trans.c (loop_info_d): Add low_bound...

	* gcc-interface/trans.c (loop_info_d): Add low_bound, high_bound,
	artificial, has_checks and warned_aggressive_loop_optimizations.
	(gigi): Set warn_aggressive_loop_optimizations to 0.
	(inside_loop_p): New inline predicate.
	(push_range_check_info): Rename into...
	(find_loop_for): ...this and do not push range_check_info_d object.
	(Loop_Statement_to_gnu): Set artificial, low_bound and high_bound
	fields of gnu_loop_info.  Adjust detection of checks enabled by
	-funswitch-loops and adds one for -faggressive-loop-optimizations.
	(gnat_to_gnu) <N_Indexed_Component>: If aggressive loop optimizations
	are enabled, warn for loops overrunning an array of size 1 not at the
	end of a record.

From-SVN: r224998

6 files changed, 161 insertions, 18 deletions

diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog
index 3926d2df39f..b2319aa0d5b 100644
--- a/gcc/ada/ChangeLog
+++ b/gcc/ada/ChangeLog
@@ -1,3 +1,18 @@
+2015-06-26  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gcc-interface/trans.c (loop_info_d): Add low_bound, high_bound,
+	artificial, has_checks and warned_aggressive_loop_optimizations.
+	(gigi): Set warn_aggressive_loop_optimizations to 0.
+	(inside_loop_p): New inline predicate.
+	(push_range_check_info): Rename into...
+	(find_loop_for): ...this and do not push range_check_info_d object.
+	(Loop_Statement_to_gnu): Set artificial, low_bound and high_bound
+	fields of gnu_loop_info.  Adjust detection of checks enabled by
+	-funswitch-loops and adds one for -faggressive-loop-optimizations.
+	(gnat_to_gnu) <N_Indexed_Component>: If aggressive loop optimizations
+	are enabled, warn for loops overrunning an array of size 1 not at the
+	end of a record.
+
 2015-06-25  Andrew MacLeod  <amacleod@redhat.com>
 
 	* gcc-interface/trans.c: Remove ipa-ref.h and plugin-api.h from include
diff --git a/gcc/ada/gcc-interface/trans.c b/gcc/ada/gcc-interface/trans.c
index e9a9e4ae5f8..ff910cec343 100644
--- a/gcc/ada/gcc-interface/trans.c
+++ b/gcc/ada/gcc-interface/trans.c
@@ -209,7 +209,12 @@ typedef struct range_check_info_d *range_check_info;
 struct GTY(()) loop_info_d {
   tree stmt;
   tree loop_var;
+  tree low_bound;
+  tree high_bound;
   vec<range_check_info, va_gc> *checks;
+  bool artificial;
+  bool has_checks;
+  bool warned_aggressive_loop_optimizations;
 };
 
 typedef struct loop_info_d *loop_info;
@@ -671,6 +676,10 @@ gigi (Node_Id gnat_root,
   /* Now translate the compilation unit proper.  */
   Compilation_Unit_to_gnu (gnat_root);
 
+  /* Disable -Waggressive-loop-optimizations since we implement our own
+     version of the warning.  */
+  warn_aggressive_loop_optimizations = 0;
+
   /* Then process the N_Validate_Unchecked_Conversion nodes.  We do this at
      the very end to avoid having to second-guess the front-end when we run
      into dummy nodes during the regular processing.  */
@@ -2622,12 +2631,19 @@ Case_Statement_to_gnu (Node_Id gnat_node)
   return gnu_result;
 }
 
-/* Find out whether VAR is an iteration variable of an enclosing loop in the
-   current function.  If so, push a range_check_info structure onto the stack
-   of this enclosing loop and return it.  Otherwise, return NULL.  */
+/* Return true if we are in the body of a loop.  */
+
+static inline bool
+inside_loop_p (void)
+{
+  return !vec_safe_is_empty (gnu_loop_stack);
+}
+
+/* Find out whether VAR is the iteration variable of an enclosing loop in the
+   current function.  If so, return the loop; otherwise, return NULL.  */
 
-static struct range_check_info_d *
-push_range_check_info (tree var)
+static struct loop_info_d *
+find_loop_for (tree var)
 {
   struct loop_info_d *iter = NULL;
   unsigned int i;
@@ -2648,14 +2664,7 @@ push_range_check_info (tree var)
     if (var == iter->loop_var)
       break;
 
-  if (iter)
-    {
-      struct range_check_info_d *rci = ggc_alloc<range_check_info_d> ();
-      vec_safe_push (iter->checks, rci);
-      return rci;
-    }
-
-  return NULL;
+  return iter;
 }
 
 /* Return true if VAL (of type TYPE) can equal the minimum value if MAX is
@@ -2746,6 +2755,7 @@ Loop_Statement_to_gnu (Node_Id gnat_node)
 
   /* Save the statement for later reuse.  */
   gnu_loop_info->stmt = gnu_loop_stmt;
+  gnu_loop_info->artificial = !Comes_From_Source (gnat_node);
 
   /* Set the condition under which the loop must keep going.
      For the case "LOOP .... END LOOP;" the condition is always true.  */
@@ -2941,6 +2951,8 @@ Loop_Statement_to_gnu (Node_Id gnat_node)
 	  SET_DECL_INDUCTION_VAR (gnu_loop_var, gnu_loop_iv);
 	}
       gnu_loop_info->loop_var = gnu_loop_var;
+      gnu_loop_info->low_bound = gnu_low;
+      gnu_loop_info->high_bound = gnu_high;
 
       /* Do all the arithmetics in the base type.  */
       gnu_loop_var = convert (gnu_base_type, gnu_loop_var);
@@ -5334,7 +5346,7 @@ Raise_Error_to_gnu (Node_Id gnat_node, tree *gnu_result_type_p)
 	{
 	  Node_Id gnat_range, gnat_index, gnat_type;
 	  tree gnu_index, gnu_low_bound, gnu_high_bound;
-	  struct range_check_info_d *rci;
+	  struct loop_info_d *loop;
 
 	  switch (Nkind (Right_Opnd (gnat_cond)))
 	    {
@@ -5382,24 +5394,36 @@ Raise_Error_to_gnu (Node_Id gnat_node, tree *gnu_result_type_p)
 	     one of which has the checks eliminated and the other has
 	     the original checks reinstated, and a run time selection.
 	     The former loop will be suitable for vectorization.  */
-	  if (flag_unswitch_loops
-	      && !vec_safe_is_empty (gnu_loop_stack)
+	  if (optimize
+	      && flag_unswitch_loops
+	      && inside_loop_p ()
 	      && (!gnu_low_bound
 		  || (gnu_low_bound = gnat_invariant_expr (gnu_low_bound)))
 	      && (!gnu_high_bound
 		  || (gnu_high_bound = gnat_invariant_expr (gnu_high_bound)))
-	      && (rci = push_range_check_info (gnu_index)))
+	      && (loop = find_loop_for (gnu_index)))
 	    {
+	      struct range_check_info_d *rci = ggc_alloc<range_check_info_d> ();
 	      rci->low_bound = gnu_low_bound;
 	      rci->high_bound = gnu_high_bound;
 	      rci->type = get_unpadded_type (gnat_type);
 	      rci->invariant_cond = build1 (SAVE_EXPR, boolean_type_node,
 					    boolean_true_node);
+	      vec_safe_push (loop->checks, rci);
+	      loop->has_checks = true;
 	      gnu_cond = build_binary_op (TRUTH_ANDIF_EXPR,
 					  boolean_type_node,
 					  rci->invariant_cond,
 					  gnat_to_gnu (gnat_cond));
 	    }
+
+	  /* Or else, if aggressive loop optimizations are enabled, we just
+	     record that there are checks applied to iteration variables.  */
+	  else if (optimize
+		   && flag_aggressive_loop_optimizations
+		   && inside_loop_p ()
+		   && (loop = find_loop_for (gnu_index)))
+	    loop->has_checks = true;
 	}
       break;
 
@@ -5939,11 +5963,13 @@ gnat_to_gnu (Node_Id gnat_node)
 	    gnat_expr_array[i] = gnat_temp;
 
 	for (i = 0, gnu_type = TREE_TYPE (gnu_array_object);
-	     i < ndim; i++, gnu_type = TREE_TYPE (gnu_type))
+	     i < ndim;
+	     i++, gnu_type = TREE_TYPE (gnu_type))
 	  {
 	    gcc_assert (TREE_CODE (gnu_type) == ARRAY_TYPE);
 	    gnat_temp = gnat_expr_array[i];
 	    gnu_expr = gnat_to_gnu (gnat_temp);
+	    struct loop_info_d *loop;
 
 	    if (Do_Range_Check (gnat_temp))
 	      gnu_expr
@@ -5965,6 +5991,31 @@ gnat_to_gnu (Node_Id gnat_node)
 		&& !(Nkind (gnat_temp) == N_Identifier
 		     && Ekind (Entity (gnat_temp)) == E_Constant))
 	      TREE_THIS_NOTRAP (gnu_result) = 1;
+
+	    /* If aggressive loop optimizations are enabled, we warn for loops
+	       overrunning a simple array of size 1 not at the end of a record.
+	       This is aimed to catch misuses of the trailing array idiom.  */
+	    if (optimize
+		&& flag_aggressive_loop_optimizations
+		&& inside_loop_p ()
+		&& TREE_CODE (TREE_TYPE (gnu_type)) != ARRAY_TYPE
+		&& TREE_CODE (gnu_array_object) != ARRAY_REF
+		&& tree_int_cst_equal (TYPE_MIN_VALUE (TYPE_DOMAIN (gnu_type)),
+				       TYPE_MAX_VALUE (TYPE_DOMAIN (gnu_type)))
+		&& !array_at_struct_end_p (gnu_result)
+		&& (loop = find_loop_for (skip_simple_arithmetic (gnu_expr)))
+		&& !loop->artificial
+		&& !loop->has_checks
+		&& tree_int_cst_equal (TYPE_MIN_VALUE (TYPE_DOMAIN (gnu_type)),
+				       loop->low_bound)
+		&& can_be_lower_p (loop->low_bound, loop->high_bound)
+		&& !loop->warned_aggressive_loop_optimizations
+		&& warning (OPT_Waggressive_loop_optimizations,
+			    "out-of-bounds access may be optimized away"))
+	      {
+		inform (EXPR_LOCATION (loop->stmt), "containing loop");
+		loop->warned_aggressive_loop_optimizations = true;
+	      }
 	  }
 
 	gnu_result_type = get_unpadded_type (Etype (gnat_node));
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index bccda4a31df..e3ae30a0a38 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2015-06-26  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gnat.dg/warn11.adb: Add missing dg directive.
+	* gnat.dg/warn12.adb: New test.
+	* gnat.dg/warn12_pkg.ads: New helper.
+
 2015-06-26  Richard Biener  <rguenther@suse.de>
 
 	* gfortran.dg/reassoc_3.f90: Adjust.
diff --git a/gcc/testsuite/gnat.dg/warn11.adb b/gcc/testsuite/gnat.dg/warn11.adb
index ff24d7c336c..e92835f0533 100644
--- a/gcc/testsuite/gnat.dg/warn11.adb
+++ b/gcc/testsuite/gnat.dg/warn11.adb
@@ -1,3 +1,5 @@
+-- { dg-do compile }
+
 with Ada.Text_IO; use Ada.Text_IO;
 
 procedure Warn11 is
diff --git a/gcc/testsuite/gnat.dg/warn12.adb b/gcc/testsuite/gnat.dg/warn12.adb
new file mode 100644
index 00000000000..8ffd0c7dff0
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/warn12.adb
@@ -0,0 +1,48 @@
+-- { dg-do compile }

+-- { dg-options "-O2" }

+

+with Text_IO; use Text_IO;

+with System.Storage_Elements; use System.Storage_Elements;

+with Warn12_Pkg; use Warn12_Pkg;

+

+procedure Warn12 (N : Natural) is

+

+   Buffer_Size : constant Storage_Offset

+      := Token_Groups'Size/System.Storage_Unit + 4096;

+

+   Buffer : Storage_Array (1 .. Buffer_Size);

+   for Buffer'Alignment use 8;

+

+   Tg1 : Token_Groups;

+   for Tg1'Address use Buffer'Address;

+

+   Tg2 : Token_Groups;

+   pragma Warnings (Off, Tg2);

+

+   sid : Sid_And_Attributes;

+

+   pragma Suppress (Index_Check, Sid_And_Attributes_Array);

+

+begin

+

+   for I in 0 .. 7 loop

+      sid :=  Tg1.Groups(I);  -- { dg-bogus "out-of-bounds access" }

+      Put_Line("Iteration");

+   end loop;

+

+   for I in 0 .. N loop

+      sid :=  Tg1.Groups(I);  -- { dg-bogus "out-of-bounds access" }

+      Put_Line("Iteration");

+   end loop;

+

+   for I in 0 .. 7 loop

+      sid :=  Tg2.Groups(I);  -- { dg-warning "out-of-bounds access" }

+      Put_Line("Iteration");

+   end loop;

+

+   for I in 0 .. N loop

+      sid :=  Tg2.Groups(I);  -- { dg-warning "out-of-bounds access" }

+      Put_Line("Iteration");

+   end loop;

+

+end;

diff --git a/gcc/testsuite/gnat.dg/warn12_pkg.ads b/gcc/testsuite/gnat.dg/warn12_pkg.ads
new file mode 100644
index 00000000000..b3191cc304f
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/warn12_pkg.ads
@@ -0,0 +1,21 @@
+with Interfaces.C; use Interfaces.C;
+with System;
+
+package Warn12_Pkg is
+
+   Anysize_Array: constant := 0;
+
+   type Sid_And_Attributes is record
+      Sid        : System.Address;
+      Attributes : Interfaces.C.Unsigned_Long;
+   end record;
+
+   type Sid_And_Attributes_Array
+      is array (Integer range 0..Anysize_Array) of aliased Sid_And_Attributes;
+
+   type Token_Groups is record
+      GroupCount : Interfaces.C.Unsigned_Long;
+      Groups     : Sid_And_Attributes_Array;
+   end record;
+
+end Warn12_Pkg;