Introduce PROB_UNINITIALIZED constant and use it in predict.def.

2018-01-19  Martin Liska  <mliska@suse.cz>

	* predict.c (predict_insn_def): Add new assert.
	(struct branch_predictor): Change type to signed integer.
	(test_prediction_value_range): Amend test to cover
	PROB_UNINITIALIZED.
	* predict.def (PRED_LOOP_ITERATIONS): Use the new constant.
	(PRED_LOOP_ITERATIONS_GUESSED): Likewise.
	(PRED_LOOP_ITERATIONS_MAX): Likewise.
	(PRED_LOOP_IV_COMPARE): Likewise.
	* predict.h (PROB_UNINITIALIZED): Define new constant.

From-SVN: r256887

gcc/ChangeLog

 2018-01-19  Martin Liska  <mliska@suse.cz>
 
+	* predict.c (predict_insn_def): Add new assert.
+	(struct branch_predictor): Change type to signed integer.
+	(test_prediction_value_range): Amend test to cover
+	PROB_UNINITIALIZED.
+	* predict.def (PRED_LOOP_ITERATIONS): Use the new constant.
+	(PRED_LOOP_ITERATIONS_GUESSED): Likewise.
+	(PRED_LOOP_ITERATIONS_MAX): Likewise.
+	(PRED_LOOP_IV_COMPARE): Likewise.
+	* predict.h (PROB_UNINITIALIZED): Define new constant.
+
+2018-01-19  Martin Liska  <mliska@suse.cz>
+
 	* predict.c (dump_prediction): Add new format for
 	analyze_brprob.py script which is enabled with -details
 	suboption.

gcc/predict.c

@@ -545,6 +545,7 @@ predict_insn_def (rtx_insn *insn, enum br_predictor predictor,
 		  enum prediction taken)
 {
    int probability = predictor_info[(int) predictor].hitrate;
+   gcc_assert (probability != PROB_UNINITIALIZED);
 
    if (taken != TAKEN)
      probability = REG_BR_PROB_BASE - probability;
@@ -4196,7 +4197,7 @@ namespace selftest {
 struct branch_predictor
 {
   const char *name;
-  unsigned probability;
+  int probability;
 };
 
 #define DEF_PREDICTOR(ENUM, NAME, HITRATE, FLAGS) { NAME, HITRATE },
@@ -4211,6 +4212,9 @@ test_prediction_value_range ()
 
   for (unsigned i = 0; predictors[i].name != NULL; i++)
     {
+      if (predictors[i].probability == PROB_UNINITIALIZED)
+	continue;
+
       unsigned p = 100 * predictors[i].probability / REG_BR_PROB_BASE;
       ASSERT_TRUE (p > 50 && p <= 100);
     }

gcc/predict.def

@@ -54,7 +54,7 @@ DEF_PREDICTOR (PRED_UNCONDITIONAL, "unconditional jump", PROB_ALWAYS,
 /* Use number of loop iterations determined by # of iterations
    analysis to set probability.  We don't want to use Dempster-Shaffer
    theory here, as the predictions is exact.  */
-DEF_PREDICTOR (PRED_LOOP_ITERATIONS, "loop iterations", PROB_ALWAYS,
+DEF_PREDICTOR (PRED_LOOP_ITERATIONS, "loop iterations", PROB_UNINITIALIZED,
 	       PRED_FLAG_FIRST_MATCH)
 
 /* Assume that any given atomic operation has low contention,
@@ -71,11 +71,11 @@ DEF_PREDICTOR (PRED_BUILTIN_EXPECT, "__builtin_expect", PROB_VERY_LIKELY,
 
 /* Use number of loop iterations guessed by the contents of the loop.  */
 DEF_PREDICTOR (PRED_LOOP_ITERATIONS_GUESSED, "guessed loop iterations",
-	       PROB_ALWAYS, PRED_FLAG_FIRST_MATCH)
+	       PROB_UNINITIALIZED, PRED_FLAG_FIRST_MATCH)
 
 /* Use number of loop iterations guessed by the contents of the loop.  */
 DEF_PREDICTOR (PRED_LOOP_ITERATIONS_MAX, "guessed loop iterations",
-	       PROB_ALWAYS, PRED_FLAG_FIRST_MATCH)
+	       PROB_UNINITIALIZED, PRED_FLAG_FIRST_MATCH)
 
 /* Branch containing goto is probably not taken.  */
 DEF_PREDICTOR (PRED_CONTINUE, "continue", HITRATE (67), 0)
@@ -151,7 +151,7 @@ DEF_PREDICTOR (PRED_LOOP_IV_COMPARE_GUESS, "guess loop iv compare",
 
 /* Use number of loop iterations determined by # of iterations analysis
    to set probability of branches that compares IV to loop bound variable.  */
-DEF_PREDICTOR (PRED_LOOP_IV_COMPARE, "loop iv compare", PROB_VERY_LIKELY,
+DEF_PREDICTOR (PRED_LOOP_IV_COMPARE, "loop iv compare", PROB_UNINITIALIZED,
 	       PRED_FLAG_FIRST_MATCH)
 
 /* In the following code

gcc/predict.h

@@ -31,6 +31,7 @@ along with GCC; see the file COPYING3.  If not see
 #define PROB_ALWAYS		(REG_BR_PROB_BASE)
 #define PROB_UNLIKELY           (REG_BR_PROB_BASE / 5 - 1)
 #define PROB_LIKELY             (REG_BR_PROB_BASE - PROB_UNLIKELY)
+#define PROB_UNINITIALIZED      (-1)
 
 #define DEF_PREDICTOR(ENUM, NAME, HITRATE, FLAGS) ENUM,
 enum br_predictor