[53/77] Pass a mode to const_scalar_mask_from_tree

[Richard Sandiford]

The caller of const_scalar_mask_from_tree has proven that
the mode is a MODE_INT, so this patch passes it down as a
scalar_int_mode.  It also expands the comment a little.

2017-07-13  Richard Sandiford  <richard.sandif...@linaro.org>
            Alan Hayward  <alan.hayw...@arm.com>
            David Sherwood  <david.sherw...@arm.com>

gcc/
        * expr.c (const_scalar_mask_from_tree): Add a mode argument.
        Expand commentary.
        (expand_expr_real_1): Update call accordingly.

Index: gcc/expr.c
===================================================================
--- gcc/expr.c  2017-07-13 09:18:46.702152995 +0100
+++ gcc/expr.c  2017-07-13 09:18:47.609081780 +0100
@@ -99,7 +99,7 @@ static void emit_single_push_insn (machi
 static void do_tablejump (rtx, machine_mode, rtx, rtx, rtx,
                          profile_probability);
 static rtx const_vector_from_tree (tree);
-static rtx const_scalar_mask_from_tree (tree);
+static rtx const_scalar_mask_from_tree (scalar_int_mode, tree);
 static tree tree_expr_size (const_tree);
 static HOST_WIDE_INT int_expr_size (tree);
 
@@ -9962,7 +9962,7 @@ expand_expr_real_1 (tree exp, rtx target
        if (is_int_mode (mode, &int_mode))
          {
            if (VECTOR_BOOLEAN_TYPE_P (TREE_TYPE (exp)))
-             return const_scalar_mask_from_tree (exp);
+             return const_scalar_mask_from_tree (int_mode, exp);
            else
              {
                tree type_for_mode
@@ -11717,12 +11717,12 @@ const_vector_mask_from_tree (tree exp)
   return gen_rtx_CONST_VECTOR (mode, v);
 }
 
-/* Return a CONST_INT rtx representing vector mask for
-   a VECTOR_CST of booleans.  */
+/* EXP is a VECTOR_CST in which each element is either all-zeros or all-ones.
+   Return a constant scalar rtx of mode MODE in which bit X is set if element
+   X of EXP is nonzero.  */
 static rtx
-const_scalar_mask_from_tree (tree exp)
+const_scalar_mask_from_tree (scalar_int_mode mode, tree exp)
 {
-  machine_mode mode = TYPE_MODE (TREE_TYPE (exp));
   wide_int res = wi::zero (GET_MODE_PRECISION (mode));
   tree elt;
   unsigned i;