. */
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ {
+ bool insert = false;
+ void **entry;
+
+ if (loop_exit_edge_p (loop, e))
+ continue;
+
+ if (e == loop_latch_edge (loop)
+ && latch_index < bound_index)
+ latch_index = bound_index;
+ else if (!(entry = pointer_map_contains (block_priority, e->dest)))
+ {
+ insert = true;
+ *pointer_map_insert (block_priority, e->dest) = (void *)bound_index;
+ }
+ else if ((ptrdiff_t)*entry < bound_index)
+ {
+ insert = true;
+ *entry = (void *)bound_index;
+ }
+
+ if (insert)
+ {
+ bb_queue queue2 = VEC_index (bb_queue, queues, bound_index);
+ VEC_safe_push (basic_block, heap, queue2, e->dest);
+ VEC_replace (bb_queue, queues, bound_index, queue2);
+ }
+ }
+ }
+ }
+ else
+ VEC_free (basic_block, heap, VEC_index (bb_queue, queues, queue_index));
+ }
+
+ gcc_assert (latch_index >= 0);
+ if (latch_index < VEC_length (double_int, bounds))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Found better loop bound ");
+ dump_double_int (dump_file,
+ VEC_index (double_int, bounds, latch_index), true);
+ fprintf (dump_file, "\n");
+ }
+ record_niter_bound (loop, VEC_index (double_int, bounds, latch_index),
+ false, true);
+ }
+
+ VEC_free (bb_queue, heap, queues);
+ pointer_map_destroy (bb_bounds);
+ pointer_map_destroy (block_priority);
+}
+
/* See if every path cross the loop goes through a statement that is known
to not execute at the last iteration. In that case we can decrese iteration
count by 1. */
@@ -3108,6 +3326,8 @@ estimate_numbers_of_iterations_loop (struct loop *loop)
infer_loop_bounds_from_undefined (loop);
+ discover_iteration_bound_by_body_walk (loop);
+
maybe_lower_iteration_bound (loop);
/* If we have a measured profile, use it to estimate the number of
--
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