[5/9] Add mode_for_int_vector helper functions

[Richard Sandiford <richard dot sandiford at linaro dot org>]

There are at least a few places that want to create an integer vector
with a specified element size and element count, or to create the
integer equivalent of an existing mode.  This patch adds helpers
for doing that.

The require ()s are all used in functions that go on to emit
instructions that use the result as a vector mode.

2017-09-04  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* machmode.h (mode_for_int_vector): New function.
	* stor-layout.c (mode_for_int_vector): Likewise.
	* config/aarch64/aarch64.c (aarch64_emit_approx_sqrt): Use it.
	* config/powerpcspe/powerpcspe.c (rs6000_do_expand_vec_perm): Likewise.
	* config/rs6000/rs6000.c (rs6000_do_expand_vec_perm): Likewise.
	* config/s390/s390.c (s390_expand_vec_compare_cc): Likewise.
	(s390_expand_vcond): Likewise.

Index: gcc/machmode.h
===================================================================
--- gcc/machmode.h	2017-09-04 12:18:50.674859598 +0100
+++ gcc/machmode.h	2017-09-04 12:18:53.153306182 +0100
@@ -706,6 +706,21 @@ extern machine_mode bitwise_mode_for_mod
 
 extern machine_mode mode_for_vector (scalar_mode, unsigned);
 
+extern opt_machine_mode mode_for_int_vector (unsigned int, unsigned int);
+
+/* Return the integer vector equivalent of MODE, if one exists.  In other
+   words, return the mode for an integer vector that has the same number
+   of bits as MODE and the same number of elements as MODE, with the
+   latter being 1 if MODE is scalar.  The returned mode can be either
+   an integer mode or a vector mode.  */
+
+inline opt_machine_mode
+mode_for_int_vector (machine_mode mode)
+{
+  return mode_for_int_vector (GET_MODE_UNIT_BITSIZE (mode),
+			      GET_MODE_NUNITS (mode));
+}
+
 /* A class for iterating through possible bitfield modes.  */
 class bit_field_mode_iterator
 {
Index: gcc/stor-layout.c
===================================================================
--- gcc/stor-layout.c	2017-09-04 12:18:50.675762071 +0100
+++ gcc/stor-layout.c	2017-09-04 12:18:53.153306182 +0100
@@ -517,6 +517,23 @@ mode_for_vector (scalar_mode innermode,
   return mode;
 }
 
+/* Return the mode for a vector that has NUNITS integer elements of
+   INT_BITS bits each, if such a mode exists.  The mode can be either
+   an integer mode or a vector mode.  */
+
+opt_machine_mode
+mode_for_int_vector (unsigned int int_bits, unsigned int nunits)
+{
+  scalar_int_mode int_mode;
+  if (int_mode_for_size (int_bits, 0).exists (&int_mode))
+    {
+      machine_mode vec_mode = mode_for_vector (int_mode, nunits);
+      if (vec_mode != BLKmode)
+	return vec_mode;
+    }
+  return opt_machine_mode ();
+}
+
 /* Return the alignment of MODE. This will be bounded by 1 and
    BIGGEST_ALIGNMENT.  */
 
Index: gcc/config/aarch64/aarch64.c
===================================================================
--- gcc/config/aarch64/aarch64.c	2017-09-04 12:18:44.874165502 +0100
+++ gcc/config/aarch64/aarch64.c	2017-09-04 12:18:53.144272229 +0100
@@ -8282,9 +8282,6 @@ aarch64_emit_approx_sqrt (rtx dst, rtx s
       return false;
     }
 
-  machine_mode mmsk
-    = mode_for_vector (int_mode_for_mode (GET_MODE_INNER (mode)).require (),
-		       GET_MODE_NUNITS (mode));
   if (!recp)
     {
       if (!(flag_mlow_precision_sqrt
@@ -8302,7 +8299,7 @@ aarch64_emit_approx_sqrt (rtx dst, rtx s
     /* Caller assumes we cannot fail.  */
     gcc_assert (use_rsqrt_p (mode));
 
-
+  machine_mode mmsk = mode_for_int_vector (mode).require ();
   rtx xmsk = gen_reg_rtx (mmsk);
   if (!recp)
     /* When calculating the approximate square root, compare the
Index: gcc/config/powerpcspe/powerpcspe.c
===================================================================
--- gcc/config/powerpcspe/powerpcspe.c	2017-09-04 12:18:44.919414816 +0100
+++ gcc/config/powerpcspe/powerpcspe.c	2017-09-04 12:18:53.148287319 +0100
@@ -38739,8 +38739,7 @@ rs6000_do_expand_vec_perm (rtx target, r
 
   imode = vmode;
   if (GET_MODE_CLASS (vmode) != MODE_VECTOR_INT)
-    imode = mode_for_vector
-      (int_mode_for_mode (GET_MODE_INNER (vmode)).require (), nelt);
+    imode = mode_for_int_vector (vmode).require ();
 
   x = gen_rtx_CONST_VECTOR (imode, gen_rtvec_v (nelt, perm));
   x = expand_vec_perm (vmode, op0, op1, x, target);
Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c	2017-09-04 12:18:44.929470219 +0100
+++ gcc/config/rs6000/rs6000.c	2017-09-04 12:18:53.151298637 +0100
@@ -35584,8 +35584,7 @@ rs6000_do_expand_vec_perm (rtx target, r
 
   imode = vmode;
   if (GET_MODE_CLASS (vmode) != MODE_VECTOR_INT)
-    imode = mode_for_vector
-      (int_mode_for_mode (GET_MODE_INNER (vmode)).require (), nelt);
+    imode = mode_for_int_vector (vmode).require ();
 
   x = gen_rtx_CONST_VECTOR (imode, gen_rtvec_v (nelt, perm));
   x = expand_vec_perm (vmode, op0, op1, x, target);
Index: gcc/config/s390/s390.c
===================================================================
--- gcc/config/s390/s390.c	2017-09-04 11:50:24.561571751 +0100
+++ gcc/config/s390/s390.c	2017-09-04 12:18:53.153306182 +0100
@@ -6472,10 +6472,7 @@ s390_expand_vec_compare_cc (rtx target,
 	case LE:   cc_producer_mode = CCVFHEmode; code = GE; swap_p = true; break;
 	default: gcc_unreachable ();
 	}
-      scratch_mode = mode_for_vector
-	(int_mode_for_mode (GET_MODE_INNER (GET_MODE (cmp1))).require (),
-	 GET_MODE_NUNITS (GET_MODE (cmp1)));
-      gcc_assert (scratch_mode != BLKmode);
+      scratch_mode = mode_for_int_vector (GET_MODE (cmp1)).require ();
 
       if (inv_p)
 	all_p = !all_p;
@@ -6581,9 +6578,7 @@ s390_expand_vcond (rtx target, rtx then,
 
   /* We always use an integral type vector to hold the comparison
      result.  */
-  result_mode = mode_for_vector
-    (int_mode_for_mode (GET_MODE_INNER (cmp_mode)).require (),
-     GET_MODE_NUNITS (cmp_mode));
+  result_mode = mode_for_int_vector (cmp_mode).require ();
   result_target = gen_reg_rtx (result_mode);
 
   /* We allow vector immediates as comparison operands that