[53/77] Pass a mode to const_scalar_mask_from_tree

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.

2017-08-30  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

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

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

From-SVN: r251505

gcc/ChangeLog

@@ -2,6 +2,14 @@
 	    Alan Hayward  <alan.hayward@arm.com>
 	    David Sherwood  <david.sherwood@arm.com>
 
+	* expr.c (const_scalar_mask_from_tree): Add a mode argument.
+	Expand commentary.
+	(expand_expr_real_1): Update call accordingly.
+
+2017-08-30  Richard Sandiford  <richard.sandiford@linaro.org>
+	    Alan Hayward  <alan.hayward@arm.com>
+	    David Sherwood  <david.sherwood@arm.com>
+
 	* expmed.c (store_bit_field_using_insv): Add op0_mode and
 	value_mode arguments.  Use scalar_int_mode internally.
 	(store_bit_field_1): Rename the new integer mode from imode

gcc/expr.c

@@ -99,7 +99,7 @@ static void emit_single_push_insn (machine_mode, rtx, tree);
 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);
 
@@ -9969,7 +9969,7 @@ expand_expr_real_1 (tree exp, rtx target, machine_mode tmode,
 	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
@@ -11724,12 +11724,12 @@ 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;