re PR c/79153 (-Wimplicit-fallthrough missed warning)

	PR c/79153
	* tree.h (SWITCH_BREAK_LABEL_P): Define.
	* gimplify.c (collect_fallthrough_labels): Handle GIMPLE_BIND
	starting with a GIMPLE_SWITCH and ending with GIMPLE_LABEL with
	SWITCH_BREAK_LABEL_P set on the label.
	(gimplify_switch_expr): Set SWITCH_BREAK_LABEL_P on the label
	added for default case if it was missing and not all cases covered.
	Wrap GIMPLE_SWITCH and the switch_body_seq into a GIMPLE_BIND if
	switch_body_seq ends with a GIMPLE_LABEL with SWITCH_BREAK_LABEL_P
	set on the label.
	* tree-chrec.c (evolution_function_is_univariate_p): Add return true;
	to avoid -Wimplicit-fallthrough warning.
	* config/i386/i386.c (ix86_expand_special_args_builtin): Add
	FALLTHRU comment to avoid -Wimplicit-fallthrough warning.
c/
	* c-parser.c: Include tree-iterator.h.
	(c_parser_switch_statement): Emit LABEL_EXPR for the break label
	into SWITCH_BODY instead of after it and set SWITCH_BREAK_LABEL_P
	on it.
cp/
	* cp-gimplify.c (genericize_switch_stmt): Emit LABEL_EXPR for the
	break label into SWITCH_BODY instead of after it and set
	SWITCH_BREAK_LABEL_P on it.
	* parser.c (cp_parser_objc_expression): Add FALLTHRU comment to avoid
	-Wimplicit-fallthrough warning.
fortran/
	* match.c (gfc_match): Add FALLTHRU comment to avoid
	-Wimplicit-fallthrough warning.
testsuite/
	* c-c++-common/Wimplicit-fallthrough-7.c: Adjust expected warning
	line.
	* c-c++-common/Wimplicit-fallthrough-36.c: New test.

From-SVN: r255298

15 files changed, 188 insertions, 8 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 46c4545..bd2626e 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,20 @@
 2017-12-01  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c/79153
+	* tree.h (SWITCH_BREAK_LABEL_P): Define.
+	* gimplify.c (collect_fallthrough_labels): Handle GIMPLE_BIND
+	starting with a GIMPLE_SWITCH and ending with GIMPLE_LABEL with
+	SWITCH_BREAK_LABEL_P set on the label.
+	(gimplify_switch_expr): Set SWITCH_BREAK_LABEL_P on the label
+	added for default case if it was missing and not all cases covered.
+	Wrap GIMPLE_SWITCH and the switch_body_seq into a GIMPLE_BIND if
+	switch_body_seq ends with a GIMPLE_LABEL with SWITCH_BREAK_LABEL_P
+	set on the label.
+	* tree-chrec.c (evolution_function_is_univariate_p): Add return true;
+	to avoid -Wimplicit-fallthrough warning.
+	* config/i386/i386.c (ix86_expand_special_args_builtin): Add
+	FALLTHRU comment to avoid -Wimplicit-fallthrough warning.
+
 	PR tree-optimization/83221
 	* tree-ssa-reassoc.c (sort_by_operand_rank): Shift bb_rank
 	down by 16.
diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index 90db38a..1fb0c3d 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,5 +1,11 @@
 2017-12-01  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c/79153
+	* c-parser.c: Include tree-iterator.h.
+	(c_parser_switch_statement): Emit LABEL_EXPR for the break label
+	into SWITCH_BODY instead of after it and set SWITCH_BREAK_LABEL_P
+	on it.
+
 	PR c/83222
 	* c-tree.h (decl_constant_value_1): Declare.
 	* c-typeck.c (decl_constant_value_1): New function.
diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index 755cd2b..e9267fe 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -67,6 +67,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "run-rtl-passes.h"
 #include "intl.h"
 #include "c-family/name-hint.h"
+#include "tree-iterator.h"
 
 /* We need to walk over decls with incomplete struct/union/enum types
    after parsing the whole translation unit.
@@ -5846,14 +5847,15 @@ c_parser_switch_statement (c_parser *parser, bool *if_p)
   if (!open_brace_p && c_parser_peek_token (parser)->type != CPP_SEMICOLON)
     warn_for_multistatement_macros (loc_after_labels, next_loc, switch_loc,
 				    RID_SWITCH);
-  c_finish_case (body, ce.original_type);
   if (c_break_label)
     {
       location_t here = c_parser_peek_token (parser)->location;
       tree t = build1 (LABEL_EXPR, void_type_node, c_break_label);
       SET_EXPR_LOCATION (t, here);
-      add_stmt (t);
+      SWITCH_BREAK_LABEL_P (c_break_label) = 1;
+      append_to_statement_list_force (t, &body);
     }
+  c_finish_case (body, ce.original_type);
   c_break_label = save_break;
   add_stmt (c_end_compound_stmt (switch_loc, block, flag_isoc99));
   c_parser_maybe_reclassify_token (parser);
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 145b1c6..9f9db38 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -34987,6 +34987,7 @@ ix86_expand_special_args_builtin (const struct builtin_description *d,
 	default:
 	  break;
 	}
+      /* FALLTHRU */
     case V64QI_FTYPE_PCCHAR_V64QI_UDI:
     case V32QI_FTYPE_PCCHAR_V32QI_USI:
     case V16QI_FTYPE_PCCHAR_V16QI_UHI:
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index bb0e2bb..31b69bf 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,12 @@
+2017-12-01  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/79153
+	* cp-gimplify.c (genericize_switch_stmt): Emit LABEL_EXPR for the
+	break label into SWITCH_BODY instead of after it and set
+	SWITCH_BREAK_LABEL_P on it.
+	* parser.c (cp_parser_objc_expression): Add FALLTHRU comment to avoid
+	-Wimplicit-fallthrough warning.
+
 2017-11-30  Jason Merrill  <jason@redhat.com>
 
 	PR c++/82219 - bogus -Wignored-qualifiers with template
diff --git a/gcc/cp/cp-gimplify.c b/gcc/cp/cp-gimplify.c
index 3187a64..68a253a 100644
--- a/gcc/cp/cp-gimplify.c
+++ b/gcc/cp/cp-gimplify.c
@@ -330,11 +330,13 @@ genericize_switch_stmt (tree *stmt_p, int *walk_subtrees, void *data)
   cp_walk_tree (&type, cp_genericize_r, data, NULL);
   *walk_subtrees = 0;
 
+  if (TREE_USED (break_block))
+    SWITCH_BREAK_LABEL_P (break_block) = 1;
+  finish_bc_block (&body, bc_break, break_block);
   *stmt_p = build2_loc (stmt_locus, SWITCH_EXPR, type, cond, body);
   SWITCH_ALL_CASES_P (*stmt_p) = SWITCH_STMT_ALL_CASES_P (stmt);
   gcc_checking_assert (!SWITCH_STMT_NO_BREAK_P (stmt)
 		       || !TREE_USED (break_block));
-  finish_bc_block (stmt_p, bc_break, break_block);
 }
 
 /* Genericize a CONTINUE_STMT node *STMT_P.  */
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 03aeaea..707c6f5 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -29003,6 +29003,7 @@ cp_parser_objc_expression (cp_parser* parser)
 	default:
 	  break;
 	}
+      /* FALLTHRU */
     default:
       error_at (kwd->location,
 		"misplaced %<@%D%> Objective-C++ construct",
diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index e6c0480..7154ac3 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,9 @@
+2017-12-01  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/79153
+	* match.c (gfc_match): Add FALLTHRU comment to avoid
+	-Wimplicit-fallthrough warning.
+
 2017-12-01  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	PR fortran/83224
diff --git a/gcc/fortran/match.c b/gcc/fortran/match.c
index dcabe26..c437c85 100644
--- a/gcc/fortran/match.c
+++ b/gcc/fortran/match.c
@@ -1240,6 +1240,7 @@ loop:
 	default:
 	  gfc_internal_error ("gfc_match(): Bad match code %c", c);
 	}
+      /* FALLTHRU */
 
     default:
 
diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index 2c2abd7..16a86ce 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -1897,6 +1897,27 @@ collect_fallthrough_labels (gimple_stmt_iterator *gsi_p,
 
   do
     {
+      if (gimple_code (gsi_stmt (*gsi_p)) == GIMPLE_BIND)
+	{
+	  /* Recognize the special GIMPLE_BIND added by gimplify_switch_expr,
+	     which starts on a GIMPLE_SWITCH and ends with a break label.
+	     Handle that as a single statement that can fall through.  */
+	  gbind *bind = as_a <gbind *> (gsi_stmt (*gsi_p));
+	  gimple *first = gimple_seq_first_stmt (gimple_bind_body (bind));
+	  gimple *last = gimple_seq_last_stmt (gimple_bind_body (bind));
+	  if (last
+	      && gimple_code (first) == GIMPLE_SWITCH
+	      && gimple_code (last) == GIMPLE_LABEL)
+	    {
+	      tree label = gimple_label_label (as_a <glabel *> (last));
+	      if (SWITCH_BREAK_LABEL_P (label))
+		{
+		  prev = bind;
+		  gsi_next (gsi_p);
+		  continue;
+		}
+	    }
+	}
       if (gimple_code (gsi_stmt (*gsi_p)) == GIMPLE_BIND
 	  || gimple_code (gsi_stmt (*gsi_p)) == GIMPLE_TRY)
 	{
@@ -2315,6 +2336,7 @@ gimplify_switch_expr (tree *expr_p, gimple_seq *pre_p)
       preprocess_case_label_vec_for_gimple (labels, index_type,
 					    &default_case);
 
+      bool add_bind = false;
       if (!default_case)
 	{
 	  glabel *new_default;
@@ -2322,14 +2344,46 @@ gimplify_switch_expr (tree *expr_p, gimple_seq *pre_p)
 	  default_case
 	    = build_case_label (NULL_TREE, NULL_TREE,
 				create_artificial_label (UNKNOWN_LOCATION));
+	  if (old_in_switch_expr)
+	    {
+	      SWITCH_BREAK_LABEL_P (CASE_LABEL (default_case)) = 1;
+	      add_bind = true;
+	    }
 	  new_default = gimple_build_label (CASE_LABEL (default_case));
 	  gimplify_seq_add_stmt (&switch_body_seq, new_default);
 	}
+      else if (old_in_switch_expr)
+	{
+	  gimple *last = gimple_seq_last_stmt (switch_body_seq);
+	  if (last && gimple_code (last) == GIMPLE_LABEL)
+	    {
+	      tree label = gimple_label_label (as_a <glabel *> (last));
+	      if (SWITCH_BREAK_LABEL_P (label))
+		add_bind = true;
+	    }
+	}
 
       switch_stmt = gimple_build_switch (SWITCH_COND (switch_expr),
-					   default_case, labels);
-      gimplify_seq_add_stmt (pre_p, switch_stmt);
-      gimplify_seq_add_seq (pre_p, switch_body_seq);
+					 default_case, labels);
+      /* For the benefit of -Wimplicit-fallthrough, if switch_body_seq
+	 ends with a GIMPLE_LABEL holding SWITCH_BREAK_LABEL_P LABEL_DECL,
+	 wrap the GIMPLE_SWITCH up to that GIMPLE_LABEL into a GIMPLE_BIND,
+	 so that we can easily find the start and end of the switch
+	 statement.  */
+      if (add_bind)
+	{
+	  gimple_seq bind_body = NULL;
+	  gimplify_seq_add_stmt (&bind_body, switch_stmt);
+	  gimple_seq_add_seq (&bind_body, switch_body_seq);
+	  gbind *bind = gimple_build_bind (NULL_TREE, bind_body, NULL_TREE);
+	  gimple_set_location (bind, EXPR_LOCATION (switch_expr));
+	  gimplify_seq_add_stmt (pre_p, bind);
+	}
+      else
+	{
+	  gimplify_seq_add_stmt (pre_p, switch_stmt);
+	  gimplify_seq_add_seq (pre_p, switch_body_seq);
+	}
       labels.release ();
     }
   else
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e41a29d..ea2f2c7 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,10 @@
 2017-12-01  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c/79153
+	* c-c++-common/Wimplicit-fallthrough-7.c: Adjust expected warning
+	line.
+	* c-c++-common/Wimplicit-fallthrough-36.c: New test.
+
 	PR sanitizer/81275
 	* c-c++-common/tsan/pr81275.c: Remove dg-skip-if.
 
diff --git a/gcc/testsuite/c-c++-common/Wimplicit-fallthrough-36.c b/gcc/testsuite/c-c++-common/Wimplicit-fallthrough-36.c
new file mode 100644
index 0000000..1821e48
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Wimplicit-fallthrough-36.c
@@ -0,0 +1,72 @@
+/* PR c/79153 */
+/* { dg-do compile } */
+/* { dg-options "-Wimplicit-fallthrough" } */
+
+int
+test (int v1, int v2)
+{
+  switch (v1)
+    {
+    case 3:
+      switch (v2)	/* { dg-warning "this statement may fall through" } */
+	{
+	case 1:
+	  return 28;
+	case 2:
+	  return 38;
+	case 3:
+	  return 88;
+	default:
+	  break;
+	}
+    case 4:		/* { dg-message "here" } */
+      return 168;
+    case 5:
+      switch (v2)	/* { dg-warning "this statement may fall through" } */
+	{
+	case 4:
+	  break;
+	case 5:
+	  return 38;
+	case 6:
+	  return 88;
+	}
+    case 6:		/* { dg-message "here" } */
+      return 169;
+    case 7:
+      switch (v2)	/* { dg-warning "this statement may fall through" } */
+	{
+	case 7:
+	  return 38;
+	case 8:
+	  return 88;
+	}
+    case 8:		/* { dg-message "here" } */
+      return 170;
+    case 9:
+      switch (v2)	/* { dg-bogus "this statement may fall through" } */
+	{
+	case 9:
+	  return 38;
+	case 10:
+	  return 88;
+	default:
+	  return 89;
+	}
+    case 10:
+      return 171;
+    case 11:
+      switch (v2)	/* { dg-bogus "this statement may fall through" } */
+	{
+	case -__INT_MAX__ - 1 ... 31:
+	  return 38;
+	case 32:
+	  return 88;
+	case 33 ... __INT_MAX__:
+	  return 89;
+	}
+    case 12:
+      return 172;
+    }
+  return -1;
+}
diff --git a/gcc/testsuite/c-c++-common/Wimplicit-fallthrough-7.c b/gcc/testsuite/c-c++-common/Wimplicit-fallthrough-7.c
index 24a573b..a602216 100644
--- a/gcc/testsuite/c-c++-common/Wimplicit-fallthrough-7.c
+++ b/gcc/testsuite/c-c++-common/Wimplicit-fallthrough-7.c
@@ -51,9 +51,9 @@ f (int i)
     {
     case 1:
       {
-	switch (i + 2)
+	switch (i + 2) /* { dg-warning "statement may fall through" } */
 	  case 4:
-	    bar (1); /* { dg-warning "statement may fall through" } */
+	    bar (1);
 	  case 5:
 	    bar (5);
 	    return;
diff --git a/gcc/tree-chrec.c b/gcc/tree-chrec.c
index beddf10..9c14374 100644
--- a/gcc/tree-chrec.c
+++ b/gcc/tree-chrec.c
@@ -1161,6 +1161,7 @@ evolution_function_is_univariate_p (const_tree chrec)
 	    return false;
 	  break;
 	}
+      return true;
 
     default:
       return true;
diff --git a/gcc/tree.h b/gcc/tree.h
index db67858..e5a37af 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -766,6 +766,11 @@ extern void omp_clause_range_check_failed (const_tree, const char *, int,
 #define FALLTHROUGH_LABEL_P(NODE) \
   (LABEL_DECL_CHECK (NODE)->base.private_flag)
 
+/* Set on the artificial label created for break; stmt from a switch.
+   This is used to implement -Wimplicit-fallthrough.  */
+#define SWITCH_BREAK_LABEL_P(NODE) \
+  (LABEL_DECL_CHECK (NODE)->base.protected_flag)
+
 /* Nonzero means this expression is volatile in the C sense:
    its address should be of type `volatile WHATEVER *'.
    In other words, the declared item is volatile qualified.