Index: gcc/machmode.h
===================================================================
--- gcc/machmode.h	2017-07-13 09:18:28.588718099 +0100
+++ gcc/machmode.h	2017-07-13 09:18:29.217658709 +0100
@@ -558,6 +558,16 @@ #define GET_MODE_COMPLEX_MODE(MODE) ((ma
 
 extern machine_mode mode_for_size (unsigned int, enum mode_class, int);
 
+/* Return the machine mode to use for a MODE_INT of SIZE bits, if one
+   exists.  If LIMIT is nonzero, modes wider than MAX_FIXED_MODE_SIZE
+   will not be used.  */
+
+inline opt_scalar_int_mode
+int_mode_for_size (unsigned int size, int limit)
+{
+  return dyn_cast <scalar_int_mode> (mode_for_size (size, MODE_INT, limit));
+}
+
 /* Return the machine mode to use for a MODE_FLOAT of SIZE bits, if one
    exists.  */
 
Index: gcc/builtins.c
===================================================================
--- gcc/builtins.c	2017-07-13 09:18:24.772086898 +0100
+++ gcc/builtins.c	2017-07-13 09:18:29.209659459 +0100
@@ -10429,9 +10429,9 @@ set_builtin_user_assembler_name (tree de
   if (DECL_FUNCTION_CODE (decl) == BUILT_IN_FFS
       && INT_TYPE_SIZE < BITS_PER_WORD)
     {
+      scalar_int_mode mode = *int_mode_for_size (INT_TYPE_SIZE, 0);
       set_user_assembler_libfunc ("ffs", asmspec);
-      set_optab_libfunc (ffs_optab, mode_for_size (INT_TYPE_SIZE, MODE_INT, 0),
-			 "ffs");
+      set_optab_libfunc (ffs_optab, mode, "ffs");
     }
 }
 
Index: gcc/calls.c
===================================================================
--- gcc/calls.c	2017-06-12 17:05:23.274759395 +0100
+++ gcc/calls.c	2017-07-13 09:18:29.210659365 +0100
@@ -1045,12 +1045,15 @@ save_fixed_argument_area (int reg_parm_s
 	*high_to_save = high;
 
 	num_to_save = high - low + 1;
-	save_mode = mode_for_size (num_to_save * BITS_PER_UNIT, MODE_INT, 1);
 
 	/* If we don't have the required alignment, must do this
 	   in BLKmode.  */
-	if ((low & (MIN (GET_MODE_SIZE (save_mode),
-			 BIGGEST_ALIGNMENT / UNITS_PER_WORD) - 1)))
+	scalar_int_mode imode;
+	if (int_mode_for_size (num_to_save * BITS_PER_UNIT, 1).exists (&imode)
+	    && (low & (MIN (GET_MODE_SIZE (imode),
+			    BIGGEST_ALIGNMENT / UNITS_PER_WORD) - 1)) == 0)
+	  save_mode = imode;
+	else
 	  save_mode = BLKmode;
 
 	if (ARGS_GROW_DOWNWARD)
Index: gcc/combine.c
===================================================================
--- gcc/combine.c	2017-07-13 09:18:22.914280096 +0100
+++ gcc/combine.c	2017-07-13 09:18:29.211659271 +0100
@@ -7308,19 +7308,16 @@ expand_field_assignment (const_rtx x)
       /* Don't attempt bitwise arithmetic on non scalar integer modes.  */
       if (! SCALAR_INT_MODE_P (compute_mode))
 	{
-	  machine_mode imode;
-
 	  /* Don't do anything for vector or complex integral types.  */
 	  if (! FLOAT_MODE_P (compute_mode))
 	    break;
 
 	  /* Try to find an integral mode to pun with.  */
-	  imode = mode_for_size (GET_MODE_BITSIZE (compute_mode), MODE_INT, 0);
-	  if (imode == BLKmode)
+	  if (!int_mode_for_size (GET_MODE_BITSIZE (compute_mode), 0)
+	      .exists (&compute_mode))
 	    break;
 
-	  compute_mode = imode;
-	  inner = gen_lowpart (imode, inner);
+	  inner = gen_lowpart (compute_mode, inner);
 	}
 
       /* Compute a mask of LEN bits, if we can do this on the host machine.  */
@@ -7391,7 +7388,6 @@ make_extraction (machine_mode mode, rtx
   machine_mode wanted_inner_reg_mode = word_mode;
   machine_mode pos_mode = word_mode;
   machine_mode extraction_mode = word_mode;
-  machine_mode tmode = mode_for_size (len, MODE_INT, 1);
   rtx new_rtx = 0;
   rtx orig_pos_rtx = pos_rtx;
   HOST_WIDE_INT orig_pos;
@@ -7439,7 +7435,8 @@ make_extraction (machine_mode mode, rtx
      For MEM, we can avoid an extract if the field starts on an appropriate
      boundary and we can change the mode of the memory reference.  */
 
-  if (tmode != BLKmode
+  scalar_int_mode tmode;
+  if (int_mode_for_size (len, 1).exists (&tmode)
       && ((pos_rtx == 0 && (pos % BITS_PER_WORD) == 0
 	   && !MEM_P (inner)
 	   && (pos == 0 || REG_P (inner))
@@ -10466,8 +10463,8 @@ simplify_shift_const_1 (enum rtx_code co
 	      && ! mode_dependent_address_p (XEXP (varop, 0),
 					     MEM_ADDR_SPACE (varop))
 	      && ! MEM_VOLATILE_P (varop)
-	      && (tmode = mode_for_size (GET_MODE_BITSIZE (mode) - count,
-					 MODE_INT, 1)) != BLKmode)
+	      && (int_mode_for_size (GET_MODE_BITSIZE (mode) - count, 1)
+		  .exists (&tmode)))
 	    {
 	      new_rtx = adjust_address_nv (varop, tmode,
 				       BYTES_BIG_ENDIAN ? 0
@@ -12394,7 +12391,7 @@ simplify_comparison (enum rtx_code code,
 				   & GET_MODE_MASK (mode))
 				  + 1)) >= 0
 	      && const_op >> i == 0
-	      && (tmode = mode_for_size (i, MODE_INT, 1)) != BLKmode)
+	      && int_mode_for_size (i, 1).exists (&tmode))
 	    {
 	      op0 = gen_lowpart_or_truncate (tmode, XEXP (op0, 0));
 	      continue;
@@ -12554,8 +12551,8 @@ simplify_comparison (enum rtx_code code,
 	      && CONST_INT_P (XEXP (op0, 1))
 	      && GET_CODE (XEXP (op0, 0)) == ASHIFT
 	      && XEXP (op0, 1) == XEXP (XEXP (op0, 0), 1)
-	      && (tmode = mode_for_size (mode_width - INTVAL (XEXP (op0, 1)),
-					 MODE_INT, 1)) != BLKmode
+	      && (int_mode_for_size (mode_width - INTVAL (XEXP (op0, 1)), 1)
+		  .exists (&tmode))
 	      && (((unsigned HOST_WIDE_INT) const_op
 		   + (GET_MODE_MASK (tmode) >> 1) + 1)
 		  <= GET_MODE_MASK (tmode)))
@@ -12573,8 +12570,8 @@ simplify_comparison (enum rtx_code code,
 	      && CONST_INT_P (XEXP (XEXP (op0, 0), 1))
 	      && GET_CODE (XEXP (XEXP (op0, 0), 0)) == ASHIFT
 	      && XEXP (op0, 1) == XEXP (XEXP (XEXP (op0, 0), 0), 1)
-	      && (tmode = mode_for_size (mode_width - INTVAL (XEXP (op0, 1)),
-					 MODE_INT, 1)) != BLKmode
+	      && (int_mode_for_size (mode_width - INTVAL (XEXP (op0, 1)), 1)
+		  .exists (&tmode))
 	      && (((unsigned HOST_WIDE_INT) const_op
 		   + (GET_MODE_MASK (tmode) >> 1) + 1)
 		  <= GET_MODE_MASK (tmode)))
Index: gcc/dojump.c
===================================================================
--- gcc/dojump.c	2017-06-30 12:50:38.242662721 +0100
+++ gcc/dojump.c	2017-07-13 09:18:29.212659178 +0100
@@ -594,7 +594,7 @@ do_jump (tree exp, rtx_code_label *if_fa
           && TREE_CODE (TREE_OPERAND (exp, 1)) == INTEGER_CST
           && TYPE_PRECISION (TREE_TYPE (exp)) <= HOST_BITS_PER_WIDE_INT
           && (i = tree_floor_log2 (TREE_OPERAND (exp, 1))) >= 0
-          && (mode = mode_for_size (i + 1, MODE_INT, 0)) != BLKmode
+	  && int_mode_for_size (i + 1, 0).exists (&mode)
           && (type = lang_hooks.types.type_for_mode (mode, 1)) != 0
           && TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (exp))
           && have_insn_for (COMPARE, TYPE_MODE (type)))
Index: gcc/dwarf2out.c
===================================================================
--- gcc/dwarf2out.c	2017-07-13 09:18:23.797186067 +0100
+++ gcc/dwarf2out.c	2017-07-13 09:18:29.214658990 +0100
@@ -15169,13 +15169,12 @@ mem_loc_descriptor (rtx rtl, machine_mod
 	      || GET_MODE_BITSIZE (mode) == HOST_BITS_PER_DOUBLE_INT))
 	{
 	  dw_die_ref type_die = base_type_for_mode (mode, 1);
-	  machine_mode amode;
+	  scalar_int_mode amode;
 	  if (type_die == NULL)
 	    return NULL;
-	  amode = mode_for_size (DWARF2_ADDR_SIZE * BITS_PER_UNIT,
-				 MODE_INT, 0);
 	  if (INTVAL (rtl) >= 0
-	      && amode != BLKmode
+	      && (int_mode_for_size (DWARF2_ADDR_SIZE * BITS_PER_UNIT, 0)
+		  .exists (&amode))
 	      && trunc_int_for_mode (INTVAL (rtl), amode) == INTVAL (rtl)
 	      /* const DW_OP_convert <XXX> vs.
 		 DW_OP_const_type <XXX, 1, const>.  */
Index: gcc/emit-rtl.c
===================================================================
--- gcc/emit-rtl.c	2017-07-13 09:18:28.024771545 +0100
+++ gcc/emit-rtl.c	2017-07-13 09:18:29.215658896 +0100
@@ -5885,8 +5885,7 @@ init_derived_machine_modes (void)
 
   byte_mode = *opt_byte_mode;
   word_mode = *opt_word_mode;
-  ptr_mode = as_a <scalar_int_mode> (mode_for_size (POINTER_SIZE,
-						    MODE_INT, 0));
+  ptr_mode = *int_mode_for_size (POINTER_SIZE, 0);
 }
 
 /* Create some permanent unique rtl objects shared between all functions.  */
Index: gcc/expmed.c
===================================================================
--- gcc/expmed.c	2017-07-13 09:18:22.925278914 +0100
+++ gcc/expmed.c	2017-07-13 09:18:29.215658896 +0100
@@ -363,7 +363,7 @@ check_reverse_float_storage_order_suppor
 rtx
 flip_storage_order (machine_mode mode, rtx x)
 {
-  machine_mode int_mode;
+  scalar_int_mode int_mode;
   rtx result;
 
   if (mode == QImode)
@@ -383,16 +383,13 @@ flip_storage_order (machine_mode mode, r
   if (__builtin_expect (reverse_storage_order_supported < 0, 0))
     check_reverse_storage_order_support ();
 
-  if (SCALAR_INT_MODE_P (mode))
-    int_mode = mode;
-  else
+  if (!is_a <scalar_int_mode> (mode, &int_mode))
     {
       if (FLOAT_MODE_P (mode)
 	  && __builtin_expect (reverse_float_storage_order_supported < 0, 0))
 	check_reverse_float_storage_order_support ();
 
-      int_mode = mode_for_size (GET_MODE_PRECISION (mode), MODE_INT, 0);
-      if (int_mode == BLKmode)
+      if (!int_mode_for_size (GET_MODE_PRECISION (mode), 0).exists (&int_mode))
 	{
 	  sorry ("reverse storage order for %smode", GET_MODE_NAME (mode));
 	  return x;
@@ -1428,11 +1425,10 @@ convert_extracted_bit_field (rtx x, mach
      value via a SUBREG.  */
   if (!SCALAR_INT_MODE_P (tmode))
     {
-      machine_mode smode;
-
-      smode = mode_for_size (GET_MODE_BITSIZE (tmode), MODE_INT, 0);
-      x = convert_to_mode (smode, x, unsignedp);
-      x = force_reg (smode, x);
+      scalar_int_mode int_mode
+	= *int_mode_for_size (GET_MODE_BITSIZE (tmode), 0);
+      x = convert_to_mode (int_mode, x, unsignedp);
+      x = force_reg (int_mode, x);
       return gen_lowpart (tmode, x);
     }
 
Index: gcc/expr.c
===================================================================
--- gcc/expr.c	2017-07-13 09:18:26.362931356 +0100
+++ gcc/expr.c	2017-07-13 09:18:29.216658803 +0100
@@ -2671,9 +2671,9 @@ copy_blkmode_from_reg (rtx target, rtx s
   copy_mode = word_mode;
   if (MEM_P (target))
     {
-      machine_mode mem_mode = mode_for_size (bitsize, MODE_INT, 1);
-      if (mem_mode != BLKmode)
-	copy_mode = mem_mode;
+      opt_scalar_int_mode mem_mode = int_mode_for_size (bitsize, 1);
+      if (mem_mode.exists ())
+	copy_mode = *mem_mode;
     }
   else if (REG_P (target) && GET_MODE_BITSIZE (tmode) < BITS_PER_WORD)
     copy_mode = tmode;
Index: gcc/graphite-isl-ast-to-gimple.c
===================================================================
--- gcc/graphite-isl-ast-to-gimple.c	2017-05-31 10:02:28.656477076 +0100
+++ gcc/graphite-isl-ast-to-gimple.c	2017-07-13 09:18:29.217658709 +0100
@@ -61,7 +61,7 @@ #define INCLUDE_MAP
    should use isl to derive the optimal type for each subexpression.  */
 
 static int max_mode_int_precision =
-  GET_MODE_PRECISION (mode_for_size (MAX_FIXED_MODE_SIZE, MODE_INT, 0));
+  GET_MODE_PRECISION (*int_mode_for_size (MAX_FIXED_MODE_SIZE, 0));
 static int graphite_expression_type_precision = 128 <= max_mode_int_precision ?
 						128 : max_mode_int_precision;
 
Index: gcc/internal-fn.c
===================================================================
--- gcc/internal-fn.c	2017-07-13 09:18:22.929278484 +0100
+++ gcc/internal-fn.c	2017-07-13 09:18:29.217658709 +0100
@@ -1445,7 +1445,7 @@ expand_mul_overflow (location_t loc, tre
     {
       struct separate_ops ops;
       int prec = GET_MODE_PRECISION (mode);
-      machine_mode hmode = mode_for_size (prec / 2, MODE_INT, 1);
+      scalar_int_mode hmode;
       machine_mode wmode;
       ops.op0 = make_tree (type, op0);
       ops.op1 = make_tree (type, op1);
@@ -1481,7 +1481,8 @@ expand_mul_overflow (location_t loc, tre
 				       profile_probability::very_likely ());
 	    }
 	}
-      else if (hmode != BLKmode && 2 * GET_MODE_PRECISION (hmode) == prec)
+      else if (int_mode_for_size (prec / 2, 1).exists (&hmode)
+	       && 2 * GET_MODE_PRECISION (hmode) == prec)
 	{
 	  rtx_code_label *large_op0 = gen_label_rtx ();
 	  rtx_code_label *small_op0_large_op1 = gen_label_rtx ();
Index: gcc/lower-subreg.c
===================================================================
--- gcc/lower-subreg.c	2017-07-13 09:18:22.929278484 +0100
+++ gcc/lower-subreg.c	2017-07-13 09:18:29.217658709 +0100
@@ -349,8 +349,7 @@ simple_move (rtx_insn *insn, bool speed_
      size.  */
   mode = GET_MODE (SET_DEST (set));
   if (!SCALAR_INT_MODE_P (mode)
-      && (mode_for_size (GET_MODE_SIZE (mode) * BITS_PER_UNIT, MODE_INT, 0)
-	  == BLKmode))
+      && !int_mode_for_size (GET_MODE_BITSIZE (mode), 0).exists ())
     return NULL_RTX;
 
   /* Reject PARTIAL_INT modes.  They are used for processor specific
Index: gcc/optabs-libfuncs.c
===================================================================
--- gcc/optabs-libfuncs.c	2017-07-13 09:18:24.309132693 +0100
+++ gcc/optabs-libfuncs.c	2017-07-13 09:18:29.218658615 +0100
@@ -858,8 +858,10 @@ init_optabs (void)
   /* The ffs function operates on `int'.  Fall back on it if we do not
      have a libgcc2 function for that width.  */
   if (INT_TYPE_SIZE < BITS_PER_WORD)
-    set_optab_libfunc (ffs_optab, mode_for_size (INT_TYPE_SIZE, MODE_INT, 0),
-		       "ffs");
+    {
+      scalar_int_mode mode = *int_mode_for_size (INT_TYPE_SIZE, 0);
+      set_optab_libfunc (ffs_optab, mode, "ffs");
+    }
 
   /* Explicitly initialize the bswap libfuncs since we need them to be
      valid for things other than word_mode.  */
Index: gcc/simplify-rtx.c
===================================================================
--- gcc/simplify-rtx.c	2017-07-13 09:18:23.800185748 +0100
+++ gcc/simplify-rtx.c	2017-07-13 09:18:29.218658615 +0100
@@ -1484,12 +1484,11 @@ simplify_unary_operation_1 (enum rtx_cod
 	  && XEXP (XEXP (op, 0), 1) == XEXP (op, 1)
 	  && GET_MODE_BITSIZE (GET_MODE (op)) > INTVAL (XEXP (op, 1)))
 	{
-	  machine_mode tmode
-	    = mode_for_size (GET_MODE_BITSIZE (GET_MODE (op))
-			     - INTVAL (XEXP (op, 1)), MODE_INT, 1);
+	  scalar_int_mode tmode;
 	  gcc_assert (GET_MODE_BITSIZE (mode)
 		      > GET_MODE_BITSIZE (GET_MODE (op)));
-	  if (tmode != BLKmode)
+	  if (int_mode_for_size (GET_MODE_BITSIZE (GET_MODE (op))
+				 - INTVAL (XEXP (op, 1)), 1).exists (&tmode))
 	    {
 	      rtx inner =
 		rtl_hooks.gen_lowpart_no_emit (tmode, XEXP (XEXP (op, 0), 0));
@@ -1601,10 +1600,9 @@ simplify_unary_operation_1 (enum rtx_cod
 	  && XEXP (XEXP (op, 0), 1) == XEXP (op, 1)
 	  && GET_MODE_PRECISION (GET_MODE (op)) > INTVAL (XEXP (op, 1)))
 	{
-	  machine_mode tmode
-	    = mode_for_size (GET_MODE_PRECISION (GET_MODE (op))
-			     - INTVAL (XEXP (op, 1)), MODE_INT, 1);
-	  if (tmode != BLKmode)
+	  scalar_int_mode tmode;
+	  if (int_mode_for_size (GET_MODE_PRECISION (GET_MODE (op))
+				 - INTVAL (XEXP (op, 1)), 1).exists (&tmode))
 	    {
 	      rtx inner =
 		rtl_hooks.gen_lowpart_no_emit (tmode, XEXP (XEXP (op, 0), 0));
Index: gcc/stor-layout.c
===================================================================
--- gcc/stor-layout.c	2017-07-13 09:18:25.916974620 +0100
+++ gcc/stor-layout.c	2017-07-13 09:18:29.219658521 +0100
@@ -2454,10 +2454,11 @@ vector_type_mode (const_tree t)
       /* For integers, try mapping it to a same-sized scalar mode.  */
       if (GET_MODE_CLASS (innermode) == MODE_INT)
 	{
-	  mode = mode_for_size (TYPE_VECTOR_SUBPARTS (t)
-				* GET_MODE_BITSIZE (innermode), MODE_INT, 0);
-
-	  if (mode != VOIDmode && have_regs_of_mode[mode])
+	  unsigned int size = (TYPE_VECTOR_SUBPARTS (t)
+			       * GET_MODE_BITSIZE (innermode));
+	  scalar_int_mode mode;
+	  if (int_mode_for_size (size, 0).exists (&mode)
+	      && have_regs_of_mode[mode])
 	    return mode;
 	}
 
Index: gcc/tree-ssa-strlen.c
===================================================================
--- gcc/tree-ssa-strlen.c	2017-07-04 12:48:28.889063149 +0100
+++ gcc/tree-ssa-strlen.c	2017-07-13 09:18:29.219658521 +0100
@@ -2122,8 +2122,8 @@ handle_builtin_memcmp (gimple_stmt_itera
       unsigned align1 = get_pointer_alignment (arg1);
       unsigned align2 = get_pointer_alignment (arg2);
       unsigned align = MIN (align1, align2);
-      machine_mode mode = mode_for_size (leni, MODE_INT, 1);
-      if (mode != BLKmode
+      scalar_int_mode mode;
+      if (int_mode_for_size (leni, 1).exists (&mode)
 	  && (align >= leni || !SLOW_UNALIGNED_ACCESS (mode, align)))
 	{
 	  location_t loc = gimple_location (stmt2);
Index: gcc/tree-vect-data-refs.c
===================================================================
--- gcc/tree-vect-data-refs.c	2017-07-13 09:17:19.693324483 +0100
+++ gcc/tree-vect-data-refs.c	2017-07-13 09:18:29.220658428 +0100
@@ -59,15 +59,14 @@ Software Foundation; either version 3, o
 vect_lanes_optab_supported_p (const char *name, convert_optab optab,
 			      tree vectype, unsigned HOST_WIDE_INT count)
 {
-  machine_mode mode, array_mode;
+  machine_mode mode;
+  scalar_int_mode array_mode;
   bool limit_p;
 
   mode = TYPE_MODE (vectype);
   limit_p = !targetm.array_mode_supported_p (mode, count);
-  array_mode = mode_for_size (count * GET_MODE_BITSIZE (mode),
-			      MODE_INT, limit_p);
-
-  if (array_mode == BLKmode)
+  if (!int_mode_for_size (count * GET_MODE_BITSIZE (mode),
+			  limit_p).exists (&array_mode))
     {
       if (dump_enabled_p ())
 	dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
Index: gcc/tree-vect-generic.c
===================================================================
--- gcc/tree-vect-generic.c	2017-07-13 09:18:21.537428606 +0100
+++ gcc/tree-vect-generic.c	2017-07-13 09:18:29.220658428 +0100
@@ -288,7 +288,6 @@ expand_vector_parallel (gimple_stmt_iter
 			enum tree_code code)
 {
   tree result, compute_type;
-  machine_mode mode;
   int n_words = tree_to_uhwi (TYPE_SIZE_UNIT (type)) / UNITS_PER_WORD;
   location_t loc = gimple_location (gsi_stmt (*gsi));
 
@@ -312,7 +311,8 @@ expand_vector_parallel (gimple_stmt_iter
   else
     {
       /* Use a single scalar operation with a mode no wider than word_mode.  */
-      mode = mode_for_size (tree_to_uhwi (TYPE_SIZE (type)), MODE_INT, 0);
+      scalar_int_mode mode
+	= *int_mode_for_size (tree_to_uhwi (TYPE_SIZE (type)), 0);
       compute_type = lang_hooks.types.type_for_mode (mode, 1);
       result = f (gsi, compute_type, a, b, NULL_TREE, NULL_TREE, code, type);
       warning_at (loc, OPT_Wvector_operation_performance,
Index: gcc/tree-vect-stmts.c
===================================================================
--- gcc/tree-vect-stmts.c	2017-07-13 09:18:21.538428497 +0100
+++ gcc/tree-vect-stmts.c	2017-07-13 09:18:29.221658334 +0100
@@ -7007,7 +7007,7 @@ vectorizable_load (gimple *stmt, gimple_
 		 to a larger load.  */
 	      unsigned lsize
 		= group_size * TYPE_PRECISION (TREE_TYPE (vectype));
-	      machine_mode elmode = mode_for_size (lsize, MODE_INT, 0);
+	      scalar_int_mode elmode = *int_mode_for_size (lsize, 0);
 	      machine_mode vmode = mode_for_vector (elmode,
 						    nunits / group_size);
 	      /* If we can't construct such a vector fall back to
Index: gcc/ada/gcc-interface/decl.c
===================================================================
--- gcc/ada/gcc-interface/decl.c	2017-07-13 09:18:22.913280204 +0100
+++ gcc/ada/gcc-interface/decl.c	2017-07-13 09:18:29.208659553 +0100
@@ -3625,11 +3625,12 @@ gnat_to_gnu_entity (Entity_Id gnat_entit
 	/* True if we make a dummy type here.  */
 	bool made_dummy = false;
 	/* The mode to be used for the pointer type.  */
-	machine_mode p_mode = mode_for_size (esize, MODE_INT, 0);
+	scalar_int_mode p_mode;
 	/* The GCC type used for the designated type.  */
 	tree gnu_desig_type = NULL_TREE;
 
-	if (!targetm.valid_pointer_mode (p_mode))
+	if (!int_mode_for_size (esize, 0).exists (&p_mode)
+	    || !targetm.valid_pointer_mode (p_mode))
 	  p_mode = ptr_mode;
 
 	/* If either the designated type or its full view is an unconstrained
@@ -5939,12 +5940,11 @@ gnat_to_gnu_subprog_type (Entity_Id gnat
 	      unsigned int size
 		= TREE_INT_CST_LOW (TYPE_SIZE (gnu_cico_return_type));
 	      unsigned int i = BITS_PER_UNIT;
-	      machine_mode mode;
+	      scalar_int_mode mode;
 
 	      while (i < size)
 		i <<= 1;
-	      mode = mode_for_size (i, MODE_INT, 0);
-	      if (mode != BLKmode)
+	      if (int_mode_for_size (i, 0).exists (&mode))
 		{
 		  SET_TYPE_MODE (gnu_cico_return_type, mode);
 		  SET_TYPE_ALIGN (gnu_cico_return_type,
Index: gcc/ada/gcc-interface/utils.c
===================================================================
--- gcc/ada/gcc-interface/utils.c	2017-07-13 09:18:23.793186493 +0100
+++ gcc/ada/gcc-interface/utils.c	2017-07-13 09:18:29.208659553 +0100
@@ -1166,8 +1166,9 @@ make_type_from_size (tree type, tree siz
 	 may need to return the thin pointer.  */
       if (TYPE_FAT_POINTER_P (type) && size < POINTER_SIZE * 2)
 	{
-	  machine_mode p_mode = mode_for_size (size, MODE_INT, 0);
-	  if (!targetm.valid_pointer_mode (p_mode))
+	  scalar_int_mode p_mode;
+	  if (!int_mode_for_size (size, 0).exists (&p_mode)
+	      || !targetm.valid_pointer_mode (p_mode))
 	    p_mode = ptr_mode;
 	  return
 	    build_pointer_type_for_mode
