Fix merging of 2 predictors (PR tree-optimization/86925).

2018-08-15  Martin Liska  <mliska@suse.cz>

        PR tree-optimization/86925
	* predict.c (expr_expected_value_1): When taking
        later predictor, assign also probability.
        Use fold_build2_initializer_loc in order to fold
        the expression in -frounding-math.
2018-08-15  Martin Liska  <mliska@suse.cz>

        PR tree-optimization/86925
	* gcc.dg/predict-20.c: New test.
	* gcc.dg/predict-21.c: New test.

From-SVN: r263552

gcc/ChangeLog

+2018-08-15  Martin Liska  <mliska@suse.cz>
+
+        PR tree-optimization/86925
+	* predict.c (expr_expected_value_1): When taking
+        later predictor, assign also probability.
+        Use fold_build2_initializer_loc in order to fold
+        the expression in -frounding-math.
+
 2018-08-14 Allan Sandfeld Jensen <allan.jensen@qt.io>
 
 	* config/i386/i386.c (expand_vec_perm_movs): New method matching movs

gcc/predict.c

@@ -2332,13 +2332,17 @@ expr_expected_value_1 (tree type, tree op0, enum tree_code code,
 	      if (arg == PHI_RESULT (def))
 		continue;
 
+	      HOST_WIDE_INT probability2;
 	      new_val = expr_expected_value (arg, visited, &predictor2,
-					     probability);
+					     &probability2);
 
 	      /* It is difficult to combine value predictors.  Simply assume
 		 that later predictor is weaker and take its prediction.  */
 	      if (*predictor < predictor2)
-		*predictor = predictor2;
+		{
+		  *predictor = predictor2;
+		  *probability = probability2;
+		}
 	      if (!new_val)
 		return NULL;
 	      if (!val)
@@ -2423,7 +2427,8 @@ expr_expected_value_1 (tree type, tree op0, enum tree_code code,
 		  tree base = build_int_cst (integer_type_node,
 					     REG_BR_PROB_BASE);
 		  base = build_real_from_int_cst (t, base);
-		  tree r = fold_build2 (MULT_EXPR, t, prob, base);
+		  tree r = fold_build2_initializer_loc (UNKNOWN_LOCATION,
+							MULT_EXPR, t, prob, base);
 		  HOST_WIDE_INT probi
 		    = real_to_integer (TREE_REAL_CST_PTR (r));
 		  if (probi >= 0 && probi <= REG_BR_PROB_BASE)

gcc/testsuite/ChangeLog

+2018-08-15  Martin Liska  <mliska@suse.cz>
+
+        PR tree-optimization/86925
+	* gcc.dg/predict-20.c: New test.
+	* gcc.dg/predict-21.c: New test.
+
 2018-08-15  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* g++.dg/init/goto3.C: Adjust for error instead of permerror.

gcc/testsuite/gcc.dg/predict-20.c

+/* PR tree-optimization/86925 */
+
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-profile_estimate" } */
+
+int a, b;
+
+void
+c ()
+{
+  for (;;)
+    {
+      if (__builtin_expect (b < 0, 0))
+	break;
+      if (__builtin_expect (a, 1))
+	break;
+    }
+  int d = b < 0;
+  if (__builtin_expect (d, 0))
+    asm("");
+}
+
+/* { dg-final { scan-tree-dump-times "__builtin_expect heuristics of edge" 3 "profile_estimate"} } */

gcc/testsuite/gcc.dg/predict-21.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-profile_estimate -frounding-math" } */
+
+extern int global;
+
+void foo (int base)
+{
+  for (int i = 0; __builtin_expect_with_probability (i < base, 1, 0.05f); i++)
+    global++;
+}
+
+/* { dg-final { scan-tree-dump "first match heuristics: 5.00%" "profile_estimate"} } */
+/* { dg-final { scan-tree-dump "__builtin_expect_with_probability heuristics of edge .*->.*: 5.00%" "profile_estimate"} } */