[PATCH 1/2 V3] Setup predicate for switch default case in IPA (PR ipa/91089)

[Feng Xue OS <fxue@os.amperecomputing.com>]

>> +       if (this_code != ERROR_MARK
>> +           && !dominated_by_p (CDI_POST_DOMINATORS, bb, e->dest))
>>           {
>>             predicate p
>>               = add_condition (summary, index, size, &aggpos, this_code,

> So this change is handling the diamond conditional you describe above?
> This is bit of hack since it leaves the edge predicate unnecesarily
> conservative though I see it saves some conditions to be inserted and
> makes things to go smoother.
>
> Please add a comment that explain this and reffers to the other places
> where we do this (in the switch handling below).
Done.

> I believe the case ranges always has to be INTEGER_CST. In this case all
> this can be written using wide ints and produce a lot better code
> (avoiding need to build & lookup & share all temporary tree codes).
> You can take a look at the tree-switch-conversion code which does quite
> some of this wide int handling.
> 
> Richard may have an opinion on this.
Done.

> So this basically  the idea is to or BB's predicate to the
> post-dominator predicate.  This seems safe to do (we need to be careful
> so that the dataflow still converges), but I would preffer to get this
> in separately possibly with a testcase that shows an improvement in the
> dataflow answer.
I've split the patch to two.

Thanks for your comments.
Feng
---
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 1391a562c35..7f312c96f37 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -11960,6 +11960,12 @@ not spend too much time analyzing huge functions, it gives up and
 consider all memory clobbered after examining
 @option{ipa-max-aa-steps} statements modifying memory.
 
+@item ipa-max-switch-predicate-bounds
+Maximal number of boundary endpoints of case ranges of switch statement.
+For switch exceeding this limit, IPA-CP will not construct cloning cost
+predicate, which is used to estimate cloning benefit, for default case
+of the switch statement.
+
 @item lto-partitions
 Specify desired number of partitions produced during WHOPR compilation.
 The number of partitions should exceed the number of CPUs used for compilation.
diff --git a/gcc/ipa-fnsummary.c b/gcc/ipa-fnsummary.c
index 278bf606661..1bf1806eaf8 100644
--- a/gcc/ipa-fnsummary.c
+++ b/gcc/ipa-fnsummary.c
@@ -1269,13 +1269,21 @@ set_switch_stmt_execution_predicate (struct ipa_func_body_info *fbi,
   if (!unmodified_parm_or_parm_agg_item (fbi, last, op, &index, &size, &aggpos))
     return;
 
+  auto_vec<std::pair<tree, tree> > ranges;
+  tree type = TREE_TYPE (op);
+  int bound_limit = PARAM_VALUE (PARAM_IPA_MAX_SWITCH_PREDICATE_BOUNDS);
+  int bound_count = 0;
+  wide_int vr_wmin, vr_wmax;
+  value_range_kind vr_type = get_range_info (op, &vr_wmin, &vr_wmax);
+
   FOR_EACH_EDGE (e, ei, bb->succs)
     {
       e->aux = edge_predicate_pool.allocate ();
       *(predicate *) e->aux = false;
     }
+
   n = gimple_switch_num_labels (last);
-  for (case_idx = 0; case_idx < n; ++case_idx)
+  for (case_idx = 1; case_idx < n; ++case_idx)
     {
       tree cl = gimple_switch_label (last, case_idx);
       tree min, max;
@@ -1285,12 +1293,7 @@ set_switch_stmt_execution_predicate (struct ipa_func_body_info *fbi,
       min = CASE_LOW (cl);
       max = CASE_HIGH (cl);
 
-      /* For default we might want to construct predicate that none
-         of cases is met, but it is bit hard to do not having negations
-         of conditionals handy.  */
-      if (!min && !max)
-	p = true;
-      else if (!max)
+      if (!max)
 	p = add_condition (summary, index, size, &aggpos, EQ_EXPR,
 			   unshare_expr_without_location (min));
       else
@@ -1304,7 +1307,113 @@ set_switch_stmt_execution_predicate (struct ipa_func_body_info *fbi,
 	}
       *(class predicate *) e->aux
 	= p.or_with (summary->conds, *(class predicate *) e->aux);
+
+      /* If there are too many disjoint case ranges, predicate for default
+	 case might become too complicated.  So add a limit here.  */
+      if (bound_count > bound_limit)
+	continue;
+
+      bool new_range = true;
+
+      if (!ranges.is_empty ())
+	{
+	  wide_int curr_wmin = wi::to_wide (min);
+	  wide_int last_wmax = wi::to_wide (ranges.last ().second);
+
+	  /* Merge case ranges if they are continuous.  */
+	  if (curr_wmin == last_wmax + 1)
+	    new_range = false;
+	  else if (vr_type == VR_ANTI_RANGE)
+	    {
+	      /* If two disjoint case ranges can be connected by anti-range
+		 of switch index, combine them to one range.  */
+	      if (wi::lt_p (vr_wmax, curr_wmin - 1, TYPE_SIGN (type)))
+		vr_type = VR_UNDEFINED;
+	      else if (wi::le_p (vr_wmin, last_wmax + 1, TYPE_SIGN (type)))
+		new_range = false;
+	    }
+	}
+
+      if (!max)
+	max = min;
+
+      /* Create/extend a case range.  And we count endpoints of range set,
+	 this number nearly equals to number of conditions that we will create
+	 for predicate of default case.  */
+      if (new_range)
+	{
+	  bound_count += (min == max) ? 1 : 2;
+	  ranges.safe_push (std::make_pair (min, max));
+	}
+      else
+	{
+	  bound_count += (ranges.last ().first == ranges.last ().second);
+	  ranges.last ().second = max;
+	}
+    }
+
+  e = gimple_switch_edge (cfun, last, 0);
+  if (bound_count > bound_limit)
+    {
+      *(class predicate *) e->aux = true;
+      return;
     }
+
+  predicate p_seg = true;
+  predicate p_all = false;
+
+  if (vr_type != VR_RANGE)
+    {
+      vr_wmin = wi::to_wide (TYPE_MIN_VALUE (type));
+      vr_wmax = wi::to_wide (TYPE_MAX_VALUE (type));
+    }
+
+  /* Construct predicate to represent default range set that is negation of
+     all case ranges.  Case range is classified as containing single/non-single
+     values.  Suppose a piece of case ranges in the following.
+
+                [D1...D2]  [S1] ... [Sn]  [D3...D4]
+
+     To represent default case's range sets between two non-single value
+     case ranges (From D2 to D3), we construct predicate as:
+
+              D2 < x < D3 && x != S1 && ... && x != Sn
+   */
+  for (size_t i = 0; i < ranges.length (); i++)
+    {
+      tree min = ranges[i].first;
+      tree max = ranges[i].second;
+
+      if (min == max)
+	p_seg &= add_condition (summary, index, size, &aggpos, NE_EXPR,
+				unshare_expr_without_location (min));
+      else
+	{
+	  /* Do not create sub-predicate for range that is beyond low bound
+	     of switch index.  */
+	  if (wi::lt_p (vr_wmin, wi::to_wide (min), TYPE_SIGN (type)))
+	    {
+	      p_seg &= add_condition (summary, index, size, &aggpos, LT_EXPR,
+				      unshare_expr_without_location (min));
+	      p_all = p_all.or_with (summary->conds, p_seg);
+	    }
+
+	  /* Do not create sub-predicate for range that is beyond up bound
+	     of switch index.  */
+	  if (wi::le_p (vr_wmax, wi::to_wide (max), TYPE_SIGN (type)))
+	    {
+	      p_seg = false;
+	      break;
+	    }
+
+	  p_seg = add_condition (summary, index, size, &aggpos, GT_EXPR,
+				 unshare_expr_without_location (max));
+	}
+    }
+
+  p_all = p_all.or_with (summary->conds, p_seg);
+  *(class predicate *) e->aux
+    = p_all.or_with (summary->conds, *(class predicate *) e->aux);
 }
 
 
diff --git a/gcc/params.def b/gcc/params.def
index 13001a7bb2d..1461aa4849d 100644
--- a/gcc/params.def
+++ b/gcc/params.def
@@ -1123,6 +1123,14 @@ DEFPARAM (PARAM_IPA_MAX_AA_STEPS,
 	  "parameter analysis based on alias analysis in any given function.",
 	  25000, 0, 0)
 
+DEFPARAM (PARAM_IPA_MAX_SWITCH_PREDICATE_BOUNDS,
+	  "ipa-max-switch-predicate-bounds",
+	  "Maximal number of boundary endpoints of case ranges of switch "
+	  "statement.  For switch exceeding this limit, do not construct cost-"
+	  "evaluating predicate for default case during IPA function summary"
+	  "generation.",
+	  5, 0, 0)
+
 /* WHOPR partitioning configuration.  */
 
 DEFPARAM (PARAM_LTO_PARTITIONS,
diff --git a/gcc/testsuite/gcc.dg/ipa/pr91089.c b/gcc/testsuite/gcc.dg/ipa/pr91089.c
new file mode 100644
index 00000000000..e9e206fc24d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ipa/pr91089.c
@@ -0,0 +1,62 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-ipa-cp-details -fdump-ipa-fnsummary-details --param ipa-max-switch-predicate-bounds=10 -fno-inline" } */
+
+int fn ();
+
+int data;
+
+int callee (int i)
+{
+  switch (i)
+    {
+      case -126:  return i + 13;
+      case -127:  return i + 5;
+      case -8:    return i * i;
+      case 0:     return i % 9;
+      case 5:
+      case 7:
+      case 6:     return 3;
+      default:
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+	fn ();
+     }
+
+  return data += i;
+}
+
+int caller ()
+{
+  return callee (-127) +
+	 callee (-126) +
+	 callee (-8) +
+	 callee (0) +
+	 callee (5) +
+	 callee (6) +
+	 callee (7) +
+	 callee (100);
+}
+ 
+/* { dg-final { scan-ipa-dump-times "Creating a specialized node of callee" 7 "cp" } } */
+/* { dg-final { scan-ipa-dump "op0 < -127" "fnsummary" } } */
+/* { dg-final { scan-ipa-dump "op0 > -126" "fnsummary" } } */
+/* { dg-final { scan-ipa-dump "op0 != -8"  "fnsummary" } } */
+/* { dg-final { scan-ipa-dump "op0 != 0"   "fnsummary" } } */
+/* { dg-final { scan-ipa-dump "op0 < 5"    "fnsummary" } } */
+/* { dg-final { scan-ipa-dump "op0 > 7"    "fnsummary" } } */
-- 
2.17.1