[Bug middle-end/54201] XMM constant duplicated

[rguenth at gcc dot gnu.org]

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

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |rguenth at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #7 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-08-14 
13:20:26 UTC ---
The following works.

Index: gcc/varasm.c
===================================================================
--- gcc/varasm.c        (revision 190381)
+++ gcc/varasm.c        (working copy)
@@ -3482,8 +3482,9 @@ force_const_mem (enum machine_mode mode,
 {
   struct constant_descriptor_rtx *desc, tmp;
   struct rtx_constant_pool *pool;
+  enum machine_mode orig_mode = mode;
   char label[256];
-  rtx def, symbol;
+  rtx def, symbol, res;
   hashval_t hash;
   unsigned int align;
   void **slot;
@@ -3500,6 +3501,18 @@ force_const_mem (enum machine_mode mode,
          ? shared_constant_pool
          : crtl->varasm.pool);

+  /* Canonicalize CONST_VECTORs to the mode with the least number of
+     elements assuming that alignment requirements are not worse
+     for the original mode.  */
+  if (GET_CODE (x) == CONST_VECTOR)
+    {
+      while (GET_MODE_SIZE (mode)
+            == GET_MODE_SIZE (GET_MODE_WIDER_MODE (mode)))
+       mode = GET_MODE_WIDER_MODE (mode);
+      x = simplify_subreg (mode, x, orig_mode, 0);
+      gcc_assert (x != NULL_RTX);
+    }
+
   /* Lookup the value in the hashtable.  */
   tmp.constant = x;
   tmp.mode = mode;
@@ -3509,7 +3522,11 @@ force_const_mem (enum machine_mode mode,

   /* If the constant was already present, return its memory.  */
   if (desc)
-    return copy_rtx (desc->mem);
+    {
+      res = copy_rtx (desc->mem);
+      PUT_MODE (res, orig_mode);
+      return res;
+    }

   /* Otherwise, create a new descriptor.  */
   desc = ggc_alloc_constant_descriptor_rtx ();
@@ -3573,7 +3590,9 @@ force_const_mem (enum machine_mode mode,
   if (GET_CODE (x) == LABEL_REF)
     LABEL_PRESERVE_P (XEXP (x, 0)) = 1;

-  return copy_rtx (def);
+  res = copy_rtx (def);
+  PUT_MODE (res, orig_mode);
+  return res;
 }


but we still create two references to the constant pool:

test:
.LFB517:
        .cfi_startproc
        pand    .LC0(%rip), %xmm0
        pcmpeqb .LC0(%rip), %xmm0
        ret

Mine again.