Add VEC_DUPLICATE_EXPR and associated optab

SVE needs a way of broadcasting a scalar to a variable-length vector.
This patch adds VEC_DUPLICATE_EXPR for when CONSTRUCTOR would be used
for fixed-length vectors; this is the tree equivalent of the existing
rtl code VEC_DUPLICATE.

The patch also adds a vec_duplicate_optab to go with VEC_DUPLICATE_EXPR.

2017-12-16  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hawyard@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* doc/generic.texi (VEC_DUPLICATE_EXPR): Document.
	(VEC_COND_EXPR): Add missing @tindex.
	* doc/md.texi (vec_duplicate@var{m}): Document.
	* tree.def (VEC_DUPLICATE_EXPR): New tree codes.
	* tree.c (build_vector_from_val): Add stubbed-out handling of
	variable-length vectors, using VEC_DUPLICATE_EXPR.
	(uniform_vector_p): Handle VEC_DUPLICATE_EXPR.
	* cfgexpand.c (expand_debug_expr): Likewise.
	* tree-cfg.c (verify_gimple_assign_unary): Likewise.
	* tree-inline.c (estimate_operator_cost): Likewise.
	* tree-pretty-print.c (dump_generic_node): Likewise.
	* tree-vect-generic.c (ssa_uniform_vector_p): Likewise.
	* fold-const.c (const_unop): Fold VEC_DUPLICATE_EXPRs of a constant.
	(test_vec_duplicate_folding): New function.
	(fold_const_c_tests): Call it.
	* optabs.def (vec_duplicate_optab): New optab.
	* optabs-tree.c (optab_for_tree_code): Handle VEC_DUPLICATE_EXPR.
	* optabs.h (expand_vector_broadcast): Declare.
	* optabs.c (expand_vector_broadcast): Make non-static.  Try using
	vec_duplicate_optab.
	* expr.c (store_constructor): Try using vec_duplicate_optab for
	uniform vectors.
	(expand_expr_real_2): Handle VEC_DUPLICATE_EXPR.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r255740

1 files changed, 6 insertions, 1 deletions

diff --git a/gcc/tree.c b/gcc/tree.c
index ed1852b..8e0313c 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -1785,6 +1785,8 @@ build_vector_from_val (tree vectype, tree sc)
       v.quick_push (sc);
       return v.build ();
     }
+  else if (0)
+    return fold_build1 (VEC_DUPLICATE_EXPR, vectype, sc);
   else
     {
       vec<constructor_elt, va_gc> *v;
@@ -10468,7 +10470,10 @@ uniform_vector_p (const_tree vec)
 
   gcc_assert (VECTOR_TYPE_P (TREE_TYPE (vec)));
 
-  if (TREE_CODE (vec) == VECTOR_CST)
+  if (TREE_CODE (vec) == VEC_DUPLICATE_EXPR)
+    return TREE_OPERAND (vec, 0);
+
+  else if (TREE_CODE (vec) == VECTOR_CST)
     {
       if (VECTOR_CST_NPATTERNS (vec) == 1 && VECTOR_CST_DUPLICATE_P (vec))
 	return VECTOR_CST_ENCODED_ELT (vec, 0);