[4/77] Add FOR_EACH iterators for modes

The new iterators are:

- FOR_EACH_MODE_IN_CLASS: iterate over all the modes in a mode class.

- FOR_EACH_MODE_FROM: iterate over all the modes in a class,
  starting at a given mode.

- FOR_EACH_WIDER_MODE: iterate over all the modes in a class,
  starting at the next widest mode after a given mode.

- FOR_EACH_2XWIDER_MODE: same, but considering only modes that
  are two times wider than the previous mode.

- FOR_EACH_MODE_UNTIL: iterate over all the modes in a class until
  a given mode is reached.

- FOR_EACH_MODE: iterate over all the modes in a class between
  two given modes, inclusive of the first but not the second.

These help with the stronger type checking added by later patches,
since every new mode will be in the same class as the previous one.

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

gcc/
	* machmode.h (mode_traits): New structure.
	(get_narrowest_mode): New function.
	(mode_iterator::start): Likewise.
	(mode_iterator::iterate_p): Likewise.
	(mode_iterator::get_wider): Likewise.
	(mode_iterator::get_known_wider): Likewise.
	(mode_iterator::get_2xwider): Likewise.
	(FOR_EACH_MODE_IN_CLASS): New mode iterator.
	(FOR_EACH_MODE): Likewise.
	(FOR_EACH_MODE_FROM): Likewise.
	(FOR_EACH_MODE_UNTIL): Likewise.
	(FOR_EACH_WIDER_MODE): Likewise.
	(FOR_EACH_2XWIDER_MODE): Likewise.
	* builtins.c (expand_builtin_strlen): Use new mode iterators.
	* combine.c (simplify_comparison): Likewise
	* config/i386/i386.c (type_natural_mode): Likewise.
	* cse.c (cse_insn): Likewise.
	* dse.c (find_shift_sequence): Likewise.
	* emit-rtl.c (init_derived_machine_modes): Likewise.
	(init_emit_once): Likewise.
	* explow.c (hard_function_value): Likewise.
	* expmed.c (extract_fixed_bit_field_1): Likewise.
	(extract_bit_field_1): Likewise.
	(expand_divmod): Likewise.
	(emit_store_flag_1): Likewise.
	* expr.c (init_expr_target): Likewise.
	(convert_move): Likewise.
	(alignment_for_piecewise_move): Likewise.
	(widest_int_mode_for_size): Likewise.
	(emit_block_move_via_movmem): Likewise.
	(copy_blkmode_to_reg): Likewise.
	(set_storage_via_setmem): Likewise.
	(compress_float_constant): Likewise.
	* omp-low.c (omp_clause_aligned_alignment): Likewise.
	* optabs-query.c (get_best_extraction_insn): Likewise.
	* optabs.c (expand_binop): Likewise.
	(expand_twoval_unop): Likewise.
	(expand_twoval_binop): Likewise.
	(widen_leading): Likewise.
	(widen_bswap): Likewise.
	(expand_parity): Likewise.
	(expand_unop): Likewise.
	(prepare_cmp_insn): Likewise.
	(prepare_float_lib_cmp): Likewise.
	(expand_float): Likewise.
	(expand_fix): Likewise.
	(expand_sfix_optab): Likewise.
	* postreload.c (move2add_use_add2_insn): Likewise.
	* reg-stack.c (reg_to_stack): Likewise.
	* reginfo.c (choose_hard_reg_mode): Likewise.
	* rtlanal.c (init_num_sign_bit_copies_in_rep): Likewise.
	* stor-layout.c (mode_for_size): Likewise.
	(smallest_mode_for_size): Likewise.
	(mode_for_vector): Likewise.
	(finish_bitfield_representative): Likewise.
	* tree-ssa-math-opts.c (target_supports_divmod_p): Likewise.
	* tree-vect-generic.c (type_for_widest_vector_mode): Likewise.
	* tree-vect-stmts.c (vectorizable_conversion): Likewise.
	* var-tracking.c (prepare_call_arguments): Likewise.

gcc/ada/
	* gcc-interface/misc.c (fp_prec_to_size): Use new mode iterators.
	(fp_size_to_prec): Likewise.

gcc/c-family/
	* c-common.c (c_common_fixed_point_type_for_size): Use new mode
	iterators.
	* c-cppbuiltin.c (c_cpp_builtins): Likewise.

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

From-SVN: r251455

1 files changed, 139 insertions, 0 deletions

diff --git a/gcc/machmode.h b/gcc/machmode.h
index 330fdf9..c272888 100644
--- a/gcc/machmode.h
+++ b/gcc/machmode.h
@@ -29,6 +29,44 @@ extern const unsigned short mode_unit_precision[NUM_MACHINE_MODES];
 extern const unsigned char mode_wider[NUM_MACHINE_MODES];
 extern const unsigned char mode_2xwider[NUM_MACHINE_MODES];
 
+template<typename T>
+struct mode_traits
+{
+  /* For use by the machmode support code only.
+
+     There are cases in which the machmode support code needs to forcibly
+     convert a machine_mode to a specific mode class T, and in which the
+     context guarantees that this is valid without the need for an assert.
+     This can be done using:
+
+       return typename mode_traits<T>::from_int (mode);
+
+     when returning a T and:
+
+       res = T (typename mode_traits<T>::from_int (mode));
+
+     when assigning to a value RES that must be assignment-compatible
+     with (but possibly not the same as) T.
+
+     Here we use an enum type distinct from machine_mode but with the
+     same range as machine_mode.  T should have a constructor that
+     accepts this enum type; it should not have a constructor that
+     accepts machine_mode.
+
+     We use this somewhat indirect approach to avoid too many constructor
+     calls when the compiler is built with -O0.  For example, even in
+     unoptimized code, the return statement above would construct the
+     returned T directly from the numerical value of MODE.  */
+  enum from_int { dummy = MAX_MACHINE_MODE };
+};
+
+template<>
+struct mode_traits<machine_mode>
+{
+  /* machine_mode itself needs no conversion.  */
+  typedef machine_mode from_int;
+};
+
 /* Get the name of mode MODE as a string.  */
 
 extern const char * const mode_name[NUM_MACHINE_MODES];
@@ -395,6 +433,16 @@ extern const unsigned char class_narrowest_mode[MAX_MODE_CLASS];
 #define GET_CLASS_NARROWEST_MODE(CLASS) \
   ((machine_mode) class_narrowest_mode[CLASS])
 
+/* Return the narrowest mode in T's class.  */
+
+template<typename T>
+inline T
+get_narrowest_mode (T mode)
+{
+  return typename mode_traits<T>::from_int
+    (class_narrowest_mode[GET_MODE_CLASS (mode)]);
+}
+
 /* Define the integer modes whose sizes are BITS_PER_UNIT and BITS_PER_WORD
    and the mode whose class is Pmode and whose size is POINTER_SIZE.  */
 
@@ -425,4 +473,95 @@ struct int_n_data_t {
 extern bool int_n_enabled_p[NUM_INT_N_ENTS];
 extern const int_n_data_t int_n_data[NUM_INT_N_ENTS];
 
+namespace mode_iterator
+{
+  /* Start mode iterator *ITER at the first mode in class MCLASS, if any.  */
+
+  inline void
+  start (machine_mode *iter, enum mode_class mclass)
+  {
+    *iter = GET_CLASS_NARROWEST_MODE (mclass);
+  }
+
+  /* Return true if mode iterator *ITER has not reached the end.  */
+
+  inline bool
+  iterate_p (machine_mode *iter)
+  {
+    return *iter != E_VOIDmode;
+  }
+
+  /* Set mode iterator *ITER to the next widest mode in the same class,
+     if any.  */
+
+  inline void
+  get_wider (machine_mode *iter)
+  {
+    *iter = GET_MODE_WIDER_MODE (*iter);
+  }
+
+  /* Set mode iterator *ITER to the next widest mode in the same class.
+     Such a mode is known to exist.  */
+
+  inline void
+  get_known_wider (machine_mode *iter)
+  {
+    *iter = GET_MODE_WIDER_MODE (*iter);
+    gcc_checking_assert (*iter != VOIDmode);
+  }
+
+  /* Set mode iterator *ITER to the mode that is two times wider than the
+     current one, if such a mode exists.  */
+
+  inline void
+  get_2xwider (machine_mode *iter)
+  {
+    *iter = GET_MODE_2XWIDER_MODE (*iter);
+  }
+}
+
+/* Make ITERATOR iterate over all the modes in mode class CLASS,
+   from narrowest to widest.  */
+#define FOR_EACH_MODE_IN_CLASS(ITERATOR, CLASS)  \
+  for (mode_iterator::start (&(ITERATOR), CLASS); \
+       mode_iterator::iterate_p (&(ITERATOR)); \
+       mode_iterator::get_wider (&(ITERATOR)))
+
+/* Make ITERATOR iterate over all the modes in the range [START, END),
+   in order of increasing width.  */
+#define FOR_EACH_MODE(ITERATOR, START, END) \
+  for ((ITERATOR) = (START); \
+       (ITERATOR) != (END); \
+       mode_iterator::get_known_wider (&(ITERATOR)))
+
+/* Make ITERATOR iterate over START and all wider modes in the same
+   class, in order of increasing width.  */
+#define FOR_EACH_MODE_FROM(ITERATOR, START) \
+  for ((ITERATOR) = (START); \
+       mode_iterator::iterate_p (&(ITERATOR)); \
+       mode_iterator::get_wider (&(ITERATOR)))
+
+/* Make ITERATOR iterate over modes in the range [NARROWEST, END)
+   in order of increasing width, where NARROWEST is the narrowest mode
+   in END's class.  */
+#define FOR_EACH_MODE_UNTIL(ITERATOR, END) \
+  FOR_EACH_MODE (ITERATOR, get_narrowest_mode (END), END)
+
+/* Make ITERATOR iterate over modes in the same class as MODE, in order
+   of increasing width.  Start at the first mode wider than START,
+   or don't iterate at all if there is no wider mode.  */
+#define FOR_EACH_WIDER_MODE(ITERATOR, START) \
+  for ((ITERATOR) = (START), mode_iterator::get_wider (&(ITERATOR)); \
+       mode_iterator::iterate_p (&(ITERATOR)); \
+       mode_iterator::get_wider (&(ITERATOR)))
+
+/* Make ITERATOR iterate over modes in the same class as MODE, in order
+   of increasing width, and with each mode being twice the width of the
+   previous mode.  Start at the mode that is two times wider than START,
+   or don't iterate at all if there is no such mode.  */
+#define FOR_EACH_2XWIDER_MODE(ITERATOR, START) \
+  for ((ITERATOR) = (START), mode_iterator::get_2xwider (&(ITERATOR)); \
+       mode_iterator::iterate_p (&(ITERATOR)); \
+       mode_iterator::get_2xwider (&(ITERATOR)))
+
 #endif /* not HAVE_MACHINE_MODES */