[Bug middle-end/54201] XMM constant duplicated

["jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54201

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #11 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The .rodata duplication should now be gone with the above commit.

I've tried

--- gcc/varasm.c.jj     2020-08-31 10:26:56.978179325 +0200
+++ gcc/varasm.c        2020-08-31 19:15:34.563274307 +0200
@@ -3818,6 +3818,38 @@ force_const_mem (machine_mode in_mode, r
   if (!is_a <fixed_size_mode> (in_mode, &mode))
     return NULL_RTX;

+  /* Try to canonicalize CONST_VECTORs.  See PR54201.  */
+  if (GET_CODE (x) == CONST_VECTOR)
+    {
+      machine_mode cmode = MIN_MODE_VECTOR_INT;
+      machine_mode altmode = VOIDmode;
+
+      /* Choose a MODE_VECTOR_INT mode with the same size as in_mode
+        and as large as possible element, as long as the element is
+        at most HWI sized (so that CONST_INTs can be used rather
+        than CONST_DOUBLEs or CONST_WIDE_INTs.  */
+      FOR_EACH_MODE_FROM (cmode, cmode)
+       if (known_eq (GET_MODE_SIZE (cmode), GET_MODE_SIZE (in_mode))
+           && known_le (GET_MODE_SIZE (GET_MODE_INNER (cmode)),
+                        HOST_BITS_PER_WIDE_INT)
+           && (altmode == VOIDmode
+               || (GET_MODE_SIZE (GET_MODE_INNER (cmode))
+                   > GET_MODE_SIZE (GET_MODE_INNER (altmode)))))
+         altmode = cmode;
+      if (altmode != VOIDmode && altmode != in_mode)
+       {
+         rtx altx = simplify_subreg (altmode, x, in_mode, 0);
+         if (altx && GET_CODE (altx) == CONST_VECTOR)
+           {
+             rtx altret = force_const_mem (altmode, altx);
+             if (altret)
+               {
+                 PUT_MODE (altret, in_mode);
+                 return altret;
+               }
+           }
+       }
+    }
   /* If we're not allowed to drop X into the constant pool, don't.  */
   if (targetm.cannot_force_const_mem (mode, x))
     return NULL_RTX;

as a variant of Richi's patch, but e.g. on
typedef int V __attribute__((vector_size (16)));
typedef long long int W __attribute__((vector_size (16)));
typedef float X __attribute__((vector_size (16)));

void
foo (V *v, W *w, X *x)
{
  *v += (V) (X) { 2.0f, 2.0f, 2.0f, 2.0f };
  *w += (W) (X) { 2.0f, 2.0f, 2.0f, 2.0f };
  *x += (X) { 2.0f, 2.0f, 2.0f, 2.0f };
}
nothing will really try to share the loads, so the question is if it would gain
us anything.