[PATCH] machmode, v2: Introduce GET_MODE_NEXT_MODE with previous GET_MODE_WIDER_MODE meaning, add new GET_MODE_WIDER_MODE

[Jakub Jelinek <jakub@redhat.com>]

On Wed, Oct 12, 2022 at 11:15:40AM +0100, Richard Sandiford wrote:
> Looks good to me, just some minor comments below.

Here is an updated patch.

> How robust is the mechanism that guarantees HF comes before BF,
> and so is the mode that appears in the (new) wider list?

genmodes.cc seems to have cmp_modes which does a lot of different
comparisons to make sure it is a total order.
I think the BFmode vs. HFmode ordering is about the last case:
  if (m->counter < n->counter)
    return -1;
  else
    return 1;
there because everything else is equal and ->counter is about which
mode is declared first in *-modes.def.
And my code for the new mode_wider in genmodes.cc always uses VOIDmode
for !CLASS_HAS_WIDER_MODES_P classes and for CLASS_HAS_WIDER_MODES_P
classes provides a subset of the total ordering, in the already computed
->wider chain it skips modes with the same size/precision.

> > -  /* Set mode iterator *ITER to the next widest mode in the same class.
> > +  /* Set mode iterator *ITER to the next wider mode in the same class.
> >       Such a mode is known to exist.  */
> 
> I'll take your word for it that this is correct. ;-)  I would say
> "next widest", but it's very likely that I'm wrong.

I'm not a native english speaker, but to me next with superlative would be
if we have the widest mode, next widest would be the one whose only
wider mode is the widest mode.

Everything else changed.

2022-10-12  Jakub Jelinek  <jakub@redhat.com>

	* genmodes.cc (emit_mode_wider): Emit previous content of
	mode_wider array into mode_next array and for mode_wider
	emit always VOIDmode for !CLASS_HAS_WIDER_MODES_P classes,
	otherwise skip through modes with the same precision.
	* machmode.h (mode_next): Declare.
	(GET_MODE_NEXT_MODE): New inline function.
	(mode_iterator::get_next, mode_iterator::get_known_next): New
	function templates.
	(FOR_EACH_MODE_IN_CLASS): Use get_next instead of get_wider.
	(FOR_EACH_MODE): Use get_known_next instead of get_known_wider.
	(FOR_EACH_MODE_FROM): Use get_next instead of get_wider.
	(FOR_EACH_WIDER_MODE_FROM): Define.
	(FOR_EACH_NEXT_MODE): Define.
	* expmed.cc (emit_store_flag_1): Use FOR_EACH_WIDER_MODE_FROM
	instead of FOR_EACH_MODE_FROM.
	* optabs.cc (prepare_cmp_insn): Likewise.  Remove redundant
	!CLASS_HAS_WIDER_MODES_P check.
	(prepare_float_lib_cmp): Use FOR_EACH_WIDER_MODE_FROM instead of
	FOR_EACH_MODE_FROM.
	* config/i386/i386-expand.cc (get_mode_wider_vector): Use
	GET_MODE_NEXT_MODE instead of GET_MODE_WIDER_MODE.

--- gcc/genmodes.cc.jj	2022-10-12 10:15:21.444381490 +0200
+++ gcc/genmodes.cc	2022-10-12 12:28:02.414528652 +0200
@@ -1527,7 +1527,7 @@ emit_mode_wider (void)
   int c;
   struct mode_data *m;
 
-  print_decl ("unsigned char", "mode_wider", "NUM_MACHINE_MODES");
+  print_decl ("unsigned char", "mode_next", "NUM_MACHINE_MODES");
 
   for_all_modes (c, m)
     tagged_printf ("E_%smode",
@@ -1535,6 +1535,37 @@ emit_mode_wider (void)
 		   m->name);
 
   print_closer ();
+  print_decl ("unsigned char", "mode_wider", "NUM_MACHINE_MODES");
+
+  for_all_modes (c, m)
+    {
+      struct mode_data *m2 = 0;
+
+      if (m->cl == MODE_INT
+	  || m->cl == MODE_PARTIAL_INT
+	  || m->cl == MODE_FLOAT
+	  || m->cl == MODE_DECIMAL_FLOAT
+	  || m->cl == MODE_COMPLEX_FLOAT
+	  || m->cl == MODE_FRACT
+	  || m->cl == MODE_UFRACT
+	  || m->cl == MODE_ACCUM
+	  || m->cl == MODE_UACCUM)
+	for (m2 = m->wider; m2 && m2 != void_mode; m2 = m2->wider)
+	  {
+	    if (m2->bytesize == m->bytesize
+		&& m2->precision == m->precision)
+	      continue;
+	    break;
+	  }
+
+      if (m2 == void_mode)
+	m2 = 0;
+      tagged_printf ("E_%smode",
+		     m2 ? m2->name : void_mode->name,
+		     m->name);
+    }
+
+  print_closer ();
   print_decl ("unsigned char", "mode_2xwider", "NUM_MACHINE_MODES");
 
   for_all_modes (c, m)
--- gcc/machmode.h.jj	2022-10-12 10:15:21.491380846 +0200
+++ gcc/machmode.h	2022-10-12 12:33:36.795975117 +0200
@@ -28,6 +28,7 @@ extern const unsigned char mode_inner[NU
 extern CONST_MODE_NUNITS poly_uint16_pod mode_nunits[NUM_MACHINE_MODES];
 extern CONST_MODE_UNIT_SIZE unsigned char mode_unit_size[NUM_MACHINE_MODES];
 extern const unsigned short mode_unit_precision[NUM_MACHINE_MODES];
+extern const unsigned char mode_next[NUM_MACHINE_MODES];
 extern const unsigned char mode_wider[NUM_MACHINE_MODES];
 extern const unsigned char mode_2xwider[NUM_MACHINE_MODES];
 
@@ -760,7 +761,23 @@ GET_MODE_NUNITS (const T &mode)
 }
 #endif
 
-/* Get the next wider natural mode (eg, QI -> HI -> SI -> DI -> TI).  */
+/* Get the next natural mode (not narrower, eg, QI -> HI -> SI -> DI -> TI
+   or HF -> BF -> SF -> DF -> XF -> TF).  */
+
+template<typename T>
+ALWAYS_INLINE opt_mode<T>
+GET_MODE_NEXT_MODE (const T &m)
+{
+  return typename opt_mode<T>::from_int (mode_next[m]);
+}
+
+/* Get the next wider mode (eg, QI -> HI -> SI -> DI -> TI
+   or { HF, BF } -> SF -> DF -> XF -> TF).
+   This is similar to GET_MODE_NEXT_MODE, but while GET_MODE_NEXT_MODE
+   can include mode that have the same precision (e.g.
+   GET_MODE_NEXT_MODE (HFmode) can be BFmode even when both have the same
+   precision), this one will skip those.  And always VOIDmode for
+   modes whose class is !CLASS_HAS_WIDER_MODES_P.  */
 
 template<typename T>
 ALWAYS_INLINE opt_mode<T>
@@ -1098,7 +1115,33 @@ namespace mode_iterator
     return *iter != E_VOIDmode;
   }
 
-  /* Set mode iterator *ITER to the next widest mode in the same class,
+  /* Set mode iterator *ITER to the next mode in the same class,
+     if any.  */
+
+  template<typename T>
+  inline void
+  get_next (opt_mode<T> *iter)
+  {
+    *iter = GET_MODE_NEXT_MODE (iter->require ());
+  }
+
+  inline void
+  get_next (machine_mode *iter)
+  {
+    *iter = GET_MODE_NEXT_MODE (*iter).else_void ();
+  }
+
+  /* Set mode iterator *ITER to the next mode in the same class.
+     Such a mode is known to exist.  */
+
+  template<typename T>
+  inline void
+  get_known_next (T *iter)
+  {
+    *iter = GET_MODE_NEXT_MODE (*iter).require ();
+  }
+
+  /* Set mode iterator *ITER to the next wider mode in the same class,
      if any.  */
 
   template<typename T>
@@ -1114,7 +1157,7 @@ namespace mode_iterator
     *iter = GET_MODE_WIDER_MODE (*iter).else_void ();
   }
 
-  /* Set mode iterator *ITER to the next widest mode in the same class.
+  /* Set mode iterator *ITER to the next wider mode in the same class.
      Such a mode is known to exist.  */
 
   template<typename T>
@@ -1146,20 +1189,27 @@ namespace mode_iterator
 #define FOR_EACH_MODE_IN_CLASS(ITERATOR, CLASS)  \
   for (mode_iterator::start (&(ITERATOR), CLASS); \
        mode_iterator::iterate_p (&(ITERATOR)); \
-       mode_iterator::get_wider (&(ITERATOR)))
+       mode_iterator::get_next (&(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)))
+       mode_iterator::get_known_next (&(ITERATOR)))
 
-/* Make ITERATOR iterate over START and all wider modes in the same
+/* Make ITERATOR iterate over START and all non-narrower 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_next (&(ITERATOR)))
+
+/* Make ITERATOR iterate over START and all wider modes in the same
+   class, in order of strictly increasing width.  */
+#define FOR_EACH_WIDER_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)
@@ -1169,6 +1219,14 @@ namespace mode_iterator
   FOR_EACH_MODE (ITERATOR, get_narrowest_mode (END), END)
 
 /* Make ITERATOR iterate over modes in the same class as MODE, in order
+   of non-decreasing width.  Start at next such mode after START,
+   or don't iterate at all if there is no such mode.  */
+#define FOR_EACH_NEXT_MODE(ITERATOR, START) \
+  for ((ITERATOR) = (START), mode_iterator::get_next (&(ITERATOR)); \
+       mode_iterator::iterate_p (&(ITERATOR)); \
+       mode_iterator::get_next (&(ITERATOR)))
+
+/* 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) \
--- gcc/expmed.cc.jj	2022-10-12 10:15:21.335382983 +0200
+++ gcc/expmed.cc	2022-10-12 12:28:02.417528612 +0200
@@ -5712,7 +5712,7 @@ emit_store_flag_1 (rtx target, enum rtx_
 
   /* Next try expanding this via the backend's cstore<mode>4.  */
   mclass = GET_MODE_CLASS (mode);
-  FOR_EACH_MODE_FROM (compare_mode, mode)
+  FOR_EACH_WIDER_MODE_FROM (compare_mode, mode)
     {
      machine_mode optab_mode = mclass == MODE_CC ? CCmode : compare_mode;
      icode = optab_handler (cstore_optab, optab_mode);
--- gcc/optabs.cc.jj	2022-10-12 10:15:21.542380147 +0200
+++ gcc/optabs.cc	2022-10-12 12:28:02.418528598 +0200
@@ -4384,7 +4384,6 @@ prepare_cmp_insn (rtx x, rtx y, enum rtx
   machine_mode mode = *pmode;
   rtx libfunc, test;
   machine_mode cmp_mode;
-  enum mode_class mclass;
 
   /* The other methods are not needed.  */
   gcc_assert (methods == OPTAB_DIRECT || methods == OPTAB_WIDEN
@@ -4490,9 +4489,8 @@ prepare_cmp_insn (rtx x, rtx y, enum rtx
       return;
     }
 
-  mclass = GET_MODE_CLASS (mode);
   test = gen_rtx_fmt_ee (comparison, VOIDmode, x, y);
-  FOR_EACH_MODE_FROM (cmp_mode, mode)
+  FOR_EACH_WIDER_MODE_FROM (cmp_mode, mode)
     {
       enum insn_code icode;
       icode = optab_handler (cbranch_optab, cmp_mode);
@@ -4515,7 +4513,7 @@ prepare_cmp_insn (rtx x, rtx y, enum rtx
 	  delete_insns_since (last);
 	}
 
-      if (methods == OPTAB_DIRECT || !CLASS_HAS_WIDER_MODES_P (mclass))
+      if (methods == OPTAB_DIRECT)
 	break;
     }
 
@@ -4711,7 +4709,7 @@ prepare_float_lib_cmp (rtx x, rtx y, enu
   bool reversed_p = false;
   scalar_int_mode cmp_mode = targetm.libgcc_cmp_return_mode ();
 
-  FOR_EACH_MODE_FROM (mode, orig_mode)
+  FOR_EACH_WIDER_MODE_FROM (mode, orig_mode)
     {
       if (code_to_optab (comparison)
 	  && (libfunc = optab_libfunc (code_to_optab (comparison), mode)))
--- gcc/config/i386/i386-expand.cc.jj	2022-09-26 18:47:26.892350579 +0200
+++ gcc/config/i386/i386-expand.cc	2022-10-12 12:28:02.421528557 +0200
@@ -14941,7 +14941,7 @@ static machine_mode
 get_mode_wider_vector (machine_mode o)
 {
   /* ??? Rely on the ordering that genmodes.cc gives to vectors.  */
-  machine_mode n = GET_MODE_WIDER_MODE (o).require ();
+  machine_mode n = GET_MODE_NEXT_MODE (o).require ();
   gcc_assert (GET_MODE_NUNITS (o) == GET_MODE_NUNITS (n) * 2);
   gcc_assert (GET_MODE_SIZE (o) == GET_MODE_SIZE (n));
   return n;


	Jakub