[11/77] Add a float_mode_for_size helper function

This provides a type-safe way to ask for a float mode and get it as a
scalar_float_mode.

2017-08-30  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* coretypes.h (opt_scalar_float_mode): New typedef.
	* machmode.h (float_mode_for_size): New function.
	* emit-rtl.c (double_mode): Delete.
	(init_emit_once): Use float_mode_for_size.
	* stor-layout.c (layout_type): Likewise.
	* gdbhooks.py (build_pretty_printer): Handle opt_scalar_float_mode.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r251463

gcc/ChangeLog

@@ -2,6 +2,17 @@
 	    Alan Hayward  <alan.hayward@arm.com>
 	    David Sherwood  <david.sherwood@arm.com>
 
+	* coretypes.h (opt_scalar_float_mode): New typedef.
+	* machmode.h (float_mode_for_size): New function.
+	* emit-rtl.c (double_mode): Delete.
+	(init_emit_once): Use float_mode_for_size.
+	* stor-layout.c (layout_type): Likewise.
+	* gdbhooks.py (build_pretty_printer): Handle opt_scalar_float_mode.
+
+2017-08-30  Richard Sandiford  <richard.sandiford@linaro.org>
+	    Alan Hayward  <alan.hayward@arm.com>
+	    David Sherwood  <david.sherwood@arm.com>
+
 	* output.h (assemble_real): Take a scalar_float_mode.
 	* config/arm/arm.c (arm_assemble_integer): Update accordingly.
 	* config/arm/arm.md (consttable_4): Likewise.

gcc/coretypes.h

@@ -57,6 +57,7 @@ typedef struct rtx_def *rtx;
 typedef const struct rtx_def *const_rtx;
 class scalar_float_mode;
 template<typename> class opt_mode;
+typedef opt_mode<scalar_float_mode> opt_scalar_float_mode;
 
 /* Subclasses of rtx_def, using indentation to show the class
    hierarchy, along with the relevant invariant.

gcc/emit-rtl.c

@@ -72,7 +72,6 @@ struct target_rtl *this_target_rtl = &default_target_rtl;
 
 machine_mode byte_mode;	/* Mode whose width is BITS_PER_UNIT.  */
 machine_mode word_mode;	/* Mode whose width is BITS_PER_WORD.  */
-machine_mode double_mode;	/* Mode whose width is DOUBLE_TYPE_SIZE.  */
 machine_mode ptr_mode;	/* Mode whose width is POINTER_SIZE.  */
 
 /* Datastructures maintained for currently processed function in RTL form.  */
@@ -5889,7 +5888,7 @@ init_emit_once (void)
 {
   int i;
   machine_mode mode;
-  machine_mode double_mode;
+  scalar_float_mode double_mode;
 
   /* Initialize the CONST_INT, CONST_WIDE_INT, CONST_DOUBLE,
      CONST_FIXED, and memory attribute hash tables.  */
@@ -5933,7 +5932,7 @@ init_emit_once (void)
   else
     const_true_rtx = gen_rtx_CONST_INT (VOIDmode, STORE_FLAG_VALUE);
 
-  double_mode = mode_for_size (DOUBLE_TYPE_SIZE, MODE_FLOAT, 0);
+  double_mode = float_mode_for_size (DOUBLE_TYPE_SIZE).require ();
 
   real_from_integer (&dconst0, double_mode, 0, SIGNED);
   real_from_integer (&dconst1, double_mode, 1, SIGNED);

gcc/gdbhooks.py

@@ -542,6 +542,8 @@ def build_pretty_printer():
 
     pp.add_printer_for_regex(r'opt_mode<(\S+)>',
                              'opt_mode', OptMachineModePrinter)
+    pp.add_printer_for_types(['opt_scalar_float_mode'],
+                             'opt_mode', OptMachineModePrinter)
     pp.add_printer_for_types(['scalar_float_mode'],
                              'scalar_float_mode', MachineModePrinter)
 

gcc/machmode.h

@@ -520,7 +520,16 @@ extern const unsigned char mode_complex[NUM_MACHINE_MODES];
 
 extern machine_mode mode_for_size (unsigned int, enum mode_class, int);
 
-/* Similar, but find the smallest mode for a given width.  */
+/* Return the machine mode to use for a MODE_FLOAT of SIZE bits, if one
+   exists.  */
+
+inline opt_scalar_float_mode
+float_mode_for_size (unsigned int size)
+{
+  return dyn_cast <scalar_float_mode> (mode_for_size (size, MODE_FLOAT, 0));
+}
+
+/* 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);

gcc/stor-layout.c

@@ -2205,14 +2205,17 @@ layout_type (tree type)
       break;
 
     case REAL_TYPE:
-      /* Allow the caller to choose the type mode, which is how decimal
-	 floats are distinguished from binary ones.  */
-      if (TYPE_MODE (type) == VOIDmode)
-	SET_TYPE_MODE (type,
-		       mode_for_size (TYPE_PRECISION (type), MODE_FLOAT, 0));
-      TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (TYPE_MODE (type)));
-      TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (TYPE_MODE (type)));
-      break;
+      {
+	/* Allow the caller to choose the type mode, which is how decimal
+	   floats are distinguished from binary ones.  */
+	if (TYPE_MODE (type) == VOIDmode)
+	  SET_TYPE_MODE
+	    (type, float_mode_for_size (TYPE_PRECISION (type)).require ());
+	scalar_float_mode mode = as_a <scalar_float_mode> (TYPE_MODE (type));
+	TYPE_SIZE (type) = bitsize_int (GET_MODE_BITSIZE (mode));
+	TYPE_SIZE_UNIT (type) = size_int (GET_MODE_SIZE (mode));
+	break;
+      }
 
    case FIXED_POINT_TYPE:
      /* TYPE_MODE (type) has been set already.  */