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* [gcc(refs/users/marxin/heads/loop-unswitch-improvement-v3)] Support budgeting in loop unswitching.
@ 2021-11-29 11:13 Martin Liska
0 siblings, 0 replies; only message in thread
From: Martin Liska @ 2021-11-29 11:13 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:121b02fbc47138cb52bc2dc25688bcc56df8d92a
commit 121b02fbc47138cb52bc2dc25688bcc56df8d92a
Author: Martin Liska <mliska@suse.cz>
Date: Mon Nov 29 12:12:00 2021 +0100
Support budgeting in loop unswitching.
Diff:
---
gcc/tree-ssa-loop-unswitch.c | 33 ++++++++++++++++++++++-----------
1 file changed, 22 insertions(+), 11 deletions(-)
diff --git a/gcc/tree-ssa-loop-unswitch.c b/gcc/tree-ssa-loop-unswitch.c
index aa9f25e1907..12fa6b86088 100644
--- a/gcc/tree-ssa-loop-unswitch.c
+++ b/gcc/tree-ssa-loop-unswitch.c
@@ -106,7 +106,8 @@ typedef auto_vec<std::pair<unswitch_predicate *, bool>> predicate_vector;
static class loop *tree_unswitch_loop (class loop *, basic_block, tree);
static bool tree_unswitch_single_loop (class loop *, int,
- predicate_vector &predicate_path);
+ predicate_vector &predicate_path,
+ unsigned budget);
static void
find_unswitching_predicates_for_bb (basic_block bb, class loop *loop,
vec<unswitch_predicate *> &candidates);
@@ -136,11 +137,14 @@ set_predicates_for_bb (basic_block bb, vec<unswitch_predicate *> predicates)
bb_predicates->safe_push (predicates);
}
-/* Initialize LOOP information reused during the unswitching pass. */
+/* Initialize LOOP information reused during the unswitching pass.
+ Return total number of instructions in the loop. */
-static void
+static unsigned
init_loop_unswitch_info (class loop *loop)
{
+ unsigned total_insns = 0;
+
/* Calculate instruction count. */
basic_block *bbs = get_loop_body (loop);
for (unsigned i = 0; i < loop->num_nodes; i++)
@@ -151,6 +155,7 @@ init_loop_unswitch_info (class loop *loop)
insns += estimate_num_insns (gsi_stmt (gsi), &eni_size_weights);
bbs[i]->aux = (void *)(size_t)insns;
+ total_insns += insns;
}
/* Find all unswitching candidates. */
@@ -171,6 +176,8 @@ init_loop_unswitch_info (class loop *loop)
}
free (bbs);
+
+ return total_insns;
}
/* Main entry point. Perform loop unswitching on all suitable loops. */
@@ -191,9 +198,12 @@ tree_ssa_unswitch_loops (void)
bb_predicates->safe_push (vec<unswitch_predicate *> ());
/* Unswitch innermost loop. */
- init_loop_unswitch_info (loop);
+ unsigned int budget
+ = init_loop_unswitch_info (loop) + param_max_unswitch_insns;
+
predicate_vector predicate_path;
- changed |= tree_unswitch_single_loop (loop, 0, predicate_path);
+ changed |= tree_unswitch_single_loop (loop, 0, predicate_path,
+ budget);
delete bb_predicates;
bb_predicates = NULL;
@@ -548,11 +558,12 @@ evaluate_loop_insns_for_predicate (class loop *loop, basic_block *bbs,
/* Unswitch single LOOP. NUM is number of unswitchings done; we do not allow
it to grow too much, it is too easy to create example on that the code would
grow exponentially. PREDICATE_PATH contains so far used predicates
- for unswitching. */
+ for unswitching. BUDGET is number of instruction for which we can increase
+ the loop. */
static bool
tree_unswitch_single_loop (class loop *loop, int num,
- predicate_vector &predicate_path)
+ predicate_vector &predicate_path, unsigned budget)
{
basic_block *bbs = NULL;
class loop *nloop;
@@ -601,17 +612,17 @@ tree_unswitch_single_loop (class loop *loop, int num,
vec<unswitch_predicate *> &preds = get_predicates_for_bb (bbs[i]);
for (auto pred: preds)
{
- // FIXME: update badget costing
unsigned cost
= evaluate_loop_insns_for_predicate (loop, bbs, predicate_path,
pred);
/* FIXME: right now we select first candidate, but we can choose
a cheapest (best) one. */
- if (cost <= (unsigned)param_max_unswitch_insns)
+ if (cost <= budget)
{
predicate = pred;
bb = bbs[i];
+ budget -= cost;
break;
}
else if (dump_file && (dump_flags & TDF_DETAILS))
@@ -659,12 +670,12 @@ tree_unswitch_single_loop (class loop *loop, int num,
/* Invoke itself on modified loops. */
predicate_path.safe_push (std::make_pair (predicate, false));
changed |= simplify_loop_version (nloop, predicate_path);
- tree_unswitch_single_loop (nloop, num + 1, predicate_path);
+ tree_unswitch_single_loop (nloop, num + 1, predicate_path, budget);
predicate_path.pop ();
predicate_path.safe_push (std::make_pair (predicate, true));
changed |= simplify_loop_version (loop, predicate_path);
- tree_unswitch_single_loop (loop, num + 1, predicate_path);
+ tree_unswitch_single_loop (loop, num + 1, predicate_path, budget);
predicate_path.pop ();
changed = true;
}
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