Add comment for last change.

diff --git a/gas/config/tc-sh.c b/gas/config/tc-sh.c
index cd6f90c861a7f1cec98bf58d1097878cf528ac1b..f7aa62515d8740f982aee9031d06aa3c0acbf620 100644 (file)
--- a/gas/config/tc-sh.c
+++ b/gas/config/tc-sh.c
@@ -1383,6 +1383,21 @@ parse_at (src, op)
                }
              else if (mode == A_PC)
                {
+                 /* We want @(expr, pc) to uniformly address . + expr,
+                    no matter if expr is a constant, or a more complex
+                    expression, e.g. sym-. or sym1-sym2.
+                    However, we also used to accept @(sym,pc)
+                    as adressing sym, i.e. meaning the same as plain sym.
+                    Some existing code does use the @(sym,pc) syntax, so
+                    we give it the old semantics for now, but warn about
+                    its use, so that users have some time to fix their code.
+
+                    Note that due to this backward compatibility hack,
+                    we'll get unexpected results when @(offset, pc) is used,
+                    and offset is a symbol that is set later to an an address
+                    difference, or an external symbol that is set to an
+                    address difference in another source file, so we want to
+                    eventually remove it.  */
                  if (op->immediate.X_op == O_symbol)
                    {
                      op->type = A_DISP_PC;