Learn CFG cleanup to transform single case switches to gcond.

2017-09-05  Martin Liska  <mliska@suse.cz>

	PR tree-optimization/82032
	* tree-cfg.c (generate_range_test): New function.
	* tree-cfg.h (generate_range_test): Declared here.
	* tree-cfgcleanup.c (convert_single_case_switch): New function.
	(cleanup_control_expr_graph): Use it.
	* tree-switch-conversion.c (try_switch_expansion): Remove
	assert.
	(emit_case_nodes): Use generate_range_test.
2017-09-05  Martin Liska  <mliska@suse.cz>

	PR tree-optimization/82032
	* g++.dg/other/pr82032.C: New test.
	* gcc.dg/tree-ssa/pr68198.c: Update scanned pattern.
	* gcc.dg/tree-ssa/vrp34.c: Likewise.
	* gcc.dg/switch-10.c: Likewise.

From-SVN: r251690

gcc/ChangeLog

+2017-09-05  Martin Liska  <mliska@suse.cz>
+
+	PR tree-optimization/82032
+	* tree-cfg.c (generate_range_test): New function.
+	* tree-cfg.h (generate_range_test): Declared here.
+	* tree-cfgcleanup.c (convert_single_case_switch): New function.
+	(cleanup_control_expr_graph): Use it.
+	* tree-switch-conversion.c (try_switch_expansion): Remove
+	assert.
+	(emit_case_nodes): Use generate_range_test.
+
 2017-09-04  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR target/82098

gcc/testsuite/ChangeLog

+2017-09-05  Martin Liska  <mliska@suse.cz>
+
+	PR tree-optimization/82032
+	* g++.dg/other/pr82032.C: New test.
+	* gcc.dg/tree-ssa/pr68198.c: Update scanned pattern.
+	* gcc.dg/tree-ssa/vrp34.c: Likewise.
+	* gcc.dg/switch-10.c: Likewise.
+
 2017-09-04  Uros Bizjak  <ubizjak@gmail.com>
 
 	* gcc.target/i386/mpx/mpx-os-support.h: New file.

gcc/testsuite/g++.dg/other/pr82032.C

+/* { dg-do compile } */
+/* { dg-options "-O3 -Wno-return-type" } */
+
+template <typename a> class b
+{
+public:
+  typename a::aa operator[] (typename a::c) { }
+};
+class d
+{
+public:
+  typedef long c;
+  typedef int aa;
+};
+struct e
+{
+  int af[4];
+  int ag;
+};
+b<d> f;
+bool
+g (e &i)
+{
+  for (int h; h; ++h)
+    switch (f[h])
+      {
+      case 'x':
+      case 'a':
+	i.af[h] = 3;
+	break;
+      default:
+	return false;
+      }
+
+  return true;
+}

gcc/testsuite/gcc.dg/switch-10.c

 /* { dg-options "-O2 -fdump-tree-cfg" }  */
-/* { dg-final { scan-tree-dump "case 0:" "cfg" } }  */
-/* { dg-final { scan-tree-dump-not "case 1 ... 255:" "cfg" } }  */
 #include <stdint.h>
 
 void foo (void);
@@ -20,3 +18,6 @@ test (uint8_t ch)
      break;
    }
 }
+
+/* Switch statement is converted to GIMPLE condition.  */
+/* { dg-final { scan-tree-dump-not "switch" "cfg" } }  */

gcc/testsuite/gcc.dg/tree-ssa/pr68198.c

@@ -37,7 +37,5 @@ c_finish_omp_clauses (tree clauses)
     }
 }
 
-/* There are 3 FSM jump threading opportunities, two of which will
-  get filtered out.  */
-/* { dg-final { scan-tree-dump-times "Registering FSM" 1 "thread1"} } */
-/* { dg-final { scan-tree-dump-times "FSM Thread through multiway branch without threading a multiway branch" 2 "thread1"} } */
+/* There are 3 FSM jump threading opportunities.  */
+/* { dg-final { scan-tree-dump-times "Registering FSM" 3 "thread1"} } */

gcc/testsuite/gcc.dg/tree-ssa/vrp34.c

@@ -15,5 +15,6 @@ foo (int a)
     }
 }
 
-/* Both ifs should be optimized.  */
-/* { dg-final { scan-tree-dump-times "if \\\(" 0 "vrp1" } } */
+/* Both ifs should be optimized (and switch statement will be the only if
+   in the function).  */
+/* { dg-final { scan-tree-dump-times "if \\\(" 1 "vrp1" } } */

gcc/tree-cfg.c

@@ -8927,7 +8927,31 @@ extract_true_false_controlled_edges (basic_block dom, basic_block phiblock,
   return true;
 }
 
+/* Generate a range test LHS CODE RHS that determines whether INDEX is in the
+    range [low, high].  Place associated stmts before *GSI.  */
 
+void
+generate_range_test (basic_block bb, tree index, tree low, tree high,
+		     tree *lhs, tree *rhs)
+{
+  tree type = TREE_TYPE (index);
+  tree utype = unsigned_type_for (type);
+
+  low = fold_convert (type, low);
+  high = fold_convert (type, high);
+
+  tree tmp = make_ssa_name (type);
+  gassign *sub1
+    = gimple_build_assign (tmp, MINUS_EXPR, index, low);
+
+  *lhs = make_ssa_name (utype);
+  gassign *a = gimple_build_assign (*lhs, NOP_EXPR, tmp);
+
+  *rhs = fold_build2 (MINUS_EXPR, utype, high, low);
+  gimple_stmt_iterator gsi = gsi_last_bb (bb);
+  gsi_insert_before (&gsi, sub1, GSI_SAME_STMT);
+  gsi_insert_before (&gsi, a, GSI_SAME_STMT);
+}
 
 /* Emit return warnings.  */
 

gcc/tree-cfg.h

@@ -109,6 +109,8 @@ extern basic_block insert_cond_bb (basic_block, gimple *, gimple *,
 extern bool gimple_find_sub_bbs (gimple_seq, gimple_stmt_iterator *);
 extern bool extract_true_false_controlled_edges (basic_block, basic_block,
 						 edge *, edge *);
+extern void generate_range_test (basic_block bb, tree index, tree low,
+				 tree high, tree *lhs, tree *rhs);
 
 /* Return true if the LHS of a call should be removed.  */
 

gcc/tree-cfgcleanup.c

@@ -74,6 +74,49 @@ remove_fallthru_edge (vec<edge, va_gc> *ev)
   return false;
 }
 
+/* Convert a SWTCH with single non-default case to gcond and replace it
+   at GSI.  */
+
+static bool
+convert_single_case_switch (gswitch *swtch, gimple_stmt_iterator &gsi)
+{
+  if (gimple_switch_num_labels (swtch) != 2)
+    return false;
+
+  tree index = gimple_switch_index (swtch);
+  tree default_label = CASE_LABEL (gimple_switch_default_label (swtch));
+  tree label = gimple_switch_label (swtch, 1);
+  tree low = CASE_LOW (label);
+  tree high = CASE_HIGH (label);
+
+  basic_block default_bb = label_to_block_fn (cfun, default_label);
+  basic_block case_bb = label_to_block_fn (cfun, CASE_LABEL (label));
+
+  basic_block bb = gimple_bb (swtch);
+  gcond *cond;
+
+  /* Replace switch statement with condition statement.  */
+  if (high)
+    {
+      tree lhs, rhs;
+      generate_range_test (bb, index, low, high, &lhs, &rhs);
+      cond = gimple_build_cond (LE_EXPR, lhs, rhs, NULL_TREE, NULL_TREE);
+    }
+  else
+    cond = gimple_build_cond (EQ_EXPR, index,
+			      fold_convert (TREE_TYPE (index), low),
+			      NULL_TREE, NULL_TREE);
+
+  gsi_replace (&gsi, cond, true);
+
+  /* Update edges.  */
+  edge case_edge = find_edge (bb, case_bb);
+  edge default_edge = find_edge (bb, default_bb);
+
+  case_edge->flags |= EDGE_TRUE_VALUE;
+  default_edge->flags |= EDGE_FALSE_VALUE;
+  return true;
+}
 
 /* Disconnect an unreachable block in the control expression starting
    at block BB.  */
@@ -93,6 +136,12 @@ cleanup_control_expr_graph (basic_block bb, gimple_stmt_iterator gsi,
       bool warned;
       tree val = NULL_TREE;
 
+      /* Try to convert a switch with just a single non-default case to
+	 GIMPLE condition.  */
+      if (gimple_code (stmt) == GIMPLE_SWITCH
+	  && convert_single_case_switch (as_a<gswitch *> (stmt), gsi))
+	stmt = gsi_stmt (gsi);
+
       fold_defer_overflow_warnings ();
       switch (gimple_code (stmt))
 	{

gcc/tree-switch-conversion.c

@@ -2057,9 +2057,8 @@ try_switch_expansion (gswitch *stmt)
      expressions being INTEGER_CST.  */
   gcc_assert (TREE_CODE (index_expr) != INTEGER_CST);
 
-  /* Optimization of switch statements with only one label has already
-     occurred, so we should never see them at this point.  */
-  gcc_assert (ncases > 1);
+  if (ncases == 1)
+    return false;
 
   /* Find the default case target label.  */
   tree default_label = CASE_LABEL (gimple_switch_default_label (stmt));
@@ -2701,27 +2700,13 @@ emit_case_nodes (basic_block bb, tree index, case_node_ptr node,
 	    }
 	  else if (!low_bound && !high_bound)
 	    {
-	      tree type = TREE_TYPE (index);
-	      tree utype = unsigned_type_for (type);
-
-	      tree lhs = make_ssa_name (type);
-	      gassign *sub1
-		= gimple_build_assign (lhs, MINUS_EXPR, index, node->low);
-
-	      tree converted = make_ssa_name (utype);
-	      gassign *a = gimple_build_assign (converted, NOP_EXPR, lhs);
-
-	      tree rhs = fold_build2 (MINUS_EXPR, utype,
-				      fold_convert (type, node->high),
-				      fold_convert (type, node->low));
-	      gimple_stmt_iterator gsi = gsi_last_bb (bb);
-	      gsi_insert_before (&gsi, sub1, GSI_SAME_STMT);
-	      gsi_insert_before (&gsi, a, GSI_SAME_STMT);
-
+	      tree lhs, rhs;
+	      generate_range_test (bb, index, node->low, node->high,
+				   &lhs, &rhs);
 	      probability
 		= conditional_probability (default_prob,
 					   subtree_prob + default_prob);
-	      bb = emit_cmp_and_jump_insns (bb, converted, rhs, GT_EXPR,
+	      bb = emit_cmp_and_jump_insns (bb, lhs, rhs, GT_EXPR,
 					    default_bb, probability,
 					    phi_mapping);
 	    }