ada: Avoid doing unnecessary work in elaborate_expression_2

This prevents the expression from being tweaked by the match.pd machinery
in the process, which can damage the readability of the -gnatR3 output.

gcc/ada/ChangeLog:

	* gcc-interface/decl.cc (elaborate_expression_2): Do not divide and
	multiply back if the alignment factor is already explicit.

diff --git a/gcc/ada/gcc-interface/decl.cc b/gcc/ada/gcc-interface/decl.cc
index 32e476c69936605a93dac01887b1f840c53538f1..024bf456bc9fe0842401a5a76551dcfa17a5a598 100644 (file)
--- a/gcc/ada/gcc-interface/decl.cc
+++ b/gcc/ada/gcc-interface/decl.cc
@@ -7355,15 +7355,30 @@ static tree
 elaborate_expression_2 (tree gnu_expr, Entity_Id gnat_entity, const char *s,
                        bool definition, bool need_for_debug, unsigned int align)
 {
-  tree unit_align = size_int (align / BITS_PER_UNIT);
-  return
-    size_binop (MULT_EXPR,
-               elaborate_expression_1 (size_binop (EXACT_DIV_EXPR,
-                                                   gnu_expr,
-                                                   unit_align),
-                                       gnat_entity, s, definition,
-                                       need_for_debug),
-               unit_align);
+  /* Nothing more to do if the factor is already explicit in the tree.  */
+  if (TREE_CODE (gnu_expr) == MULT_EXPR
+      && TREE_CONSTANT (TREE_OPERAND (gnu_expr, 1))
+      && value_factor_p (TREE_OPERAND (gnu_expr, 1), align / BITS_PER_UNIT))
+    return
+      size_binop (MULT_EXPR,
+                 elaborate_expression_1 (TREE_OPERAND (gnu_expr, 0),
+                                         gnat_entity, s, definition,
+                                         need_for_debug),
+                 TREE_OPERAND (gnu_expr, 1));
+
+  /* Otherwise divide by the factor, elaborate the result and multiply back.  */
+  else
+    {
+      tree unit_align = size_int (align / BITS_PER_UNIT);
+      return
+       size_binop (MULT_EXPR,
+                   elaborate_expression_1 (size_binop (EXACT_DIV_EXPR,
+                                                       gnu_expr,
+                                                       unit_align),
+                                           gnat_entity, s, definition,
+                                           need_for_debug),
+                   unit_align);
+    }
 }
 
 /* Structure to hold internal data for elaborate_reference.  */