+2005-10-31 Jan Hubicka <jh@suse.cz>
+
+ PR profile/24487
+ * predict.c (predict_loops): Do not estimate more than
+ MAX_PRED_LOOP_ITERATIONS in PRED_LOOP_ITERATIONS heuristic.
+ * predict.def (MAX_PRED_LOOP_ITERATIONS): Define.
+
2005-10-31 Andrew MacLeod <amacleod@redhat.com>
PR tree-optimization/19097
niter = desc.niter + 1;
if (niter == 0) /* We might overflow here. */
niter = desc.niter;
+ if (niter > MAX_PRED_LOOP_ITERATIONS)
+ niter = MAX_PRED_LOOP_ITERATIONS;
prob = (REG_BR_PROB_BASE
- (REG_BR_PROB_BASE + niter /2) / niter);
if (host_integerp (niter, 1)
&& tree_int_cst_lt (niter,
build_int_cstu (NULL_TREE,
- REG_BR_PROB_BASE - 1)))
+ MAX_PRED_LOOP_ITERATIONS - 1)))
{
HOST_WIDE_INT nitercst = tree_low_cst (niter, 1) + 1;
- probability = (REG_BR_PROB_BASE + nitercst / 2) / nitercst;
+ probability = ((REG_BR_PROB_BASE + nitercst / 2)
+ / nitercst);
}
else
- probability = 1;
+ probability = ((REG_BR_PROB_BASE
+ + MAX_PRED_LOOP_ITERATIONS / 2)
+ / MAX_PRED_LOOP_ITERATIONS);
predict_edge (exits[j], PRED_LOOP_ITERATIONS, probability);
}
DEF_PREDICTOR (PRED_LOOP_ITERATIONS, "loop iterations", PROB_ALWAYS,
PRED_FLAG_FIRST_MATCH)
+/* For guessed profiles, the loops having unknown number of iterations
+ are predicted to iterate relatively few (10) times at average.
+ For functions containing one loop with large known number of iterations
+ and other loops having unbounded loops we would end up predicting all
+ the other loops cold that is not usually the case. So we need to artifically
+ flatten the profile.
+
+ We need to cut the maximal predicted iterations to large enought iterations
+ so the loop appears important, but safely within HOT_BB_COUNT_FRACTION
+ range. */
+#define MAX_PRED_LOOP_ITERATIONS 100
+
/* Hints dropped by user via __builtin_expect feature. */
DEF_PREDICTOR (PRED_BUILTIN_EXPECT, "__builtin_expect", PROB_VERY_LIKELY,
PRED_FLAG_FIRST_MATCH)