[19/67] Add a smallest_int_mode_for_size helper function

[Richard Sandiford <richard.sandiford@arm.com>]

This patch adds a wrapper around smallest_mode_for_size
for cases in which the mode class is MODE_INT.  Unlike
(int_)mode_for_size, smallest_mode_for_size always returns
a mode of the specified class, asserting if no such mode exists.
smallest_int_mode_for_size therefore returns a scalar_int_mode
rather than an opt_scalar_int_mode.

gcc/
2016-11-24  Richard Sandiford  <richard.sandiford@arm.com>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

	* machmode.h (smallest_mode_for_size): Fix formatting.
	(smallest_int_mode_for_size): New function.
	* cfgexpand.c (expand_debug_expr): Use smallest_int_mode_for_size
	instead of smallest_mopde_for_size.
	* combine.c (make_extraction): Likewise.
	* config/arc/arc.c (arc_expand_movmem): Likewise.
	* config/i386/i386.c (ix86_get_mask_mode): Likewise.
	* config/i386/i386.md (define_split): Likewise.
	* config/s390/s390.c (s390_expand_insv): Likewise.
	* config/sparc/sparc.c (assign_int_registers): Likewise.
	* config/spu/spu.c (spu_function_value): Likewise.
	(spu_function_arg): Likewise.
	* coverage.c (get_gcov_type): Likewise.
	(get_gcov_unsigned_t): Likewise.
	* dse.c (find_shift_sequence): Likewise.
	* expr.c (convert_move): Likewise.
	(store_field): Likewise.
	* internal-fn.c (expand_arith_overflow): Likewise.
	* optabs-query.c (get_best_extraction_insn): Likewise.
	* optabs.c (expand_twoval_binop_libfunc): Likewise.
	* stor-layout.c (layout_type): Likewise.
	(initialize_sizetypes): Likewise.
	* targhooks.c (default_get_mask_mode): Likewise.
	* tree-ssa-loop-manip.c (canonicalize_loop_ivs): Likewise.

diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index 3915c97..b531996 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -4486,7 +4486,7 @@ expand_debug_expr (tree exp)
 	  {
 	    if (mode1 == VOIDmode)
 	      /* Bitfield.  */
-	      mode1 = smallest_mode_for_size (bitsize, MODE_INT);
+	      mode1 = smallest_int_mode_for_size (bitsize);
 	    if (bitpos >= BITS_PER_UNIT)
 	      {
 		op0 = adjust_address_nv (op0, mode1, bitpos / BITS_PER_UNIT);
diff --git a/gcc/combine.c b/gcc/combine.c
index 573c558..29b849a 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -7586,7 +7586,7 @@ make_extraction (machine_mode mode, rtx inner, HOST_WIDE_INT pos,
     {
       /* Be careful not to go beyond the extracted object and maintain the
 	 natural alignment of the memory.  */
-      wanted_inner_mode = smallest_mode_for_size (len, MODE_INT);
+      wanted_inner_mode = smallest_int_mode_for_size (len);
       while (pos % GET_MODE_BITSIZE (wanted_inner_mode) + len
 	     > GET_MODE_BITSIZE (wanted_inner_mode))
 	wanted_inner_mode = *GET_MODE_WIDER_MODE (wanted_inner_mode);
diff --git a/gcc/config/arc/arc.c b/gcc/config/arc/arc.c
index 2b25a37..bc5c031 100644
--- a/gcc/config/arc/arc.c
+++ b/gcc/config/arc/arc.c
@@ -7621,7 +7621,7 @@ arc_expand_movmem (rtx *operands)
 
       while (piece > size)
 	piece >>= 1;
-      mode = smallest_mode_for_size (piece * BITS_PER_UNIT, MODE_INT);
+      mode = smallest_int_mode_for_size (piece * BITS_PER_UNIT);
       /* If we don't re-use temporaries, the scheduler gets carried away,
 	 and the register pressure gets unnecessarily high.  */
       if (0 && tmpx[i] && GET_MODE (tmpx[i]) == mode)
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 0fbb3ed..4d74bc4 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -50331,11 +50331,11 @@ ix86_get_mask_mode (unsigned nunits, unsigned vector_size)
       || (TARGET_AVX512VL && (vector_size == 32 || vector_size == 16)))
     {
       if (elem_size == 4 || elem_size == 8 || TARGET_AVX512BW)
-	return smallest_mode_for_size (nunits, MODE_INT);
+	return smallest_int_mode_for_size (nunits);
     }
 
-  machine_mode elem_mode
-    = smallest_mode_for_size (elem_size * BITS_PER_UNIT, MODE_INT);
+  scalar_int_mode elem_mode
+    = smallest_int_mode_for_size (elem_size * BITS_PER_UNIT);
 
   gcc_assert (elem_size * nunits == vector_size);
 
diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index f2248a5..1433cbf 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -7936,7 +7936,7 @@
 	 no matter the size of the test.  So find a mode that works.  */
       if (! MEM_VOLATILE_P (val))
 	{
-	  mode = smallest_mode_for_size (pos + len, MODE_INT);
+	  mode = smallest_int_mode_for_size (pos + len);
 	  val = adjust_address (val, mode, 0);
 	}
     }
diff --git a/gcc/config/s390/s390.c b/gcc/config/s390/s390.c
index a3bb952..510c24c 100644
--- a/gcc/config/s390/s390.c
+++ b/gcc/config/s390/s390.c
@@ -6093,7 +6093,7 @@ s390_expand_insv (rtx dest, rtx op1, rtx op2, rtx src)
       return true;
     }
 
-  smode = smallest_mode_for_size (bitsize, MODE_INT);
+  smode = smallest_int_mode_for_size (bitsize);
   smode_bsize = GET_MODE_BITSIZE (smode);
   mode_bsize = GET_MODE_BITSIZE (mode);
 
diff --git a/gcc/config/sparc/sparc.c b/gcc/config/sparc/sparc.c
index 995b0af..28bb0c5 100644
--- a/gcc/config/sparc/sparc.c
+++ b/gcc/config/sparc/sparc.c
@@ -6626,8 +6626,8 @@ assign_int_registers (HOST_WIDE_INT bitpos, assign_data_t *data)
      the latter case we may pick up unwanted bits.  It's not a problem
      at the moment but may wish to revisit.  */
   if (intoffset % BITS_PER_WORD != 0)
-    mode = smallest_mode_for_size (BITS_PER_WORD - intoffset % BITS_PER_WORD,
-			  	   MODE_INT);
+    mode = smallest_int_mode_for_size (BITS_PER_WORD
+				       - intoffset % BITS_PER_WORD);
   else
     mode = word_mode;
 
diff --git a/gcc/config/spu/spu.c b/gcc/config/spu/spu.c
index e8fd572..ea449e0 100644
--- a/gcc/config/spu/spu.c
+++ b/gcc/config/spu/spu.c
@@ -3808,8 +3808,7 @@ spu_function_value (const_tree type, const_tree func ATTRIBUTE_UNUSED)
 	{
 	  if (byte_size < 4)
 	    byte_size = 4;
-	  smode =
-	    smallest_mode_for_size (byte_size * BITS_PER_UNIT, MODE_INT);
+	  smode = smallest_int_mode_for_size (byte_size * BITS_PER_UNIT);
 	  RTVEC_ELT (v, n) =
 	    gen_rtx_EXPR_LIST (VOIDmode,
 			       gen_rtx_REG (smode, FIRST_RETURN_REGNUM + n),
@@ -3847,7 +3846,7 @@ spu_function_arg (cumulative_args_t cum_v,
       rtx gr_reg;
       if (byte_size < 4)
 	byte_size = 4;
-      smode = smallest_mode_for_size (byte_size * BITS_PER_UNIT, MODE_INT);
+      smode = smallest_int_mode_for_size (byte_size * BITS_PER_UNIT);
       gr_reg = gen_rtx_EXPR_LIST (VOIDmode,
 				  gen_rtx_REG (smode, FIRST_ARG_REGNUM + *cum),
 				  const0_rtx);
diff --git a/gcc/coverage.c b/gcc/coverage.c
index 4167e26..bd351e5 100644
--- a/gcc/coverage.c
+++ b/gcc/coverage.c
@@ -143,8 +143,8 @@ static void coverage_obj_finish (vec<constructor_elt, va_gc> *);
 tree
 get_gcov_type (void)
 {
-  machine_mode mode
-    = smallest_mode_for_size (LONG_LONG_TYPE_SIZE > 32 ? 64 : 32, MODE_INT);
+  scalar_int_mode mode
+    = smallest_int_mode_for_size (LONG_LONG_TYPE_SIZE > 32 ? 64 : 32);
   return lang_hooks.types.type_for_mode (mode, false);
 }
 
@@ -153,7 +153,7 @@ get_gcov_type (void)
 static tree
 get_gcov_unsigned_t (void)
 {
-  machine_mode mode = smallest_mode_for_size (32, MODE_INT);
+  scalar_int_mode mode = smallest_int_mode_for_size (32);
   return lang_hooks.types.type_for_mode (mode, true);
 }
 \f
diff --git a/gcc/dse.c b/gcc/dse.c
index c8e22a7..93ff9a7 100644
--- a/gcc/dse.c
+++ b/gcc/dse.c
@@ -1573,7 +1573,7 @@ find_shift_sequence (int access_size,
 		     int shift, bool speed, bool require_cst)
 {
   machine_mode store_mode = GET_MODE (store_info->mem);
-  machine_mode new_mode;
+  scalar_int_mode new_mode;
   rtx read_reg = NULL;
 
   /* Some machines like the x86 have shift insns for each size of
@@ -1583,14 +1583,15 @@ find_shift_sequence (int access_size,
      justify the value we want to read but is available in one insn on
      the machine.  */
 
-  FOR_EACH_MODE_FROM (new_mode,
-		      smallest_mode_for_size (access_size * BITS_PER_UNIT,
-					      MODE_INT))
+  opt_scalar_int_mode new_mode_iter;
+  FOR_EACH_MODE_FROM (new_mode_iter,
+		      smallest_int_mode_for_size (access_size * BITS_PER_UNIT))
     {
       rtx target, new_reg, new_lhs;
       rtx_insn *shift_seq, *insn;
       int cost;
 
+      new_mode = *new_mode_iter;
       if (GET_MODE_BITSIZE (new_mode) > BITS_PER_WORD)
 	break;
 
diff --git a/gcc/expr.c b/gcc/expr.c
index 8141016..2e59bfd 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -344,8 +344,8 @@ convert_move (rtx to, rtx from, int unsignedp)
      xImode for all MODE_PARTIAL_INT modes they use, but no others.  */
   if (GET_MODE_CLASS (to_mode) == MODE_PARTIAL_INT)
     {
-      machine_mode full_mode
-	= smallest_mode_for_size (GET_MODE_BITSIZE (to_mode), MODE_INT);
+      scalar_int_mode full_mode
+	= smallest_int_mode_for_size (GET_MODE_BITSIZE (to_mode));
 
       gcc_assert (convert_optab_handler (trunc_optab, to_mode, full_mode)
 		  != CODE_FOR_nothing);
@@ -359,8 +359,8 @@ convert_move (rtx to, rtx from, int unsignedp)
   if (GET_MODE_CLASS (from_mode) == MODE_PARTIAL_INT)
     {
       rtx new_from;
-      machine_mode full_mode
-	= smallest_mode_for_size (GET_MODE_BITSIZE (from_mode), MODE_INT);
+      scalar_int_mode full_mode
+	= smallest_int_mode_for_size (GET_MODE_BITSIZE (from_mode));
       convert_optab ctab = unsignedp ? zext_optab : sext_optab;
       enum insn_code icode;
 
@@ -6898,7 +6898,7 @@ store_field (rtx target, HOST_WIDE_INT bitsize, HOST_WIDE_INT bitpos,
 	  HOST_WIDE_INT size = int_size_in_bytes (TREE_TYPE (exp));
 	  rtx temp_target;
 	  if (mode == BLKmode || mode == VOIDmode)
-	    mode = smallest_mode_for_size (size * BITS_PER_UNIT, MODE_INT);
+	    mode = smallest_int_mode_for_size (size * BITS_PER_UNIT);
 	  temp_target = gen_reg_rtx (mode);
 	  emit_group_store (temp_target, temp, TREE_TYPE (exp), size);
 	  temp = temp_target;
@@ -6916,7 +6916,7 @@ store_field (rtx target, HOST_WIDE_INT bitsize, HOST_WIDE_INT bitpos,
 	    {
 	      HOST_WIDE_INT size = int_size_in_bytes (TREE_TYPE (exp));
 	      rtx temp_target;
-	      mode = smallest_mode_for_size (size * BITS_PER_UNIT, MODE_INT);
+	      mode = smallest_int_mode_for_size (size * BITS_PER_UNIT);
 	      temp_target = gen_reg_rtx (mode);
 	      temp_target
 	        = extract_bit_field (temp, size * BITS_PER_UNIT, 0, 1,
diff --git a/gcc/internal-fn.c b/gcc/internal-fn.c
index cdcbaa4..49075c2 100644
--- a/gcc/internal-fn.c
+++ b/gcc/internal-fn.c
@@ -2171,7 +2171,7 @@ expand_arith_overflow (enum tree_code code, gimple *stmt)
       if (orig_precres == precres && precop <= BITS_PER_WORD)
 	{
 	  int p = MAX (min_precision, precop);
-	  machine_mode m = smallest_mode_for_size (p, MODE_INT);
+	  scalar_int_mode m = smallest_int_mode_for_size (p);
 	  tree optype = build_nonstandard_integer_type (GET_MODE_PRECISION (m),
 							uns0_p && uns1_p
 							&& unsr_p);
@@ -2213,7 +2213,7 @@ expand_arith_overflow (enum tree_code code, gimple *stmt)
       if (orig_precres == precres)
 	{
 	  int p = MAX (prec0, prec1);
-	  machine_mode m = smallest_mode_for_size (p, MODE_INT);
+	  scalar_int_mode m = smallest_int_mode_for_size (p);
 	  tree optype = build_nonstandard_integer_type (GET_MODE_PRECISION (m),
 							uns0_p && uns1_p
 							&& unsr_p);
diff --git a/gcc/machmode.h b/gcc/machmode.h
index f1519a8..b3d2d76 100644
--- a/gcc/machmode.h
+++ b/gcc/machmode.h
@@ -589,9 +589,16 @@ float_mode_for_size (unsigned int size)
 
 /* Similar to mode_for_size, but find the smallest mode for a given width.  */
 
-extern machine_mode smallest_mode_for_size (unsigned int,
-						 enum mode_class);
+extern machine_mode smallest_mode_for_size (unsigned int, enum mode_class);
 
+/* Find the narrowest integer mode that contains at least SIZE bits.
+   Such a mode must exist.  */
+
+inline scalar_int_mode
+smallest_int_mode_for_size (unsigned int size)
+{
+  return as_a <scalar_int_mode> (smallest_mode_for_size (size, MODE_INT));
+}
 
 /* Return an integer mode of exactly the same size as the input mode.  */
 
diff --git a/gcc/optabs-query.c b/gcc/optabs-query.c
index fdde578..e664587 100644
--- a/gcc/optabs-query.c
+++ b/gcc/optabs-query.c
@@ -193,13 +193,15 @@ get_best_extraction_insn (extraction_insn *insn,
 			  unsigned HOST_WIDE_INT struct_bits,
 			  machine_mode field_mode)
 {
-  machine_mode mode = smallest_mode_for_size (struct_bits, MODE_INT);
-  FOR_EACH_MODE_FROM (mode, mode)
+  opt_scalar_int_mode mode_iter;
+  FOR_EACH_MODE_FROM (mode_iter, smallest_int_mode_for_size (struct_bits))
     {
+      scalar_int_mode mode = *mode_iter;
       if (get_extraction_insn (insn, pattern, type, mode))
 	{
-	  FOR_EACH_MODE_FROM (mode, mode)
+	  FOR_EACH_MODE_FROM (mode_iter, mode)
 	    {
+	      mode = *mode_iter;
 	      if (GET_MODE_SIZE (mode) > GET_MODE_SIZE (field_mode)
 		  || TRULY_NOOP_TRUNCATION_MODES_P (insn->field_mode,
 						    field_mode))
diff --git a/gcc/optabs.c b/gcc/optabs.c
index b2c8006..edafe4a 100644
--- a/gcc/optabs.c
+++ b/gcc/optabs.c
@@ -2082,8 +2082,7 @@ expand_twoval_binop_libfunc (optab binoptab, rtx op0, rtx op1,
 
   /* The value returned by the library function will have twice as
      many bits as the nominal MODE.  */
-  libval_mode = smallest_mode_for_size (2 * GET_MODE_BITSIZE (mode),
-					MODE_INT);
+  libval_mode = smallest_int_mode_for_size (2 * GET_MODE_BITSIZE (mode));
   start_sequence ();
   libval = emit_library_call_value (libfunc, NULL_RTX, LCT_CONST,
 				    libval_mode, 2,
diff --git a/gcc/stor-layout.c b/gcc/stor-layout.c
index 6337764..91e79ad 100644
--- a/gcc/stor-layout.c
+++ b/gcc/stor-layout.c
@@ -2121,12 +2121,15 @@ layout_type (tree type)
     case BOOLEAN_TYPE:
     case INTEGER_TYPE:
     case ENUMERAL_TYPE:
-      SET_TYPE_MODE (type,
-		     smallest_mode_for_size (TYPE_PRECISION (type), MODE_INT));
-      TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
-      /* Don't set TYPE_PRECISION here, as it may be set by a bitfield.  */
-      TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
-      break;
+      {
+	scalar_int_mode mode
+	  = smallest_int_mode_for_size (TYPE_PRECISION (type));
+	SET_TYPE_MODE (type, mode);
+	TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
+	/* Don't set TYPE_PRECISION here, as it may be set by a bitfield.  */
+	TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
+	break;
+      }
 
     case REAL_TYPE:
       {
@@ -2571,8 +2574,7 @@ initialize_sizetypes (void)
 
   bprecision
     = MIN (precision + LOG2_BITS_PER_UNIT + 1, MAX_FIXED_MODE_SIZE);
-  bprecision
-    = GET_MODE_PRECISION (smallest_mode_for_size (bprecision, MODE_INT));
+  bprecision = GET_MODE_PRECISION (smallest_int_mode_for_size (bprecision));
   if (bprecision > HOST_BITS_PER_DOUBLE_INT)
     bprecision = HOST_BITS_PER_DOUBLE_INT;
 
@@ -2587,17 +2589,18 @@ initialize_sizetypes (void)
   TYPE_UNSIGNED (bitsizetype) = 1;
 
   /* Now layout both types manually.  */
-  SET_TYPE_MODE (sizetype, smallest_mode_for_size (precision, MODE_INT));
+  scalar_int_mode mode = smallest_int_mode_for_size (precision);
+  SET_TYPE_MODE (sizetype, mode);
   SET_TYPE_ALIGN (sizetype, GET_MODE_ALIGNMENT (TYPE_MODE (sizetype)));
   TYPE_SIZE (sizetype) = bitsize_int (precision);
-  TYPE_SIZE_UNIT (sizetype) = size_int (GET_MODE_SIZE (TYPE_MODE (sizetype)));
+  TYPE_SIZE_UNIT (sizetype) = size_int (GET_MODE_SIZE (mode));
   set_min_and_max_values_for_integral_type (sizetype, precision, UNSIGNED);
 
-  SET_TYPE_MODE (bitsizetype, smallest_mode_for_size (bprecision, MODE_INT));
+  mode = smallest_int_mode_for_size (bprecision);
+  SET_TYPE_MODE (bitsizetype, mode);
   SET_TYPE_ALIGN (bitsizetype, GET_MODE_ALIGNMENT (TYPE_MODE (bitsizetype)));
   TYPE_SIZE (bitsizetype) = bitsize_int (bprecision);
-  TYPE_SIZE_UNIT (bitsizetype)
-    = size_int (GET_MODE_SIZE (TYPE_MODE (bitsizetype)));
+  TYPE_SIZE_UNIT (bitsizetype) = size_int (GET_MODE_SIZE (mode));
   set_min_and_max_values_for_integral_type (bitsizetype, bprecision, UNSIGNED);
 
   /* Create the signed variants of *sizetype.  */
diff --git a/gcc/targhooks.c b/gcc/targhooks.c
index 90892fa..4f7744f 100644
--- a/gcc/targhooks.c
+++ b/gcc/targhooks.c
@@ -1184,8 +1184,8 @@ machine_mode
 default_get_mask_mode (unsigned nunits, unsigned vector_size)
 {
   unsigned elem_size = vector_size / nunits;
-  machine_mode elem_mode
-    = smallest_mode_for_size (elem_size * BITS_PER_UNIT, MODE_INT);
+  scalar_int_mode elem_mode
+    = smallest_int_mode_for_size (elem_size * BITS_PER_UNIT);
   machine_mode vector_mode;
 
   gcc_assert (elem_size * nunits == vector_size);
diff --git a/gcc/tree-ssa-loop-manip.c b/gcc/tree-ssa-loop-manip.c
index f2d3492..e624a46 100644
--- a/gcc/tree-ssa-loop-manip.c
+++ b/gcc/tree-ssa-loop-manip.c
@@ -1462,7 +1462,6 @@ canonicalize_loop_ivs (struct loop *loop, tree *nit, bool bump_in_latch)
   gcond *stmt;
   edge exit = single_dom_exit (loop);
   gimple_seq stmts;
-  machine_mode mode;
   bool unsigned_p = false;
 
   for (psi = gsi_start_phis (loop->header);
@@ -1489,7 +1488,7 @@ canonicalize_loop_ivs (struct loop *loop, tree *nit, bool bump_in_latch)
       precision = TYPE_PRECISION (type);
     }
 
-  mode = smallest_mode_for_size (precision, MODE_INT);
+  scalar_int_mode mode = smallest_int_mode_for_size (precision);
   precision = GET_MODE_PRECISION (mode);
   type = build_nonstandard_integer_type (precision, unsigned_p);