[Patch] Propagate vector constants into VEC_PERM_EXPR while lowering.

[Ramana Radhakrishnan]

Hi,

This patch allows propagation of vector constants into VEC_PERM_EXPRs
in lower_vec_perm, motivation explained in
http://gcc.gnu.org/ml/gcc-patches/2012-06/msg00615.html

Bootstrapped and regression tested on gcc110.fsffrance.org .

Ok ?

regards,
Ramana

   * tree-vect-generic.c (lower_vec_perm): Propagate vector constants
into VEC_PERM_EXPR..

diff --git a/gcc/tree-vect-generic.c b/gcc/tree-vect-generic.c
index 06334bb..3b9f561 100644
--- a/gcc/tree-vect-generic.c
+++ b/gcc/tree-vect-generic.c
@@ -628,6 +628,14 @@ lower_vec_perm (gimple_stmt_iterator *gsi)
   location_t loc = gimple_location (gsi_stmt (*gsi));
   unsigned i;

+  if (TREE_CODE (mask) == SSA_NAME)
+    {
+      gimple def_stmt = SSA_NAME_DEF_STMT (mask);
+      if (is_gimple_assign (def_stmt)
+         && gimple_assign_rhs_code (def_stmt) == VECTOR_CST)
+       mask = gimple_assign_rhs1 (def_stmt);
+    }
+
   if (TREE_CODE (mask) == VECTOR_CST)
     {
       unsigned char *sel_int = XALLOCAVEC (unsigned char, elements);
@@ -637,7 +645,11 @@ lower_vec_perm (gimple_stmt_iterator *gsi)
                      & (2 * elements - 1));

       if (can_vec_perm_p (TYPE_MODE (vect_type), false, sel_int))
-       return;
+       {
+         gimple_assign_set_rhs3 (stmt, mask);
+         update_stmt (stmt);
+         return;
+       }
     }
   else if (can_vec_perm_p (TYPE_MODE (vect_type), true, NULL))
     return;