/* Scale profile in LOOP by P.
If ITERATION_BOUND is non-zero, scale even further if loop is predicted
- to iterate too many times. */
+ to iterate too many times.
+ Before caling this function, preheader block profile should be already
+ scaled to final count. This is necessary because loop iterations are
+ determined by comparing header edge count to latch ege count and thus
+ they need to be scaled synchronously. */
void
scale_loop_profile (struct loop *loop, profile_probability p,
gcov_type iteration_bound)
{
- gcov_type iterations = expected_loop_iterations_unbounded (loop);
- edge e;
+ edge e, preheader_e;
edge_iterator ei;
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, ";; Scaling loop %i with scale ",
loop->num);
p.dump (dump_file);
- fprintf (dump_file, " bounding iterations to %i from guessed %i\n",
- (int)iteration_bound, (int)iterations);
+ fprintf (dump_file, " bounding iterations to %i\n",
+ (int)iteration_bound);
+ }
+
+ /* Scale the probabilities. */
+ scale_loop_frequencies (loop, p);
+
+ if (iteration_bound == 0)
+ return;
+
+ gcov_type iterations = expected_loop_iterations_unbounded (loop, NULL, true);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, ";; guessed iterations after scaling %i\n",
+ (int)iterations);
}
/* See if loop is predicted to iterate too many times. */
- if (iteration_bound && iterations > 0
- && p.apply (iterations) > iteration_bound)
+ if (iterations <= iteration_bound)
+ return;
+
+ preheader_e = loop_preheader_edge (loop);
+
+ /* We could handle also loops without preheaders, but bounding is
+ currently used only by optimizers that have preheaders constructed. */
+ gcc_checking_assert (preheader_e);
+ profile_count count_in = preheader_e->count ();
+
+ if (count_in > profile_count::zero ()
+ && loop->header->count.initialized_p ())
{
- /* Fixing loop profile for different trip count is not trivial; the exit
- probabilities has to be updated to match and frequencies propagated down
- to the loop body.
+ profile_count count_delta = profile_count::zero ();
- We fully update only the simple case of loop with single exit that is
- either from the latch or BB just before latch and leads from BB with
- simple conditional jump. This is OK for use in vectorizer. */
e = single_exit (loop);
if (e)
{
edge other_e;
- profile_count count_delta;
-
- FOR_EACH_EDGE (other_e, ei, e->src->succs)
+ FOR_EACH_EDGE (other_e, ei, e->src->succs)
if (!(other_e->flags & (EDGE_ABNORMAL | EDGE_FAKE))
&& e != other_e)
break;
/* Probability of exit must be 1/iterations. */
count_delta = e->count ();
e->probability = profile_probability::always ()
- .apply_scale (1, iteration_bound);
+ .apply_scale (1, iteration_bound);
other_e->probability = e->probability.invert ();
- count_delta -= e->count ();
- /* If latch exists, change its count, since we changed
- probability of exit. Theoretically we should update everything from
- source of exit edge to latch, but for vectorizer this is enough. */
- if (loop->latch
- && loop->latch != e->src)
+ /* In code below we only handle the following two updates. */
+ if (other_e->dest != loop->header
+ && other_e->dest != loop->latch
+ && (dump_file && (dump_flags & TDF_DETAILS)))
{
- loop->latch->count += count_delta;
+ fprintf (dump_file, ";; giving up on update of paths from "
+ "exit condition to latch\n");
}
}
+ else
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, ";; Loop has multiple exit edges; "
+ "giving up on exit condition update\n");
/* Roughly speaking we want to reduce the loop body profile by the
difference of loop iterations. We however can do better if
we look at the actual profile, if it is available. */
- p = p.apply_scale (iteration_bound, iterations);
-
- if (loop->header->count.initialized_p ())
- {
- profile_count count_in = profile_count::zero ();
-
- FOR_EACH_EDGE (e, ei, loop->header->preds)
- if (e->src != loop->latch)
- count_in += e->count ();
+ p = profile_probability::always ();
- if (count_in > profile_count::zero () )
- {
- p = count_in.probability_in (loop->header->count.apply_scale
- (iteration_bound, 1));
- }
- }
+ count_in = count_in.apply_scale (iteration_bound, 1);
+ p = count_in.probability_in (loop->header->count);
if (!(p > profile_probability::never ()))
p = profile_probability::very_unlikely ();
- }
- if (p >= profile_probability::always ()
- || !p.initialized_p ())
- return;
+ if (p == profile_probability::always ()
+ || !p.initialized_p ())
+ return;
- /* Scale the actual probabilities. */
- scale_loop_frequencies (loop, p);
- if (dump_file && (dump_flags & TDF_DETAILS))
- fprintf (dump_file, ";; guessed iterations are now %i\n",
- (int)expected_loop_iterations_unbounded (loop));
+ /* If latch exists, change its count, since we changed
+ probability of exit. Theoretically we should update everything from
+ source of exit edge to latch, but for vectorizer this is enough. */
+ if (loop->latch && loop->latch != e->src)
+ loop->latch->count += count_delta;
+
+ /* Scale the probabilities. */
+ scale_loop_frequencies (loop, p);
+
+ /* Change latch's count back. */
+ if (loop->latch && loop->latch != e->src)
+ loop->latch->count -= count_delta;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, ";; guessed iterations are now %i\n",
+ (int)expected_loop_iterations_unbounded (loop, NULL, true));
+ }
}
/* Recompute dominance information for basic blocks outside LOOP. */
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